ATHENS, Ga. — Fish oil supplements are a booming, billion-dollar business. Most of that success is due to the reputation that fish oil (and the omega-3 fatty acids it carries) has tremendous health benefits — including improving heart health. Unfortunately, a new study finds only people with a certain genetic makeup will see those benefits. For the rest, researchers at the University of Georgia say fish oil pills may actually increase heart disease risk.

Study author Kaixiong Ye notes fish oil and omega-3 are famous for their impact on triglycerides. This is a type of fat in the blood and a key marker for cardiovascular disease. While the study finds some consumers can lower triglyceride levels by taking omega-3, the results are not universal.

“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,” Ye says in a university release. “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.”

Which genes fit best?

Ye’s team examined four different fats in the blood: high-density lipoprotein, low-density lipoprotein, total cholesterol, and triglycerides. Researchers say all of these lipids are biomarkers for cardiovascular health and disease risk. The data comes from 70,000 participants in the UK Biobank, a massive study of genetic and health information including half a million people.

Study authors divided the samples into two groups, those taking fish supplements (about 11,000) and participants who don’t. The team then performed a genome-wide scan, comparing eight million genetics variants in these groups.

After 64 million tests, the results uncovered a key variation at gene GJB2. Researchers say people with the AG genotype can decrease their triglycerides by taking fish oil supplements. Individuals with the AA genotype however, slightly increase this blood fat level by taking omega-3 supplements.

The team could not definitively determination what happens to people taking fish oil who have the third genotype, GG.

That may sound great, but how are you supposed to know which genotype you have? Ye says, thanks to the rise of direct-to-consumer genetic testing companies, consumers can actually find out now.

One obstacle Ye notes is that companies don’t provide information on specific genetic variants yet. To get around this, a tech-savvy customer should be able to download their raw data from the testing company. Ye says the ID for the variant of the specific genotype is rs112803755 (A>G).

So is fish oil’s healthy reputation not credible?

Researchers say their findings explain why so many studies cast doubt on fish oil’s ability to improve heart health. Meanwhile, other reports have found conflicting data on its ability to improve depression, ADHD, and cancer risk.

“One possible explanation is that those clinical trials didn’t consider the genotypes of the participants,” Ye explains. “Some participants may benefit, and some may not, so if you mix them together and do the analysis, you do not see the impact.”

After finding this specific gene that determines the body’s response to fish oil, researchers plan to test the direct effects between these supplements and cardiovascular disease.

“Personalizing and optimizing fish oil supplementation recommendations based on a person’s unique genetic composition can improve our understanding of nutrition and lead to significant improvements in human health and well-being,” the assistant professor of genetics concludes.

The study appears in the journal PLOS Genetics.

About Chris Melore

Chris Melore has been a writer, researcher, editor, and producer in the New York-area since 2006. He won a local Emmy award for his work in sports television in 2011.

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