Over-the-counter fish oil supplements account for nearly $1 billion in sales in the US, with over $4 billion spent on products fortified with omega-3 fatty acids. And it’s no wonder: Omega-3s have long been touted as treatments for everything from postpartum depression to heart disease to dry eyes. But recent studies have questioned some of the fatty acids’ purported positive health effects. Here’s a look at the benefits and some of the controversy surrounding omega-3s.
Also known as n-3 fatty acids, omega-3 refers to a group of three essential fats known as ALA, EPA, and DHA. These fats are considered “essential” fatty acids because while human bodies don’t produce them naturally, they’re required for an array of functions like preventing excessive blood clotting and building cell membranes in the brain. This means the only way to get omega-3 fatty acids is through diet (mackerel, tuna, salmon, and anchovies are especially rich sources) or supplementation. Omega-3s can be found packaged on grocery shelves in the form of fish oil, flaxseed oil, and hemp oil.
Experts don’t yet have enough evidence to agree on one specific daily amount of omega-3 fatty acids for everyone, but the American Heart Association (AHA) suggests adults consume two eight-ounce servings of fatty fish per week. Women who are pregnant, may become pregnant, or are nursing should eat no more than 12 ounces of low-mercury fish weekly. There is no official recommendation regarding plant-derived sources of omega-3s like flax, walnuts, and canola oil.
As for supplements, the AHA recommends consuming no more than three grams of omega-3 fatty acids from capsules daily, unless otherwise instructed by a physician. The AHA also recommends that people with elevated levels of triglycerides (a type of fat in the blood that can increase the risk for heart disease at high levels) consume two to four grams of EPA plus DHA daily in capsule form under a doctor’s care.
The Good News
Many studies over the years have presented strong evidence linking omega-3s to various health benefits. Research has shown that omega-3s may lower triglycerides, reduce blood pressure, ease symptoms of rheumatoid arthritis, lower levels of cholesterol, and more.
Some studies have suggested that omega-3 fatty acids may improve depression, and while more research is required, other studies have found links between high omega-3 consumption and a lowered risk of developing neurological disorders like Alzheimer’s.
A recent report in the British Medical Journal found that higher consumption of marine n-3 fatty acids was associated with a lowered risk of breast cancer. The effect was most pronounced in Asian populations, but the investigators found no association between fish intake and breast cancer-the benefit was only associated with supplement use. The authors suggest that some other elements, like pesticides, present in the fish, may have been responsible for that difference.
While plenty of research has suggested associations between omega-3 intake and various health benefits, two recent studies have indicated some of the fatty acids’ limitations. A report in the New England Journal of Medicine failed to demonstrate any benefit on heart health in participants with at least four risk factors for cardiovascular disease (like being over 65 years old or being a smoker) who took a daily dose of fatty acids.
Another report in the Journal of the National Cancer Institute found that men with the highest levels of omega-3 fatty acids in their blood had a 43 percent increased risk of prostate cancer. More importantly, the study found that these men had a 71 percent increase in aggressive prostate cancer that can prove fatal.
What This Means for You
The follow-up period in these studies was relatively short (in most cases, no greater than three years), and is probably insufficient to demonstrate a meaningful effect. The prostate cancer study, for example, demonstrated only an association, not a proven causal relationship. Studies of longer duration will help shed more light on the topic, but in the absence of more information, if you have questions about starting or continuing omega-3 supplementation, talk to your health care provider.