After breakfast this morning, I went to YouTube to watch a new music video a friend sent me. Before it began, there was an advertisement from someone named Dr. Steven Gundry. He’s sitting on a set that is made to look like a doctor’s office. There’s a small human skeleton model on a credenza behind him. A map of the world is hanging on the wall. (Why a map of the world?) Two prop diplomas hang in cheap frames next to the map. There are no reference books on the sparsely filled bookshelf behind him. Looking straight at the camera, he says, grim-faced, “This is a tomato. Think it’s good for you? Think again.” He pauses. “My name is Dr. Steven Gundry, author of the bestselling books Dr. Gundry’s Diet Evolution and The Plant Paradox.” Now my BS detector is kicking in. Writing bestselling books does not make you an authority. And in fact, tomatoes are good for you, especially when cooked, as is shown in solid, peer-reviewed studies (the lycopene they contain decreases the risk of prostate and breast cancer, heart disease, osteoporosis, and other chronic diseases).
Gundry continues, “And I’m here today to blow your mind.” He wags his finger at the camera emphatically on each of those last three words. “You see, over the last thirty years of research and performing over ten thousand surgeries, I’ve discovered some shocking things about the human body.” Now my BS detector is going haywire. Performing surgeries, whether it’s one or ten thousand, doesn’t give you any scientific data on what people should eat. By the end of the ad, we learn that he is selling a line of supplements he created.
I noticed that Mehmet Oz endorses his work. Another red flag. Dr. Oz is widely regarded within the medical community as a charlatan, spewing a plethora of pseudoscientific nonsense and assorted quackery. The American Medical Association has admonished him as a “dangerous rogue.”
Next I went to PubMed, a database of medical and scientific articles managed by the US National Library of Medicine at the National Institutes of Health. A research finding is not considered “science” until it has been subjected to peer review—validation of the paper, its methods, and its conclusions by an independent panel, typically of three expert scientists. I was not able to find any peer-reviewed studies by Dr. Steven Gundry supporting his assertions. This, and the fact that he is promoting his own brand of supplements, makes me suspicious. Is his just another in a long line of faddish diets on which people will pin their hopes, only to be disappointed?
Maybe you’re fed up with science and are ready to try anything, especially when it’s recommended by a freethinking renegade—just in case it works. Every ten years or so, it seems scientists have a completely different view of what we should and shouldn’t eat to promote longevity and health—the meatless diet, the no-fat diet, the no-carbohydrates diet, the all-carb diet, the paleo diet. First fat was the enemy. Then sugar. Then carbs, which break down into sugars. You’d be forgiven for thinking that scientists don’t know what they are talking about!
The problem here has to do with the economics and logistics of properly applying the scientific method. Most of what we know (or think we know) about foods and health comes from observational studies or samples of convenience, not proper experiments. In observational studies, as the name implies, we simply watch people who have different diets over a period of years and see how they fare. Any differences between groups of people are attributed to the difference in diets. The scientific problem is that people who eat different foods may have other differences as well that we’re not keeping track of: different tendencies to exercise (or not), sleep duration, attitudes toward medicine, hydration, different daily stressors endured. Someone has just lost their job, another just had their first child, another is a heroin addict, another is a professional athlete, and so on and so on. This goes to the core theme of personal psychology and individual differences versus the generalizations neuroscience allows.
What you’d really want is to be able to take people who are identical in every lifestyle metric and then tell them exactly what to eat, putting that one variable completely under the experimenter’s control. Some would get Diet A, some Diet B. This is difficult to do. The kinds of people who would volunteer for such an experiment may not be typical of the rest of the population. Unless you monitor your subjects twenty-four hours a day, many will sneak forbidden foods into their diet. And if you have any preexisting thought that one of the diets could cause harm, it would be unethical to ask anybody to follow it. Even if you could do all of this, you’d have to follow people for years in order to see effects.
By the way, this issue is what has hampered smoking research. You can’t demand that some people smoke in a controlled experiment because it seems, from observational studies and animal models, that smoking significantly increases your chances of dying from cancer. We infer that smoking is bad, but it has not been shown in controlled experiments in humans (just rodents and monkeys). Similarly, we infer that saturated fats and sugars are bad, but we don’t have controlled experiments that prove it.
So the history of dietary research has been hobbled by the lack of controlled experiments and by the very real possibility that there are individual differences (hello!) in the ways that people metabolize food and nutrients, their glucose metabolism, the activity of lipoprotein lipase (an enzyme that promotes fat storage versus fat oxidation), and genetic factors. On average, Diet A may seem no better than Diet B, but for some people, there might be big differences. What is clear is that there are no data (yet) to help clinicians match a patient’s food metabolic genotype to the optimally beneficial diet. The new field of nutrigenomics promises to fill this gap. But these gaps don’t mean that we know nothing. The last fifteen years of research have moved us closer to the goal of understanding how diet affects health, well-being, and longevity.
Our digestive systems today are the product of tens of thousands of years of hominid evolution. Our ancestors of the Paleolithic age, about fifty thousand years ago, subsisted by gathering plants and fishing and by hunting or scavenging wild animals. As a result, their diet was primarily lean meat, fish, fruits, vegetables, roots, eggs, and nuts. This is the so-called Paleolithic diet, or paleo diet. This diet is based on the fact that we have not evolved to eat the high amounts of sugar, salt, or saturated animal fats that are in the typical American diet; those are products of technology and industrial food production that our bodies—our genetics—have not yet caught up to.
The drive to carve out a special selection of foods to promote weight loss or health has been around as long as recorded history. In ancient Greece (home of the Mediterranean diet), the great physician Hippocrates advised overweight citizens to follow a strict regimen of “exercise and vomiting.” William the Conqueror, beginning around 1080, followed an all-alcohol diet. (He later died in a horseback riding accident.) In the early 1800s Lord Byron followed a vinegar diet. The early 1900s saw the tapeworm diet. (Yes, it is what it sounds like. The idea is that tapeworms would consume some of the food you eat and then you just expel the tapeworms—what could possibly go wrong?) The annals of diets feature grapefruit diets, cabbage soup diets, the red-pepper-lemon-juice-cleanse diet, cigarette diets, the placenta diet (celebrated by January Jones and Kim Kardashian), the cotton ball diet (stanches hunger but causes serious intestinal obstruction, and sometimes death), and the SlimFast diet. Many popular diets that seem contemporary, such as vegetarianism, veganism, and raw food, have their origins in the 1800s, and the über-faddish keto diet goes back to the 1920s. You’d think that if one was clearly superior to the others, after all this time we’d know about it.
Stanford nutrition scientist Christopher Gardner notes that “no matter how crazy a diet might be, it will work for someone if enough people try it. . . . If you give it to 100 people, it might work for only two of them, but the people promoting the diet don’t test it that way; they simply focus on the two successful stories.”
Maybe what’s really going on is that following a diet, any diet, causes you to pay more attention to the foods you’re eating—to engage in mindfulness—and that’s where their effectiveness is, not in the particulars. In this respect, all diets involve some kind of lifestyle change. People on a diet typically increase their physical activity at the same time, and that is likely to be a much more important lifestyle change than the actual composition of the foods one eats. The fact is, outcomes don’t differ all that much among the leading diets. The Journal of the American Medical Association published a research article that compared the Ornish, Atkins, Zone, and Weight Watchers diets and found no difference among them in weight loss or reduction of risk for cardiovascular disease. The researchers note that more than one thousand diet books are available, with a great many “departing substantially from mainstream medical advice,” a nice way of saying that they are not evidence-based. But I don’t think we should be nice about it, we should call them what they are—uninformed guesses and speculation.
Many of the bestselling diet books promote carbohydrate restriction—for example, Dr. Atkins’ New Diet Revolution, The Carbohydrate Addict’s Diet, and The Complete Low Carb Cookbook. As of this writing, Simply Keto is the thirty-third bestselling book on Amazon. This dietary advice is counter to that endorsed by governmental agencies—the US Department of Agriculture, Department of Health and Human Services, National Institutes of Health—and nongovernmental organizations—the Academy of Nutrition and Dietetics, American Heart Association, American Diabetes Association. And there is no scientific consensus that extreme carbohydrate restriction is healthful.
The most-read article of 2018 published in the British Medical Journal claimed that restricting dietary carbohydrates offers a metabolic advantage for keeping off lost weight, but the data may not support this conclusion. Kevin Hall, senior investigator at the National Institute of Diabetes and Digestive and Kidney Diseases, discovered that the British Medical Journal’s data were improperly analyzed, and when he conducted a reanalysis the effects disappeared. This sort of thing happens often in science because science is a self-correcting, self-policing process. But the corrections almost never make headlines. So the public is left with impressions created from someone’s mistakes.
Many diets are innocuous. Many inspire us to pay closer attention to what (and how much) we eat. But some can be downright dangerous, such as the cotton ball diet or the cigarette diet. Or take the protocol developed by Dr. Nicholas Gonzalez, a diet purported to treat cancer. Each patient receives individualized dietary recommendations (so far, so good), and these diets range from vegetarian to diets requiring red meat two to three times a day. All the diets require the consumption of supplements, which Dr. Gonzalez’s office sells. How many? Between 80 and 175 capsules a day. He himself died of a heart attack at age sixty-seven, but before he did, he persuaded a large number of people to follow a diet that has been rejected by the medical establishment and led to a stern reprimand from the New York State Medical Board. The American Cancer Society stated that there is no convincing scientific evidence that the Gonzalez treatment is effective in treating cancer and that the treatment may actually be harmful.
There are two separate dangers with these kinds of diets—the first is that the diet and supplements themselves can cause harm; the second is that people often refuse well-established medical treatments in favor of following these “alternative” protocols that have no evidence of success, and they thereby miss an important treatment window for actually being helped by legitimate medicine. (And a third danger is that you’ll spend your money on them.) Gonzalez lost two malpractice suits. In one, he had to pay $2.5 million to a patient who had been diagnosed with uterine cancer. He discouraged her from following the advice of her oncologist and instead recommended his own branded dietary supplements and frequent coffee enemas. After the cancer spread to her spine and blinded her, she gave up on Gonzalez and went back to the oncologist.
If this story sounds familiar, it’s because it has played out, in different versions, around the world, from psychic healers in Mexico to homeopathic doctors in Europe. Herbal remedies, vitamins and minerals, and dietary supplements are often marketed as “natural” products, but natural doesn’t always mean safe. Cow dung is “natural.” In one study, 20 percent of Indian-manufactured Ayurvedic medicines tested contained toxic levels of lead, mercury, and arsenic. The Mayo Clinic provides a helpful guide for consumers who are contemplating alternative treatments. Although terms such as purify, detoxify, and energize may sound impressive, they’re generally used to cover up a lack of scientific proof. There are only a few known “toxins” (for example, lead) and these treatments do nothing to remove them. Mayo also advises consumers to beware of testimonials. Anecdotes from individuals who have used the product are no substitute for evidence from scientific research. If the product’s claims were backed up with hard evidence, the purveyor would say so, pointing you to peer-reviewed scientific studies. Just remember: The plural of anecdote is not data. In other words, an anecdote is simply an observation or story that comes from uncontrolled conditions. True scientific data comes from a systematic attempt to isolate variables, document conditions, and observe trends over a large number of cases.
Scientific American went to the extraordinary measure of publishing an article titled “Why Almost Everything Dean Ornish Says about Nutrition Is Wrong.” Ornish launched his foray into the diet industry with a study in 1990 that was poorly controlled and studied only forty-eight patients with heart disease—twenty-four were the control group and twenty-four were put on the Ornish diet. After a year, he reported that the Ornish diet group had a lowered incidence of arteriosclerosis. Lowering the levels of something in people who already have a disease tells you nothing about whether that same treatment will prevent the disease in the first place. But that’s a minor point compared to the big flaw in the study: The diet group, but not the control group, also quit smoking, exercised more, and attended stress-management counseling. The people in the control group were told to do none of those things. As Scientific American reported:
It’s hardly surprising that quitting smoking, exercising, reducing stress and dieting—when done together—improves heart health. But the fact that [half] the participants were making all of these lifestyle changes means that we cannot make any inferences about the effect of the diet alone.
So much for faddish diets based on pseudoscience. What is the current state of good science? I briefly mentioned antioxidants in Chapters 3 and 8. Antioxidants have become the new buzzword in nutrition, diet, and longevity circles. But few outside of the laboratory understand what they are, apart from the implication that they’re good for you. You may remember from high school chemistry that electrons are negatively charged particles inside an atom, and you may also remember about electron pairing. When two atoms or molecules have electrons with opposite spins, they can become paired, and this is a stable molecular state. When an atom, molecule, or ion has an unpaired electron, it is unstable and is called a free radical. Free radicals are produced all the time as your cells convert glucose to energy. But damage to mitochondria (a subunit of the cell, found inside most cells of your body) can also lead to increased production of free radicals. And so can consuming certain substances, such as fried foods, alcohol, tobacco smoke, pesticides, and air pollutants.
Free radicals, because they’re unstable, can cause damage to DNA and cell membranes by grabbing their electrons through a process called oxidation. This easily becomes a chain reaction. One molecule with a free radical grabs the electron from another, leaving it a free radical; then this one grabs the electron from another molecule, leaving it a free radical; and pretty soon the whole thing has snowballed out of control. In the meantime, all of these molecules with free radicals can’t perform their cellular functions properly, and you get oxidative stress.
Fortunately, the body evolved a number of built-in antioxidant mechanisms. Antioxidants scavenge free radicals and thereby play a critical role in cellular health. They either reduce the formation of free radicals or react with and neutralize the ones that have already formed, by donating a hydrogen atom. Antioxidants often work by donating an electron to the free radical before it can damage other cell components. Once the electrons of the free radical are paired, the free radical is stabilized and becomes nontoxic.
Oxidative stress is believed to underlie a wide range of diseases, including cancer, diabetes, and neurological disorders such as Parkinson’s and Alzheimer’s disease, and to shorten life span. It causes high LDL levels (low density lipoprotein—the “bad” cholesterol) and the accumulation of plaques that can lead to heart disease. It even plays a role in the development of wrinkles. It’s been known since the 1960s that free radicals accelerate the aging process and that the reduction of free radicals can delay aging.
The big question is whether dietary antioxidants can mitigate the damage done by the oxidation of free radicals. The matter is further confused by the fact that there is no universal agreement among scientists about which molecules are antioxidants and which aren’t. Some of the well-known substances that are often mentioned as antioxidants are retinol (vitamin A), beta-carotene (a precursor of retinol), ascorbic acid (vitamin C), vitamin E, flavonoids, and some omega-3 fatty acids. Sometimes zinc can function as an antioxidant. The definition of antioxidants can be very broad, because they can act either directly or indirectly, and any substances that can detoxify free radicals might be justly called antioxidants. Selenium, for example, doesn’t act directly but can deoxidize certain reactive oxygen species through indirect action. Tocoferal (vitamin E), on the other hand, acts directly by donating a hydrogen atom. At issue, in part, is whether the mere fact that a food or supplement molecule can donate a hydrogen atom to a free radical means that in a real, living organism it will, and that it’s working like we think it should. We don’t know.
Recall the discussion of glucosamine supplementation in Chapter 7, on pain—taking cartilage in a pill might seem that it should help with cartilage breakdowns in your body, but the body doesn’t work like that. The same principle applies to substances in the foods we eat, such as antioxidants and cholesterol: They don’t necessarily have the effect that you might think. There is modest research evidence that eating antioxidants in food is beneficial. The problem is that there have not been enough rigorous studies of antioxidant foods to draw any definitive conclusions. One recent meta-analysis found that “there were no randomized controlled trials. . . . All studies were judged to be at moderate to substantial risk of bias.”
There is even less evidence to support taking antioxidant supplements. For example, one study followed nearly forty thousand women for ten years. Half were randomly assigned to take a vitamin E supplement and half took a placebo. After ten years, the vitamin E hadn’t significantly reduced the risk of heart attack, stroke, or cancer. The results of other randomized controlled trials with a range of antioxidant supplements, including beta-carotene, vitamins A and C, and selenium, did not show reductions in cancer. For gastrointestinal cancers, the supplements actually increased all-cause mortality. A meta-analysis reviewed the results of studies with more than 290,000 people and found no effect of antioxidant supplements on cardiovascular disease. Antioxidant supplementation might be interfering with the immune system or with defense mechanisms responsible for the elimination of impaired cells. (For some subsets of the population with a really poor diet, or for pregnant women, supplements may be helpful, but the scientific evidence is still wanting.)
Many supplement studies fail because they study only one supplement at a time, which doesn’t mimic anything like actual food. Actual foods can contain fiber, micronutrients, and beneficial gut bacteria that supplements lack. And at least some antioxidants, vitamins C and E, have been shown to block the health-promoting effects of physical exercise.
Most of us know of the link between cholesterol, dietary fats, and heart disease, but it is interesting, and illuminating, to learn what these mean at a molecular, biological level.
Cholesterol is a waxy substance that circulates in your blood and attaches to proteins there. Your body needs cholesterol to build healthy cells, including brain cells, but high levels of certain forms of cholesterol can increase your risk of heart disease. When cholesterol combines with proteins, the resulting molecule is called a lipoprotein. Low-density lipoprotein (LDL, the “bad” cholesterol) transports cholesterol particles throughout your body. It can build up in the walls of your arteries, making them hard and narrow and causing arteriosclerosis.
High-density lipoprotein (HDL, the “good” cholesterol) picks up excess cholesterol and takes it back to your liver, which then removes it from your body.
Unhealthy eating habits and obesity can raise your bad cholesterol levels. Lack of physical activity can lower your good cholesterol levels. Smoking does both, especially in women, by damaging the walls of blood vessels and making them more likely to accumulate LDL deposits. LDL levels naturally rise with age, making healthy lifestyle habits increasingly important, especially after age fifty. There is a genetic component as well—the rate at which bad cholesterol climbs and the ability of physical activity to increase good cholesterol are partly inherited. If adopting healthy lifestyle habits (physical activity, improved diet) doesn’t optimize cholesterol levels, there are medications that can lower LDL (statins; for extreme cases, there’s a procedure called lipoprotein apheresis that uses a filtering machine to remove LDLs from the blood.)
As we’ve seen, though, well-intentioned interventions don’t always have the desired effect. It isn’t entirely clear that lowering LDL through the use of statins actually lowers your risk of heart disease—the statins may simply lower a marker associated with disease, and not an actual cause. And even so, statins have a tiny effect: in some studies, three hundred people have to take a statin to delay or prevent a heart attack for one person in a given year.
Food labels in the United States and many other countries list the cholesterol content of those foods, but there is no scientific consensus about whether eating cholesterol-rich foods actually alters cholesterol levels in the blood. And many cholesterol-rich foods are high in necessary nutrients.
You do need fats in your diet: They’re a major source of energy, and they’re necessary for building the myelin sheath around neurons and for maintaining strong, healthy cells. But not all fats are created equal. The main types are:
saturated fats, found in meats, eggs, and whole-fat dairy products;
monounsaturated fats, found in olive and canola oil;
polyunsaturated fats, found in seeds, nuts, and fish and vegetable oils;
and trans fats, found in fried foods, microwave popcorn, and some commercially baked goods.
Saturated fats have long been considered the enemy of heart health, but a meta-analysis of seventy-two studies, tracking six hundred thousand people in eighteen countries, shows no association between the consumption of saturated fats and heart disease. None. Now, this is not a controlled experiment—it may be that the people in the study who ate saturated fat got more exercise; there may be genetic differences in the way their bodies metabolize saturated fats. But the real culprit in that analysis was trans fats, the ones found in fried foods, potato chips, and other junk food.
Diets high in soluble fibers are good because the fiber binds to the LDL cholesterol molecules in the digestive system and drags them out of the body before they get into circulation. Some good sources of soluble fiber are oats (oatmeal, Cheerios, Trader Joe’s O’s), barley and other whole grains, beans (including soy beans and soy milk), high-fiber fruits (apples, strawberries, citrus; the pectin they contain is a soluble fiber), eggplant, okra, fatty fish, liquid vegetable oils, and nuts (just two ounces of nuts a day can lower LDL by 5 percent). Diets high in omega-3 fatty acids, as found in fatty fish, seeds (especially chia, flaxseed, and hemp), nuts (especially walnuts), and olive and canola oils also lower LDL and reduce the risk of heart disease by 7 percent. Insoluble fibers (wheat bran, vegetables, and whole grains) are also healthy because they prevent constipation and diverticulitis.
The emerging picture is that dietary consumption of fats, even saturated ones, is not the cause of heart disease, but rather inflammatory processes that cause cholesterol to build up in arterial walls. It is the alpha-linolenic acid, polyphenols, and omega-3 fatty acids present in nuts, extra-virgin olive oil, vegetables, and oily fish that rapidly attenuate inflammation and coronary thrombosis.
Ben Franklin advised in Poor Richard’s Almanack, “To lengthen thy life, lessen thy meals.” It’s been known for more than a decade that mice and rats that have a calorie-restricted diet can live 30 to 40 percent longer. When you have easy access to food and nutrients, and your physiological stress levels are low, your genes support cellular growth and reproduction. In contrast, under harsh conditions, genetic activity shifts toward cell maintenance and protection. A number of stressors mediate this reaction, and caloric restriction is one of the most robust, working in many species, from yeast to C. elegans, from mice to primates. For years, it was thought that caloric restriction merely slows down an organism’s metabolism and therefore slows down the rate at which cellular damage accumulates. It is now well accepted that caloric restriction triggers a change in the metabolic response, in particular, a downregulation of insulin and insulin-like growth factor (IGF-1), as well as the AMP-activated protein kinase, and sirtuins. Molecular biologist Cynthia Kenyon explains the significance of this:
Slowing aging might seem like an overwhelming challenge, as the decline is so pervasive. So it is noteworthy that when we extend the lifespans of laboratory animals, we do not have to combat individually all the problems of age, such as the declining muscles, the wrinkled skin and the mutant mitochondria. Instead, we just tweak a regulatory gene, and the animal does the rest. In other words, animals have the latent potential to live much longer than they normally do.
In mammals, insulin levels rise in response to glucose, and this rise may ultimately shorten life span. When Kenyon modified the PI3K enzyme in the insulin/IGF-1 pathway, her worms lived ten times longer. There’s an important story here about sugars and insulin. Insulin is a hormone produced in the pancreas. When blood sugar levels are high, pancreatic beta cells secrete insulin into the blood, and when blood sugar levels are low, insulin is inhibited. Insulin is necessary for normal metabolism; it helps glucose in your blood enter cells in your muscle, fat, and liver, where it can be used for energy. If your insulin levels rise (hyperinsulinemia) and stay that way, a host of health problems can occur, including insulin resistance (and type 2 diabetes), obesity, immune-system suppression, and cardiac arrhythmias.
Caloric restriction, because of its interaction with the insulin signaling system, appears to be good for the brain. Why might that be? Neuroscientist Mark Mattson at Johns Hopkins University says, “If you’re hungry and haven’t found food, you’d better find food. You don’t want your brain to shut down if you’re hungry.” Some of the neural benefits that are found with fasting also occur with vigorous exercise. The neurochemical changes are similar: Both stimulate the production of brain-derived neurotrophic growth factors (BDNFs). Fasting stimulates the production of ketones, an energy source for neurons. Fasting can increase the number of mitochondria in neurons, which helps them produce more energy.
Kenyon speculates that it’s possible that if we could inhibit insulin receptors, we could promote longevity in humans if we also eat a low-carbohydrate diet. It’s also possible that we might modify the genes and signaling pathways that are affected by caloric restriction so that we can all eat whatever we want.
There’s also emerging evidence that insulin may play a role in developing Alzheimer’s disease. This has led some forward-thinking doctors to prescribe the diabetes medication metformin, a blood sugar–lowering drug, proactively to patients with a family history or other risk factors for Alzheimer’s and dementia. Although the evidence for this is scarce, what evidence there is looks promising. A meta-analysis of three studies showed that cognitive impairment was significantly less prevalent in people who took metformin, and in six studies dementia incidence was significantly reduced. Metformin was further found to have a neuroprotective effect. Now, all of these were patients with diabetes. We just don’t have evidence yet for the effectiveness of using the drug as a preventative. A protocol for testing the hypothesis was published in 2016, and a study was just begun in the United Kingdom.
For now the best bet for increasing longevity and the event horizon for the detrimental effects of aging appears to be just eating less, and there are many ways to do this, although we don’t yet know which is going to be the most effective: reduced calories throughout the day; one fast day a week; two fast days a week; fasting every other day; fasting two weeks a year; no dinners; one month of juice fast every year; and so on. At first it can feel awful, but many people find they can build up to it and get used to it. Many researchers I know have begun to do it. Jeffrey Mogil fasts one day a week. Cynthia Kenyon gave up carbs. I don’t eat if I’m not hungry and I skip dinner a couple of times a week. Mark Mattson does intermittent fasting—reducing the frequency of meals. There are, of course, dangers in following an improvised or ad hoc calorie-restrictive diet. These include malnutrition, gastrointestinal problems, and eating disorders. You shouldn’t just do this on your own—it’s best to discuss it with your doctor and work out a plan. And there haven’t been enough longitudinal studies yet for us to know whether intermittent fasting (or other forms of fasting) could have long-lasting negative consequences beyond the initial benefits.
When you do eat, certain foods show up in study after study as being healthful. These include virgin olive oil, which is rich in monounsaturated fatty acids—the good fats. Consuming olive oil (around 3 tablespoons a day) is associated with relieving oxidative stress on cells and regulating cholesterol and anti-inflammatory activity.
Cruciferous vegetables, including Brussels sprouts, broccoli, cauliflower, kale, cabbage, and bok choy, have been shown to have protective effects against many forms of cancer and can even inhibit the progression of some cancers. They do this by initiating cellular defense mechanisms and modifying cancer-related genes. Glucosinolates and 3-carbinol are the health-promoting agents in cruciferous vegetables.
Another component of the Mediterranean diet is oily fish, such as sardines and anchovies. These contain the omega-3 fatty acids that are known to be essential in the development and maintenance of brain and retinal tissue, as well as for myelination. There have also been benefits claimed for reducing the risk of heart disease and cancer. This has led to a current fad of taking omega-3 supplements, resulting in a worldwide $33-billion industry—about the size of the global music market. As with many well-intentioned interventions begun before all the data are in, omega-3 supplements do not seem to work. A Cochrane systematic review (the gold standard for meta-analyses) in 2018 examined the results of seventy-nine separate trials involving more than twelve thousand people and found that taking omega-3 supplements makes little or no difference to the risk of cardiovascular events, coronary heart deaths, coronary heart disease events, stroke, or heart irregularities. And it may even increase the incidence of some cancers.
These negative findings apply to supplements, but what about dietary consumption of omega-3s? There is increasing evidence that omega-3 acid occurring naturally in foods helps reduce inflammation and improve insulin sensitivity, but for other health outcomes the evidence is still mixed—some studies show that it is protective against cancer and heart disease, some show that it’s not. A recent report by the National Institutes of Health concludes that omega-3 supplements don’t reduce the risk of heart disease but that people who eat seafood one to four times a week are less likely to die of heart disease. It may be that the optimal amount of omega-3s (and other antioxidants) follows what engineers call a step function: Once a certain minimum is reached, additional amounts have no effect and may actually introduce harm. The Harvard Health report noted:
You should still consider eating fish and other seafood as a healthy strategy. If we could absolutely, positively say that the benefits of eating seafood comes entirely from omega-3 fats, then downing fish oil pills would be an alternative to eating fish. But it’s more than likely that you need the entire orchestra of fish fats, vitamins, minerals, and supporting molecules, rather than the lone notes of EPA and DHA. The same holds true of other foods. Taking even a handful of supplements is no substitute for [the] wealth of nutrients you get from eating fruits, vegetables, and whole grains.
As with all things involving diet, don’t overdo it: Too much fish can raise levels of mercury and other toxins. Also, the ocean is being hugely overfished and soon there won’t be any more for your grandkids.
One of the most talked about suggestions, with origins in the Mediterranean diet, is that moderate amounts of red wine with meals promote good health. Here, it’s important to disentangle the effects of red wine itself from those of its alcohol content. A systematic review found no evidence that red wine influences health outcomes differentially from the moderate, measured drinking of other alcohol products. Moderate alcohol consumption, in many studies, has been shown to lower blood pressure and thereby reduce coronary risks. But this is a complex issue. Alcohol consumption increases risks for primary tumors of the mouth, pharynx, larynx, esophagus, liver, breast, colon, and rectum. It also increases mortality in breast cancer survivors and possibly those with other cancers as well. It interferes with sleep and dream cycles and, as we saw in Chapter 8, with circadian clocks. And it can be addictive.
As with fish oil, a supplementation industry grew out of the nascent findings of red wine’s potential health effects. Researchers identified a chemical in red wine that you may have read about called resveratrol. Resveratrol has antioxidant properties and in animals reduces hypertension, heart failure, and ischemic heart disease, and it improves insulin sensitivity and reduces blood glucose levels and high-fat-diet-induced obesity. However, systematic reviews conclude that there is insufficient evidence that resveratrol supplements could prevent disease or extend life in humans. That said, another comprehensive review recommended it.
Many cognitive and physical benefits are claimed for a number of diets, including the DASH, MIND, and Mediterranean diets, but there is little evidence to support them. The putative causes of cognitive decline and Alzheimer’s are oxidative stress, inflammation of neural tissue, and vascular problems caused by the buildup of harmful substances in the circulatory system. Healthy diets that lower cholesterol and inflammation are a logical approach. But the history of medical science is full of treatments and advice that made sense but lacked evidence, and the evidence came in counter to the “logical” advice. The problem is that bodies (and brains) are complicated, there are multiple interacting factors, and we’re really only at the very beginning of being able to understand all the implications of even the simplest interventions.
Older adults absorb protein less effectively and require 0.54 grams of protein per pound of body weight per day. If you weigh 68 kilograms (150 pounds), you need to eat 81 grams of protein, or about 3 ounces. That may not seem like a lot, but remember, if you eat a chicken drumstick (4 ounces) it’s not pure protein; in fact, it probably has less than half an ounce of protein. Consider the following:
1 cup of nonfat milk = 0.3 ounces protein
2 tablespoons of peanut butter = 0.2 ounces protein
2 medium eggs = 0.4 ounces protein
½ pound of salmon = 1.7 ounces protein
If you ate everything I’ve just listed, you’d still be 0.4 ounces short of your daily requirement.
The most effective proteins for older adults are ones that are rich in the amino acid leucine—milk, cheese, beef, tuna, chicken, peanuts, soybeans, and eggs. Leucine is one of nine essential amino acids (building blocks of proteins) that we need to obtain through our diet, and it is mainly found in animal proteins.
There are competing goals here—cheese and beef contain unhealthy saturated fats, tuna can contain unhealthy levels of mercury, and chicken can contain antibiotics, yet they are effective sources of protein. (A good alternative for some is 98 percent lean beef that contains less than 2 grams of fat in a 100-gram portion.) Lack of protein can cause serious problems with your brain, muscles, and immune system.
But the story of leucine is an example of the pitfalls in focusing on only one dietary component at a time and of thinking that if something is essential, more must be better. We need leucine for protein synthesis and many metabolic functions. This amino acid helps regulate blood sugar levels, the growth and repair of muscle and bone tissue, and wound healing. It enters the brain from the blood more rapidly than any other amino acid. But when levels become too high, leucine toxicity can develop and has been associated with degradation of neural circuits, delirium, cognitive impairment, reductions in serotonin levels, and excess ammonia levels in the blood, as well as blocking the absorption of other amino acids. You need leucine, but not too much, and so the foods just listed should be eaten in moderation. Tuna sandwiches every day at lunch are not the way to go.
Vegetable proteins are a part of that balanced diet. You may have read reports that soy products interfere with sex hormones, lowering testosterone in men and leading to estrogen problems in menopausal women. These reports were based on flawed data, and the current thinking is that soy is beneficial for all except those who are allergic to soy.
Aristotle wrote that “living beings are moist and warm . . . however old age is dry and cold.” The classical Greek physician Galen of Pergamon added that “aging is associated with a decline in innate heat and body water.” Galen further lamented that dehydration is difficult to diagnose. That is still true today. It is most problematic among children and adults over seventy.
Hydration is something most of us don’t think about, but it is essential for cellular and brain health. Often if you notice yourself feeling fatigued, this is the first sign of dehydration. Other symptoms include headaches and nausea. Dehydration is a medical condition—it is not thirst. Thirst is just a symptom that may or may not be present when you’re dehydrated.
Dehydration is deadly. It is the second leading killer of children under four worldwide and the eighth leading cause of death among adults over seventy. It’s also linked to the formation of kidney stones. Common causes are too much heat or exercise (because you lose salts through your sweat), higher altitudes, and illness. Alcohol is also a culprit: It turns off hormones that help us absorb water so we lose more fluids than normal.
Older persons have an increased risk of dehydration, even when water is readily available to them, because thirst detectors in the brain degrade. Individuals at the greatest risk for dehydration include people with fever or infections, impaired cognitive status, or impaired renal function, and those who take medications that impact fluid and electrolyte balance.
Dehydration results from an imbalance of water, salts, and electrolytes in the blood. Electrolytes include sodium, chloride, potassium, and magnesium. Rehydrating does not mean simply drinking more water, because when you’re dehydrated, the body can’t retain the water that you drink and water alone doesn’t replace the depleted salts and electrolytes.
Rehydration requires drinking an oral rehydration salts (ORS) solution. An ORS solution is a mixture of water, salt, and sugar; it is absorbed in the small intestine and replaces the water and electrolytes lost in dehydration. If dehydration is accompanied by diarrhea, zinc supplements can reduce the duration of a diarrhea episode by 25 percent. Cases of severe dehydration require intravenous fluids.
For maintaining hydration, limit alcohol intake or drink at least one 8-ounce glass of water for every alcoholic beverage you ingest. Nutritious foods help maintain a proper balance of electrolytes and salts. Avoid bread or dried fruit if you’re dehydrated—they require the body to take water from the vascular system, and that leads to further dehydration. There are several oral rehydration solutions available over the counter. You might keep some in your purse or briefcase, in your desk at work, and at home, and take it about twice a week if you’re prone to dehydration. If you have a cold or flu, drink two a day. If you feel lethargic, or after a particularly hot day, intense workout, or drinking alcohol, you might take some.
As Hippocrates noted, “It is a general rule that intestines become sluggish with age.” Constipation is one of the most common and annoying problems of aging, affecting 50 percent of older adults. As we age, the intestinal muscles that help move food along weaken and the contractions are not as strong. Often, medications taken by older adults cause constipation as a side effect. Many older adults become less physically active, which also increases constipation. It disproportionately affects women, nonwhites, people from a lower socioeconomic status, and those who suffer from depression.
Why in the world is this in a book on the brain?
Clinical observations suggest that constipation interferes with cognition. Only a small number of studies have explored this, and the results, although preliminary, suggest a connection. In rats, constipation led to changes in gene expression that could in turn affect hemoglobin content and quality, the capacity of the blood to bring oxygen to neurons in the hippocampus, and alterations in the cholinergic system of the brain. In humans, an association between chronic constipation and cognitive impairment has been identified.
The noncognitive consequences can also be serious. Overstraining to produce a bowel movement can cause people to faint or blood vessels in the brain to burst. Because many people are uncomfortable or embarrassed discussing their bowel movements with their doctors and health-care providers, chronic constipation often goes untreated.
Constipation refers to two different problems: difficulty passing stools and a decreased frequency of bowel movements. Both can often be treated by increasing consumption of insoluble fibers, such as bran, whole grains and vegetables, fluids (2 liters per day), and exercise—particularly exercise that involves gently twisting or bending the abdominal region. And simply taking a good walk can get things moving. If those fail, laxatives are indicated, and there are two kinds: bulk-forming laxatives and osmotic laxatives. Before just going to the drugstore and buying something over the counter, it’s important to understand the difference between the two.
Bulk-forming laxatives aren’t digested; instead, the fiber they contain allows you to retain more fluid—that’s why you need to be sure that if you use them, you increase your consumption of fluids. The water absorption produces a softer, bulkier stool. The bulky size stimulates the intestinal muscles to contract, causing everything to move along, leading to an easier bowel movement. It can take from twelve to thirty-six hours for bulk-forming laxatives to produce results, so they do not provide immediate relief from constipation—they are best used for ongoing digestive health. Examples include psyllium husks (Metamucil), ground flaxseed, wheat dextrin (Benefiber), methylcellulose (Citrucel), and polycarbophil (FiberCon, Prodiem).
Osmotic laxatives draw water into the bowel from the intestines, thereby softening the stool. They can deplete electrolytes and cause dehydration, and so it’s also important to stay hydrated when taking them. They can work within six hours. Many are polyethylene glycol–based (Lax-A-Day, MiraLAX, PegaLAX, RestoraLAX). Unlike bulk-forming laxatives, osmotic laxatives are intended for short-term, not daily, use, they shouldn’t be taken for more than seven days, and they are habit-forming. Norman Lear, a television pioneer (creator of All in the Family, The Jeffersons, Sanford and Son) and a political activist (People for the American Way) at ninety-seven is still active and creative. Asked how he maintains such high levels of mental agility and focus, and what keeps him going, he responded with one word: “MiraLAX.”
For immediate, short-term relief, glycerin suppositories and enemas are available over the counter. If you’ve read about colonic irrigation in new-age health magazines or on the Web, it is ineffective and has no scientific basis.
Another thing that can help, and can reduce or eliminate the need for laxatives, is probiotics. The bacterial balance in the gut can be adversely affected by taking antibiotics, by changes in diet and exercise, by the normal process of aging, and by a host of factors we have not yet identified.
Your digestive system—your gut—has its own computer, known as the enteric nervous system, with half a billion neurons, and containing about 100 trillion bacteria, both good and bad. Collectively they are known as the gut microbiota, a term that is often used interchangeably with microbiome. (Just to confuse things, they used to be called the microflora.)
Lining the inside walls of your large intestine is a layer of mucus that forms a biofilm and provides a moist, warm environment for the microbiome. The thousands of different species of bacteria in there perform special jobs to keep the entire intestinal community healthy. From there these bacteria regulate a number of aspects of cellular housekeeping and health throughout the body. The particular assortment of bacteria found in your gut is unique to you, as unique as a fingerprint. It is shaped by genes, culture, and opportunity, including what your parents ate, what you ate as an infant and child, and the lifetime influences of different diseases and stressors your body has experienced.
The microbiome is important for nutrition, digestion, and immune-system function. The inside of your stomach and large intestine is a highly acidic environment. The bacteria that live there had to evolve adaptations to allow them to survive there, but the reward for them is great access to food and not a lot of competition for it. The relationship is mutually beneficial to you and them.
There is an emerging body of evidence that the gut microbiome also affects cognition, behavior, and brain health. This is cutting-edge stuff and the story is still being written. We already know that serotonin is an important neuroregulator of mood, memory, and anxiety. It turns out that 90 percent of the serotonin in the body resides in the gut, and it is manufactured there by bacteria such as Candida, Streptococcus, Escherichia, and Enterococcus.
Our gut microorganisms produce other essential neurotransmitters too. Lactobacillus and Bifidobacterium create gamma-aminobutyric acid (GABA), an important inhibitory chemical, as we saw in Chapter 2. Escherichia coli, Bacillus, and Saccharomyces produce norepinephrine, which is important for alertness; Bacillus and Serratia produce dopamine. Bifidobacterium infantis increases levels of tryptophan, an important precursor to serotonin, melatonin, and vitamin B3. Lactobacillus acidophilus increases the expression of the natural cannabinoid and opioid receptors in the brain, affecting appetite, pain, and memory.
Gut bacteria have been linked to mental well-being and depression. People who lack two particular bacteria, Coprococcus and Dialister, are more likely to be depressed, and those who have normal levels of them report a higher general quality of life. Coprococcus is associated with dopamine signaling, and it also produces butyrate, a fatty acid that is an important anti-inflammatory agent; increased inflammation has been linked to depressive symptoms. A third bacterium, Faecalibacterium, also produces butyrate and is found in people who report a higher quality of life. Neuroscientist John Cryan calls bacteria like these “melancholy microbes.” (Who says science isn’t fun?)
The gut microbiome can become out of balance, leading to a condition called dysbiosis. The most commonly known cause of dysbiosis is taking prescription antibiotics for an infection. These can kill not just the disease-causing bacteria but beneficial gut bacteria as well. Dysbiosis can also be brought on by unhealthy lifestyle behaviors, such as irregular eating times and high-fat diets. When we’re younger, the effects are so subtle we don’t notice. When we’re older, the effects can be debilitating. Misbalanced microbiomes are suspected to be involved in obesity and a number of diseases including cancer and Alzheimer’s.
Recall from earlier the work of Michael Meaney, showing that stressors early in life—such as infants being separated from their mothers—can have a lifelong impact on the brain’s stress response. Early life stressors can also have an influence on the composition of the gut microbiome. That composition is affected by the mother’s diet and stress levels and by travel through the birth canal. Children who are delivered via Caesarean section show a reduced diversity of their gut microbiome. In animals, stress caused by the separation of rhesus monkeys from their mothers changed the microbiota and decreased their Bifidobacterium and Lactobacillus levels. Rats separated from their mothers showed decreased fecal Lactobacillus levels.
The full extent of gut-brain interactions is still unknown, but links between these interactions and an imbalanced microbiome have been implicated in mental disorders as diverse as autism, schizophrenia, ADHD, bipolar disorder, and multiple sclerosis. A credible although still unconfirmed view is that an imbalanced microbiome during infancy and childhood can lead to these conditions and diseases later in life. But that doesn’t mean the conditions are irreversible.
Probiotics as contained in foods and supplements can introduce or reintroduce beneficial bacteria into the gut. These can affect such physical functions as increasing iron absorption, protecting against pesticide absorption, and the distribution of fat around the body. They have been shown to be especially effective treatments for irritable bowel syndrome, a disease that disproportionately afflicts older adults.
But where it really gets interesting is the effects that probiotics can potentially have on cognition, emotion, and behavior. Small-scale trials have shown that a single probiotic, Bifidobacterium infantis, can alleviate depression and anxiety, and a cocktail of Lactobacillus helveticus and Bifidobacterium longum can reduce cortisol levels—an indicator of stress. A preliminary report finds that a probiotic mixture containing Bifidobacterium lactis, Lactobacillus bulgaricus, Streptococcus thermophilus, and Lactobacillus lactis can substantially alter brain activity in the mid- and posterior insula, regions associated with anxiety disorders and attentional focus. Kefir, yogurt, and other fermented milk products containing probiotics have been shown to have a positive effect on mood and the brain’s emotional centers. And emerging evidence suggests that eating more fiber promotes gut health and microbiomic balance.
It was long believed that the microbiome of older adults, established over decades, is both stable and resistant to environmental influence. Recent studies, however, have suggested otherwise. The distinct microbiome of the elderly is accompanied by a marked reduction in the capacity to cope with a variety of stressors and by progressive inflammation throughout the body. Microbiomic balance can also be abruptly altered by short-term changes in diet.
A particular problem concerns older adults in long-term-care facilities. The gut microbiome of such individuals shows substantially less diversity than that of older adults who continue to live in the cities, towns, and farms they always lived in. Interacting with a large and diverse number of people (and farm animals) maintains a diverse microbiome. The extremely antiseptic nature of long-term-care facilities, and the restricted pool of inhabitants (mostly older humans), may impoverish the microbiome and reduce its diversity. In a few studies so far, the loss of diverse community-associated microbiota correlates with increased frailty, inflammatory conditions, and even death. An important new frontier in gerontology is going to be modulating the individual’s microbiome with dietary interventions designed to promote healthier aging. Indeed, an exciting consortium of researchers called ELDERMET has come together at University College Cork in Ireland. Their findings strongly suggest that gut microbiome interventions are necessary for older adults to maintain satisfactory levels of physical and mental health.
Research on this is just getting started. There are no clinical guidelines yet about how to do this, and medical science takes years. In the meantime, you may feel you don’t want to wait. The best thing you can do is check with your doctor, preferably a gerontologist or, better yet, a gastroenterologist about gut health.
Alternatively, self-dosing with probiotics is not as crazy as it might seem, according to Harvard Medical School. Unfortunately, a broad range of products are sold in the United States, the United Kingdom, and Europe, and they vary widely in the type and amounts of bacterial cultures they include. In the United States, they are not regulated by the FDA and so quality can vary dramatically. There is a small amount of evidence showing that probiotics function best when taken in the context of actual food (or liquid suspensions) rather than in pills or capsules. The big problem is that most probiotic formulations can’t survive the acidic environment of the stomach, and if they do, they don’t thrive enough to colonize the gastrointestinal tract. Because different formulations and dosages can confer differential effects, no specific recommendations can be made unless a particular product has been tested. The efficacy of any probiotic product is determined by factors including the specific microbial species, the dosage, the formulation, the viability of the probiotics both on the shelf and within the intestine, the residence time in the gut, and the means of ingestion. Therefore, any scientific findings for one probiotic product or strain cannot be assumed to apply to another probiotic. It’s difficult to be an informed consumer when these factors are rarely tested before a probiotic product goes to market.
The unregulated nature of the probiotic market makes it difficult to know what to do. One formulation that was tested and confirmed effective by published peer-reviewed studies, VSL#3, was sold by its inventor to a pharmaceutical company that inexplicably changed the formulation and rendered it ineffective. This was the subject of an $18-million jury verdict against the company. The PepsiCo-owned beverage KeVita Kombucha is advertised as containing “live probiotics,” but a lawsuit filed in 2017 argued that the pasteurization process used by PepsiCo killed the live bacteria (a second lawsuit filed in 2018 argued that sugar levels in the drink tested six times higher than what was stated on the label). In 2009, the Dannon Company settled a $35-million lawsuit for false advertising claims it made about the benefits of its Activia line of probiotic yogurt, which was priced 30 percent higher than regular yogurt but in fact had no differential effects. Two probiotic products that are known to be effective as of this writing—to reestablish a healthy gut microbiome—are listed in the notes at the end of this book. Your physician or dietician may be able to provide updated information as well.
Even less is known about prebiotics, those substances that encourage the growth of healthy bacteria in the gut. Food molecules are known to protect probiotics, so it’s usually suggested that probiotics be taken with a meal that contains prebiotics. Prebiotics are specialized plant fibers found in many fruits and vegetables, especially those that contain complex carbohydrates. These carbohydrates aren’t digestible, so they pass through the digestive system to become food for the bacteria and other microbes. Dozens of foods act as prebiotics, including apples, asparagus, bananas, chicory root, garlic, honey, mushrooms, seaweed, wheat bran, yams, and yogurt. Your doctor or a dietician can help you to choose the best for you.
Looking at this from the other end, you may have read about fecal microbiota transplantation (bacteriotherapy), in which fecal material from a healthy person, which contains beneficial bacteria, is transplanted into the patient in order to restore the normal balance of gut bacteria. Scientists see the potential for treating a range of diseases, including cancer, diabetes, and possibly even Alzheimer’s. The technique has had mixed results and is still experimental. So do not try this at home. (Or if you do, don’t let it hit the fan.)
Taken together, cardiovascular disease, stroke, cancer, and diabetes account for approximately two-thirds of all deaths in the United States and more than $700 billion in direct and indirect costs each year. If dietary changes can reduce the incidence of these diseases, it will have a truly significant effect on world health. The professional organizations that represent the researchers and clinicians who treat these diseases, the American Heart Association, the American Cancer Society, and the American Diabetes Association, published a joint statement of dietary recommendations. They concluded, simply, that higher intake of fresh fruits and vegetables, whole grains, and fish is associated with a reduced incidence of all these diseases.
Herman Pontzer, an evolutionary anthropologist at Duke, studies health among hunter-gatherer societies whose lifestyles are similar to those of our ancestors. He found that they generally exhibit excellent health in spite of following a wide range of diets. It doesn’t matter if they get 80 percent of their calories from carbohydrates, or from animal fat, or from nuts and berries—almost all eat more fiber than the average American, but that is about the only difference. (This takes a lot of wind out of the paleo diet.) Interestingly, they don’t shun sugar, consuming it in the form of honey. Notably, though, they don’t have access to processed foods or deep-fried foods. Kevin Hall did a short-term controlled experiment. Participants were admitted to the NIH Clinical Center (so they could not cheat) and he fed them ultra-processed foods for two weeks, and unprocessed foods such as fish and fresh vegetables for two weeks (in random order). He carefully matched the number of calories, and levels of sugar, fats, and nutrients that were presented in the meals, but participants could choose how much they wanted to eat. People scarfed down the ultra-processed foods more quickly, and they ate 500 more calories every day, gaining about a pound a week compared to when they were offered unprocessed foods.
Pontzer’s research, consistent with that of many other scientists, finds that there is no one best diet and that we “can be very healthy on a wide range of diets.” Pontzer notes that one reason hunter-gatherers tend not to have obesity is the lack of variety in any given individual hunter-gatherer’s diet. When we have a lot of food choices, we tend to overeat because the variety of flavors is enticing. “It’s the reason you always have room for dessert at a restaurant even when you’re full,” Pontzer says. Even though you’re full “and you can’t eat one more bite of steak, you’re still interested in the cheesecake because it’s sweet and that button hasn’t been worn out in your brain yet.”
There is a related movement called intuitive eating, developed by registered dietician Evelyn Tribole. It has been associated with reduced body mass index, reduced cholesterol, lowered blood pressure, and improved psychological health. Mallory Frayn, a doctoral student in my department at McGill University, studies people’s experiences and frustrations with most diets. She writes:
Why don’t diets work? First off, the fact that a multi-billion-dollar diet industry still exists suggests that there’s something fundamentally broken about the way we look at food and eating. We take some “expert’s” advice about how we should treat our body, try it for a bit before it inevitably fails, and then move on to the next greatest thing, all the while the behind-the-scenes bigwigs are making a pretty healthy chunk of change off of our collective struggle. . . .
Diets don’t work because they are based on restriction. God forbid you touch carbs, our most fundamental source of energy, lest they go straight to your waistline. Restriction subsequently fosters deprivation, and ultimately, you’re left craving all of the foods you’ve been told are off-limits. . . .
It’s a normal human thing to want to eat a variety of different foods that taste good.
But diets don’t tell you that . . . eventually, you’re going to break. You’re going to have a chocolate bar or order a side of fries (because both of those things are totally acceptable for a human being to eat). When it happens though, you’ll feel miserable for breaking your “healthy” streak. Plus, you won’t go blaming the diet for your “failure,” you’ll put it all on yourself for being a terrible person.
The cycle of repeatedly dieting and failing is damaging both physically and psychologically. The big idea of intuitive dieting is that your body knows what kinds of food you need—that it has an intuitive drive toward protein, carbs, and fats you can trust. Or perhaps it’s the trillions of microbes in your gut that send signals to your brain to generate that intuitive drive. Maybe your body knows what it wants to eat.
The four additional principles of intuitive dieting are:
try to eat when you’re hungry;
try to stop when you’re no longer hungry;
learn to cope with emotions in alternative forms, other than eating; and
place no restrictions on types of food eaten unless for medical reasons.
Now, like me, you may be skeptical about your body “knowing” what foods you need. It just doesn’t sound scientific. How do you distinguish intuitive eating from a decidedly maladaptive craving, such as wanting to eat a pint of ice cream every night? First, this kind of binge eating is often spurred by a desire for emotional comfort—an attempt to relieve stress and anxiety by eating traditionally forbidden foods, such as those high in fats and sugars. It results in high levels of shame and regret, not to mention weight gain and microbiome imbalance, and it feeds a vicious cycle.
In contrast, intuitive eating involves a reframing of eating for physical rather than emotional or social reasons. Thus, knowing that any food option is on the table, so to speak, makes you less likely to binge eat the forbidden foods. Proponents of intuitive eating, such as Mallory Frayn, talk about cultivating a less obsessive, healthier relationship with food and allowing the body to experience a healthy variety—in moderate amounts—of all the foods that are available to us. And all of this should be informed by good sense, and the knowledge that although you might consume them once in a while, the chocolate-cake-and-onion-rings diet is not a good long-term strategy for optimal health.
Much of the attention in the popular press about what we eat is on so-called superfoods, such as blueberries, acai, kale, and sweet potatoes. But this approach ignores what nutritionists call matrix effects, the ways in which foods in a real-life, optimal diet interact with one another. Often, you can’t try to feed a particular problem without creating another one, and that’s a central issue in nutrition journalism: There is often a narrow focus on only one aspect of nutrition, or one health outcome, while ignoring another.
The key to diet seems to be not what you eat, but what you don’t. The American diet is too high in processed foods, sugar, salt, and red meat. Junk food is addictive—it overstimulates the brain’s reward system, which evolved in an era when fats and sweets were hard to come by. Apart from that, the fact is, we just don’t know enough about nutrition to say that there is a single best diet. As a report on the state of nutritional advice at Stanford University noted, “The history of nutrition science is littered with the remains of hypotheses that were once the next big thing.”
At present, what does seem to be clear is that large amounts of refined sugar, deep-fried foods, and heavily processed foods are unhealthy. Apart from that, eating a variety of different foods, in moderation, and eating more vegetables than the average American currently consumes, all appear to contribute to longevity and health. Reducing the use of tobacco and alcohol is also indicated. After reviewing hundreds of papers, I find that the best dietary advice for older adults is the much-quoted phrase in Michael Pollan’s 2008 book In Defense of Food: “Eat food. Not too much. Mostly plants.”
And allow yourself to have fun now and then. Eat a little ice cream. Have some chocolate.