Omega-3 (n-3) fatty acids generally refer to the nutritionally essential polyunsaturated fatty acids (PUFAs) alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Fatty acids are the building blocks of lipids, making them important sources of energy for the body and the main components of cell membranes 1. There are a number of known health benefits associated with omega-3 fatty acid intake, with most current research focusing on the longer chain n-3 PUFAs EPA and DHA. However, the human body cannot synthesize n-3 fatty acids on its own, and so these nutrients must be provided by the diet 1. Food sources of ALA include flax seed, hemp seed, walnut, canola, soy bean, and dark green leaves, while the major sources of EPA and DHA are algae and cold-water oily fish, such as salmon, herring, mackerel, anchovies and sardines 2.
Dietary unsaturated fatty acids are well absorbed through the intestine and into the bloodstream. The Institute of Medicine has established an adequate intake of 1.6 g/day ALA for men and 1.1 g/day ALA for women 1. The body can form EPA and DHA from ALA, but the low rate of conversion supports direct dietary intake of EPA and DHA. The U.S. Food and Drug Administration (FDA) has determined that the use of EPA and DHA omega-3 fatty acids as dietary supplements is safe, provided that the daily intakes of EPA and DHA do not exceed 2 grams per day from dietary supplement sources such as fish oil 3. A major safety concern is the possible presence of heavy metals and toxins, which can be found in relatively high levels in fresh fish and unpurified fish oils. When considering omega-3 EPA and DHA dietary supplements, it is important to look for fish oils that have been purified to reduce the levels of these contaminants.