Cargo Cult Nutrition
Calorie restriction might be a good life-extension strategy, but at some point we do have to eat. The question is: eat what?
There are so many different diets out there that we could experiment for the rest of our lives: low-carb or low-fat? How about going vegan? Or perhaps trying the Paleo diet, the ketogenic diet, the Mediterranean diet or maybe the gummy bear diet?
When you first start looking into nutrition, it’s easy to pick a new diet with confidence. You’ll encounter a credible-sounding guru and he’ll tell you something surprising. Bacon is actually healthy! And here’s a study to back it up. The study will be legitimate, with nice graphs and fancy-sounding words. You see, says the guru, everyone else is ignorant. There’s no need to worry, my data clearly shows bacon is healthy.
One day, as you’re munching down a tray of bacon while arguing with your family members, you look up that homerun of a study again. That’ll teach them! But in the process, you find another study. This one concludes the opposite – bacon is going to give you a heart attack. The study has many references supporting it, and at the bottom of the rabbit hole is another credible-sounding guru. He matter-of-factly explains that bacon is the number one bad food, and anyone consuming it will die an early death. You push the tray aside. How could you have been so stupid?
Months pass, and one night while reading the news, you stumble on an article. ‘New study: Bacon might increase your lifespan.’ The article interviews yet another credible-sounding guru. He explains why old studies on bacon are fundamentally flawed. His new study, which corrects these flaws, proves bacon is supremely healthy. ‘I was sceptical at first,’ he says. But after going on an all-bacon diet, he has lost 100lb and can now bench-press a small family sedan.
Alright, while I might exaggerate a little, the world of nutrition science really is notoriously hard to navigate. The same foods will be healthy one day, then unhealthy the next – or maybe both at once – according to different sources. And it doesn’t take much digging before every food seems like it’s going to give you cancer.
There are a whole bunch of reasons why nutrition science is so contradictory. An obvious one is that some studies are funded by food companies. To everyone’s surprise, it turns out industry-sponsored studies often yield results that are beneficial to their donors.
In other cases, however, evil food companies are not to blame. Sometimes we are. A study claiming that chocolate is actually healthy will be celebrated on the rooftops. Meanwhile, the twenty contradicting studies will be forgotten. It’s a lot easier to convince people of something that is convenient or pleasurable; our rationalising brain will grasp at any opportunity to justify eating more chocolate. But as the famous physicist Richard Feynman said: ‘The first principle is that you must not fool yourself – and you are the easiest person to fool.’
Alongside these obvious problems, however, there are also some more subtle issues that we need to be aware of if we want to eat our way to a long life.
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During the Second World War, the American and Japanese militaries built airbases on several South Pacific islands. The bases provided many native islanders with their first face-to-face encounters with the modern world. They were astonished. Here they were, toiling for everything they had – attending to their crops and livestock, building houses and making weapons by hand. Meanwhile, the foreigners had an endless supply of food, clothes, medicine and otherworldly equipment supplied to them from above. They would perform a few rituals, like marching back and forth, yelling at each other and waving at the sky. Then huge machines would appear, carrying more goods than the natives could produce in several lifetimes. Only the gods could be powerful enough to be the source of this abundance.
Eventually, though, the war ended, the foreigners disappeared – and so did all their precious cargo. The natives desperately wanted the planes to return. But how? They tried turning to the gods, imitating the strange rituals of the foreigners. They cleared airstrips in the forest and marched up and down them with bamboo guns. They made headsets and radios from coconuts and straws. They even built wooden offices, air control towers and airplanes. Eventually, the whole thing turned into several religions dubbed ‘cargo cults’ by anthropologists. Some of these cargo cults still exist today, believing that, one day, the gods will notice their rituals and start sending cargo planes once again.
The members of the cargo cults employ one of our most powerful learning techniques: imitation of successful people. In our world, you might copy everything about your favourite sports star, musician or business person. It’s not always obvious what causes these people to be successful, so if you want similar success, it makes sense to copy pretty much everything – whether that’s starting your day at 4 a.m. with an ice bath, reading voraciously, or only wearing black turtlenecks. However, when we’re not aware of the ‘generator’ of success, we risk just copying a bunch of insignificant surface-level features like the cargo cults.
Something similar actually happens all the time in nutrition science. We study long-lived people, trying to uncover the secrets of longevity, but often we simply end up copying a bunch of the surface-level features of rich, educated people. You see, on average, rich, educated people live longer than poor, less-educated people. Someone with a bachelor’s degree can expect to live several years longer than someone with only a high school degree. This trend holds true in every country around the world and the gap seems to be growing over time.
This longevity gap is due to the fact that wealth and education make people follow health guidelines more closely. Why that is, I will leave up to sociologists. But the facts are that the wealthier and more educated you are, the more likely you are to exercise regularly, get vaccinated, be a non-smoker and have a healthy body weight. These health-promoting habits are obviously great to copy, but how do we separate them from everything else that rich, educated people are up to?
For instance, we know wearing glasses is more common among educated groups of people. If we made a study trying to find traits that correlate with living a long life, wearing glasses would thus be one of them. But the fact that someone wears glasses obviously doesn’t affect their lifespan. We couldn’t pick some guy off the street and prolong his life by putting a pair of glasses on him. Nor would I advise you to intentionally ruin your vision in a quest for longevity.
You might have heard the phrase ‘correlation doesn’t imply causation’. Essentially, two things can be correlated (even tightly) without one causing the other. The natives of the South Pacific observed that there was a tight correlation between making gestures towards the sky and the arrival of an airplane. But these gestures had nothing to do with causing the airplane to arrive. Similarly, there’s a strong correlation between how many people die of heatstroke on a given day and how much ice cream is sold. However, that doesn’t mean eating ice cream makes people get heat stroke and die. Instead, both ice cream sales and the number of heat strokes are caused by hotter temperatures, and do not affect each other whatsoever.
There’s a real-life example of a longevity cargo cult arising from the sunny town of Loma Linda in southern California. Loma Linda is known as one of the Blue Zones, and its inhabitants have been studied extensively for their longevity. Many Loma Lindans are Seventh-Day Adventists and abstain from eating meat due to their religion (originally inspired by John Harvey Kellogg, whose breakfast products you might have tried). After decades of research, the consensus is that a meatless lifestyle yields approximately three additional years of life. In Loma Linda, the vegans live the longest, then the vegetarians, followed by semi-vegetarians and finally the meat-eaters.
But as you might’ve guessed, there’s more to the numbers. Veganism and vegetarianism are mostly popular among rich, educated people. You’ll see a lot more plant-based restaurants in a university town than in a trailer park. That means vegans and vegetarians tend to have lots of other healthy habits: they exercise more than average, drink less alcohol, smoke less and have healthier body weights. Mirroring their lifespans, the vegans of Loma Linda have an average BMI of 23. The vegetarians have one of 25.5. The semi-vegetarians have a BMI of 27, while for the meat-eaters the average is 28. So is it really the lack of meat that prolongs life?
Epidemiologists are well aware of the problem, and have devised several potential solutions. The most common one is to try to account for health differences before comparing groups of people. For instance, before comparing the lifespans of vegans and meat-eaters, we could subtract the effect we know comes from extra exercise, less smoking and healthier BMIs among vegans. In this way, we can pretend we’re comparing similar groups of people. Once you actually do this, veganism no longer extends life.
Another good example is red wine. There are lots of studies claiming red wine will make you live longer because red-wine drinking and longevity are correlated. Studies have been busy trying to find the source of the health benefits and ascribed them to all sorts of molecules found in red wine. But to no one’s surprise, red wine is disproportionally favoured by rich, educated people. That means people who drink a lot of red wine are like the vegans and vegetarians discussed above. They have lower than average BMIs as well as generally healthy habits, so we cannot conclude that red wine is making these people healthy. It is most likely all their other habits.
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If we really want to know if a food or habit is not just correlated with health benefits but actually causes them, the gold standard is something called a randomised controlled trial. We’ve encountered the concept a few times already. In a randomised controlled trial, scientists gather together a bunch of people and divide them into two groups with equal baseline characteristics. One group is given an intervention – a drug, a new exercise routine, a new diet – while the other group is given placebo. Then, time is allowed to pass to see whether there is a disparity in a certain outcome, such as lifespan or the development of a disease.
For instance, we might have noticed that people eating a lot of spinach tend to have big muscles. If we want to learn whether spinach causes your muscles to grow, we could do a randomised controlled trial. Here, we would gather test subjects, divide them into two groups and ask one group to eat spinach every day for the following months. Then we would track whether this group had increased muscle growth compared to the other group who continued as normal.
While randomised controlled trials are harder to do than simply looking for correlations, you’d be surprised just how many things have been investigated this way throughout the years. We’re talking stuff like using live parasites to cure allergies, or fighting blindness using proteins from algae. However, modern medicine also has its favourites. In particular, there are two supplements that have been tested in randomised controlled trials for practically everything – and that includes their ability to prolong life.
The first one is fish oil – or more specifically, omega-3 fatty acids. Omega-3s are polyunsaturated fatty acids that serve vital roles in our physiology. Among other things, we use them in cellular membranes and as a starting material for making other important compounds. We mostly get omega-3s from our food, and the best dietary source is fatty fish such as salmon, mackerel and herring. Research has repeatedly found that a high fish consumption is associated with living a long life, and omega-3s are the main suspect. For instance, the more omega-3 fatty acids someone has in their blood or cellular membranes, the longer they tend to live.
At this point, your new bullshit filter might be springing into action. Don’t rich, educated people eat more fish than others? Is that the reason for these correlations? There are certainly more seafood dishes at fancy restaurants than at McDonald’s. Health authorities have been recommending fish for decades, and studies do indeed show that rich, educated people eat the most fish. That’s why we should skip the correlations and turn to randomised controlled trials instead.
In randomised controlled trials for fish oil, the health benefits are much more modest than we might have naively expected. It turns out, much of the correlation between fish consumption and health is due to rich, educated people eating more fish, rather than anything to do with fish itself. However, to be fair, the health benefits are not totally gone. If we put on our rose-coloured glasses and squint a little, randomised controlled trials show that fish oil supplements could have a few health benefits. They particularly seem to lower the risk of various diseases of the heart and cardiovascular systems, working better at high doses.
So given that fish is tasty and fish oil supplements are easy to take, it can’t hurt to include them in a longevity conscious diet. There are no indications of harm in the millions of people studied, meaning the worst that can happen is you experience no benefits. As always, it is preferable to eat the food itself rather than take a supplement. Fish might have other health-promoting effects beyond those obtainable from fish oil. But fish is also expensive and frankly – if you’re anything like me – hard to cook.
When using fish oil supplements, it’s important to pick one that has been tested for omega-3 content. Some contain very little, while others might contain pollutants or be of poor quality. There’s a lot of fraud out there.
There’s even fraud going on with actual fish and seafood. In a number of tragicomical studies, scientists have found that a lot of fish sold in restaurants and supermarkets is not what it claims to be. Someone, somewhere in the supply chain must have reasoned that people don’t know anything about fish. Then they’ve straight-up replaced fancy fish with something cheaper. For instance, in a study done in several countries, forty per cent of ‘snapper’ on sale was found to not actually be snapper at all. In another study, up to half of the sushi tested in Los Angeles was made with a different fish than claimed. And in a third study, many ‘prawn balls’ in Singapore didn’t contain any prawns at all. Someone managed to replace it with pork and get away with it.
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If fish oil is the prince of supplements, then vitamin D is the king. There are so many vitamin D studies out there that frankly you should feel sorry for me for having to review them.
Once again, the surface-level story is perfectly clear. Low vitamin D levels are robustly associated with dying early. However, as I’ve been repeating to the point of madness now, that doesn’t necessarily mean that there is causation. Actually, there are a bunch of reasons to believe there is no causation.
First, we might have the whole thing backwards. It turns out that many diseases cause vitamin D levels to drop – not the other way around. That means low vitamin D levels don’t cause the diseases it has been linked to. Instead the diseases are what cause the low vitamin D levels.
Second, there is our pet peeve issue that poor people tend to have lower vitamin D levels than wealthy people.
And third, vitamin D is a fat-soluble vitamin (or actually a hormone). It seems people with excess fat mass have low vitamin D levels, and this could be because of entrapment in fat tissue. In other words, being overweight might make your vitamin D levels lower, and we know excess weight also promotes the development of several diseases.
To figure out this chicken-and-egg situation, we must once again turn to randomised controlled trials. That is, studies where scientists give people vitamin D supplements and follow them to uncover whether it improves their health.
In the case of vitamin D, we really have to put on rose-coloured glasses to find a benefit. When pooling the many studies together, scientists find that vitamin D supplements do not decrease your risk of dying or your risk of the most important age-related diseases. For the sake of longevity, you can use your money on something else.
Is alcohol bad?
There’s no doubt that it’s extremely unhealthy to drink too much alcohol. The big health question, though, is whether it’s beneficial – or at least okay – to have a few drinks. In correlational studies between alcohol intake and longevity, there is a J-shaped curve that looks like hormesis. That is, people who drink a little alcohol actually live longer than those who don’t drink at all (while those that drink a lot obviously die earlier than both). The fact that light drinking extends lifespan is one of those beliefs that it is easy to convince yourself of. After all, that would be nice, wouldn’t it? As a result, the health benefits of a little alcohol are oft-touted. But of course, that also means scepticism is warranted.
The problem with these studies is that the group of people who don’t drink at all includes many former alcoholics. Years of alcohol abuse will cause lasting damage, so even if an alcoholic has managed to quit drinking, their life expectancy is still reduced (though far less than if they had continued). As a result, the group of ‘non-drinkers’ are a patchwork of lifelong teetotallers and former alcoholics. And if you remove the former alcoholics, the benefits of a few drinks a week disappear – light drinkers don’t live longer than teetotallers after all. However, to be fair, there’s still not a huge amount of difference between teetotallers and light drinkers as long as it entails staying below five drinks a week.