Healthy eating

Eat food. Not too much. Mostly plants.

I have been reading Michael Pollan’s account of the science of nutrition, and how it has been hamstrung by politics. The result is that scientific advice mediated through journalists has less value than what your grandmother taught, because she had access to cultural knowledge about food, which had kept people more or less healthy.

“Eat food” rather than “edible food-like substances” in the supermarket, as processing reduces nutrients, but foods may then be fortified. Better to eat whole foods. Drink whole milk as a low-fat diet with high sugar or carbohydrate may be worse.

Research cannot say what is useful in a diet. Mediterranean diets are thought healthy mainly because of a study from Crete in the 1950s, when people ate lots of olive oil and little meat, but also far fewer calories than modern Americans. They did a lot more physical labour. Other lifestyle matters may skew the results. Pollan thinks little of the Women’s Health Initiative, a long term clinical trial tracking over 49,000 women over eight years, which found no link between a low fat diet and heart disease or breast cancer rates. The Control group does not change its behaviour, the Intervention group does- in this case by reducing its intake of fat to 20% of calories. But now, we differentiate good from bad fats, but then they were not aware of these distinctions. And people lie about what they eat: women weighing over twelve stone claimed to eat 1800 calories a day, which cannot maintain that weight. The US produces 3,900 calories per day per person, and people claim to eat 2000. Not all the rest can be wasted.

The questionnaires were impossible, asking far too detailed questions. If you ate yams, were they fried, and if so in what kind of oil?

Studies control for all but one item, in an effort to link that item to an outcome. However different nutrients interact in a diet. If you drink coffee with your steak you will not absorb the iron in it.

We may not get all the omega-3 fatty acids we need from our diet. Fish get them from green algae, we get them from leaves, but our diet has changes from leaves to grains- which last longer, but contain omega-6 fats which fasten to the same enzymes in the body. 19th century diets had about the same amount of omega-6 and omega-3, modern diets about ten times as much omega-6. They perform different functions in the plant and the animal. Increasing omega-3 through supplements may not do good without reducing omega-6. So I should eat more leaves. I hardly eat any.

In the 19th century, food was understood as protein, fat and carbohydrates. Then beri-beri was found to be caused by removal of rice husks in Chinese labourers’ diet, called a “vitamine” by its discoverer. Since then, more and more active molecules in food have been differentiated.

A US Senate committee on nutrition in 1977 found that as people ate more red meat and dairy and less leaves, they suffered more heart disease, cancer and diabetes. They recommended that people ate less red meat and dairy, and the red meat and dairy industries were enraged. After that government advice shunned plain talk about whole foods, instead talking of nutrient parts such as “saturated fats”.

He recommends eating whole foods rather than processed or fortified foods, and less meat, more leaves. Eat more species- the wider variety is more likely to include what you need.

Trusting instincts: your body craves what it needs, and imagines the whole food which will grant it. Studies cannot identify the particular part of the food which you crave.

His explanation of the interests of various groups one might trust to give useful advice flummoxes me: whom might I trust?

Michael Pollan.

 

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