Are fish oil supplements good or bad for you? 8 things experts want you to know.

We’ve all long heard that fish oil is good for heart health, which is why millions of Americans, including 1 out of every 5 people over age 60, gulp back these golden capsules every day without a second thought. The intention is good: Fish oil contains omega-3 fatty acids, which are essential for bodily functions such as energy, blood circulation, hormone production and more.

While they’re naturally found in fatty fish such as mackerel, wild salmon and herring, many people take fish oil supplements since they’re an easy way to ensure that you’re getting enough of the important nutrient. However, mounting research is calling into question whether fish oil supplements are beneficial and if, in some cases, they cause more harm than good.

Before you start cleaning out your vitamin cabinet, however, here’s what you need to know about fish oil supplements.

Fish oil may benefit people at higher risk of Alzheimer's disease

A new study in JAMA Network Open that looked at how fish oil affects brain health in those 75 and older found that the supplement may be protective in people with a higher risk of developing dementia. The study didn't find a significant benefit for all older adults in general, but in study participants who also had the APOE4 gene — which is linked to a higher risk of developing Alzheimer’s disease — fish oil helped reduce the breakdown of nerve cells in the brain. Researchers called the results "remarkable."

They may increase heart health risks in healthy people

A new study published on May 21 in BMJ Medicine found that fish oil supplements, namely over-the-counter ones, may potentially be harmful in some people. The study followed 415,000 people ages 40 to 69 over the course of 12 years, one-third of whom used fish oil supplements. The researchers found that participants who didn't have a heart condition and took fish oil experienced a 13% increased risk of developing atrial fibrillation, an irregular heartbeat that's linked to heart-related complications. Healthy participants taking fish oil also had a 5% higher risk of having a stroke.

On the other hand, the study found that fish oil was linked to a 15% lower risk of atrial fibrillation in those who already had heart disease.

Most health claims on fish oil supplements are unfounded

A 2023 study analyzed the labels of more than 2,800 fish oil supplements and found that 2,082 — nearly 74% — made at least one health claim, most of which pertained to heart health. Of those, only 399 (19.2%) used a health claim that was supported by scientific evidence. The study also found “substantial variability” in the dosage of omega-3s in the supplements researchers tested.

“I see patients in clinic all the time taking fish oil with the belief it is helping their heart,” study co-author Dr. Ann Marie Navar, associate professor of medicine at the University of Texas Southwestern Medical School, previously told Yahoo Life. “They are often surprised when I tell them that randomized trials have shown no benefit for fish oil supplements on heart attacks or strokes.”

Many over-the-counter formulas are rancid

A 2023 study that tested 72 over-the-counter fish oil supplements over a six-year period found that the majority of them were rancid by the time they reached consumers’ cabinets. How so? In the time between production and consumption, they oxidized (were exposed to too much oxygen) and became unstable, Michelle Routhenstein, preventive cardiology dietitian at EntirelyNourished.com, who was not involved in the study, tells Yahoo Life.

Not only is that a bad deal, taking oxidized supplements “can potentially increase LDL cholesterol levels, negatively contributing to heart health,” Routhenstein says. If you’re wondering about the safety of a fish oil supplement you take, she says it may be rancid “if it has a fishy odor, or if digestive discomfort takes place after consuming it, such as burping, indigestion or diarrhea.”

In general, it’s best to store fish oil supplements in a cool, dry, dark place. You can even freeze them. According to the Arthritis Foundation, that not only helps them last longer but also allows fish oil to be digested more slowly, reducing any aftertaste.

Fish oil helps improve triglyceride levels and reduces inflammation

Not all fish oil supplements are potentially problematic. Taking high-quality fish oil can help lower triglyceride levels — a type of fat found in the blood that raises heart disease and stroke risk. Fish oil also helps lower inflammation. According to the Arthritis Foundation, research shows that it significantly reduces pain and morning stiffness in people with rheumatoid arthritis, which is an inflammatory autoimmune disease. That said, “the benefits versus risks need to be assessed and recommended on an individualized basis,” says Routhenstein.

They can interfere with certain medications

Fish oil supplements can potentially interfere with blood-thinning medications “such as aspirin, coumadin or Plavix, increasing the risk of excessive bleeding,” notes Routhenstein. So it’s important to speak with your health care provider before taking fish oil or any other supplements.

You’re better off getting omega-3s from food

While research indicates that fish oil supplements don’t lower the risk of heart disease, people who eat seafood rich in omega-3s one to four times a week are less likely to die of heart disease, according to the National Institutes of Health.

“As a general guideline, a daily consumption of 500 milligrams of EPA and DHA is recommended for optimal health and cardiovascular well-being,” says Routhenstein, adding that the fish highest in those nutrients are sardines, salmon, trout and mackerel. If you’re vegetarian, vegan or have seafood allergies, “it may be beneficial to supplement,” she adds, because plant-based sources of the nutrient are limited — but they can be found in walnuts and flaxseeds.

Doctors can prescribe fish oil for some patients

Prescription versions of fish oil are more potent than over-the-counter pills and are considered safer, but they’re also more expensive. They may be recommended by doctors for patients who need them, such as those with very high triglyceride levels. “It is best to consult with your health care team, including your registered dietitian who specializes in heart disease, to assess the risks versus benefits,” Routhenstein says. “If a supplement is recommended, individualized dosing and sourcing it from a reputable brand and dispensary is important to ensure effectiveness… and potency.”

This article was originally published on May 31, 2024 and has been updated.