When You Take Fish Oil Every Day, This Is What Happens To Your Cholesterol

Fish oil is one of the most popular supplements among people in the United States. According to the Centers for Disease Control and Prevention, more than one in five adults over 60 and one in six adults ages 40 to 59 take fish oil. Fish oil's popularity is understandable when you consider the many health claims made on fish oil supplement labels. A 2023 article in JAMA Cardiology found that most fish oil supplements claim to support heart health, yet fewer than 20% of them used a health claim approved by the Food and Drug Administration (FDA). Currently, the FDA has only approved qualified health claims regarding fish oil's effects on blood pressure and coronary heart disease.

Do you take fish oil to help lower your cholesterol? About 5% of fish oil supplements claim to "support" healthy cholesterol or lipid metabolism, but that may be somewhat misleading. Among the 47 studies reviewed in a 2009 meta-analysis in the International Journal of Cardiology, fish oil supplementation does not affect total cholesterol, LDL cholesterol, or HDL cholesterol. Fish oil supplements may reduce triglyceride levels, depending on the dosage. However, the relationship between fish oil and cholesterol is rather complex.

Not all fish oil supplements are the same. Look closely at your supplement label for two key types of omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA may help improve mood and reduce inflammation, while DHA is essential for brain function and development. The amounts of EPA and DHA can vary between fish oil products, and this may influence how the supplement affects your blood lipids.

A 2012 review in the Journal of Clinical Lipidology found that DHA may have a stronger impact on cholesterol and triglyceride levels. While DHA can lower triglycerides, it may also raise LDL ("bad") and non-HDL cholesterol. However, DHA tends to raise HDL ("good") cholesterol more than EPA. Because many clinical trials use different ratios of EPA and DHA, it's difficult to draw broad conclusions about how fish oil supplements affect cholesterol overall.

A 2023 review in the Journal of the American Heart Association noted that the ratio of EPA to DHA can lead to different effects on cholesterol and triglycerides. In general, 2 grams of fish oil per day can reduce triglycerides by about 43 points, while 3 grams may lower them by around 69 points (here's how much fish oil you should take daily). People with obesity or heart disease saw more of the triglyceride-lowering effects. Fish oil supplements have inconsistent effects on LDL cholesterol but may slightly increase HDL cholesterol.

The Dietary Guidelines for Americans recommend eating fatty fish twice a week for its protein, vitamins, minerals, and essential omega-3 and omega-6 fatty acids. While fish oil supplements contain omega-3s, the FDA notes that they may not offer the same health benefits as eating whole fish. (Here are some other foods you should eat if you want to get more omega-3.)

A 2017 study in Nutrition and Diabetes compared fish oil supplements to eating fish. One group took 2 grams of fish oil daily, while the other ate trout twice a week. A cooked trout fillet contains about 1.4 grams of omega-3s. After 8 weeks, the trout group had greater reductions in total cholesterol, LDL cholesterol, and triglycerides, along with a bigger increase in HDL cholesterol. In contrast, the fish oil group experienced a slight increase in LDL cholesterol.

So, should you stop taking fish oil? Not necessarily. Fish oil supplements may still benefit people who don't eat much fish. A 2019 study in the New England Journal of Medicine followed more than 25,000 adults over age 50 to evaluate the effects of vitamin D3 and fish oil on heart disease and cancer. While fish oil didn't prevent either condition overall, the fish oil supplement was linked to a 28% lower risk of a heart attack. Among people who rarely ate fish, the fish oil supplement reduced the risk of a major cardiovascular event by 19% and a 40% lower risk of heart attack. People who had two or more heart disease risk factors had a 44% lower risk of a heart attack when they took a fish oil supplement.