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CLINICAL RESEARCH: DIET AND ENDOTHELIAL FUNCTION

The Acute Effect of Various Glycemic Index Dietary Carbohydrates on Endothelial Function in Nondiabetic Overweight and Obese Subjects

Talya Lavi, RD^_*, Avraham Karasik, MD^_*,, Nira Koren-Morag, PhD, Hannah Kanety, PhD^_*,, Micha S. Feinberg, MD^, and Michael Shechter, MD, MA^,,_*

^_* Institute of Endocrinology, Chaim Sheba Medical Center, Tel Hashomer, Israel
Leviev Heart Center, Chaim Sheba Medical Center, Tel Hashomer, Israel
Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel

Manuscript received October 26, 2008; revised manuscript received February 18, 2009, accepted March 3, 2009.

^_* Reprint requests and correspondence: Dr. Michael Shechter, Leviev Heart Center, Chaim Sheba Medical Center, 52621 Tel Hashomer, Israel (Email: shechtes{at}netvision.net.il).

Part of this study was presented as an abstract at the XXVI Congress of the European Society of Cardiology, Stockholm, Sweden, August 30, 2005.

Objectives: This study sought to explore the effect of glycemic-index dietary carbohydrates on endothelium-dependent flow-mediated dilation (FMD) in overweight and obese nondiabetic volunteers.

Background: Post-prandial hyperglycemia has been recognized as a cardiovascular risk factor in both the diabetic and the general population. Endothelial dysfunction has been shown to occur in diabetic and hyperglycemic patients.

Methods: We prospectively assessed brachial artery FMD in 56 healthy overweight and obese nondiabetic volunteers (38 [67.9%] men, mean age 48 ± 6 years) on 4 separate mornings, 1 to 2 weeks apart. After overnight fasting, the percent FMD (%FMD) improvement and endothelium-independent nitroglycerin-mediated dilation (%NTG) were assessed, after which subjects received 1 of 4 group meals at each visit (placebo [water] or a carbohydrate meal of glucose, cornflakes, or high-fiber cereal). Meals were distributed in a rotating randomized fashion, such that each subject received all 4 meals once throughout the study period.

Results: Fasting and 2-h post-prandial serum glucose levels were similar in all 3 meals, whereas at 30 to 90 min, serum glucose levels were significantly higher after glucose and cornflakes (high glycemic) compared with fiber (low glycemic). Baseline %FMD, not significantly different in the 3 carbohydrate-based meals, was reduced 2 h post-prandially in all groups, showing statistical significance in only high-glycemic index meals: glucose (15 ± 9% vs. 10 ± 8%, p < 0.01), cornflakes (13 ± 7% vs. 9 ± 7%, p < 0.01). No correlation was observed between the %FMD reduction rate and glucose levels throughout the study period.

Conclusions: High- compared with low-glycemic carbohydrate consumption significantly suppresses FMD in nondiabetic overweight and obese volunteers, suggesting a mechanism whereby high-glycemic meals may enhance cardiovascular risk.

Key Words: endothelium • glucose • nitric oxide • nutrition • vasodilation

Abbreviations and Acronyms   BMI = body mass index   CVD = cardiovascular disease   FMD = flow-mediated dilation   hs-CRP = high-sensitivity C-reactive protein   NO = nitric oxide   NTG = nitroglycerin-mediated dilation

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J. Am. Coll. Cardiol. 2009 53: A26. [Full Text] [PDF]