About 20 percent of older adults take fish oil supplements for their heart health or to boost their overall wellbeing. A recent report suggests, however, that the claims on most of the labels on these products are not supported by evidence from reliable scientific trials, making fish oil the new snake oil.

Researchers came to this conclusion after analyzing the contents of over 2,800 supplement labels taken from the National Institutes of Health Dietary Supplement Label Database.

The University of Texas Southwestern Medical Center team specifically reviewed how often claims concerning cardiovascular health — including blood pressure — and other benefits such as immune system, mood and nervous system heath, were promoted on the labels of fish oil supplements.

Fish oil supplement labels often imply a wide range of unsubstantiated health benefits — including the ability to help the health of the heart, brain and eyes.

Nearly 75 percent of fish oil supplements made at least one health claim on their labels, most often about their ability to promote cardiovascular health. But only a quarter of the supplements with health claims used FDA-approved language that would have made it clearer to consumers that the claims on their labels were not backed by scientific evidence.

There's a good reason why this information is not included on the labels of fish oil supplements. Fish oil supplements are a multibillion-dollar industry. People take them, often daily, because of their belief that omega-3 fatty acids are good for their heart and general health, so companies selling fish oil products are not motivated to remove labels falsely promoting their products' effectiveness.

The misconceptions surrounding fish oil supplements come from studies showing that people who eat seafood regularly are less likely to die of heart disease because of the healthful fatty acids in fish.

But these studies are about consuming fish, not fish oil supplements.

Fish oil contains two omega-3 fatty acids called EPA and DHA. Both are found naturally in fatty fish such as salmon, mackerel, halibut and bluefish. The same heart benefit has not been shown regarding fish oil supplements, however; a fact you will not find on their labels.

Fatty fish such as salmon, mackerel, halibut and bluefish contain two omega-3 fatty acids that are heart protective. The same benefit has not been shown regarding supplements, however.

In fact, two large recent clinical trials showed that over-the-counter fish oil supplements do not improve cardiovascular outcomes.

The vague language used on labels may lead to misinformation about the role of these dietary supplements, according to the senior author of the study, Ann Marie Navar, associate professor of cardiology at the University of Texas Southwestern Medical Center. “It is true that omega-3 fatty acids are present in the brain and are important for all sorts of brain functions,” she said, in a press release. “What has not been consistently shown with high-quality trials is that taking more of it in the form of fish oil supplements leads to improved performance or prevention of disease.”

Navar said that after the team's inventory of the fish oil supplement claims, she was “alarmed” to find that the fish oil supplement labels often implied a wide range of health benefits — including the ability to help the health of the heart, brain and eyes. Given these marketing claims, she said, “It's not surprising to me that my patients think fish oil is helping them.”

If you are already taking fish oil supplements, or any other supplements, tell your doctor. Vitamins and supplements are not necessarily harmless. They can cause reactions such as rashes, and they may also reduce the effectiveness of prescribed medications.

There is one safe and effective way to improve your heart health with omega-3 fatty acids: Make sure fatty fish is a regular part of your diet.

The study is published in JAMA Cardiology.