![]() ![]() ![]() One subject in the 1000 mcg sequence withdrew consent after randomization because of time commitment. Sixty subjects were ultimately randomized to 500 mcg (n=30) or 1000 mcg (n=30) sequences. Of the 243 persons screened for eligibility, 80 did not meet eligibility criteria, 47 refused to participate, and 56 were not randomized for other reasons (see Figure 1). Because the time required for chromium to wash out fully is unknown, a post-treatment phase of six months was incorporated into the design following 12-months of intervention and placebo (see Figure 1). Effects of chromium at each dose were compared to placebo as a paired (crossover) comparison after six months of use. The study was designed and powered to compare the six-month effects of 500 mcg to 1000 mcg of chromium on insulin resistance (HOMA-IR), which provided adequate power (see Statistical Analysis) to detect a change in 2hrPG, and endothelial function. The study used a modified cross-over (Latin square) design encompassing both paired (crossover) and unpaired comparisons with statistical methods and sample size tailored to serve both purposes (see Statistical Analysis). This study was a randomized, double-blind, placebo controlled, modified crossover clinical trial to investigate the effects of daily chromium supplementation for six months at two dose levels (500 mcg and 1000 mcg of chromium picolinate per day) on serum measures of insulin sensitivity and glucose tolerance in adults with IGT, IFG, and metabolic syndrome. Subjects taking drugs thought to affect glucose metabolism and/or endothelial function were excluded (glucocorticoids, antineoplastic agents, psychoactive agents, and bronchodilators.) Subjects taking antihypertensive drugs and lipid-lowering agents were allowed to participate provided that doses were stable for three months prior to enrolment. Other exclusion criteria included self-reported hospitalization for treatment of cardiovascular disease six months prior to enrollment, serum creatinine >2.0 mg/dl at baseline, self-reported pancreatitis, recent or significant abdominal surgery, pregnancy and/or intention to become pregnant during the study, polycystic ovarian syndrome or irregular menses, and use of chromium supplements less than one month prior to screening. Subjects were excluded if they were diabetic (FPG >126 mg/dl 2hrPG >200 mg/dl). Metabolic syndrome was diagnosed using NCEP ATP III criteria, 12 requiring the presence of three of the following five criteria: waist circumference >102 cm in men or >88 cm in women triglyceride level ≥150 mg/dl HDL-C 130/>85 mm Hg and FPG ≥100 mg/dl. IFG was diagnosed using the ADA criteria of a FPG concentration of 100 mg/dl or greater, but less than 126 mg/dl. IGT was diagnosed by American Diabetes Association (ADA) guidelines 1 requiring the following two criteria: 1) Plasma glucose two hours (2hrPG) after consuming 75 g of glucose is at least 140 mg/dl but below 200 mg/dl and 2) fasting plasma glucose (FPG) level is less than 126 mg/dl. Patients enrolled were aged 18 years of age or older identified to have either 1) IGT 2) IFG or 3) metabolic syndrome. Because of the association of derangements in these metabolic abnormalities with endothelial dysfunction, brachial artery reactivity was also assessed before and after therapy. To assess the efficacy of this popular nutritional supplement, we performed a randomized controlled trial designed to investigate the effects of daily chromium picolinate supplementation for six months at two dose levels on serum measures of glucose tolerance and insulin sensitivity. 11 Indeed, one of the more common nutrition-related questions posed by patients with or at risk for diabetes to practicing endocrinologists concerns the effectiveness of chromium. 10 In 2002, estimated sales of chromium-based supplements was $85 million (USD). ![]() 9 Chromium picolinate is widely marketed to the public with diverse health claims pertaining to glucose metabolism, insulin action, muscle mass, weight control, and diabetes prevention. The micronutrient chromium (Cr) is of interest in this regard as a potential means of improving glucose tolerance 7, 8 by reducing insulin resistance. 4 Intensive diet and lifestyle change can play an important role in diabetes prevention 5 though adherence to these regimens is often difficult. While pharmacotherapy with such drugs as metformin, acarbose, orlistat, and thiazolidinediones can reduce risk of T2D, 3 their cost and potential adverse effects can be objectionable to patients who do not yet have an actual disease. 1 Endothelial dysfunction is also associated with increased risk for diabetes and is directly linked to insulin resistance 2 and hyperglycemia. Impaired Glucose Tolerance (IGT), impaired fasting glucose (IFG), and metabolic syndrome are considered precursors to type 2 diabetes (T2D) mellitus.
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