Ask the cardiologist: Do fish oil supplements reduce the risk of heart disease?

Ann Marie Navar, M.D., Ph.D.
Internal Medicine – Cardiology

If you have a bottle of fish oil pills at home, it’s likely that a claim such as “promotes heart health” appears somewhere on the label.

Many people believe that fish oil supplements are somehow beneficial for their heart. Unfortunately, research does not back that up. Multiple randomized trials have compared fish oil supplements with placebo to look for cardiovascular benefit – and found nothing.

Despite this lack of data for benefit, fish oil use continues to rise. It is the most common non-multivitamin/mineral supplement in the United States. The fish oil market was valued at nearly $12 billion in 2021 and is expected to exceed $17 billion by 2028.

So why do so many people take fish oil?

Research shows that people who eat more fish have lower rates of heart attack and stroke. Similarly, people with high blood levels of two key omega-3 fatty acids – docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) – also have less heart disease. The American Heart Association recommends eating two servings of fish each week to reduce your risk of heart attack and stroke.

Unfortunately, two large, randomized trials of dietary supplements, VITAL and ASCEND, both showed that taking fish oil supplements, which contain a low dose of DHA and EPA, did not lower the rate of heart disease. While there are some legitimate roles for fish oil supplements – studies have suggested they have anti-inflammatory benefits for people with rheumatoid arthritis – the bottom line is there is no proof fish oil supplements improve your heart health.

When do cardiologists recommend omega-3 fatty acids?

Although fish oil supplements don’t lower the rate of heart attack or stroke, they may be recommended in some situations. Specifically, EPA and DHA can be used to help lower triglycerides in people with very high triglycerides (over 500 mg/dL), who are at risk for complications such as pancreatitis. However, the dose of EPA and DHA needed to lower triglycerides is around 2 grams/day, much more than is typically available in fish oil supplements.

In a study presented at the 2022 AHA Scientific Sessions, our team at UT Southwestern evaluated the doses of EPA and DHA for more than 250 fish oil supplements made by the largest 16 largest retailers in the U.S. We found that only 7.1% of supplements contained at least 2 grams of EPA and DHA; the rest had much less than would be effective for triglyceride lowering.

Doctors treating patients with very high triglycerides should be specific with the dose of EPA and DHA recommended, and consumers should be aware of significant variability in dosing between different fish oil products.

Fish oil supplements vs. prescription omega-3 medication

There are two prescription-only preparations of high-dose omega-3 fatty acids available: Lovaza (omega-3-acid ethyl esters) and Vascepa (icosapent ethyl). Both medications are approved by the U.S. Food and Drug Administration (FDA) to treat severely elevated triglycerides, and both have much more omega-3 than is found in supplements and are highly purified and tightly regulated. In contrast, because fish oil supplements are not regulated as tightly as prescription medications, they often contain contaminants or other harmful substances such as saturated fat.

‘Present regulations for fish oil supplements permit manufacturers to make claims that are misleading. Consumers need to know that fish oil supplements do not prevent heart attack or stroke.’Ann Marie Navar, M.D., Ph.D.

Be wary of fish oil supplement labels

While new medications must go through a rigorous testing process created by the FDA to prove they are safe and effective, over-the-counter supplements don’t have to meet these criteria.

Supplements can’t claim to prevent or treat a disease, but they can make structure and function claims, which generally describe the role of a nutrient on the structure or function of the body. For example, “calcium builds strong bones” or “fiber maintains bowel regularity.” In the case of fish oil, structure and function claims typically include statements like “supports heart health” or “promotes brain function.”

Present regulations for fish oil supplements permit manufacturers to make claims that I believe are misleading to consumers. Despite what is commonly printed on the labels, consumers need to know that fish oil supplements do not prevent heart attack or stroke.

Risks of fish oil

High doses of EPA and DHA have been shown to lower triglycerides, and high doses of purified EPA may lower cardiovascular events, but they do come with tradeoffs. Multiple clinical trials have found that particularly at higher doses (4 grams/day), EPA and DHA increase the risk of atrial fibrillation, a heart rhythm disorder that can cause strokes. Because of this, people should talk with their doctor before beginning any high-dose fish oil supplementation regimen and consider the potential benefits against the potential risks.

So, what should people do who are currently taking fish oil supplements? A healthy lifestyle will lower the risk of heart disease far more than fish oil supplements, including regular exercise with a goal of 150 minutes per week and eating a diet low in saturated fats, sugars, and processed foods.

For those at higher risk of heart disease, many evidence-based medications have been shown to lower the risk of heart disease and stroke far more consistently than fish oil supplements. In people with type 2 diabetes, two classes of medications – SGLT2 inhibitors and GLP1 receptor agonists – can help prevent cardiovascular events. In people with high blood pressure, diet and medications can lower long-term risk of heart attack and stroke.

Some of the most effective medications to prevent heart disease, such as statins, are also some of the most affordable. Even without insurance, generic statins are available for under $10 per month, often less than the cost of a month’s supply of fish oil supplements.

We have so many evidence-proven tools to prevent heart disease – but fish oil supplements are not one of them. People looking to prevent heart attack and stroke should make sure to have their blood pressure and cholesterol monitored regularly and talk to their doctor about guideline-recommended treatments.

Benefits of eating foods high in omega-3 fatty acids

The best way to get almost any nutrient, including omega-3 fatty acids, is from a natural source in your diet. Fish high in omega-3 fatty acids are also packed with protein and other nutrients such as vitamin D, calcium, iron, and potassium.

The AHA recommends eating two servings of fish each week. One serving is 3 ounces cooked or about ¾ cup of flaked fish. The types of fish that include the most omega-3 fatty acids are:

• Mackerel
• Salmon
• Herring
• Anchovy

• Whitefish
• Tuna
• Halibut
• Sardines

• Trout
• Striped bass
• Swordfish

• Mussels
• Oysters
• Bluefish

One great way to incorporate more fish into your diet is to follow the Mediterranean diet, which focuses on fruits, vegetables, beans, nuts, and seeds, along with grains, potatoes, and lean meats such as fish and some poultry. A Mediterranean diet can reduce your risk of death from any cause, including cancer and heart disease, by up to 25%.

Some fish do have higher mercury levels than others – usually those that are higher on the food chain, such as king mackerel, swordfish, and tuna. You can still eat these types of fish; just limit how often you enjoy them. Women who are pregnant, however, should avoid fish high in mercury because they increase the risk of birth defects.

If you don’t like fish, you can get omega-3 fatty acids in other plant-based foods, such as:

• Ground flaxseed
• Flaxseed oil

• Chia seeds
• Edamame

• Walnuts
• Canola oil

• Soy oil
• Algae oil