In the analysis, scientists also found that many fish oil supplement labels make health claims not backed by science.
Fish oil supplements containing omega-3s like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been the subject of debate among scientists, healthcare providers, and the public. And this is primarily due to claims that fish oil supplements boost heart health.
For example, a 2018 meta-analysis published in JAMA Cardiology found no links between omega-3 fatty acids and cardiovascular disease. In contrast, a 2021 systematic review of research published in The Lancet's eClinicalMedicine revealed that omega-3s reduced cardiovascular mortality and improved cardiovascular outcomes.
Despite the differences in research findings, dietary supplements that contain a daily dose of fish oil, or omega-3s, are one of the most common supplements taken by people in the United States.
Because these products are so popular, scientists from the University of Texas Southwestern Medical Center in Dallas decided to examine the quantity of EPA and DHA in fish oil supplements sold in the U.S. and evaluate health claims appearing on the labels.
The cross-sectional study, published on August 23 in JAMA Cardiology, used February to June 2022 data from the labels of currently available fish oil supplements retrieved from the National Institutes of Health Dietary Supplement Label Database.
First, the scientists looked at 2819 fish oil supplements to see whether the labels made any FDA-reviewed qualified health claims or structure/function claims. Structure/function claims are not pre-approved by the FDA.
Among the supplements reviewed, 74% made at least one health claim. Of these products, only 19% made an FDA-qualified health claim, and 80% made only structure/function claims such as "promotes heart health."
Then, the researchers examined the labels of 255 fish oil supplements from 16 leading brands. They found that the daily dose of EPA and DHA varied substantially, and only 9% contained a daily dose of 2 grams or more of EPA and DHA.
"Only a small minority of supplements contained 2 g per day of combination EPA+DHA, which may be recommended for triglyceride lowering but can also increase risk of atrial fibrillation. No supplements included potential warnings about this risk, although this is not presently required by the FDA," the study authors wrote.
They also say that these findings suggest that many fish oil supplements in the U.S. make health claims not supported by science. Moreover, the differences in daily doses of EPA and DHA found across supplement brands could lead to uneven safety and efficacy between supplements.
In light of these results, the researchers suggest more regulation may be required to ensure consumers are getting correct information about their daily dose of fish oil.
In a statement by The Council for Responsible Nutrition (CRN), Steve Mister, CRN president and CEO, said, "The call for 'additional regulation of dietary supplement labeling' is both predictable and unsupported by the research. Consumers should always discuss their supplement regimens with their healthcare providers, but there is nothing in this study that should dissuade consumers to change their omega-3 regimens for better health." He adds, "Ultimately, this study demonstrates an amazing lack of understanding of the many different reasons why consumers choose to use supplements for better health."
Notably, among the study authors, two report receiving grants from Esperion — a pharmaceutical company focused on developing drugs to reduce cardiovascular risks — and personal fees from Novo Nordisk, Bayer, and others outside and unrelated to this study.
- JAMA Cardiology. Associations of Omega-3 Fatty Acid Supplement Use With Cardiovascular Disease Risks: Meta-analysis of 10 Trials Involving 77,917 Individuals.
- eClinicalMedicine. Effect of omega-3 fatty acids on cardiovascular outcomes: A systematic review and meta-analysis.
- CDC. Dietary Supplement Use Among Adults: United States, 2017–2018.
- JAMA Cardiology. Health Claims and Doses of Fish Oil Supplements in the US.
- The Council for Responsible Nutrition. Response to JAMA Cardiology, Brief Report, 'Health Claims and Doses of Fish Oil Supplements in the US.'