Low Chromium Linked to Heart Disease Risk in Patients With Diabetes

Laurie Barclay, MD

September 03, 2004

Sept. 3, 2004 — Low chromium levels as measured in toenail clippings are associated with an increased risk of cardiovascular disease (CVD) for patients with diabetes, according to the results of a cross-sectional study published in the September issue of Diabetes Care.

"Chromium may improve insulin sensitivity, which can modify the risk of diabetes and CVD," write Swapnil Rajpathak, MBBS, D DIAB, MPH, from the Harvard School of Public Health in Boston, Massachusetts, and colleagues. "Epidemiological data on chromium intake and the risk of CVD are limited, partly because of the difficulty in estimating dietary chromium considering its wide variability in food sources. Hence, a sensitive and time-integrated biomarker for chromium intake is required in epidemiological studies."

Using data from the Health Professionals Follow-up Study, the investigators performed cross-sectional and nested case-control analyses among men aged 40 to 75 years. The cross-sectional analysis compared men with diabetes only (n = 688), diabetes with prevalent CVD (n = 198), and healthy control subjects (n = 361), whereas the nested case-control study compared 202 men with baseline diabetes who developed incident CVD and 361 matched control subjects.

Mean toenail chromium was 0.71 µg/g in healthy control subjects, 0.61 µg/g in subjects with diabetes only, and 0.52 µg/g in diabetic subjects with prevalent CVD ( P = .003 for trend). Comparing men with diabetes only with healthy control subjects, cross-sectional analysis revealed that the multivariate odds ratio (OR) between the lowest and highest quartiles of chromium levels was 0.74 (95% confidence interval [CI], 0.49 - 1.11; P = .18 for trend). In a similar comparison of diabetic subjects with prevalent CVD and healthy control subjects, the OR was 0.45 (95% CI, 0.24 - 0.84; P = .003 for trend).

In the nested case-control study, comparing men with diabetes and incident CVD with healthy control subjects, the multivariate OR between the lowest and highest chromium quartiles was 0.65 (95% CI, 0.36 - 1.17; P = .16 for trend). For combined prevalent and incident CVD cases among diabetic men compared with healthy control subjects, the OR was 0.62 (95% CI, 0.39 - 1.01; P = .02 for trend) between extreme quartiles.

Study limitations include possible sample contamination producing erroneously high levels of chromium in toenails, random errors inherent in a single measurement, possible bias of "reverse causation," inability to distinguish the effects of chromium on diabetes from those on CVD, and use of toenail levels of chromium as a surrogate marker for dietary intake.

"Our results suggest that diabetic men with CVD have lower toenail chromium than healthy control subjects," the authors write. "However, this study could not distinguish between the effects of chromium on diabetes and those on CVD. Long-term clinical trials are needed to determine whether chromium supplementation is beneficial for preventing CVD among diabetic patients."

The National Institutes of Health supported this study. Nutrition 21 provided unrestricted funding for the measurement of toenail chromium levels and data analysis. One of the authors is supported in part by the American Heart Association's Established Investigator Award and has received funding from Nutrition 21.

Diabetes Care. 2004;27:2211-2216

Reviewed by Gary D. Vogin, MD

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