Individuals benefit differently from fish oil, depending on genotype

The health benefits of fish oil have expanded in recent years. As laboratory breakthroughs expand the understanding of omega-3 and omega-6 fatty acids’ impact on brain health and warding off a variety of cancers, uptake in the public has followed. 

The positive feedback loop continues to inspire new laboratory investigations, and now University of Georgia researchers have published a new study describing how genetic factors modify the effect of fish oil supplementation on the circulating level of omega-3 fatty acids.

The findings focus on homozygous genotypes, where an individual has two copies of the same allele (variant of a gene) for a particular trait, and heterozygous genotypes, in which an individual carries a specific genetic variation at a particular location in the genome.

“It is well known that taking fish oil supplements will increase the circulating level of omega-3 fatty acids,” said Kaixiong Ye, corresponding author of the study and associate professor in UGA’s Franklin College of Arts and Sciences department of genetics. “Our study found one genetic locus that modifies this effect. For individuals with a homozygous genotype, taking fish oil will increase their blood omega-3 levels by 0.45 units. For individuals with C/CT genotype (heterozygous), the increase is 0.5 units. For individuals with CT/CT, the increase is 0.60 unit.”

According to YE, the new study shows that the amount of fish oil supplementation being converted to circulating levels differs across individuals, depending on specific genotypes. 

“Our study was large-scale, involving 200,060 participants, and we analyzed over 7 million genetic variants”, said Susan Adanna Ihejirika, a graduate student at UGA’s institute of bioinformatics and co-author. 

The study builds the previous work by Ye’s research group that hypothesized causal pathways by which fish oil generates circulating omega-3 and omega-6 levels in the blood, leading to circulating lipid levels in the blood, which can help ward off certain types of cancer.

For the current study, the researchers focused on the relationships between the effects fish oil on circulating omega-3 and omega-6 levels and how this relationship differs by genotypes.

“Our two previous studies examined downstream conditions, like blood lipids and cancer.” Ye said. “The health benefits of fish oil supplementation depend on how much of it is converted to circulating omega-3 levels, the more it is absorbed and converted, the more likely it impacts the risk of cancer and other health conditions.” 

The study, “A multi-level gene-diet interaction analysis of fish oil and 14 polyunsaturated fatty acid traits identifies the FADS and GPR12 loci,” was published in Cell HGG Advances July 10.

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