New scientific studies suggest that by increasing our consumption of certain "good" fats found in fish, flaxseed oil, and walnuts, we may improve the symptoms of a number of psychiatric illnesses, including depression, bipolar disorder, and schizophrenia. For years, investigators have been exploring the link between depression and diet, especially the association between the incidence of depression and fish consumption. Fish and some land-based foods are rich in omega-3-a nutritional building block critical for the healthy development and functioning of the brain and nervous system.
In the past 100 years, the American diet has shifted away from the diet of our human ancestors-wild plants and game, including fish-which was rich in omega-3 fatty acids to one relying on mass-produced and highly processed food. By reducing our consumption of omega-3s in favor of another fat called omega-6 fatty acid, found in vegetable oils such as corn and soy, we have upset a delicate balance that may underlie the increasing rate of depression and other chronic diseases in contemporary American society. In cross-national studies comparing diet, scientists found that in countries where fish is still a large part of the diet, such as in Taiwan and Japan, rates of depression were lower than in American and many European populations.
We spoke with Joseph R. Hibbeln, M.D., about this emerging field of scientific research. Dr. Hibbeln is an internationally recognized authority on the link between essential fatty acids and depression. Chief of the Outpatient Clinic, Laboratory of Clinical Studies at the National Institute on Alcohol Abuse and Alcoholism at the National Institutes of Health in Bethesda, Maryland, Dr. Hibbeln co-organized the first "NIH Workshop on Omega-3 Essential Fatty Acids and Psychiatric Disorders," held last September.
Q: In layman's terms, what are omega-3 fatty acids?
A: Omega-3 refers to a class of polyunsaturated fatty acids that are beneficial to many aspects of health. Polyunsaturated fatty acids are all essential fatty acids in that they must be derived from the diet-they can't be manufactured by the body. Among polyunsaturated fatty acids, there are two classes or families-an omega-6 and an omega- 3.
Balance between these two families is very important to proper human functioning and well-being.
The two families are not interchangeable. For example, if you eat foods high in omega-6 fatty acids, your body composition will change over to have lots of omega-6 fatty acids. If you eat foods high in omega-3 fatty acids, your body tissues will eventually develop a higher proportion of omega-3 fatty acids.
Q: Why are omega-3s so important?
A: Of the omega-3 fatty acids, two are especially biologically important-one is EPA, eicosapentaenoic acid, and the other is DHA, decosahexaenoic acid. In a nutshell, DHA is very biologically important because it is highly concentrated in the brain-in the synapses, where brain cells communicate with one another. And DHA is one of the important fats that make up the wall of the cell.
To illustrate this point, if you are building a house and pouring concrete, DHA would be what the concrete is made of-it is literally the wall of the cell. Depending on what kind of fatty acids you put into that cell wall, the wall or membrane will possess different physical properties. If you make the foundation out of saggy concrete, it will affect many different systems in the house-windows, electrical systems, etc. In a similar manner, the type of fatty acids that you eat will eventually create the cells of your membranes and therefore affect how they function. That is one reason why DHA is important.
Q: What role does the other omega-3 fatty acid - EPA - play in our health?
A: EPA becomes a very potent, biologically active molecule that keeps platelets from coagulating or clotting. When EPA gets into white blood cells, it helps reduce inflammation and immune responses. EPA affects the body in many other ways-sleep patterns, hormones, etc.-serving as a modulator.
Q: What function do omega-6s have in the body?
A: One omega-6 fatty acid, arachodonic acid (AHA), makes biological compounds which have the opposite effect from the compounds made from EPA. For example, if you have a platelet with a lot of arachodonic acid in its cell wall, it will clot more easily and you are therefore more likely to clot off a blood vessel during a stroke. If the platelet has EPA in its cell wall, it is less likely to clot.
Once again, the important factor here is achieving a balance between these two families-the omega-3s and the omega-6s.
Q: So people need both omega-3 and omega-6, but in what proportion?
A: Proportion is a critical question. One way to answer the question is to study human evolution and look at the diet human beings evolved on. It's quite clear that even if you don't account for fish in the diet, the ratio of omega-6s to omega-3s in our paleolithic diet was about one-to-one. During our evolution, we ate a variety of different plant sources and leafy green vegetables, nuts, and free-range animals that ate leafy green vegetables: wild game has about a one-to-one ratio of omega-6 to omega-3.
Q: How has our diet changed?
A: In the past 100 years, the balance of omega-6s to omega-3s has radically changed from the diet we evolved on and what, it could be argued, we are optimally suited for. We now grow seed oils, such as corn and soybeans, in great abundance. As seed oils, they have much higher ratios of omega-6s to omega-3s. Corn oil, for example, has a ratio of about 74 or 75 omega-6s to one omega-3.
Q: Flaxseed is a seed, but it contains more omega-3, right?
A: Yes, flaxseed is an exception.