What is the healthiest diet for humans? This very basic question has not been answered scientifically. In fact, it hasn't really been asked. The main reason is that there is no scientific definition of overall physical health. It's rather difficult to specify which diet yields the greatest degree of general health when nobody knows for sure how it ought to be measured.
The traditional scientific instrument for distinguishing healthy diet patterns from unhealthy ones is the epidemiological study. Here's how it works: Scientists first gather dietary information from a large pool of individuals. Next they try to correlate these data with health outcomes such as the incidence of a specific disease. For example, a group of nutritional epidemiologists might gather data about how often people in a certain population eat fish, and then track the incidence of stroke within that population over a seven-year period to determine whether eating fish often has any effect on the risk for stroke.
What Research Does and Doesn't Reveal About Healthy Diets
Such studies often yield useful information, but they don't come anywhere close to providing an answer to the question posed at the beginning of this article. To develop a complete picture of the healthiest possible diet, nutrition scientists would need to turn their normal study format on its head, first identifying the healthiest people and then seeing what they ate.
To design such a study, researchers should begin by putting together a battery of tests, such as blood lipid levels, body fat percentage, blood pressure, C-reactive protein level (a marker of systemic inflammation), fasting glucose, total antioxidant capacity, and aerobic capacity, to calculate an overall health score for individuals. You can bet that any person who achieved optimal scores on each of these tests would still be riding a bike at age 92.
The next step would be to apply this battery of tests to thousands of men and women of all ages, assign a general physical health score to each, and statistically separate them into ranked groups. The group we're most interested in, of course, would comprise those with the highest scores. Finally, detailed information about diet would be gathered from these super-healthy people. The most widely shared patterns would constitute the world's healthiest diet by the only definition that matters: real-world outcomes.