Changes in Plasma Metabolite Concentrations after a Low-Glycemic Index Diet Intervention.

SCOPE: To examine whether a low-glycemic index (LGI) diet improves a set of plasma metabolites related to different metabolic diseases, and comparison to a high-glycemic index (HGI) diet and a low-fat (LF) diet.

METHODS AND RESULTS: A parallel, randomized trial with three intervention diets: an LGI diet, an HGI diet, and an LF diet. A total of 122 adult overweight and obese subjects were enrolled in the study for 6 months. Blood samples were collected at baseline and at the end of the intervention. The plasma metabolomic profile of 102 subjects was analyzed using three different approaches: GC/quadrupole-TOF, LC/quadrupole-TOF, and nuclear magnetic resonance. Both univariate and multivariate analysis were performed. Serine levels were significantly higher following the LGI diet compared to both the HGI and LF diets (q = 0.002), whereas leucine (q = 0.015) and valine (q = 0.024) were lower in the LGI diet compared to the LF diet. A set of two sphingomyelins, two lysophosphatidylcholines, and six phosphatidylcholines were significantly modulated after the LGI diet compared to the HGI and LF diets (q < 0.05). Significant correlations between changes in plasma amino acids and lipid species with changes in body weight, glucose, insulin, and some inflammatory markers are also reported.

CONCLUSION: These results suggest that an LGI diet modulates certain circulating amino acids and lipid levels. These findings may explain the health benefits attributed to LGI diets in metabolic diseases such as type 2 diabetes.