To Your Health

Q. I keep hearing about omega-3 fatty acids. What are they, where do they come from, and what good are they?

A. For many years linoleic acid, an omega-6 fatty acid, was the only recognized "essential fatty acid"; that is, it is essential in the diet because the body cannot produce it. In the 1970s, during research on the role of aspirin in pain and inflammation, it was found that EFAs are the starting material for an important group of hormones known as "prostaglandins." Prostaglandins had been discovered in 1935, but, partly because they are active in almost unbelievably minute amounts, their role in the inflammatory response was unknown for years.

There are numerous prostaglandins, forming a family of natural compounds that influence blood pressure, body temperature, allergic reactions, immune function, and other physiological events in mammals. It was soon noted that prostaglandins from both omega-6 and omega-3 fatty acids are needed to maintain a balance of these functions, so linolenic acid, the simplest omega-3 fatty acid, was moved into the "essential" category.

It is this difference in the nature of the prostaglandins produced by the two families of EFAs that led to the designation of omega-6 fatty acids as "bad fats" and omega-3 fatty acids as "good fats." In reality, it is the imbalance, the excess of omega-6 in relation to omega-3 fatty acids provided by the modern diet, that gets us into trouble. Currently the imbalance favors omega-6 fatty acids by about 20-25:1. Research sets the desirable ratio at about 5:1, and a ratio of 1:1 was the norm for much of human history. The shift started about 10,000 years ago with the introduction of agriculture.

The omega-6 EFAs are abundant in most cultivated plants and in the domesticated animals that eat these plants. Wild animals do not produce omega-3 EFA but are more likely to eat foods that are higher in omega-3 EFAs, thus the most widely available present-day sources of omega-3 EFAs are certain plants, wild game, and ocean fish. Omega-3 EFAs from fish also have the advantage of providing mostly eicosapentaenoic acid, which can be directly converted into anti-inflammatory prostaglandins. While linoleic acid, from game animals and plants, is in the omega-3 family, it still requires some preparation by a rather sluggish enzyme before it can become an anti-inflammatory prostaglandin.

Most, but not all, omega-6 EFAs convert to pro-inflammatory prostaglandins. Gamma linolenic acid, an omega-6 fatty acid, is one that doesn't. Although not easily found in food it is available in capsules of evening primrose oil, borage seed oil, and black currant seed oil and is made into an anti-inflammatory prostaglandin. Linoleic acid can theoretically be made into gamma linolenic acid, but sugar, alcohol, and trans-fatty acids, which are all too plentiful in the American diet, hinder this transformation.

Omega-3 EFAs may be the most under-appreciated of the nutrients. The surgeon general states that deficiencies, excesses, or an imbalance of fats is involved in 70% of deaths from cardiovascular disease, cancer, lung disease, and diabetes. This is indeed food for thought.