1.
Chromium effects on glucose tolerance and insulin sensitivity in persons at risk for diabetes mellitus.
Ali, A, Ma, Y, Reynolds, J, Wise, JP, Inzucchi, SE, Katz, DL
Endocrine practice : official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists. 2011;(1):16-25
-
-
Free full text
-
Abstract
OBJECTIVE To investigate the effects of daily chromium picolinate supplementation on serum measures of glucose tolerance and insulin sensitivity in patients at high risk for type 2 diabetes mellitus. METHODS We conducted a randomized, double-blind, placebo-controlled, modified cross-over clinical trial with 6-month sequences of intervention and placebo followed by a 6-month postintervention assessment. Adult patients with impaired fasting glucose, impaired glucose tolerance, or metabolic syndrome were enrolled. Participants received 6-month sequences of chromium picolinate or placebo at 1 of 2 dosages (500 or 1000 mcg daily). Primary outcome measures were change in fasting plasma glucose, 2-hour plasma glucose during oral glucose tolerance testing, fasting and 2-hour insulin, and homeostasis model assessment of insulin resistance (HOMA-IR). Secondary outcomes included anthropometric measures, blood pressure, endothelial function, hemoglobin A1c, lipids, and urinary microalbumin. RESULTS Fifty-nine participants were enrolled. No changes were seen in glucose level, insulin level, or HOMA-IR (all P>.05) after 6 months of chromium at either dosage level (500 mcg or 1000 mcg daily) when compared with placebo. None of the secondary outcomes improved with either chromium dosage compared with placebo (P>.05). CONCLUSIONS Chromium supplementation does not appear to ameliorate insulin resistance or impaired glucose metabolism in patients at risk for type 2 diabetes and thus is unlikely to attenuate diabetes risk.
2.
Effects of walnut consumption on endothelial function in type 2 diabetic subjects: a randomized controlled crossover trial.
Ma, Y, Njike, VY, Millet, J, Dutta, S, Doughty, K, Treu, JA, Katz, DL
Diabetes care. 2010;(2):227-32
-
-
Free full text
-
Abstract
OBJECTIVE To determine the effects of daily walnut consumption on endothelial function, cardiovascular biomarkers, and anthropometric measures in type 2 diabetic individuals. RESEARCH DESIGN AND METHODS This study was a randomized, controlled, single-blind, crossover trial. Twenty-four participants with type 2 diabetes (mean age 58 years; 14 women and 10 men) were randomly assigned to one of the two possible sequence permutations to receive an ad libitum diet enriched with 56 g (366 kcal) walnuts/day and an ad libitum diet without walnuts for 8 weeks. Subjects underwent endothelial function testing (measured as flow-mediated dilatation [FMD]) and assessment of cardiovascular biomarkers before and after each 8-week treatment phase. The primary outcome measure was the change in FMD after 8 weeks. Secondary outcome measures included changes in plasma lipids, A1C, fasting glucose, insulin sensitivity, and anthropometric measures. RESULTS Endothelial function significantly improved after consumption of a walnut-enriched ad libitum diet compared with that after consumption of an ad libitum diet without walnuts (2.2 +/- 1.7 vs. 1.2 +/- 1.6%; P = 0.04). The walnut-enriched diet increased fasting serum glucose and lowered serum total cholesterol and LDL cholesterol from baseline (10.0 +/- 20.5 mg/dl, P = 0.04; -9.7 +/- 14.5 mg/dl, P < 0.01; and -7.7 +/- 10 mg/dl, P < 0.01, respectively), although these changes were not significant compared with those for an ad libitum diet without walnuts. There were no significant changes in anthropometric measures, plasma A1C, and insulin sensitivity. CONCLUSIONS A walnut-enriched ad libitum diet improves endothelium-dependent vasodilatation in type 2 diabetic individuals, suggesting a potential reduction in overall cardiac risk.