Fish oil supplements are a billion-dollar industry built on a foundation of purported, but not proven, health benefits. Now, new research from a team led by a University of Georgia scientist indicates that taking fish oil only provides health benefits if you have the right genetic makeup.
The study, led by Kaixiong Ye and published in PLOS Genetics, focused on fish oil (and the omega-3 fatty acids it contains) and its effect on triglycerides, a type of fat in the blood and a biomarker for cardiovascular disease.
"We've known for a few decades that a higher level of omega-3 fatty acids in the blood is associated with a lower risk of heart disease," said Ye, assistant professor of genetics in the Franklin College of Arts and Sciences. "What we found is that fish oil supplementation is not good for everyone; it depends on your genotype. If you have a specific genetic background, then fish oil supplementation will help lower your triglycerides. But if you do not have that right genotype, taking a fish oil supplement actually increases your triglycerides."
Ye's team, including first author and graduate student Michael Francis, examined four blood lipids (fats) -- high-density lipoprotein, low-density lipoprotein, total cholesterol and triglycerides -- that are biomarkers for cardiovascular disease. The data for their sample of 70,000 individuals was taken from UK Biobank, a large-scale cohort study collecting genetic and health information from half a million participants.
The team divided the sample into two groups, those taking fish oil supplements (about 11,000) and those not taking fish oil supplements. Then they performed a genome-wide scan for each group, testing for 8 million genetic variants to compare. After running over 64 million tests, their results revealed a significant genetic variant at gene GJB2. Individuals with the AG genotype who took fish oil decreased their triglycerides. Individuals with the AA genotype who took fish oil slightly increased their triglycerides. (A third possible genotype, GG, was not evident in enough study volunteers to draw conclusions.)
Determining your genotype is not as far-fetched as it sounds, thanks to direct-to-consumer genetic testing companies. Companies may not report that specific genetic variant yet, but a tech-savvy consumer should be able to download the raw data and look at the specific position to discover the genotype, according to Ye. The ID for the variant is rs112803755 (A>G).
The study's findings may also shed light on previous trials, most of which found that fish oil provides no benefit in preventing cardiovascular disease.
"One possible explanation is that those clinical trials didn't consider the genotypes of the participants," Ye said. "Some participants may benefit, and some may not, so if you mix them together and do the analysis, you do not see the impact."
Now that Ye has identified a specific gene that can modify an individual's response to fish oil supplementation, his next step will be directly testing the effects of fish oil on cardiovascular disease.
"Personalizing and optimizing fish oil supplementation recommendations based on a person's unique genetic composition can improve our understanding of nutrition," he said, "and lead to significant improvements in human health and well-being."
Why do we need these fatty acids?
Omega-3 fatty acids play an important role in brain function, growth and development, and inflammation. They even lower your triglycerides, a component of cholesterol. Deficiencies are associated with a variety of health problems, like cardiovascular disease, mood disorders, and arthritis.
Supplements: Over-The-Counter or prescription?
If you can’t get enough fish oil from your diet, supplements can be purchased over-the-counter or through the pharmacy with a prescription from your doctor. The over-the-counter products contain the same omega-3 fatty acids as the prescription options. The main difference is the concentration in the prescription-only fish oils is higher. This means you will get the same dose in fewer capsules. Additionally, the prescription versions are regulated by the FDA. Over-the-counter products are not regulated by the FDA. If you buy one of these products make sure to look for the USP seal. These medications are of higher quality than over-the-counter medications that do not have the seal.
If you want to hack your nutrition for better health, performance, and recovery, some experts might steer you toward omega-3 fatty acids—a known heart-healthy fat. While you can get these healthy fats in fish and nuts, there’s some speculation about whether getting omega-3s from the diet is sufficient. And that’s where fish oil supplements come into play, helping you meet your needs so you can gain the benefits of omega-3s.
But does this mean fish oil supplements are the best choice for your health and performance? Read on to find out what experts and research have to say about fish oil benefits—and downfalls.
What are fish oil supplements?
Fish oil supplements include two out of three kinds of omega-3 fatty acids—eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—and usually come in the form of a liquid, capsule, or pill.
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EPA and DHA are essential fats that your body needs but can’t necessarily make on its own. That is, unless you consume the third form of omega-3, alpha-linolenic acid (ALA) which is found in nuts, flaxseeds, chia seeds, and some oils, but not in fish oil supplements. If you consume enough of this nutrient, according to the National Institutes of Health, then your body can convert it into small amounts of EPA and DHA. You can also get EPA and DHA in fish, seafood, and supplements.
The caveat about ALA converting to EPA and DHA in your body is that researchers don’t understand exactly how much ALA your body can convert, Jessica Garay, assistant professor in the Department of Nutrition and Food Studies at Syracuse University tells Bicycling. Based on the available research, it falls somewhere between 5 and 10 percent, she says.
“You can consume omega-3’s from non-fish sources like walnuts, and flax seeds. But we can’t assume that that’s going to then meet our daily need for EPA and DHA separately," Garay adds.
And you need these nutrients regularly, because they play such a vital role in your body including in your heart, lungs, immune system, and endocrine system (responsible for hormones).
The other issues is that according to the Dietary Guidelines for Americans, nearly 90 percent of U.S. adults don’t consume enough seafood, and a little more than 50 percent don’t consume enough nuts—two key sources of omega-3s.
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What are the benefits of fish oil supplements?
Originally, Garay explains, researchers began to study omega-3 fatty acids because of the potential benefits it posed to heart disease. “But now we see omega-3s being recommended for all sorts of conditions beyond heart disease,” she says. “Research has shown that consuming omega-3 fatty acids provide anti-inflammatory benefits to the body which can help prevent or manage diseases like diabetes, arthritis, and even cognitive conditions like .”
In terms of cardiovascular health, researchers of recent meta-analysis published in the Journal of the American Heart Association found the optimal intake of omega-3 fatty acids for lowering blood pressure is likely between 2 and 3 grams a day—above 3 grams for those at higher risk for cardiovascular disease. However, researchers included a mixture of studies in this analysis. Some of the research examined both the combination of EPA and DHA, as well as isolated forms of these omega-3s, and other research included in the analysis looked at both dietary intake and supplementation. Bottom line: The researchers of this study didn’t champion either food or supplements as superior.
Also, a 2021 meta-analysis published in eClinicalMedicine suggests EPA has a greater impact on decreasing cardiovascular risk than the combination of EPA and DHA.
Other research points to potential benefits of fish oil supplements for athletic performance. A review published in Nutrients in 2020 state that evidence suggests there are potential benefits of omega-3 fatty acids on performance, like improved endurance, reduced soreness, and enhanced recovery—at least for amateur athletes. However, they do note that clear recommendations about these supplements are hard to come by and put into practice.
“For athletes, when you engage in really intense exercise, whether it’s aerobic exercise or weightlifting exercise, if it’s really intense exercise, you’re going to cause muscle damage as a result of that exercise,” says Garay, who mentions this is why some researchers are focused on omega-3s to help you recover from this effect of exercise. Most researchers note, however, that athletes may need higher amounts of omega-3s to reap these benefits.
What are the downfalls of fish oil supplements?
Supplements aren’t regulated by the FDA in the same way as conventional food and drugs products. Meaning, the FDA doesn’t have authority to approve dietary supplements before they hit the market with the exception for anything that contains new dietary ingredients which have yet to be approved by the administration.
“A general note about all supplements is that they do not have to be proven safe or effective before being sold. With fish oil supplements specifically, there are large variations in quality,” says Garay. Because these products are so loosely regulated, she adds, there can be risk for contamination and concerns for high mercury levels.
To address this issue, look for products that have been tested by a third party like USP or NSF, two leaders in the industry. “Somewhere on the label they'll have the credential from the third party testing company,” Garay says.
Also, consider the source of the fish oil, Garay says. Fish oil supplements made from krill may be purer, and therefore, have lower levels of mercury because they likely don’t consume any other animals. Also, non-fish marine sources like algae, she says can be good options.
Another important takeaway is there’s still no way to know if you’re getting the exact dosages promised on the labels. In some instances, you might be getting less.
In fact, researchers of one study published in the Journal of Food Composition and Analysis tested 48 fish oil supplements on the U.S. market for label compliance and oxidative quality and found just the amounts were off from the label. The majority of the products tested in the study were of good quality. However, 48 percent of products contained less EPA and DHA than what was claimed on the label, while still within the legal range of what’s considered to be safe.
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In terms of performance, Chris McGlory, Ph.D, an exercise and nutrition researcher and assistant professor at Queen’s University’s School of Kinesiology and Health Studies tells Bicycling there aren’t many studies on omega-3s that include cyclists and taking supplements likely won’t impact training for healthy young individuals.
One study spearheaded by McGlory found omega-3 supplementation slowed the decline in skeletal muscle volume for participants who didn’t move much. “There is potential for omega-3 fatty acids to protect against skeletal muscle loss during immobilization in young women, but more work needs to be done,” he says.
To the contrary, he says, “the story is slightly different in older people, particularly in women. Omega-3 supplementation may help during resistance exercise training.” In other words, these supplements may benefit some populations, but not others.
Another caveat to consider when it comes to taking fish oil supplements: Researchers of a review and meta-analysis published in the American Heart Association’s journal Circulation found an association between omega-3 supplementation and atrial fibrillation (irregular and rapid heart rhythm) when participants consumed more than 1 gram of omega-3 supplements.
Finally, eating whole fish and seafood will offer the best source of EPA and DHA, Garay says. “There are many benefits to eating fish or other marine sources beyond the presence of omega-3s. Fish are a good source of protein and iron,” she explains. “Canned fish are often canned with bones, so they can actually provide some calcium, if you’re eating the bones of the fish as well.” You won’t get those extra advantages from supplements.
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The bottom line on fish oil supplements and what to know before taking them
Ultimately, fish oil supplements aren’t meant to be a miracle worker, says Garay. Meaning you need to do more than just take a supplement each day to reap the anti-inflammatory benefits of it.
“If you’re doing things that are separately promoting inflammation in the body—if you’re sedentary a lot, and not being physically active, if you’re consuming a lot of processed foods, and high-fat, high-sugar, high-calorie foods, if you smoke—you can’t just completely offset that by taking the fish oil supplements,” she says.
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Also, you shouldn’t swap out eating fish a couple times a week for a fish oil pill. According to the recent Dietary Guidelines for Americans, people who consume about 2,200 calories each day should aim to eat approximately 9 ounces of seafood each week.
Start by eating 2 to 3 ounces of fish or other seafood about two or three times a week, McGlory suggests. (That’s also the recommendation by the American Heart Association.) Fatty fish like sardines and anchovies are the best sources of omega-3’s, says Garay. But salmon, herring, flounder, and mackerel are good sources as well.
Consult with your doctor or a registered dietitian nutritionist to find out exactly how much omega-3s you’re consuming each week and where your diet is lacking—especially before taking a supplement. You can also ask your doctor for a blood test to scan for omega-3s.
In the end, if you do decide to add a fish oil supplement to your diet, McGlory suggests finding a pill that offers about 250 mg of EPA and DHA per day, which is in line with what the FDA regards as safe. The FDA also recommends consuming no more than 5 grams of EPA and DHA, combined from dietary supplements each day. So if you already eat fish, then you probably don’t need the supplement.
Monique Lebrun Monique LeBrun joined the editorial staff in October 2021 as the associate health and fitness editor. She has a master’s degree in journalism and has previously worked for ABC news and Scholastic. She is an avid runner who loves spending time outside.