Previous research on the health benefits of eating fish, fish oil supplements, and other sources of omega-3 fatty acids has shown mixed results, with some studies revealing cardiac health benefits and others finding no benefit. However, when looking at recent studies separating eating foods rich in omega-3 fatty acids versus taking supplements, it appears that eating foods has various beneficial health effects, while taking a supplement may not find health benefits (here and here).
The latest research (reported in the journal JAMA Internal Medicine) looked at heart disease events (heart attack, cardiac related death) and actually measured the actual levels of omega-3 fatty acids in the participants' blood, as opposed to relying on questionnaires in which people report what they eat. The new study could not assess the usefulness of taking fish oil supplements, as opposed to eating fish, because so few people in the study took supplements. Thus the findings were generally from eating a diet rich in omega-3s from either fish or plant-based sources. (Note: By far the best source is fish. Some plant-based sources are: flaxseed, walnuts, edamame, black beans, kidney beans).
The new study — which combined 19 studies from 16 countries with more than 45,000 participants — found that higher circulating blood levels of omega-3 fatty acids were associated with a nearly 10 percent lower risk of a fatal heart attack, on average, compared with lower levels. The participants with the highest level of omega-3s in their blood had the greatest risk reduction — a more than 25 percent lower risk of having a fatal heart attack, the study found.
From Science Daily: Consumption of omega-3s linked to lower risk of fatal heart disease
A global consortium of researchers banded together to conduct an epidemiological study analyzing specific omega-3 fatty acid biomarkers and heart disease. They found that blood levels of omega-3 fatty acids from seafood and plant-based foods are associated with a lower risk of fatal heart attack.
A total of 19 studies were involved from 16 countries and including 45,637 participants. Of these, 7,973 people developed a first heart attack over time, including 2,781 deaths and 7,157 nonfatal heart attacks.
Overall, both plant-based and seafood-based omega-3s were associated with about a 10 percent lower risk of fatal heart attacks. In contrast, these fatty acids biomarkers were generally not associated with a risk of nonfatal heart attacks, suggesting a more specific mechanism for benefits of omega-3s related to death."At a time when some but not other trials of fish oil supplementation have shown benefits, there is uncertainty about cardiovascular effects of omega-3s," said Mozaffarian. "Our results lend support to the importance of fish and omega-3 consumption as part of a healthy diet."
Fish is the major food source of omega-3 fatty acids, including eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA). According to the U.S. Department of Agriculture's National Nutrient Database, fatty fish such as salmon, trout, anchovies, sardines, and herring contain the highest amounts of omega-3 fatty acids, although all fish contain some levels. In addition to omega-3 fatty acids, fish provide specific proteins, vitamin D, selenium, and other minerals and elements. Alpha-linolenic acid (ALA) is the plant-based omega-3 fatty acid found in walnuts, flaxseed oil, and canola oil and some other seed and nuts and their oils.