Improve Heart Health in People with Type 2 Diabetes

Healthnotes Newswire (July 14, 2005)—When people with type 2 diabetes supplement with chromium, an electrocardiogram (ECG) measurement believed to indicate a reduced risk of heart disease improves, according to the American Heart Journal (2005;149:632–6).

Type 2 diabetes (sometimes called adult-onset diabetes) is a chronic disease marked by inability to control blood sugar (glucose) levels. Blood sugar regulation depends in large part on the hormone insulin, which stimulates the entry of glucose from the blood into the cells. In many people with type 2 diabetes, however, the cells are no longer sensitive to insulin, a state known as insulin resistance. In such people, both blood glucose and insulin levels are elevated, and high blood levels of glucose and insulin can damage many tissues of the body, including the blood vessels. Heart disease risk is greatly increased in people with type 2 diabetes and the degree of risk has been found to correlate closely with the QTc interval.

Chromium is an essential trace mineral that enhances the effect of insulin in the body, potentially decreasing insulin resistance. Many, though not all, studies have shown that supplementing with chromium improves blood sugar control in people with type 2 diabetes.

An ECG measures the electrical impulses associated with the contraction and relaxation cycles of the heart muscles. A single cycle shows an ECG pattern of distinct changes that are named with the letters, P, Q, R, S, and T. The P wave reflects the contraction of the atria and the set of spikes and waves known as the QRST complex reflects the contraction of the ventricles. The duration of ventricular contraction, from initiation to relaxation, is measured by the length of the QRST complex and is known as the QTc interval. A number of studies have found that a long QTc interval is a strong risk factor for stroke, heart attack, and death.

The current research studied 50 people with type 2 diabetes who were managing their diabetes with diet alone and did not have evidence of serious complications such as heart or kidney failure. They were randomly assigned to receive either 1,000 mcg of chromium picolinate per day or placebo for three months. Each person then received the other treatment for a second three months. Physical exam, blood tests, and ECGs were performed at the beginning of the study, and after three and six months.

At the end of three months, insulin levels were significantly lower in the group using chromium than in the placebo group. The reduced insulin level was maintained in this group during the second three months of the study when they did not use chromium, suggesting that the effects of chromium supplementation persisted after treatment was stopped. The group that used chromium during the second three months had a similar drop in insulin levels by the end of the study. The QTc interval was also significantly shorter in the chromium group than in the placebo group at the end of the first three months. This reduction in QTc interval was maintained in the second three months, and the group that supplemented with chromium in the second three months had a similar reduction in the length of the QTc interval by the end of the study.

The results of this study show that supplementing with chromium can shorten the QTc interval in people with type 2 diabetes. This reduction in the length of the cardiac cycle is likely to indicate that the risk of heart disease has been reduced. Longer studies are needed to verify that chromium supplementation can have this benefit for people with high cardiac risk due to type 2 diabetes.