Chromium Improves Heart
Function in Diabetics
Reduced risk for arrhythmias is linked to
improved insulin sensitivity and glucose metabolism
By Dr. Edward R. Rosick
hat’s one thing we could not live without in today’s high-tech society? Electricity, of course. Just think where we’d be if all our sources of electricity conked out for good. We would quickly revert from the twenty-first-century to the eighteenth century in terms of most of our technological capabilities. That would certainly test our ability to survive in a world that was not designed for our comfort. It underscores the extraordinary artificiality of the lifestyle cocoon we have created for ourselves since electricity began to reshape that world and allow us to go soft.
The Body Electric
Still, the human body is an amazing creation, especially when you start examining how this exquisitely designed mass of muscle, bone, and tissue functions for the better part of a century. A crucial feature of that functioning is electricity—that’s right, the same type of electricity that powers your cell phone, your computer, and your garbage disposal (not everything is high-tech). The amount of electrical energy generated in our bodies is pretty small, but without it, we’d die in a heartbeat—because the heart’s steady, life-sustaining rhythm depends on electrical impulses. Disrupt that rhythm badly enough, and it’s lights out—literally.
Disturbances in normal heart rhythm are called arrhythmias, and interpreting their meaning is part of the art and science of cardiology. There are many different kinds of arrhythmias, with different causes; some are benign, but some portend trouble—and some are fatal. In any case, they all signify some kind of cardiac abnormality, for which there are many potential causes.
Diabetes Increases Risk for Heart Disease
One such cause is type 2 diabetes, which is strongly associated with heart disease; in fact, heart disease is the number one killer of diabetics. Type 2 diabetes is a disease of impaired insulin function, which leads to elevated glucose (blood sugar) and insulin levels. The result is damage to a great variety of bodily organs and systems, including the heart, brain, kidneys, eyes, and peripheral nerves.
There are several reasons for the increased risk for heart disease with diabetes, including higher incidences of atherosclerosis and cardiac arrhythmias. A recent study has shown that abnormalities in ECG (electrocardiogram) readings in patients with type 2 diabetes can be used to predict the risk of cardiac death, as well as the risk of death from all causes (not as individual causes, of course, but as the sum of all causes—it’s all in the statistics). And in a long-term study of 471 patients with type 2 diabetes, researchers showed that a certain ECG abnormality called prolongation of the QTc interval is an accurate predictor of stroke.
QTc Does Not Mean Quite Terrific chromium
The QTc interval is a measure of that portion of the heartbeat in which the two lower chambers (the ventricles) are stimulated by an electrical impulse to contract and then relax (in an electrical sense) back to their normal state. If this interval, which normally lasts a little less than half a second, is abnormally prolonged, watch out—it’s a sign of increased risk for cardiac arrhythmias. (See the sidebar for a more detailed explanation.)
What Does Your ECG Show?
The ECG (EKG in the original German) is one of the most common and valuable noninvasive diagnostic tools used in medicine. It works by measuring the electrical signals generated by your heart every time it beats. The distinctive features of an ECG are designated by letters (as shown in the figure), and a physician’s interpretation of the trace is based on the details of these features. One complete cycle, which takes 1 second when your heart rate is 60 beats per minute, begins with the P wave. This occurs when the heart’s pacemaker nerve center sends an electrical impulse to the atria (the two upper chambers), causing them to contract and pump blood into the ventricles (the two lower chambers).
About one-tenth to one-fifth of a second later, a second impulse (from a different site) causes the ventricles to contract and pump blood out of the heart, leading to the visually striking QRS complex on the ECG. The last feature in the cycle is the T wave, which represents the electrical recovery phase of the ventricles.
In diseased states, there are many different ways in which one or more features of the ECG can change, giving the physician valuable clues as to what might be wrong. One feature of special interest is the duration of the QT interval, because it’s a sensitive indicator of a particularly important kind of problem. If the QT interval is prolonged by about 5% or more from its normal value, it indicates an increased risk of certain types of arrhythmias, some of which are life-threatening.
Some types of drugs tend to cause prolongation of the QT interval—a dangerous side effect. In clinical testing of drugs, therefore, it’s important to monitor any effect the drug may have in this regard. This poses a problem, however: the duration of the QT interval is normally about 45% of one complete cycle, but the duration of a cycle varies with heart rate: the faster the rate, the shorter the cycle and, therefore, the shorter the QT interval. And since different people have different normal heart rates, their QT intervals cannot be meaningfully compared unless the data are corrected for the different heart rates.
When this correction is made (to a standardized heart rate of 60), the interval is called the QTc interval. Prolongation of the QTc interval—and hence an increased risk for cardiac arrhythmiasis a characteristic feature of type 2 diabetes.
Chromium Improves Glucose Metabolism
The predictive value of a prolonged QTc interval for morbidity and mortality (sickness and death) in diabetic patients is independent of other cardiovascular risk factors. It correlates positively with elevated fasting blood insulin levels and with glucose intolerance, which are characteristic of diabetes. Glucose intolerance is a manifestation of insulin resistance (bad), the opposite of which is insulin sensitivity (good). And it has long been know that insulin sensitivity can be improved by supplemental chromium, a trace mineral that plays a vital role in glucose metabolism. Chromium deficiency may, in fact, represent a primary risk factor for cardiovascular disease in diabetic patients.
A randomized, placebo-controlled study published in 1997 gave evidence that chromium supplementation can lead to improved glucose metabolism. For 4 months, 180 men and women with type 2 diabetes were given either 100 mcg (micrograms) or 400 mcg of chromium or placebo daily. The results showed significant decreases, vs. placebo, in fasting glucose levels, fasting insulin levels, and 2-hour insulin levels, all of which point to an improvement in insulin sensitivity and hence glucose metabolism.
The lead author of that study was Richard Anderson, a prominent diabetes researcher with the U.S. Department of Agriculture’s Human Nutrition Research Center. In 1998 Anderson published a review article that examined multiple studies on the use of chromium for both glucose intolerance and diabetes. He concluded, “… supplemental chromium has been shown to have beneficial effects, without any documented side effects, on people with varying degrees of glucose intolerance, ranging from mild glucose intolerance to overt type 2 diabetes mellitus.”
Chromium Benefits the Heart—Persistently
Now Dr. Anderson, together with a team of colleagues at the Ljubljana University Medical Center in Slovenia, has published a randomized, double-blind, placebo-controlled study of the effects of chromium (as chromium picolinate) on the QTc interval in 60 patients with type 2 diabetes. The patients were assigned to either of two groups: Group A received 1000 mcg (1 mg) per day of chromium picolinate for 3 months, then placebo for 3 months. Group B followed the reverse pattern: 3 months of placebo followed by 3 months of chromium picolinate. An advantage of this type of trial (called a crossover trial, for obvious reasons) is that all the patients serve as their own controls, so any concerns about possible differences between the treatment group and the control group are eliminated.
The results of the study showed a positive effect of chromium supplementation. During the first 3 months, the patients in Group A experienced a significant decrease in their QTc interval, as well as in their plasma insulin levels, whereas no such changes were observed in Group B. During the second 3 months, however, Group B experienced the same benefits as Group A had earlier. Interestingly, during the second 3 months, the benefits previously realized by Group A did not disappear but remained largely intact, indicating a persistent effect of the chromium even after it was discontinued.
The authors stated,
… in patients with type 2 diabetes mellitus, chromium metabolism is altered because of impaired chromium utilization. Chromium supplementation in these patients has been shown to improve glucose control and increase insulin sensitivity. … chromium supplementation appears to shorten QTc interval of diabetic patients, suggesting that increased intake of chromium may lower cardiovascular risk in type 2 diabetes mellitus.
The Overweight Benefited the Most
An interesting and potentially important additional finding was that QTc shortening was statistically associated with a higher BMI (body mass index), i.e., it was strongest in those patients who were most overweight. This suggests that chromium supplementation may be most valuable for overweight diabetic patients. Obesity, by the way, is far and away the predominant cause of type 2 diabetes, making this disease relatively easy to prevent through a combination of healthy diet and regular exercise.
There’s Room for Other Supplements Too
Chromium is not the only nutritional supplement that has been shown to be beneficial in preventing or treating type 2 diabetes. Other supplements backed by scientific studies in this regard include cinnamon extract (especially a water-soluble component called MHCP and some related compounds), green tea extract (especially its potent component EGCG), the antioxidant bioflavonoid quercetin, the metabolically vital amino acid acetyl L-carnitine, and the antioxidant fatty acid lipoic acid. (For a discussion of the last two of these compounds, which are biochemical allies, see the article on page 25 of this issue.)
Although diabetes is running rampant in our overfed and underexercised society, there’s plenty you can do to prevent yourself from falling victim to it. A diet low in carbohydrates and high in monounsaturated fats is advisable, as is a daily 30-minute exercise regimen. If you’re overweight, exercise that leads to weight loss is best, but even exercise that does not is beneficial—and not just for preventing diabetes, but also for improving just about every imaginable aspect of your health.
Finally, you should consider the judicious use of antidiabetic supplements, such as chromium, as an integral part of your health program. By doing so, you could help preserve and protect that masterpiece of electrical machinery—your heart.
- Plutzky J, Viberti G, Haffner S. Atherosclerosis in type 2 diabetes mellitus and insulin resistance: mechanistic links and therapeutic agents. J Diabetes Comp 2002;16:401-15.
- Okin PM, Devereux RB, Lee ET, et al. Electrocardiographic repolarization complexity and abnormality predict all-cause and cardiovascular mortality in diabetes: the Strong Heart Study. Diabetes 2004;53:434-40.
- Cardoso CRL, Salles GF, Deccache W. QTc interval prolongation is a predictor of future strokes in patients with type 2 diabetes mellitus. Stroke 2003;34:2187-94.
- Dekker JM, Feskens EJ, Schouten EG, et al. QT duration is associated with levels of insulin and glucose intolerance. The Zutphen Elderly Study. Diabetes 1996;45:376-80.
- Simonoff M. Chromium deficiency and cardiovascular risk. Cardiovasc Res 1984;18:591-6.
- Anderson RA, Cheng N, Bryden NA, et al. Elevated intakes of supplemental chromium improve glucose and insulin variables in individuals with type 2 diabetes. Diabetes 1997;46:1786-91.
- Anderson RA. Chromium, glucose intolerance and diabetes. J Am Coll Nutr 1998 Dec;17(6):548-55.
- Vrtovec M, Vrtovec B, Briski A, Kocijancic A, Anderson RA, Radovancevic B. Chromium supplementation shortens QTc interval duration in patients with type 2 diabetes mellitus. Am Heart J 2005;149:632-6.
Caution: If you have diabetes, do not take any supplement that may affect your blood sugar levels without first consulting your physician. Diabetes is a serious disease requiring careful professional management.
Dr. Rosick is an attending physician and clinical assistant professor of medicine at Pennsylvania State University, where he specializes in preventive and alternative medicine. He also holds a master’s degree in healthcare administration.