Omega-3s are great for your health—but supplements may not be
Fish oil can reduce inflammation and lower cardiovascular disease risk. Yet a growing body of research suggests that supplements may not offer those same benefits.
Science has proven time and again that omega-3 fatty acids, or omega-3s, can be among the most important parts of a well-balanced diet. The studies show that the healthy fats can help lower blood pressure, improve immunity, reduce joint inflammation, support mental health, and even diminish risks of cardiovascular disease and stroke.
But most people aren't getting enough. In fact, research shows that some 95 percent of kids aren't meeting the recommended levels of omega-3s in their diet—and about 68 percent of adults aren't either.
(How omega-3 fatty acids help reduce inflammation.)
To increase intake, one in five people over age 60 is taking a fish oil supplement regularly and countless younger adults are doing so as well—causing the worldwide omega-3s supplement market to be valued at a staggering 8.3 billion dollars.
While omega-3 supplements are helpful for people with certain heart conditions, experts say their benefits remain largely unproven for most people. There’s also compelling research showing that taking fish oil may even cause harm.
Why omega-3 foods are so good for you
The two main omega-3s—eicosatetraenoic acid (EPA) and docosahexaenoic acid (DHA)—provide a wide variety of health benefits through a series of mechanisms that center around reducing inflammation.
The fatty acids also decrease your levels of unsafe triglycerides and limit oxidative stress, which could otherwise cause cell and tissue damage. EPA and DHA improve blood flow as well, “and boost the function of mitochondria—the energy makers in our cells,” explains Daniel Monti, a physician and professor at the Sidney Kimmel Medical College Department of Integrative Medicine & Nutritional Sciences at Thomas Jefferson University.
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(These are some of the best foods to eat to reduce inflammation.)
Getting enough omega-3s starts with eating more fish—especially cold water, oily varieties like salmon, mackerel, anchovies, herring, sardines, and tuna. This is a top reason the American Heart Association recommends eating two servings (about 3 to 4 ounces cooked) of such fish every week.
But fish meat isn't your only natural food option. "People often forget that fish gain the oil we seek by eating plant-based algae," says Andrew Freeman, a cardiologist and director of cardiovascular prevention and wellness at National Jewish Health in Denver.
Other plant-based omega-3 food sources include seaweed, walnuts, edamame (soybeans), flax seeds, chia seeds, and hemp seeds. "Fortified foods like omega-3-enriched eggs and certain dairy products can also provide some omega-3s in the diet," says Amy Goodson, a nutritionist and registered dietitian based in Dallas. Another beneficial omega-3 is known as alpha linolenic acid (ALA), which is found abundantly in canola and soybean oils.
No matter which animal-based or plant-based options you consume, "we know it's preferable to increase omega-3 intake from foods rather than from supplements," says JoAnn Manson, chief of preventive medicine at Brigham and Women's Hospital and Harvard Medical School and the principal investigator of key omega-3s VITAL research.
Why fish oil supplements are not all they’re cracked up to be
Omega-3 properties are most powerful when they come directly from food—which offers a wider array of nutrients and more concentrated amounts of EPA, DHA, and ALA. There’s also a difference in the chemical structure of the fat in whole fish versus extracted fish oil, says Monti; and the manufacturing process can degrade the quality of nutrients in supplements and can even introduce worrisome contaminants.
An even more compelling reason to stick with food over omega-3 supplements? The purported cardiovascular benefits of fish oil supplements remain largely unproven in healthy people. "A lot of people became obsessed with fish oil about two decades back because there was initially some compelling data on improved heart health," says Freeman, "but this data has since been largely refuted."
(5 things you should know before trusting that supplement.)
Indeed, much of this early research relied almost entirely on observational studies that were unable to prove causation. In subsequent randomized controlled trials—where causation can be measured—"supplementation with omega-3 fatty acids have shown no benefits," says Steven Nissen, chief academic officer of the Cleveland Clinic Heart, Vascular, and Thoracic Institute. Many recent randomized trials have even tested fish oil pills against placebos and found no one more beneficial than the other.
This hasn't stopped over-the-counter fish oil supplement brands from touting purported heart-healthy benefits on their bottles though. "Over 20 years ago, the U.S. Food and Drug Administration (FDA) approved a qualified health claim for fish oil that it may reduce the risk of coronary heart disease—but we didn't have the trial data we now do," says Ann Marie Navar, a cardiologist at UT Southwestern Medical Center in Texas.
She explains that the FDA stipulated at the time that its approval was based largely on observational studies and that randomized controlled trials were still needed. "Although subsequent large, well-conducted trials have since been done for omega-3 supplements and shown no benefit on cardiovascular events,” Navar says, “this outdated claim still hasn't been re-reviewed by the FDA.”
An FDA spokesperson tells National Geographic that qualified health claims like this one means they were originally supported by scientific evidence but are not required to “meet the more rigorous ‘significant scientific agreement’ standard required for an authorized health claim.”
To prevent consumers from being misled about the level of science supporting a claim, the FDA official notes that “a qualified health claim is accompanied by a disclaimer or other qualifying language that describes the level of scientific evidence supporting the claim.”
Why caution is warranted when taking omega-3 supplements
Not only has recent research failed to show meaningful heart-health benefits associated with taking fish oil, but randomized control trials have shown that “taking the supplements may actually cause harm,” says Navar.
A 2024 BMJ Medicine study, for instance, found that taking fish oil was associated with a five percent increased risk of stroke and a 13 percent higher risk of atrial fibrillation—a type of irregular heartbeat—in people who don’t suffer from heart disease. A meta-analysis of 36 other studies similarly concluded that omega-3 supplements “are significantly related to coronary heart disease risk.”
While the reasons for the increased risk remain unclear, one leading theory is that omega-3s may change mineral currents in heart tissue that could be causing the unwanted arrhythmia.
Omega-3 supplements also have the disadvantage of not being regulated by the FDA the same way food and drugs are. This has opened the doors for some lower-quality fish oils “to contain large amounts of filler oils with minimal omega-3s,” cautions Goodson. Other brands, adds Freeman, may contain heavy metals or other toxins– “you just never know.”
Taking too much fish oil can also “lead to unwanted side effects such as blood thinning, excessive bleeding, digestive discomfort, and even immune suppression,” says Goodson.
Another factor to consider is that fish oils can go rancid through oxidation, Monti explains, which can ultimately damage cells the body and can contribute to any number of inflammatory and digestive conditions or issues. Indeed, in a 2023 Journal of Dietary Supplements study, researchers looked at 72 of the most popular fish oil brands and found that 45 percent of them tested positive for rancidity—with many containing added flavoring that masked the rancid taste.
Such concerns are why “we're long past the point where just anyone should feel the need to take over-the-counter fish oil,” says Freeman.
How to choose the best omega-3 supplements
Still, people with certain medical conditions or dietary restrictions may need to take fish oil supplements as the BMJ research and other studies have found that, paradoxically, fish oil supplements can still benefit people with certain heart conditions. Fish oil is also sometimes recommended to help prevent pancreatitis in people with very high triglycerides, Navar says.
But when supplementation is needed, "nearly every doctor will recommend a prescription version of fish oil over underregulated over-the-counter ones," says Freeman.
Anyone choosing to navigate the world of over-the-counter omega-3 supplements without a prescription can still take steps to protect themselves. "When choosing supplements, look for those with independent certification such as ConsumerLab.com, NSF International, and U.S. Pharmacopeia (USP)," recommends Alice Lichtenstein, director of the cardiovascular nutrition team at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University. Such nonprofit organizations, she explains, "regularly test and certify different supplements, including fish oil."
Monti says it’s also important to pay attention to sell-by dates and to store fish oil supplements in a cool, dark environment to prevent oxidation.
In the end, "omega-3s are an important nutrient to overall health and longevity, but it's best to get them from the diet," he says. "Supplementation may be warranted, but it’s a nuanced process that should be carefully guided by your healthcare professional."
