Marine sources of omega-3s are rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the two most frequently studied forms and those that have been most strongly linked to potential health benefits. Plant sources contain higher levels of alpha-linolenic acid (ALA).
Your body absorbs and uses each type of omega-3 in different measures. Most potential health benefits are attributes to EPA and DHA, which are readily absorbed and put to use. Enzymes in your liver convert plant-sourced ALA to EPA, but this process is innefficient. "When you eat plant sources of omega-3, only about five percent is converted to EPA, says Penny Kris-Etherton, PhD, professor of nutrition at Pennsylvania State University. For this reason, many scientific studies use fish and fish oil, which both contain fats composed mostly of EPA and DHA, interchangeably. Use the chart below to monitor your own consumption of omega-3 fatty acids: