The benefits of fish oil have been debated for years. Recent studies have suggested that taking them doesn't have any effect. New research has suggested, however, that if you have certain genetic characteristics, fish oil can actually help reduce the risk of heart disease. This can help explain why research on the impact of fish oil has been inconclusive - in some people, it's helpful while in others it may be a bit harmful. The work has been reported in PLOS Genetics.
"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," said study leader Kaixiong Ye, assistant professor of genetics in the Franklin College of Arts and Sciences at the University of Georgia. "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."
In this work, the researchers investigated the impact of fish oil's omega-3 fatty acids on four types of fat that are found in the blood, low-density lipoprotein, high-density lipoprotein, total cholesterol, and triglycerides, which are considered cardiovascular disease biomarkers.
The scientists utilized the UK Biobank, which contains health and genetic data from many people; this work focused on a sample of 70,000 people in the biobank. There were two groups in that cohort: one group of about 11,000 took fish oil supplements, and the rest did not. They compared 8 million genetic variants in these individuals, and after millions of computational tests, determined that one variant was significant in a gene called GJB2. Of fish oil consumers, those with an AG genotype had lower triglycerides, while those with an AA genotype had a slight increase in triglycerides. (There weren't enough individuals with the GG genotype to draw any conclusions.)
Since genetic testing is widely available, people can find out what variant they have if they're able to examine the raw data. The name of the relevant genetic variant or SNP is rs112803755 (A>G). This research can also explain why other trials have not shown that fish oil is beneficial. The purity of the supplement should also be considered by people who use them.
"One possible explanation is that those clinical trials didn't consider the genotypes of the participants," Ye said. "Some participants may benefit, and some may not, so if you mix them together and do the analysis, you do not see the impact."
Ye wants to learn more about exactly how fish oil can influence cardiovascular disease.
"Personalizing and optimizing fish oil supplementation recommendations based on a person's unique genetic composition can improve our understanding of nutrition," he said, "and lead to significant improvements in human health and well-being."
Sources: AAAS/Eurekalert! via University of Georgia, PLOS Genetics