FADS1 and FADS2 Gene Polymorphisms Affect Omega-3 and Omega-6 Erythrocyte Fatty Acid Composition and Influence the Association Between Dietary Fatty Acid Intake and Lipid Profile in Brazilian Adults

Background: Polymorphisms in the FADS1 and FADS2 genes influence fatty acid metabolism. However, evidence of gene–diet interactions in population-based studies from Brazil remains limited. The objective of this study was to examine associations between FADS1–FADS2 single-nucleotide polymorphisms (SNPs) and erythrocyte fatty acid composition and serum lipid concentrations, as well as to explore potential gene–diet interactions. Methods: Data were analyzed from 294 adults (20–93 years) enrolled in the 2015 ISA-Nutrition study. Erythrocyte fatty acid composition and serum lipids were measured using standard enzymatic methods. Dietary intake was assessed by 24 h recalls, and participants were classified into tertiles according to fatty acid intake. Five SNPs were genotyped; FADS1 rs174546 and FADS2 rs174570 were prioritized based on linkage disequilibrium. Associations and interactions were assessed using generalized linear models, adjusting for confounders. Results: Carriers of the minor alleles for rs174546 and rs174570 had significantly lower erythrocyte levels of long-chain polyunsaturated fatty acids, particularly along the ω-6 pathway, suggesting reduced desaturase activity. The rs174546 TT genotype was associated with higher total, very-low-density lipoprotein cholesterol (VLDL), and non–high-density lipoprotein (non-HDL) cholesterolconcentrations. Higher dietary intakes of docosahexaenoic acid (DHA) or a higher linoleic acid to alpha-linolenic acid ratio(LA/ALA ratio) among these carriers were linked to lower serum lipid levels, indicating gene–diet interactions that attenuate adverse genotype effects. In addition, rs174570 TT carriers showed elevated VLDL concentrations, with a significant dietary interaction observed with the LA/ALA ratio. Conclusions: FADS1 and FADS2 polymorphisms influence fatty acid metabolism and interact with diet to shape lipid profiles. These findings highlight the importance of considering gene-diet interactions in cardiometabolic risk.