Research over the past 20 years has continued to find the hidden health benefits of omega-3 fatty acids. Omega-3 fatty acids are a type of fat found mostly in seafood. Fatty fish, such as salmon, tuna, and mackerel, are high in omega-3 fatty acids, as are tofu, flaxseed, canola oil, and walnuts. Omega-3 fatty acids are essential for good health and must be consumed in the diet because they cannot be made by the body.

Many studies have found that omega-3 fatty acids can protect against cardiovascular disease by forestalling the accumulation of atherosclerotic plaques in the arteries. In addition, omega-3s have been shown to decrease the risk of arrhythmias (irregular heart beat), which can lead to sudden death.

Some epidemiologic studies have suggested that diets high in omega-3 fatty acids may be associated with a reduced rate of some types of cancer. Smaller studies have attempted to assess the effect of omega-3 intake on cancer risk, but with mixed results. A new study published in the January 25, 2006 issue of the Journal of the American Medical Association searched almost four decades of literature on the subject and failed to find a significant association between omega-3 intake and cancer risk.

About the Study

The study was a review of published and unpublished articles from 1966 to 2005. The researchers combed through more than 1,000 articles relevant to their study topic. They found 38 well-designed studies that described the effect of omega-3 intake on the incidence of 11 different types of cancers (listed in the table below). The size of these studies ranged from 6,000 to 121,000 participants, with a study length of 3-30 years. The amount of omega-3 in the participants’ diets was estimated using dietary questionnaires. Cancer registries were used to assess cancer incidence.


# of studies

Upper digestive tract






















The researchers found no overall trend across the different studies and not enough evidence to suggest an association between omega-3 intake and cancer risk. In fact, breast, lung, and prostate cancer studies suggested both an increased risk and decreased risk. The authors concluded that high consumption of omega-3 fatty acids, either in the diet or through dietary supplementation, is unlikely to prevent cancer.

Although these findings are interesting, there are limitations to this study. The researchers looked at data from 38 different studies. Differences in the characteristics of the populations studied and the methods in which the studies were conducted may limit the ability to interpret the findings collectively. Also, the majority of the studies assessed omega-3 consumption once and assumed it was predictive of the participant’s average diet, which may or may not have been true.

How Does This Affect You?

Based on this study’s findings, should you take an omega-3 fatty acid supplement? Although the findings do not support its use in cancer prevention, the evidence for its benefits against cardiovascular disease is more convincing. If you wish to increase your intake, however, it is best to consume foods rich in omega-3’s rather than take a supplement.

The dietary supplement industry is not regulated like the pharmaceutical industry. Unless you are buying from a reputable company, you cannot be sure that the product actually contains what the label says it does. If you do decide you want to take an omega-3 fatty acid supplement, talk with your doctor first. Also, be aware that higher doses are associated with some unpleasant side effects, such as nausea, bloating, and prolonged bleeding time.