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Fish oil supplement claims often vague, not supported by data

UT Southwestern researchers say product labels with broad statements can be misleading to consumers

Front view of many fish oil capsules spilling out from the bottle surrounded by an assortment of food rich in omega-3 such as salmon, flax seeds, broccoli, sardines, spinach, olives and olive oil.
For most people, there is no cardiovascular benefit in taking over-the-counter fish oil supplements even though their labels often contain health-related claims. (Photo credit: Getty Images)

DALLAS – Aug. 30, 2023 – Your daily dose of omega-3s may not be doing what you think it is. Most fish oil supplements on the market today have labels boasting health benefits that aren’t supported by clinical data, according to a study published in JAMA Cardiology by researchers at UT Southwestern Medical Center.

“About 1 in 5 Americans over the age of 60 take fish oil supplements, often because they think it is helping their heart,” said Ann Marie Navar, M.D., Ph.D., Associate Professor of Internal Medicine in the Division of Cardiology and a member of the Peter O’Donnell Jr. School of Public Health at UT Southwestern, who led the study. “But extensive research has shown that for most people, there is no cardiovascular benefit in taking over-the-counter fish oil supplements, and at high doses, they can even increase the risk of atrial fibrillation.”

Ann Marie Navar, M.D., Ph.D.
Ann Marie Navar, M.D., Ph.D., Associate Professor of Internal Medicine in the Division of Cardiology and a member of the Peter O'Donnell Jr. School of Public Health at UT Southwestern, led the study.

Researchers analyzed data from fish oil supplement labels obtained from the National Institutes of Health Dietary Supplement Label Database. Of the 2,819 labels studied, 2,082 (73.9%) made at least one health-related claim. 

The majority of supplements with a label making a health claim (80.3%) used what is called a structure/function claim, which is intended to describe in broad terms the effect of the nutrient on a body system.

“Structure/function claims are allowed by the FDA, but they can be vague and misleading,” said Dr. Navar, a board-certified cardiologist. “And they are being made for fish oil for a broad number of organ systems, including for the heart, brain, joints, eyes, and immune system. Structure/function claims can include statements like ‘supports cognitive health’ or ‘supports healthy joints.’ Technically, these cannot be used to claim that the supplement treats or prevents a disease, but we feel that this type of language can be very confusing to consumers who may be unaware these statements do not require support from randomized trials.”

Researchers also compared the amounts of two key omega-3 fatty acids – eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) – in 255 fish oil supplements from 16 leading brands. In certain patients with very high triglyceride levels (above 500 milligrams per deciliter), these omega-3 fatty acids can be used to lower triglycerides, but a daily dose of 2 grams or more is required.

The study showed that only 24 (9.4%) of the 255 supplements contained a daily dose high enough to lower triglycerides. In addition, there was significant variability in the dosage of EPA and DHA across brands.

Joanna Assadourian
Joanna Assadourian, a fourth-year UT Southwestern medical student, is the study's first author.

“Triglyceride lowering on its own does not prevent heart disease, but some people with very high triglycerides at risk for pancreatitis may be recommended to take fish oil,” Dr. Navar said. “In this case, doctors should be specific about the dose of omega-3 recommended, and patients should read the labels carefully to be sure they’re getting the right amount.”

The study suggests that stricter regulations on dietary supplement labeling may be needed to prevent consumer misinformation. 

“Supplement labels can be confusing even for the savviest consumers,” said Joanna Assadourian, the study’s first author and a fourth-year UT Southwestern medical student. “Patients should talk to their doctor about what supplements they are taking and why they are taking them – they may be surprised to learn they are not getting the health benefits they think they are.”

Other UTSW researchers who contributed to the study are Eric D. Peterson, M.D., M.P.H., Professor of Internal Medicine; Samuel A. McDonald, M.D., M.S., Assistant Professor of Emergency Medicine; and Anand Gupta, M.B.B.S., M.P.H.

Dr. Peterson serves as Vice Provost and Senior Associate Dean for Clinical Research and Vice President for Health System Research. He holds the Adelyn and Edmund M. Hoffman Distinguished Chair in Medical Science at UTSW. 

About UT Southwestern Medical Center  
UT Southwestern, one of the nation’s premier academic medical centers, integrates pioneering biomedical research with exceptional clinical care and education. The institution’s faculty has received six Nobel Prizes, and includes 26 members of the National Academy of Sciences, 19 members of the National Academy of Medicine, and 14 Howard Hughes Medical Institute Investigators. The full-time faculty of more than 2,900 is responsible for groundbreaking medical advances and is committed to translating science-driven research quickly to new clinical treatments. UT Southwestern physicians provide care in more than 80 specialties to more than 100,000 hospitalized patients, more than 360,000 emergency room cases, and oversee nearly 4 million outpatient visits a year.