The Omnivore's Dilemma: A Natural History of Four Meals

by Michael Pollan

One of the most important yet unnoticed changes to the human diet in modern times has been in the ratio between omega-3 and omega-6, the other essential fatty acid in our food. Omega-6 is produced in the seeds of plants; omega-3 in the leaves. As the name indicates, both kinds of fat are essential, but problems arise when they fall out of balance. (In fact, there’s research to suggest that the ratio of these fats in our diet may be more important than the amounts.) Too high a ratio of omega-6 to omega-3 can contribute to heart disease, probably because omega-6 helps blood clot, while omega-3 helps it flow. (Omega-6 is an inflammatory; omega-3 an anti-inflammatory.) As our diet—and the diet of the animals we eat—shifted from one based on green plants to one based on grain (from grass to corn), the ratio of omega-6 to omega-3 has gone from roughly one to one (in the diet of hunter-gatherers) to more than ten to one. (The process of hydrogenating oil also eliminates omega-3s.) We may one day come to regard this shift as one of the most deleterious dietary changes wrought by the industrialization of our food chain.