Fish oils are a type of polyunsaturated fatty acid found in moderate to high concentrations in fatty fish, as well as in other foods. Also known as omega-3 fatty acids, fish oils are classified as being essential; meaning that they must be consumed in the diet in order to survive. DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) are two of the omega-3 fatty acids that have received the most attention to date.
Most cold and deep water fatty fish contain significant amounts of DHA and EPA. Among them are anchovy, herring, salmon, mackerel, sardines, trout, swordfish, white (albacore) tuna, and striped bass.
We have known for some time that omega-3 fatty acids help to reduce resting blood pressure, resting heart rate, and blood triglyceride levels in patients who have elevated values. In fact, several years ago the American Heart Association began recommending at least 2 servings of fatty fish a week for the general adult population to help prevent cardiovascular disease.
Omega-3 Fatty Acids and Brain Health
Over the past three decades, many clinical studies have been published regarding the relationship between omega-3 fatty acid intake and brain health. Dr. Joseph Hibbeln was the first to hypothesize that low dietary intake of omega-3’s may increase the risk of depression and other mental health conditions, and that dietary replenishment of omega 3’s may have a role in treating these conditions.
One cause of depression is poor communication between brain cells. Neurotransmitters such as serotonin, norepinephrine, and GABA are important for optimal brain cell communication. DHA is the major polyunsaturated fatty acid found in the cell membranes of brain tissue. It has been established that both DHA and EPA play a role in signal transmission (communication) between brain cells. On the other hand, omega-6 fatty acids such as linoleic acid compete with omega-3’s at the cell membrane. Omega-6 fatty acids are found in high concentrations in corn oil, safflower oil, and soybean oil. The ratio between omega-6 and omega-3 intake is very high in the U.S. diet; and has been estimated at 20:1. It has been suggested that the population decrease their intake of omega-6 fatty acids and increase their intake of omega-3 fatty acids so that the ratio is closer to ~5:1. We will next discuss some studies linking omega-3 fatty acids with brain health, with a primary focus on maternal depression during pregnancy and post-partum.
In a 2007 study, the authors examined per capita fish consumption and rates of depression, postpartum depression, and other psychiatric disorders in several different countries. They found a 30-60 fold higher rate of the previously mentioned disorders in countries with the lowest per capita fish consumption. In countries with high per capita fish consumption, such as Iceland and Japan, lower rates of seasonal affective disorders (SAD) were seen than what was predicted from their latitude.
During pregnancy, it is common for maternal stores of omega-3 fatty acids to decrease because they are being delivered to the fetus. Omega-3 fatty acids play an important role in fetal development of the brain and nervous system. Fish intake during pregnancy in the U.S. is relatively low. To date, several studies have examined maternal fish intake during pregnancy as it relates to perinatal and post-partum depression, as well as baby’s health, development, and subsequent IQ. The results are too impressive to ignore! In a study published in Lancet, maternal fish intake during pregnancy was inversely correlated with perinatal and post-partum depression. In other words, as maternal fish intake increased during pregnancy, risk of depression was significantly decreased. A study published in the American Journal of Clinical Nutrition found that maternal fish intake during pregnancy was positively correlated with normal growth and visual development of the fetus.
In yet another published study, researchers examined 11,875 women and infant pairs in the Avon Longitudinal Study of Parents and Children. Women who had relatively low fish consumption during pregnancy were more likely to have children with suboptimal verbal IQ, as well as suboptimal fine motor development, communications development, and social development at age 3.
These and many other studies prompted the following statement in an issue of the Journal of Clinical Psychiatry: “The majority of studies support a protective effect of EPA and DHA in mood disorders. EPA and DHA have negligible risks and some potential benefit in depressive and bipolar disorders.” The American Psychiatric Association now recommends 2-3 servings of fatty fish per week to help improve mental health.
Safety Concerns Regarding Fish Intake
It is well-established that certain types of fish contain contaminants such as mercury, dioxins, and polychlorinated biphenyls (PCBs). However, the levels of contaminants vary considerably among species. Large, predatory fish such as shark, swordfish, king mackerel, and golden bass (tilefish) contain the highest concentrations of contaminants. The Food and Drug Administration (FDA) recommends that young children and women who are pregnant or nursing eliminate the previously mentioned fish from their diets. However, it is very safe for these individuals to consume up to 12 ounces per week of other types of fish. In fact, the most recent Dietary Guidelines for Americans state that women who are pregnant or breast feeding should consume 8-12 ounces of seafood per week. So the bottom line is that fish oils are not only good for your heart, but for your brain as well!