Medical expert Dr. Mohan S. Palaniswami answers common questions about diet and fitness:

Q: I have recently started lifting weights and some of the people at my gym use creatine. Does it work and is it safe?

A: While there have been many studies to determine if creatine works, almost all of them have tested a small group of subjects with varying standards of what exactly a good response is. It is believed that creatine works as a reservoir of phosphate needed for regenerating adenosine triphosphate (ATP), which is the main fuel for the enzyme motors of the muscle in initial high-intensity muscle activity. During muscle contraction, ATP loses a phosphate molecule to create energy. Creatine is a fuel source that resupplies phosphate to ATP. Theoretically, the more creatine, the more energy for brief high-intensity activity.

Most studies have evaluated muscular performance in brief high-intensity resistance exercise while evaluating factors such as increase in total muscle creatine concentration, resynthesis of ATP, and increase in the buffering of the highly acidic environment of a working muscle. Athletes who engage in activities requiring sudden short-term increases in muscle activity seem to experience a benefit (4 percent in some studies). These benefits were seen in conjunction with a regimented training program. Other than a few isolated reports, there hasn't been much evidence to support that there is improvement in performance in endurance activities (e.g., long-distance running).

Safety is another issue. There have been reports of kidney troubles with regular use or abuse of creatine supplements. The Food and Drug Administration is conducting ongoing studies to determine the side effects of creatine use, especially as there are no good studies of the long-term effects of creatine use. Also, since creatine is not regulated, different manufacturers have different standards for purity and concentration of creatine. Care must be taken along with consultation with your primary care provider to determine whether you should take this supplement OR You should consult with your primary care provider before taking creatine.

For more information, try www.fda.gov for updated studies on creatine.