The role of fats in the diet has become very contentious, leaving the average person desperately confused. This has been contributed to by ongoing scientific reductionism, with studies isolating one nutrient (for example, saturated fat) for study, with the big picture getting lost or distorted or both. This was clearly illustrated in last week’s column by the parable of the blind men and the elephant.
Prof Ken Carrol from the University of Western Ontario published a great international study in 1986 - “Fat and Cancer” which showed a very strong relationship between dietary fat and breast cancer. This fat was actually a marker for the amount of animal protein being eaten.
In 1976 researchers at the Harvard School of Public Health enrolled 120 000 nurses from around the USA to start the now-famous Nurses’ Health Study. It was intended to investigate the relationship between various diseases and oral contraceptives, postmenopausal hormones, cigarettes and other factors such as hair dyes.
In 1980, Dr Walter Willet, also from Harvard, decided to use the study to investigate the theory that fat increased the risk for breast cancer and added a questionnaire on diet to the study. Unfortunately it has become an example of how reductionism in science can create confusion and misinformation, even when the scientists are trustworthy, well intentioned and originate from a Ivy League university.
One of the findings of the Nurses Health Study published in 1992, was that it did not detect a relationship between dietary fat and fibre and breast cancer risk. The women in the study who ate the least fat (20-25% of their calories from fat,) and the women in the highest range, (who ate up to 55% of calories from fat) all had the same risk for breast cancer - so it seemed that fat didn't make a difference. And so confusion reigned!
Prof T Colin Campbell wrote a critique on this conclusion pointing out that the women in the Nurses’ study all ate a diet very high in animal based foods, higher even than in the average North American diet. Even when they were eating chicken instead of steaks, or skim milk instead of full cream milk for skim milk, their diet was still very high in animal based protein, which carries risks for cancer independent of the saturated fat level.
Rural populations that have a whole food plant based diet have less than 10% of protein from animal protein, and by far the lowest incidence of many cancers. The intake of plant based foods was uniformly low in the participants so there was no high fibre group to compare with.
In discussions with Dr Willet, Prof Campbell pointed out that there were no participants in the Nurses study who followed a whole food plant based diet. Dr Willet’s response to Prof Campbell on more than one occasion: “You may be right, Colin, but people don’t want to go there!”
I would argue that it’s 2017 and people do want to go there!