March 26, 2010 -- Cyclists who are 50 and older may be able to ride farther and faster if they take a commercially available supplement containing the amino acid arginine and antioxidants that help boost the body’s natural exercise capabilities, according to new research in the Journal of the International Society of Sports Nutrition.
“The loss of exercise capacity with age often results in a reduction in physical fitness and more rapid [cell death],” says researcher Zhaoping Li, MD, of the University of California at Los Angeles. “A dietary supplement that increases exercise capacity might help to preserve physical fitness by optimizing performance and improving general health and well being in older people.”
Niteworks, made by Herbalife International, is a lemon-flavored powder that is mixed with water. It contains 5.2 grams of L-arginine and L-citrulline, 300 milligrams of L-taurine, 500 milligrams of vitamin C, 400 international units (IU) of vitamin E, 400 micrograms of folic acid, 10 milligrams of alpha lipoic acid, and 50 milligrams of lemon balm extract.
Our bodies’ production of nitric oxide tends to dim with advancing age. Nitric oxide helps stimulate the blood vessels around the heart and other organs to dilate, and it also plays a role in increasing exercise capacity.
Arginine is a precursor to nitric oxide development. Nitric oxide production is also hampered by damaging free radicals. Antioxidants, such as those contained in the new supplement, sop up these free radicals, stopping them in their tracks. The new supplement hits nitric oxide from both ends -- triggering its production with arginine and preventing its destruction with antioxidants.
Exercise Capacity and Nitric Oxide
In the new study of 16 male cyclists aged 50 to 73, men who were given the supplement showed a 16.7% increase in their anaerobic threshold at three weeks. By contrast, their counterparts who received the placebo did not see any increase in their anaerobic thresholds. Anaerobic threshold is the point at which lactic acid starts to accumulate in the muscles and is known as a powerful predictor of performance in aerobic exercise.
“We have just studied elderly since human exercise capacity declines with advancing age and many individuals lose the inclination to participate in regular physical activity,” Li tells WebMD. “Our study has shown that the supplements help the muscles work much more efficiently in our study population.
Study participants took the supplements at bedtime, which is when nitric oxide levels are lowest. Arginine may dilate the blood vessels and cause dizziness when standing, which is another reason to take the supplement before bed, Li says.
Study volunteers did not show any evidence of heart disease. The role of L-arginine among people with heart disease is considered controversial, study authors say.
“It is also unclear if arginine supplementation in the sedentary population can have the same results," the study authors write. They say further research is needed.