Consumption of a high glycemic load but not a high glycemic index diet is marginally associated with oxidative stress in young women

Research studies have suggested that chronic consumption of high glycemic index foods may lead to chronically high oxidative stress. This is important because oxidative stress is suspected to be an early event in the etiology of many disease processes. We hypothesized that dietary glycemic index and glycemic load were positively associated with oxidative stress assessed by plasma F₂-isoprostanes in healthy, premenopausal women (body mass index [BMI] = 24.7 ± 4.8 kg/m² and age 25.3 ± 3.5 years, mean ± SD). We measured plasma F₂-isoprostanes in 306 healthy premenopausal women at the baseline visit for the Women In Steady Exercise Research study, using gas chromatography-mass spectrometry. Dietary glycemic index and load were calculated from the National Cancer Institute Diet History Questionnaire, and participants were divided into quartiles of dietary glycemic index and of glycemic load. Plasma F₂-isoprostanes were compared across quartile groups of dietary glycemic index and glycemic load using linear regression models. Plasma F₂-isoprostanes (pg/mL) increased with quartile of glycemic load (test for linear trend, P = 033), and also increased with quartile of glycemic index in participants with BMI ≥25 (P = 035) but not in those with BMI <25 (P = 924). After adjustment for BMI, alcohol consumption and total energy intake, both these positive trends remained marginally significant (P = 123 for quartiles of glycemic index and P = 065 for quartiles of glycemic load).