There is only one diet that humans have not been able to adapt to – the modern 'western diet', writes WILLIAM REVILLE
‘EAT FOOD. Not too much. Mostly plants. That, more or less, is the short answer to the supposedly incredibly complicated and confusing question of what we humans should eat in order to be maximally healthy.” These lines open Michael Pollan’s book In Defence of Food (Penguin, 2008). I fully agree with the message in these lines and with almost everything else in this book, a tour de force of common sense about food and diet and a devastating critique of the ideology of nutritionism.
When Pollan advises us to eat “food”, he means to eat things our grandmothers would recognise as food, ie whole foods such as a cabbage, a turnip, a steak, a fish, an apple, a potato, milk, etc – as opposed to the thousands of highly processed foods and edible food-like products that now pack our supermarket shelves, eg highly processed meats, potato crisps, pizza, crackers.
Pollan points out that humans have lived on food for many thousands of years with no apparent ill-effects and that we can adapt to a wide variety of diets. For example, the Masai live almost entirely on meat, blood and milk, eating almost no vegetables. Various peoples have lived on diets that were all meat, all plants, high fat, low fat, and so on, and they thrived on these without the benefit of advice from an army of nutritionists.
However, there is one diet that humans are unable to adapt to, even with the dedicated assistance of nutritionists. This is the “western diet” that arose with the industrialisation of food in the 20th century. This diet is characterised by lots of processed food, meats and refined grains, lots of added sugar and fat, but few vegetables, fruits and whole grains. The western diet is associated with a series of diseases – obesity, diabetes, cardiovascular disease and cancer – diseases that are quite uncommon among people who live on traditional diets. Everywhere people give up traditional diets and take up the western diet, these “western diseases” soon follow.
Nutritionism arose in tandem with the industrialisation of food. Pollan claims that we are now in the grip of a “nutritional industrial complex” comprised of error-
prone but well meaning nutritional scientists and a food industry ever eager to pounce on the frequent twists, turns and reversals of nutritional advice in order to sell more food.
Pollan describes nutritionism as an ideology that has convinced the public of three myths: (a) that food is simply a carrier of nutrients – protein, carbohydrate, fat, vitamins, minerals, etc, and that the nutrients are what matter, not the food; (b) that we need experts to tell us what to eat because nutrients are invisible and mysterious to everyone but scientists; (c) that the entire purpose of eating is to promote a narrow concept of physical health.
Pollan points out that all this is to ignore the fact that eating is as much about culture and pleasure as biological necessity. People eat together, thereby emphasising community, family and spirituality, expressing identity and links to the natural world. It is also to ignore the fact that, despite nutritionism’s orchestration of the details of our diets, we remain confronted with an epidemic of obesity, diabetes, heart disease and cancer.
Pollan’s analysis of the science of nutrition is damning.
He concludes that the reductionist approach used, concentrating on investigating the effect of one nutrient at a time, is hopelessly inadequate to accurately diagnose what is good and what is not good to eat – both food and the human body are far too complex for this approach to be fruitful.
The story of margarine illustrates the problem with nutritional science. From the 1950s onwards, a correlation between dietary intake of saturated animal fat and heart disease was noted. Butter was labelled as “bad” because of its saturated fat and cholesterol content. Margarine was invented in the 19th century as a cheap substitute for butter. It is made by bubbling hydrogen through vegetable oil (unsaturated fat).
Margarine was enthusiastically promoted by nutritionists in the 1960s/1970s as a substitute for butter and lard in cooking. Alas, 20 years later, with butter sales destroyed, it was discovered that bubbling hydrogen through vegetable oil produces fats called trans fats. Trans fats are more dangerous than saturated fats and margarine was more dangerous than the butter it replaced. Unfortunately, nobody knew about the health effects of trans fats in the 1960s.
Nutrition is a complex area and it is very difficult to formulate dietary advice guaranteed to stand the test of time. Don’t get me wrong – nutritional science is very important, but it needs to be more cautious in formulating advice. In the meantime, the average healthy person will not go far wrong with Pollan’s advice – Eat food. Not a lot. Mostly plants.
William Reville is associate professor of biochemistry and public awareness of science officer at UCC – understandingscience.ucc.ie