A fish tale

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AS CLINICAL and epidemiological studies suggest, omega-3 fatty acids are extremely important to our overall health. Because our bodies cannot make enough of these special fats to meet our needs, we are dependent on obtaining them from our diets. That is the simple definition of an "essential" fatty acid, but it really should not be that hard to get enough omega-3s from our food. All we have to do is eat a minimum of two servings of fatty fish each week and we will consume the American Heart Association's recommended intake. Excellent sources are herring, mackerel, sea bass, sardines, salmon, and trout, points out Machelle M. Seibel, professor of clinical obstetrics and gynecology at the University of Massachusetts, Worcester, and medical director of Inverness Medical Innovations, Inc., Waltham.

However, according to the ICR Survey Research Group, Americans are far less likely to eat fresh fish than almost any other food. In fact, just over one-third ate fresh fish during a recent one-week period--compared with 77% who consumed beef; 52%, pizza; and 50%, french fries. The survey further revealed that of those who did eat fish, the median intake was only one serving per week.

Why don't Americans eat more seafood? With so many media reports describing worrisome levels of toxins such as mercury, dioxins, and PCBs, it is not surprising that the most commonly expressed reason was concern about contaminants (48%). Other reasons were smell (46%), cost (43%), and availability (44%). Although many consumers feel that farm-raised fish are safer because they are spared from the contaminants that are present in the ocean, scientists have found that farm-raised salmon actually carried higher levels of pollutants than wild salmon due to the fishmeal fed to them. That is cause for concern, Seibel maintains, since 90% of the fresh salmon consumed in the U.S. is farmed. This particularly is worrisome for pregnant women and nursing moms whose babies would be exposed at a vulnerable time in life.

Despite the risk of pollutants, we still need to get the omega-3 fatty acids found in fish, Seibel advises, as their benefits to the heart are longstanding. In the 1970s, researchers found that Eskimos in Greenland virtually had no heart disease even though their diets were extremely high in fat. It was determined that a majority of the fat they were consuming was omega-3 fatty acids derived from fish, which help to reduce the very processes that lead to some of the most common causes of heart attack. Another research project, the DART study, suggests that eating just one serving of fish per week lowers the risk of heart attack by 29% in patients who had a previous heart attack. However, the people who ate the most fish also tend to have healthier lifestyles, making it difficult to be certain that eating fish was the main benefit. Omega-3 then got a boost from the GISSI trial in which patients with heart disease received about one gram a day of fatty acids. Those individuals had a 45% reduction in their risk of dying of a sudden heart attack and a 30% reduction in their risk of dying of heart disease in general.

Likewise, the Lyon Diet Heart Study showed the benefits of omega-3 fatty acids for heart health. The study was designed so that heart attack survivors were divided into two groups--one following the American Heart Association recommendations (the USDA Food Pyramid) and the other following a Mediterranean-type diet rich in vegetables, fruits, and fish. After four years, both groups had similarly reduced cholesterol levels. Yet, the Mediterranean group had a 70% lower incidence of heart attacks. Analysis of blood tests showed they had higher omega-3 fatty acid levels than the other group.

Omega-3 fatty acids also are good for the brain, Seibel declares. Sixty percent of the human brain's weight is fat and, of that, roughly 20% is comprised of omega-3 fatty acids. Nerves in the brain are wrapped in a special tissue that largely is made up of omega-3s. These membranes help transfer information, allowing the brain to work at peak efficiency. That is why their importance to mental health begins even before birth. Omega-3s help a baby's central nervous system develop in utero, particularly in the last trimester when brain growth and development is quite rapid--an estimated rate of 250,000 nerve cells per minute. That requires a lot of building blocks.

According to recent studies, children whose mothers have higher blood levels of omega-3 fatty acids bear children who are less hyperactive and have better sleeping patterns. In related research, Seibel relates, mothers who are depleted of the omega-3 fatty acid DHA (docosahexaenoic acid) have a greater incidence of postpartum depression and, in an ecological study of 23 countries, mothers with higher concentrations of DHA in their breast milk and greater seafood consumption experienced a lower incidence of postpartum depression. Over the past few years, there have been at least 20 clinical trials demonstrating that omega-3 fatty acids employed either alone or along with psychiatric medications are useful in combating the symptoms of depression.