Why Are Fish-Oil Pills Supposedly Good for Me?

Photo-Illustration: by Preeti Kinha; Photos: Getty

Recently a woman approached my friend at the dog park to suggest that she feed her dog more Omega-3s, specifically in the form of sardines. Another friend takes fish-oil pills (another name for Omega-3 supplements), and a third friend claims her cat’s dandruff disappeared after she started squirting fish oil into her food. I buy eggs fortified with Omega-3s, although I’m not completely sure why. Snake oil — actual snake oil, made from the fat of Chinese water snakes — was, and is, an effective treatment for arthritis and bursitis, likely because of its Omega-3 content.

Found most abundantly in fish and marine life, Omega-3s are a type of fatty acid chains (the basic building blocks of the fat in our diet) generally thought of as heart-healthy and anti-inflammatory. In the human diet, Omega-3s have also been linked to reduced irregular heart rhythms and lower triglyceride levels. In supplement form, however, the benefits of Omega-3s have been harder to prove or demonstrate.

Earlier this year, Harvard T.H. Chan School of Public Health epidemiology professor JoAnn Manson and her team published the results of a five-year study on Omega-3 supplementation in the New England Journal of Medicine. Called VITAL, Manson’s study (which also tracked longer term Vitamin D supplementation) aimed to determine how Omega-3 supplementation affected human rates of disease, in a nationwide trial of nearly 26,000 men and women, midlife and older.

Although Manson’s study found that Omega-3 supplementation did not appear to significantly affect the overall incidence of disease, there were significant findings within subgroups: Among people who didn’t eat fish, taking an Omega-3 supplement was associated with a 40 percent lower likelihood of heart attack (and a 19 percent lower likelihood of having any kind of cardiovascular event); among all participants, taking an Omega-3 supplement was associated with a 28 percent lower likelihood of heart attack; and among African-Americans, regardless of their fish consumption, taking an Omega-3 supplement was associated with a 77 percent lower likelihood of heart attack.

I spoke with Manson about what qualifies as low fish intake, who — if anyone — might stand to benefit from taking fish-oil pills, and whether to keep buying Omega-3-enriched eggs (short answer: probably not).

My understanding is that fish provide the best source of Omega-3s, but are foods like walnuts and avocados also good sources of Omega-3s?
Yes. In addition to fish-derived Omega-3s, which are called EPA and DHA — eicosapentaenoic acid and docosahexaenoic acid, which are easiest for the human body to use — there are also plant-derived Omega-3s, such as ALA, or alpha linolenic acid, which can be found in vegetable oils, walnuts, and other plant-based sources. But those ALA Omega-3s are harder for the human body to use, compared to marine-source Omega-3s. Then there are also algae-based Omega-3s, and some of the ALA there does get converted to EPA and DHA, which are, again, the main marine forms of Omega-3.

In your study, the people who didn’t eat fish seemed to benefit the most from taking Omega-3 supplements. Whereas the fish-eaters seemed to be covered, for the most part — almost like there’s an internal quota met by naturally eating fish. 
Right. We tested supplementation with one gram of Omega-3s a day — this contained both EPA and DHA forms of Omega-3s, with the ratio of EPA to DHA being 1.3 to 1.

But yes, it appears there may be a threshold: If you’re already getting one-and-a-half servings of fish per week, or more, you may not get a significant benefit from taking Omega-3s. Whereas if you have lower intake than that, you appear to benefit — to have cardiovascular benefit from the Omega-3 fish-oil supplement.

Is two servings of fish a week a good amount?
Yes. Fish and seafood with the highest levels of Omega-3s include salmon, trout, sardines, mussels, and tuna.

So for people who don’t eat fish, supplementation could be worth considering. 
I would still recommend people try to increase fish consumption to two servings of fish per week, before supplementation, but people have been hearing that recommendation for a long time, and some people just don’t like fish, and so they don’t eat fish.

The advantage of doing it through the diet — increasing fish intake — is that a fish meal also replaces less healthful foods, such as red meat and processed foods, in addition to providing the valuable marine Omega-3s. But if someone is not going to eat fish, I think there’s reason for them to talk with their health-care provider about whether they’re a candidate for taking a fish-oil supplement.

What about vegetarians or people who otherwise don’t eat fish, including fish-oil pills? 
If they’re allergic to fish, or they’re vegetarian, they can take an algae-based supplement.

Also, African-Americans, especially if they’re at increased risk of heart disease, may want to talk with their health-care providers about whether they could benefit from a fish-oil supplement.

Your study found that among African-Americans, taking a fish-oil pill — the Omega-3 supplement — was associated with a 77 percent reduced likelihood of having a heart attack. That seems huge.
Right. More research on that is needed, and we hope to look further into these issues. African-Americans in the study also had a lower rates of Omega-3s, regardless of their fish intake.

What do you think makes people more or less inclined to adopt new dietary behaviors, in general? 
I think that some people have become skeptical of health-related claims. Certainly there are many supplements on the market that have made unsubstantiated claims about benefits. There have also been some flip-flop messages about diet and nutrition, that people can fall back on as a reason not to make difficult behavioral changes.

But I think that the fundamental principles of diet have been borne out over time: Having a diet that’s high in fruits and vegetables, predominantly plant-based, higher in fish, lower in red meat, higher in the polyunsaturated rather than saturated or trans fat — I think the evidence that eating this way is healthful is quite strong and has stayed consistent for many, many years.

But regarding fish, in particular — some people just don’t like it. And they’re not going to eat it, and they may be the ones who would benefit the most from an Omega-3 supplement. They may want to discuss that with their health-care provider.

What does your own diet look like? 
I eat a lot of fish. I really like fish. I have probably three servings a week or more.

Do you have favorites? 
I like salmon. I like herring. Sardines. I like cod, I like some of the fish that aren’t normally thought of as dark fish as well. I like shrimp. I pretty much like all seafood.

A recent Johns Hopkins meta-analysis on dietary supplements found that the “vast majority of dietary supplements don’t improve heart health or put off death.” But they did find that among certain studies of Omega-3 supplementation, there was a modest benefit.
Recently there’s been a reversal of fortune for the Omega-3s, in terms of several of the recent studies suggesting benefit, which affects the updated meta-analyses. Close to a year ago, the meta-analyses were showing minimal if any reduction in cardiovascular events, in the Omega-3 randomized trials. Over the last year, there have been three trials that have shown some benefit, even though the benefits are not seen across the board for all cardiovascular endpoints.

But our study, VITAL, showed the significant reduction in heart attack and overall coronary benefits associated with Omega-3 supplementation. Another study, the ASCEND trial, which was a large trial in participants with diabetes, showed a significant reduction in vascular death, and the REDUCE IT trial, which tested a high dose, EPA-only Omega-3 supplement, showed very substantial benefit, for a wide range of cardiovascular outcomes.

In aggregate, the research is now revealing at least a small benefit of the Omega-3 supplements for heart health, and it’s interesting because low-dose aspirin is falling into disfavor for people who don’t already have a history of cardiovascular disease. And it’s quite plausible that the Omega-3 fatty acid supplements will begin to fill that void, providing benefits. It may be an intervention that could be considered for people who are at high risk of cardiovascular disease but are not candidates for aspirin.

Aspirin is associated with a fairly high risk of bleeding, and the bleeding risk can offset the benefits. Whereas the Omega-3 fatty acids have minimal bleeding risk, or risk of other adverse events. In fact, in VITAL, we found that taking one gram a day was quite safe: It did not increase the risk of bleeding or of gastrointestinal symptoms or disorders.

Are eggs fortified with Omega-3s worth spending extra money on? 
In fortified eggs, some do have the “good,” more easily usable Omega-3s — the EPA and DHA. It’s just usually a really small amount.

With food products that say “Omega-3-fortified,” you have to look closely to see if they’re fortified with the marine Omega-3s, specifically — EPA, DHA — or if it’s with ALA. There is some conversion of ALA to the long-chain EPA and DHA, but it’s a small amount.

Generally, I think it’s better to get the marine Omega-3s from fish. Walnuts have large amounts of ALA, and so do some other plants and nuts, but I don’t think it’s critically important to look for fortified foods.

If someone were choosing an Omega-3 supplement, what criteria should they use? 
There are some prescription products that are FDA-approved, and those go through very rigorous quality-control testing. There’s Lovaza and Vascepa, for instance, in the United States.

If you’re getting it over the counter, you want to look for signs of quality control on it, such as approval from U.S. Pharmacopeia, the U.S. Pharmaceutical Corporation, the National Science Foundation, and Consumer Lab, or some mention of independent testing for quality, because some of the products can have problems. They can have lower amounts of EPA and DHA than you’re expecting, for instance, and they can become oxidized. They also can contain contaminants. But there are reputable and reliable products on the market. I don’t want to promote any particular brand, though.

Do you take any supplements?
Well, because I have moderate fish consumption, I would not expect to benefit from supplementation. At least not from a moderate dose of Omega-3s, like the one-gram dose. So right now, no. I try to get it from diet.

Why Are Fish-Oil Pills Supposedly Good For Me?