Diet advice changes so fast it’s almost a full-time job to keep up with it. Avoid cholesterol; no, avoid saturated fats; no, avoid trans-fats. Avocados are bad; no, avocados are good. Wheat germ is passé; now omega 3s are de rigueur. The supermarket overwhelms us with an embarras de richesses, a confusing superabundance of choices from “organic” to low-sodium. How can we decide what to have for dinner?
Michael Pollan, the author of The Omnivore’s Dilemma, has written a new book: In Defense of Food: An Eater’s Manifesto. He argues for a simplification of diet advice. He hones it down to seven words: Eat food. Not too much. Mostly plants.
When people from traditional cultures adopt Western lifestyles, they become more likely to develop “Western diseases”: obesity, diabetes, cardiovascular diseases and cancer. Pollan blames the Western diet: processed foods, lots of meat, refined grains, chemicals, industrial production methods, monocultures, a superabundance of cheap calories from sugar and fat, and a narrowing of biological diversity. Lots of everything except vegetables, fruits and whole grains.
We realize our diet is not optimum and we are forever trying to do better, but we’re not succeeding very well. We’re overfed and undernourished. Pollan calls it the American paradox: we are obsessed with eating the right foods, yet we are getting fatter and less healthy.
We have been bamboozled by “nutritionism” – the idea that food can be reduced to a mixture of identifiable nutrients, that we can’t be trusted to eat right without scientific help, that we should choose foods to make us healthy rather than to provide pleasure (which fits right into the time-honored guilt trip that anything that feels good must be bad).
Nutrition science is notoriously fallible: it’s impossible to do an accurate controlled long-term study comparing two diets because you can’t trust people to accurately report what they eat, and you can’t hope to randomize and get adequate cooperation. Science can never be absolutely sure it has identified every nutrient important to health. We test what we can isolate and test: when we learned how to identify cholesterol we did lots of cholesterol studies. When we discovered trans-fats we did trans-fat studies. Foods have too many ingredients to test them all separately even if we knew what they all were. 35 antioxidants have been identified in thyme alone, from apigenin to ursolic acid. Even if you could test each ingredient, you couldn’t be sure combinations of ingredients don’t act in unexpected ways – turning the expression of a gene on or off, interfering with each other’s absorption, synergizing for good or bad.
The good news is
…we can enjoy thyme in the knowledge that it probably doesn’t do any harm (since people have been eating it forever), and that it might actually do some good (since people have been eating it forever), and even if it does nothing at all, we like the way it tastes.
The lipid hypothesis
The lipid fiasco started with the idea that a diet high in meats and dairy foods was associated with heart disease. In 1977, a congressional committee called for Americans to cut down on their consumption of red meat and dairy products. That didn’t go over well with the meat and dairy industries, so the recommendations were re-written advising us to choose foods that will reduce cholesterol and saturated fat intake. We succeeded entirely too well at getting that message across. A recent survey found that many Americans thought a no-fat diet was healthier than a low-fat diet. They didn’t realize that fat is essential to health, and that fat-soluble vitamins depend on it. We don’t get enough vitamin A and D as it is. So what did we do? We added those vitamins to processed foods.
Remember when fake foods had to be labeled “imitation”? No longer. Now they needn’t be labeled as imitation as long as they are “nutritionally equivalent” – so fats in sour cream can be replaced with hydrogenated oils or guar gum or carrageenan, and bacon bits can be replaced with soy protein without being considered fake. But they are still fake. A rose by any other name…
We substituted margarine for butter to avoid cholesterol, only to realize belatedly that the trans-fats in margarine were far more dangerous. Oops. We reduced the percentage of fat in our diets, but we ate more carbohydrates and ended up eating more total calories. Double oops.
We’re finding that controlling fats in the diet makes very little difference in the risk of heart attacks for most people. We still recommend it for patients at high risk, but it was a mistake to try to change the diet of the whole population. We didn’t foresee all the consequences. People got fatter. We only made things worse.
The carbohydrate hypothesis
We needed a new villain: enter the carbohydrate hypothesis. Gary Taubes wrote Good Calories, Bad Calories to try to convince us that heart disease, obesity, cancer, diabetes, and a lot of other ills could all be blamed on refined carbohydrates. Pollan thinks Taubes left his skepticism at the door when he pinpointed one culprit. He says:
Taubes is so single-minded in his demonization of the carbohydrates that he overlooks several other possible explanations for the deleterious effects of the Western diet, including deficiencies of omega-3s and micronutrients from plants. He also downplays the risks (to health as well as eating pleasure) of the high-protein Atkins diet that the carbohydrate hypothesis implies is a sound way to eat.
Organic is not always better
As Pollan pointed out in his previous book, “organic” has been industrialized and hyped to make it seem better than it really is. The “organic” designation is no guarantee of freshness, quality, or safety; and in some cases it is even worse for the environment. Sometimes you’re better off buying local produce that is fresher, hasn’t required fossil fuels for long-distance transport, is grown by an environmentally-conscious small farm, but isn’t technically “organic.” He recommends shopping at the farmers’ market and asking the farmer about his methods.
What to Eat
Pollan’s book ends with long lists of practical advice, such as:
- Don’t eat anything your great-grandmother wouldn’t recognize as food (non-dairy creamer?)
- Avoid food products with ingredients that are unfamiliar, unpronounceable, more than 5 in number, or that contain high-fructose corn syrup (none of these is necessarily bad in itself, but they raise red flags).
- Avoid food products that make health claims. Broccoli and tomatoes are silent. If a product needs to crow about being healthy, chances are it isn’t.
- Shop the periphery of the supermarket where the fresh food resides.
- Get out of the supermarket and shop at a farmers’ market.
- Eat mostly plants: more leaves than seeds.
- Choose quality over quantity.
- Eat until you’re no longer hungry, not until you’re full.
- Sit down to real meals with other people; eat slowly and mindfully; enjoy your food.
I got a kick out of one of his recommendations. He says to be the kind of person who takes supplements – don’t actually take supplements, just be the kind of person who does (concerned and informed about health).
I don’t agree with everything Pollan says, but I endorse his 7-word formula. Only I worry that if you eat too much of one thing you may miss out on micronutrients. I’d prefer a 10 word formula: Eat a variety of foods. Not too much. Mostly plants.
This article was originally published in the Science-Based Medicine Blog.