Fish oil benefits depend on genotype, research finds

Taking fish oil only provides health benefits if someone has the right genetic makeup, according to a new study by researchers at the University of Georgia published in the journal PLOS Genetics.

The study focused on fish oil, and the omega-3 fatty acids it contains, and its effect on triglycerides. Researchers examined four blood lipids, 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 U.K. Biobank, a large-scale cohort study collecting genetic and health information from half a million participants.

The researchers divided the sample into two groups, those taking fish oil supplements 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, according to the study.

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, the researchers said.

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," Kaixiong Ye, PhD, lead author of the study, in a statement. "Some participants may benefit, and some may not, so if you mix them together and do the analysis, you do not see the impact. 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.”