Food
Marion Nestle cautions against taking the diet out of the context of the lifestyle. The Mediterranean diet is widely believed to be one of the most healthful ways to eat, yet much of what we know about it is based on studies of people living on the island of Crete in the 1950s, who did physical labor, fasted regularly, ate a lot of wild greens (weeds), and consumed far fewer total calories than we do. Similarly, much of what we know about the health benefits of a vegetarian diet is based on studies of Seventh Day Adventists, who drink no alcohol and never smoke. People who take supplements are healthier than the population at large, but their health probably has nothing to do with the supplements they take — which recent studies have suggested are worthless. Supplement-takers are better-educated, more-affluent people who, almost by definition, take a greater-than-normal interest in personal health.
Studies suggest that people on average eat between 1/5 and 1/3 more than they claim to on questionnaires. How do researchers know that? By comparing what people report on questionnaires with interviews about their dietary intake over the previous 24 hours, thought to be somewhat more reliable. The magnitude of the lie could be much greater, judging by the huge disparity between the total number of food calories produced every day for each American (3,900 calories) and the average number of those calories Americans own up to chomping: 2,000. (Waste accounts for some of the disparity, but nowhere near all of it.)
People who eat the way we do in the US today suffer much higher rates of cancer, heart disease, diabetes and obesity than people eating more traditional diets. (4 of the 10 leading killers in the US are linked to diet.)
Today, a mere 4 crops — corn, soybeans, wheat & rice — account for two-thirds of the calories humans eat. Humankind has historically consumed some 80,000 edible species, and that 3,000 of these have been in widespread use. Humans require somewhere between 50 and 100 different chemical compounds and elements to be healthy.
Many researchers say that these historically low levels of omega-3 (or, conversely, high levels of omega-6) bear responsibility for many of the chronic diseases associated with the Western diet, especially heart disease and diabetes. (Some researchers implicate omega-3 deficiency in rising rates of depression and learning disabilities as well.) Nutritionists argue for taking omega-3 supplements or fortifying food products, but adding more omega-3s to the diet may not do much good unless you also reduce your intake of omega-6.
Americans spend, on average, less than 10% of their income on food, down from 24% in 1947, and less than the citizens of any other nation.
“Calorie restriction” has repeatedly been shown to slow aging in animals, and many researchers believe it offers the single strongest link between diet and cancer prevention. Once one of the longest-lived people on earth, the Okinawans practiced a principle they called “Hara Hachi Bu”: eat until you are 80% full.
Vegetarians are healthier than carnivores, but near vegetarians are as healthy as vegetarians.