Chapter 1

Nutrition Equals Life: Knowing What to Eat to Get What You Need

IN THIS CHAPTER

Understanding the importance of nutrition

Determining how nutrients build your body

Evaluating nutrition information

Figuring out how to read (and question) a nutrition study

You are what you eat. You are also how you eat. And when you eat.

Choosing a varied diet of healthful foods supports any healthy mind and body, but which healthful foods you choose says much about your personal tastes as well as the culture from which you come.

How you eat may do the same: Do you use a knife and fork? A pair of sticks? Your hands and a round of bread? Each is a cultural statement. As for when you eat (and when you stop), that is a purely personal physiological response to signals from your digestive organs and your brain: “Get food now!” or “Thank you, that’s enough.”

Understanding more about nutrition means exploring what happens to what you eat and drink as it moves from your plate to your mouth to your digestive tract and into every tissue and cell and discovering how your organs and systems work. You observe firsthand why some foods and beverages are essential to your health. And you find out how to manage your diet so that you can get the biggest bang (nutrients) for your buck (calories).

Discovering the First Principles of Nutrition

Technically speaking, nutrition is the science of how the body uses food. In fact, nutrition is life. All living things, including you, need food and water to live. Beyond that, you need good food, meaning food with the proper nutrients, to live well. If you don’t eat and drink, you’ll die. Period. If you don’t eat and drink nutritious food and beverages your body may pay the price:

• Your bones may bend or break (not enough calcium).
• Your gums may bleed (not enough vitamin C).
• Your blood may not carry oxygen to every cell (not enough iron).

And on, and on, and on. Understanding how good nutrition protects you requires a familiarity with the language and concepts of nutrition.

Knowing some basic chemistry is helpful. (Don’t panic: Chemistry can be a cinch when you read about it in plain English.) A smattering of sociology and psychology is also useful, because although nutrition is mostly about how food revs up and sustains your body, it’s also — as I explain in Chapter 15 — about the cultural traditions and individual differences that explain why you like the food you like.

You’ve heard “You are what you eat” before. As a matter of fact, it’s the first sentence at the top of this chapter. But it bears repeating, because the human body is built with the nutrients it gets from food: water, protein, fat, carbohydrates, vitamins, and minerals.

Nutrition’s primary task is to figure out which foods and beverages (in what quantities) are required to construct and maintain every one of your organs and systems. To do this, nutrition concentrates on food’s two basic attributes: energy and nutrients.

• Energy is the ability to do work. The amount of energy in food is measured in calories, the amount of heat produced when food is burned (metabolized) in your body cells. You can read all about calories in Chapter 5, but for starters, all you need to know is that food is the fuel on which your body runs. Without enough food, you don’t have enough energy. No surprise there.

• Nutrients are the natural chemical substances your body uses to build, maintain, and repair tissues. They also make it possible for cells to send messages back and forth to conduct essential chemical reactions such as the ones that make it possible for you to

  • Breathe
  • Move
  • Eliminate waste
  • Think
  • See
  • Hear
  • Smell
  • Taste

  … and do everything else common to a healthy living body.

Breaking nutrients into two groups

Each of the nutrients in food fall into one of two distinct groups, macronutrients and micronutrients:

• Macronutrients (macro = big): Protein, fat, carbohydrates, and water
• Micronutrients (micro = small): Vitamins and minerals and a multitude of other substances

What’s the difference between these two groups? The amount you need each day.

Your daily requirements for macronutrients generally exceed 1 gram. An ounce of solid material, such as chicken, has 28 grams, and an ounce of liquid, such as water, has 30 grams. To give you an idea of how that translates into nutrient requirements, the average man needs about 63 grams of protein a day (slightly more than 2 ounces), and the average woman needs about 50 grams (slightly less than 2 ounces). And remember: That’s grams of protein, not grams of a high-protein food such as meat, fish, or poultry.

For example, the USDA National Nutrient Database for Standard Reference (http://ndb.nal.usda.gov), one of the ten thoroughly reliable sources listed in Chapter 27, provides the following information for grams of meat versus grams of protein:

• Chicken: 3 ounces/86 grams breast meat (no bones, no skin), roasted, provides 26.7 grams/0.96 ounces protein
• Lean ground beef (7% fat): 4 ounces/113 grams provides 23.6 grams/0.86 ounces protein
• Canned salmon: 3.5 ounces/100 grams provides 19.68 grams/0.70 ounces protein

Your daily requirements for micronutrients are much smaller. Consider vitamins. The Recommended Dietary Allowance (RDA) for vitamin C is measured in milligrams ( of a gram), while the RDAs for vitamin D, vitamin B12, and folate are even smaller, measured in micrograms ( of a gram). For more about the RDAs, including how they vary for people of different ages, check out Chapter 3.

Looking at essential nutrients

A reasonable person may assume that an essential nutrient is one you need to sustain a healthy body. But who says a reasonable person thinks like a nutritionist? In nutrition speak, an essential nutrient is a very special thing:

• An essential nutrient can’t be manufactured in the body. You have to get essential nutrients from food or from a nutritional supplement.
• An essential nutrient is linked to a specific deficiency disease, such as scurvy, the deficiency disease that may afflict people who go without sufficient vitamin C for extended periods of time, or kwashiorkor, the protein deficiency disease. A diet rich in the essential nutrient prevents or cures the deficiency disease, but you need the proper nutrient. In other words, you can’t cure a vitamin C deficiency with extra amounts of protein.

Not all nutrients are essential for all species of animals. Take vitamin C (and you should, every day). It’s an essential nutrient for human beings but not for dogs because a dog’s body manufactures the vitamin C it needs. Check out the list of nutrients on a can or bag of dog food. See? No vitamin C. The dog already has the vitamin C it — sorry, he or she — requires.

Here are three other examples of nutrients that are essential for some pets and plants but not necessarily for humans:

• Myo-inositol: Myo-inositol, an organic compound similar to glucose — the fuel we get from carbohydrates — is an essential nutrient for gerbils and rats who can’t make it in their own bodies and thus must get what they need from food. It’s nonessential for human beings who can synthesize myo-inositol and then use it in dozens of important body processes, such as transmitting signals between cells.
• Taurine: The amino acid taurine is essential for cats, but conditionally essential for humans, which means essential for some people but not all. All human bodies except newborns synthesize taurine from the amino acids methionine and cysteine (see Chapter 6), so although adults can make their own taurine, newborns need to get theirs from food, either breast milk or formula. That’s why its essential nature is conditional.
• Boron: Several minerals, such as boron, are essential for plants but haven’t been proven essential for either microorganisms, such as bacteria, or for animals, including people.

For more on the vitamins and minerals, amino acids (the so-called building blocks of proteins), and fatty acids that are considered essential for your human body, check out Chapters 6, 7, 10, and 11.

WHAT’S A BODY MADE OF?

Sugar and spice and everything nice … well, more precisely water and fat and protein and carbohydrates (the simple and complex sugars described in Chapter 8) and vitamins and minerals.

On average, when you step on the scale, approximately 60 percent of your weight is water, 20 percent is body fat (slightly less for a man), and 20 percent is a combination of mostly protein, plus carbohydrates, minerals, vitamins, and other naturally occurring biochemicals.

Based on these percentages, you can reasonably expect that an average 140-pound person’s body weight consists of about

• 84 pounds of water
• 28 pounds of body fat
• 28 pounds of a combination of protein (up to 25 pounds), minerals (up to 7 pounds), carbohydrates (up to 1.4 pounds), and vitamins (a trace)

Yep, you’re right: Those last figures do total more than 28 pounds. That’s because “up to” (as in “up to 25 pounds of protein”) means that the amounts may vary from person to person. Ditto for minerals and carbohydrates.

Why? And how? Because a young person’s body has proportionately more muscle and less fat than an older person’s, and a woman’s body has proportionately less muscle and more fat than a man’s. As a result, more of a man’s weight comes from protein and muscle and bone mass, while more of a woman’s weight comes from fat. Protein-packed muscles and mineral-packed bones are denser tissue than fat.

Weigh a man and a woman of roughly the same height and size, and his greater bone and muscle mass means he’s likely to tip the scale higher every time.

Protecting the Nutrients in Your Food

Identifying nutrients is one thing. Making sure you get them into your body is another. What’s essential is keeping nutritious food nutritious by preserving and protecting its components.

Some people see the term food processing as a nutritional dirty word, or two words. They’re wrong. Without food processing and preservatives, you and I would still be forced to gather or kill our food each morning and down it fast before it spoiled. For more about which processing and preservative techniques produce the safest, most nutritious — and yes, delicious — dinners, check out Part 4.

Considering how vital food preservation can be, you may want to think about when you last heard a rousing cheer for the anonymous cook who first noticed that salting or pickling food could extend food’s shelf life. Or for the guys who invented the refrigeration and freezing techniques that slow food’s natural tendency to spoil. Or for Louis Pasteur, the man who made it absolutely clear that heating food to boiling kills bugs (microorganisms) that might otherwise cause food poisoning. So give them a hand, right here.

Knowing Your Nutritional Status

Nutritional status is a phrase that describes the state of your health as related to your diet. Malnutrition is what happens when the diet goes wrong. Most people think of malnutrition as the result of diet too low in calories and essential nutrients, such as vitamins, but a diet that delivers too much food leads to malnutrition in the form of obesity. The latter is more common in developed countries with an abundant food supply and a relatively sedentary population. The former may arise from

• A diet that simply doesn’t provide enough food: This situation can occur in times of famine or through voluntary starvation because of an eating disorder or because something in your life disturbs your appetite. Among older people, malnutrition may follow tooth loss or age-related loss of appetite or because they live alone and sometimes just forget to eat.
• A diet that, while otherwise adequate, is deficient in a specific nutrient: This kind of nutritional inadequacy can lead to a deficiency disease, such as beriberi — the disease caused by a lack of vitamin B1 (thiamine).
• A metabolic disorder or medical condition that prevents your body from absorbing specific nutrients, such as carbohydrates or protein: One common example is diabetes, the inability to produce enough insulin, the hormone your body uses to metabolize (digest) carbohydrates. Another is celiac disease, a condition that makes it impossible for the body to digest gluten, a protein in wheat. Need more info on either diabetes or celiac disease? Check out Diabetes For Dummies, by Alan L. Rubin, MD; Diabetes Meal Planning and Nutrition For Dummies, by Toby Smithson and Alan L. Rubin; and Gluten-Free All-in-One For Dummies, a five-books-in-one bargain on living with celiac disease (all books published by Wiley).

Doctors and registered dieticians have many tools with which to rate your nutritional status. They can

• Review your medical history to see whether you have any conditions (such as dentures) that may make eating certain foods difficult or that interfere with your ability to absorb nutrients.
• Perform a physical examination to look for obvious signs of nutritional deficiency, such as dull hair and eyes (a lack of vitamins?), poor posture (not enough calcium to protect the spinal bones?), or extreme thinness (not enough food? an underlying disease?).
• Order laboratory blood and urine tests that may identify early signs of malnutrition, such as the lack of red blood cells that characterizes anemia caused by an iron deficiency.

At every stage of life, the aim of a good diet is to maintain a healthy nutritional status.

Fitting Food into the Medicine Chest

Food is medicine for the body and the soul. Good meals make good friends, and modern research validates the virtues not only of Granny’s chicken soup but also of heart-healthy sulfur compounds in garlic and onions, anticholesterol dietary fiber in grains and beans, bone-building calcium in milk and greens, and mood elevators in coffee, tea, and chocolate.

Of course, foods pose some risks as well: food allergies, food intolerances, food and drug interactions, and the occasional harmful substances, such as the dreaded saturated fats and trans fats (see Chapter 7). In other words, constructing a healthful diet can mean tailoring food choices to your own special body, which is the subject of Part 5.

Finding Nutrition Facts

Getting reliable information about nutrition can be a challenge. For the most part, you’re likely to get your nutrition information from TV and radio talk shows or news, your daily newspaper, your favorite magazine, a variety of nutrition-oriented books, and the Internet.

If you’re not a nutrition expert, how can you tell whether what you hear or read is really right? By looking for the validation from people who are, of course, and by knowing what questions to ask.

Nutrition people

Not every piece of nutrition news is nutritious. The person who makes the news may simply have wandered in with a new theory — “Artichokes cure cancer!” “Never eat cherries and cheese at the same meal!” “Women who take vitamin C are more likely to give birth to twins!” The more bizarre, the better.

Those most likely to give you news you can use with confidence are

• Nutrition scientists and researchers: These are people with undergraduate or graduate degrees in science subjects, such as chemistry, biology, biochemistry, or physics, and are engaged in research dealing primarily with the biological effects of food on animals and human beings. Some nutrition investigators come from other fields entirely, such as a historian or sociologist, whose research concentrates on food history and habits.
• Dietitians and nutritionists: These people have undergraduate degrees in food and nutrition science or the management of food programs. A person with the letters RD (registered dietitian) after his name has completed a dietetic internship and passed an American Dietetic Association licensing exam. In some states, a person who claims the title “nutritionist” must have a graduate degree in basic science courses related to nutrition.
• Nutrition reporters and writers: These are people who specialize in giving you information about the medical and/or scientific aspects of food. Most have the science background required to translate technical information into language nonscientists can understand. Some have been trained as dietitians, nutritionists, or nutrition scientists; others gain their expertise through years of covering their beat.

Regardless of the source, nutrition news should always pass what you might call The Reasonableness Test. In other words, if a story or report or study or theory sounds ridiculous, as in the earlier examples, it probably is.

Questions to ask about any study

You open your morning newspaper or turn on the evening news and read or hear that a group of researchers at an impeccably prestigious scientific organization has published a study showing that yet another thing you’ve always taken for granted is hazardous to your health. So you throw out the offending food or drink or rearrange your daily routine to avoid the once-acceptable, now-dangerous food, beverage, or additive. And then what happens? Two weeks, two months, or two years down the road, a second, equally prestigious group of scientists publishes a study conclusively proving that the first group got it wrong.

Consider the saga of dietary fiber and colon cancer. In the early 1990s, based on a respectably large number of studies including a 1992 meta-analysis of 13 case-control efforts in nine different nations, all kinds of health experts urged everyone to increase his or her consumption of high-fiber foods to reduce the risk of colon cancer. Then in 1999, data from the long-running Nurses’ Health Study at the Harvard School of Public Health showed absolutely no difference in the risk of colon and rectal cancer between women who ate lots of high-fiber foods and those who didn’t.

Imagine the confusion. Imagine the number of boxes of high-fiber cereal tossed in favor of French toast for breakfast. Imagine the reaction to a report in the Journal of the National Cancer Institute two years later saying that while cereal high in dietary fiber may not be protective, people whose diets are low in fruit and vegetables have the greatest risk of colorectal cancer. What to do? Toss the cereal? Keep the banana?

Nobody seems to know. That leaves you, a layperson, on your own to come up with the answer. Never fear — you may not be a nutritionist, but that doesn’t mean you can’t ask five common-sense questions about any study to arrive at a sensible conclusion that says, “Yes, this may be true,” or “No, this may not be.”

Does this study include human beings?

True, animal studies can alert researchers to potential problems, but working with animals alone can’t give you conclusive proof of the effect in human beings because different species react differently to various foods and chemicals and diseases. Cows and horses can digest grass and hay; humans can’t. Mouse and rat embryos suffer no ill effects when their mothers are given thalidomide, the sedative that’s known to cause deformed fetal limbs when given to pregnant monkeys — and human beings — at the point in pregnancy when limbs are developing.

Are there enough people in this study?

No, a researcher’s saying, “Well, I did give this to a couple of people,” is not enough. To provide a reliable conclusion, a study must include sufficient numbers of people to establish a pattern. Otherwise, there’s always the possibility that an effect occurred by chance.

Equally important, the study needs people of different ages, races, ethnicity, and, yes, gender. Without them, the results may not apply across the board. One good example can be found in the original studies linking high blood cholesterol levels to an increased risk of heart disease and linking small doses of aspirin to a reduced risk of a second heart attack involved only men. It wasn’t until follow-up studies were conducted with women that researchers were able to say with any certainty that high cholesterol may be hazardous for men and women and that aspirin is protective for women as well as men — but not in quite the same way. As cardiovascular researchers eventually learned, men taking low-dose aspirin tend to lower their risk of heart attack. For women, the aspirin reduces the risk of stroke. Vive la difference!

Is there anything in the design or method of this study that may affect the accuracy of its conclusions?

Some testing methods are more likely than others to lead to biased or inaccurate conclusions. A retrospective study (which asks people to tell what they did in the past) is always considered less accurate than a prospective study (one that follows people while they’re actually doing what the researchers are studying), because memory isn’t always reliable. People tend to forget details or, without meaning to, alter them to fit the researchers’ questions.

Was this study reviewed by the author’s peers?

Serious researchers subject their studies to peer review, which means they have others working in the same field read the data and approve the conclusions. All reliable scientific journals require peer review before publishing a study.

Are the study’s conclusions reasonable?

If you find a study’s conclusions illogical, chances are the researchers feel the same way. In 1990, the Nurses’ Health Study reported that a high-fat diet raised the risk of colon cancer. But the data showed a link only to diets high in beef. No link was found to diets high in dairy fat. In short, this study was begging for a second study to confirm (or deny) its results, and in 2005, a large study of more than 60,000 Swedish women, reported in the American Journal of Clinical Nutrition, showed that eating lots of high-fat dairy foods actually reduced the risk of colorectal cancer.

THE GOLDEN RULE

Call it the Golden Rule of All Science, including nutrition: Be prepared to be surprised.

Life is a continuing series of who-would-have-thought-that moments, even in nutrition. Consider dioxin, a toxic contaminant found in some fish. Consider olestra, the calorie-free fat substitute that made some tummies rumble. As you read this, dioxin’s still a bad actor, and olestra’s been banned in Canada and several European countries. But in 2005, researchers at the University of Cincinnati and the University of Western Australia announced that eating foods containing olestra may speed your body’s elimination of — you guessed it — dioxin.

On a more prosaic note, consider coffee. You know it’s bad for you, right? Wrong. Chapter 30 lists ten surprising facts — all good — about coffee. And here’s a late-breaking bonus: In 2015, a new, really big study from Boston’s Dana-Farber Cancer Institute reported that drinking caffeinated coffee may help prevent the return of colon cancer after treatment and improve the chances of a cure. Surprise!