Fatty acid imbalance hurts our health
Throughout most of human history, our ancestors ate a diet that was nearly perfect in its balance between two essential fatty acids, omega-3s and omega-6s, which have crucial, though sometimes opposite, roles to play in metabolism.
In the last few decades, however, this delicate balance has been thrown out of whack, with most of us eating far more omega-6s, which come chiefly from prepared foods made with corn and safflower oils, than omega-3s, found in fatty, cold-water fish such as salmon and tuna as well as walnuts and flax-seed oil. This relative lack of omega-3s could contribute to arthritis, cystic fibrosis, heart attacks and other diseases.
"We are drowning in omega-6 relative to omega-3s," said Dr. George L. Blackburn, associate director of nutrition in the Division of Nutrition at Harvard Medical School. Throughout evolution, the ratio of omega-6 to omega-3 was two 6's to one 3, he said. "Now it's about 20 to one. We have wiped out a lot of sources of omega-3 and have a huge intake of omega-6-heavy products like corn and safflower oils."
Dr. Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health, said, "We need some of both," and it's better to fix the ratio by adding omega-3s than decreasing omega-6s. Blackburn sees it somewhat differently: "Omega-6s are indeed better for you than the worst fats, saturated fats," which are found in dairy and meat, he said. But most people get their omega-6s from junk food like french fries and packaged snacks, which are high in calories. In terms of importance, it's calories first, then the healthy balance of the fatty acids that counts."
Omega-6 fatty acids get converted in the body to substances that boost blood clotting and rev up the immune system and inflammatory response -- a good thing for fighting infections.
Omega-3s, by contrast, get converted in the body to substances that decrease the immune response, a benefit for people with auto-immune problems, and increase the time it takes for blood to clot, a benefit for people at risk of heart disease. Omega-3s also decrease potentially fatal cardiac arrhythmias and are crucial to the healthy development of the spinal cord, brain and retina in infants, and to healthy brain functioning in older people.
Because Americans are relatively deficient in omega-3s, doctors and scientists are now scrambling to find ways to increase omega-3s in our diet. Last week, researchers at Massachusetts General Hospital announced that they had genetically altered mice to produce omega-3 fatty acids. Scientists from Beth Israel Deaconess Medical Center and UMass Memorial Medical Center in Worcester also reported on research that suggests that people with cystic fibrosis may be helped by increasing omega-3s.
Later this month, the Institute of Medicine, an arm of the National Academy of Sciences, is expected to issue a report evaluating the methods used to assess the safety of additives to infant formula, including DHA, an omega-3 fatty acid, and AA, an omega-6. European countries have long added DHA and AA to baby formulas; American manufacturers began doing so two years ago to bring formulas closer to the composition of breast milk.
There are several kinds of omega-6 fatty acids, and the one people need to consume in the diet -- that is, the "essential" fatty acid -- is linoleic acid. The body converts that to AA (arachidonic acid), which helps boost the immune system and clotting factors by increasing a hormone called prostaglandin E2.
There are also many kinds of omega-3 fatty acids, the most important of which are DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid), both of which are found in fish. The body's biochemical machinery uses these acids to make prostaglandin E1, which slows down the immune system and increases the time it takes for blood to clot. The body can also make these acids from vegetable sources like walnuts and flax-seed oil.
Omega-6 and omega-3 are both polyunsaturated fatty acids. Polyunsaturated fats are considered "good" because they are more fluid than saturated and monounsaturated fats. That fluidity allows them to help create cell membranes.
Because omega-3 fatty acid suppresses immune function and increases the time it takes for blood to clot, one might think that getting too much of it would lead to infections and bleeding problems, but that doesn't seem to be the case. "We're not even close to those dangers -- maybe the Eskimos are," said Dr. Ernst Schaefer, chief of the lipid metabolism laboratory at the Human Nutrition Research Center at Tufts University.
The bottom line? Increase omega-3 however you can.
If you hate fish, try taking 1 gram a day of fish oil supplements containing omega-3 fatty acids. But beware: Fish oil capsules vary greatly in quality. To reduce the chance that the supplements have the same pollutants as in fish, it may be wise to stick with well-known national brands.
Food sources of fatty acids
Fish is the best source of omega-3 fatty acids, which are important for the heart, healthy development in infants and proper brain function. Some vegetables are also good sources of linolenic acid, which the body breaks down into omega-3s.Fish sources: salmon, tuna, herring, sardines, mackerel, trout, halibutVegetable sources: walnuts, pecans, flax seed and flax seed oil, black beans, kidney beans, pinto beans, spinach, cale and collards.
Omega 6 fatty acids, which boost the immune system and promote clotting, occur in prepared foods made with corn oil, safflower oil, canola oil, cotton seed oil and soy beans (in all forms, from oil to soy nuts).
SOURCE: US Department of Agriculture
