Carbohydrate quality and quantity affects the composition of the red blood cell fatty acid membrane in overweight and obese individuals.

BACKGROUND Cell membrane fatty acid (FA) composition may play a role in human metabolic diseases. However, the modulatory effect of nutrients other than fat is poorly explored. OBJECTIVE To investigate the effect of moderate-carbohydrate diets with different glycemic indices (GI) and a low-fat diet (LF) on red blood cell (RBC) FA membrane composition. DESIGN The RBC FA profile was measured in 87 subjects from the GLYNDIET study. Participants were randomly assigned to one of the following energy-restricted diet for 6 months: moderate-carbohydrate/low-GI diet (LGI, n = 31), moderate-carbohydrate/high-GI diet (HGI, n = 30) or LF-diet (n = 26). RESULTS We observed a significant increase in C20:0 and decrease in C20:3n-6 in the LGI and HGI groups compared to LF group. Compared to LF-diet, C22:4n-6 was lower after the HGI while C22:6n-3 was higher after LGI diet. Also, a tendency was found for higher concentrations of long-chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) in LGI compared to HGI and LF groups. The intra-group analysis showed significantly increased levels of total monounsaturated fatty acids (MUFA) after LGI and HGI interventions, as well as a significant increase in C22:5n-6 and a decrease in LCn-3PUFA and omega-3-index after the LF diet. The decrease in C20:5n-3 after HGI and LF diets was also significant. CONCLUSION Diets with a moderate amount of carbohydrates and healthy fat, mainly with LGI, modify the RBC fatty acid membrane composition.