Perhaps the biggest problem with medical studies is the ability to find a large group of people willing to subject themselves to the rigor, discipline, and honesty. Remeber, that for a study to be beneficial, it has to examine the impact of an intervention over an extended period. Imagine you want to consider the impact of brushing your teeth five times a day with some new salt toothpaste. How many people would be able to stick with the program?
The PURE study or the Prospective Rural Epidemiology study was a ten-year long program that studied 125,257 people in ten countries. The countries included North & South America, Europe, Africa and Asia to account for genetic differences. The objective of the study was to evaluate the change in risk of cardiovascular disease as an outcome of the foods you ate. The study was able to monitor the habits of large groups of people because it examined their diet in its natural state and then measured its impact over time. Their findings were startling.
The study found for example that there was no correlation between fats, saturated, unsaturated, monosaturated or polyunsaturated fats, and cardiac disease. Consumption of fats made no difference to your risk profile. Also, switching saturated fats with unsaturated fats did not seem to make any difference. Similarly, the findings appeared to contradict the recommendation of eating up to five helpings of fruits and vegetables. Instead, only three servings seemed to be helpful, and anymore the benefits appeared to plateau. The study did seem to validate the belief that eating a diet that primarily consisted of fruits, vegetables, nuts and seeds, and legumes was the best for your health.
The typical criticisms of research studies center around the absence of genetic differentiation, duration or size or worse; that it was performed on animals. It was therefore hard to be critical of this study. Your ancestors already knew all of this; we are just finding out.