Acute effects of dietary glycemic index on antioxidant capacity in a nutrient-controlled feeding study

Obesity (Silver Spring). 2009 Sep;17(9):1664-70. doi: 10.1038/oby.2009.203. Epub 2009 Jun 18.


Oxidative stress, caused by an imbalance between antioxidant capacity and reactive oxygen species, may be an early event in a metabolic cascade elicited by a high glycemic index (GI) diet, ultimately increasing the risk for cardiovascular disease and diabetes. We conducted a feeding study to evaluate the acute effects of low-GI compared with high-GI diets on oxidative stress and cardiovascular disease risk factors. The crossover study comprised two 10-day in-patient admissions to a clinical research center. For the admissions, 12 overweight or obese (BMI: 27-45 kg/m(2)) male subjects aged 18-35 years consumed low-GI or high-GI diets controlled for potentially confounding nutrients. On day 7, after an overnight fast and then during a 5-h postprandial period, we assessed total antioxidant capacity (total and perchloric acid (PCA) protein-precipitated plasma oxygen radical absorbance capacity (ORAC) assay) and oxidative stress status (urinary F(2alpha)-isoprostanes (F(2)IP)). On day 10, we measured cardiovascular disease risk factors. Under fasting conditions, total antioxidant capacity was significantly higher during the low-GI vs. high-GI diet based on total ORAC (11,736 +/- 668 vs. 10,381 +/- 612 micromol Trolox equivalents/l, P = 0.002) and PCA-ORAC (1,276 +/- 96 vs. 1,210 +/- 96 micromol Trolox equivalents/l, P = 0.02). Area under the postprandial response curve also differed significantly between the two diets for total ORAC and PCA-ORAC. No diet effects were observed for the other variables. Enhancement in plasma total antioxidant capacity occurs within 1 week on a low-GI diet, before changes in other risk factors, raising the possibility that this phenomenon may mediate, at least in part, the previously reported effects of GI on health.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Antioxidants / metabolism*
  • Biomarkers / blood
  • Biomarkers / urine
  • Blood Glucose / metabolism*
  • Cardiovascular Diseases / blood
  • Cardiovascular Diseases / etiology
  • Cross-Over Studies
  • Diet, Carbohydrate-Restricted*
  • Dietary Carbohydrates / adverse effects*
  • Energy Intake
  • F2-Isoprostanes / urine
  • Fasting / blood
  • Glycemic Index*
  • Humans
  • Hyperglycemia / blood*
  • Hyperglycemia / etiology
  • Insulin / blood
  • Male
  • Obesity / blood
  • Obesity / complications
  • Obesity / diet therapy*
  • Oxidative Stress*
  • Postprandial Period
  • Time Factors
  • Young Adult


  • Antioxidants
  • Biomarkers
  • Blood Glucose
  • Dietary Carbohydrates
  • F2-Isoprostanes
  • Insulin