Case Study: Fat

Western nutrition scientists' beliefs re fat have undergone drastic fluctuations over the past century (Table 10.2.1). The advice coming out of the nutritional science community, as filtered through government proclamations such as the food pyramid, have also caused enormous changes in the American diet, which have benefited some such as the vegetable oil processing industry, while hurting others such as cattle ranchers and the beef lobby. In brief, scientists discovered a relationship between cholesterol and cardiovascular disease and noticed that saturated fats have more cholesterol than other oils. Consequently, there was a big push to replace butter with margarine and to cut back on consumption of red meats, lard etc. Initially, it was believed that polyunsaturated fats such as characterize safflower oil are most heart healthy and so there was a major promotion of such oils. Later, interest developed in the "Mediterranean diet" because of the presence of many very old people in Mediterranean Europe, and nutritionists came to believe that monounsaturated fats such as in olive oil were best for us. Polyunsaturated oils, on the other hand, were increasingly shown to be not beneficial. Meanwhile, further research showed that cholesterol in the blood does not correlate with cholesterol in the diet, undermining the assumption that saturated fats are unhealthy. Trans fats, high in margarine and other processed fatty foods, were shown to be very inimical to heart health. Also, fish oils were recognized as being high in omega 3 fatty acids, which are deficient in the typical American diet today. Recently, butter has been officially accepted as a "good" fat, reversing a half century of denigration of its nutritional value. While other saturated are not yet accepted, there is nothing to distinguish butter from the others that would explain how it could be "good" and the others "bad".

Compare now with traditional diets. The Japanese have the longest life span of any nation. Within Japan, the longest lived are Okinawans. On Okinawa the only fat used for cooking is lard (of course, being on an island Okinawans also consume considerable fish oil although they do not cook with it).

So, what is going on here? Are scientists idiots? Is science corrupted by the political power of certain food lobbies such as the food processing industry? While the latter undoubtedly has had some influence, and for that matter, the dairy lobby has managed to keep milk and cheese as part of the recommended diet despite the negative scientific beliefs (until recently) about dairy fat, that is an incomplete explanation. The beef lobby was once extremely powerful. The all-American meal was a steak, a baked potato, and a tossed salad. But the onslaught of negative pronouncements about red meat from completely sincere scientists and the medical profession has caused beef consumption (and the use of pork fat for cooking) to be demonized, at least among the educated and the middle class.

The story of fat recommendations illustrates the nature of science, that it proceeds piece by piece and never is complete. Each research finding, such as that cholesterol is associated with cardiovascular disease, was correct. But that gave rise to recommendations that were wrong, because other facts, such as that dietary cholesterol does not correlate with blood cholesterol, were not yet known.