Relations of glycemic index and glycemic load with plasma oxidative stress markers.

BACKGROUND Recent data suggest that acute hyperglycemia may increase in vivo free radical production. This increased production has been implicated in many disease processes. OBJECTIVE The objective was to investigate whether a diet with a high glycemic index (GI) or glycemic load (GL) is associated with greater oxidative stress as measured by 2 lipid peroxidation markers, malondialdehyde (MDA) and F2-isoprostanes (IsoPs). DESIGN Plasma MDA and IsoP concentrations were measured in 292 healthy adults, and dietary GI and GL were assessed by using a validated food-frequency questionnaire. Cross-sectional associations between GI, GL, and the 2 markers were examined by using multiple regression techniques with adjustment for potential confounding variables. RESULTS Dietary GI was positively associated with both plasma MDA and IsoPs. The mean multivariate-adjusted MDA concentrations increased from 0.55 to 0.73 micromol/L as GI increased from the lowest to the highest quartile (P for trend = 0.02); the corresponding IsoP concentrations increased from 0.034 to 0.040 ng/mL (P for trend = 0.03). GL was positively associated with both MDA and IsoPs, but the linear relation was significant only for MDA. In addition, a marginally significant interaction between overall GI and body mass index (BMI; in kg/m2) for plasma MDA was observed (P = 0.09). The positive association between overall GI and MDA was stronger in those with a BMI < 26.5 than for those with a BMI > or = 26.5. CONCLUSIONS Chronic consumption of high-GI foods may lead to chronically high oxidative stress. A low-GI diet, not a low-carbohydrate diet, appears to be beneficial in reducing oxidative stress.