Source and Gender Matter for Omega-3s and Heart Health

by Irfan Qureshi, ND

Omega-3 fatty acids work to benefit a number of biological processes in the human body. These include marine-sourced omega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as the shorter chain plant-based form known as alpha-linolenic acid (ALA). ALA is present in significant quantities in the western diet (found in walnuts, flax seeds, soybeans and canola oil). Research has pointed to significant effects of EPA and DHA on enhancing cardiovascular function. Some research has indicated that ALA may have cardiovascular benefits as well. However, other studies have shown no benefits with increased ALA intake. Often, there are conversion issues in the body where ALA is not appreciably converted to the long chain omega-3s in humans. The conversion problem seems to be more of an issue in people who consume higher amounts of fish and marine-based foods in their diet.

Recent studies have started to investigate the differential effects of dietary intake of ALA versus the long-chain omega-3s (DHA and EPA) on heart health. One group investigating these differences hails from the Institute of Preventative Medicine, Aarhus University and the University of Copenhagen. Their recent paper published in The American Journal of Clinical Nutrition describes a prospective trial which followed 3,277 healthy men and women for a median period of 23.3 years. The primary outcome measure was the risk of developing poor heart health associated with a decreased oxygen supply to heart tissue.

Researchers assessed the ALA intake of study participants to determine the effect of increasing intake on heart health. As fish and marine-based foods are not an appreciable portion of the diet in many western countries, and ALA is the main source of omega-3s in many western diets, the theory was that ALA may have beneficial effects on heart health in populations on such diets. The results of the study, however, found no significant enhancements in long-term heart health with increasing ALA intake in this group of individuals.

Another interesting finding from this study was that a high intake of the omega-3 long chain fatty acids (including EPA and DHA) showed a significant cardioprotective effect in women. However, no similar effect of long-chain omega-3s was found in men in the study group. This finding suggests that in addition to differential dietary content and source of omega-3 fatty acids, gender differences may also play a significant part in determining the magnitude of benefit with omega-3 supplementation. Studies exploring these gender-specific effects of omega-3s are merited in order to be able to make more informed decisions regarding supplementation in women versus men. In the meantime, however, given the wealth of research already published in the area of cardiovascular health and omega-3s, it certainly seems prudent for men and women to preferentially supplement with marine-based sources of these fatty acids, including fish oil and krill oil.