Performance boost or just fungus?

Cordyceps fungus grows on the backs of high-altitude caterpillars native to China, Nepal and Tibet. Highly valued in ancient China for its medicinal powers, the fungus was often reserved for emperors and other royalty because it was such a challenge to harvest. Today, cordyceps is cultured in laboratories and marketed as an exercise performance enhancer and antioxidant.

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Uses: In traditional Chinese medicine, cordyceps is used to increase life expectancy and energy and improve kidney and lung function. Commercial supplements are often taken to improve exercise performance, oxygen uptake, strength and stamina.

Dose: One to three grams a day in separate doses.

Precautions: Few serious side effects have been tied to cordyceps use, though it can lower blood sugar and may cause a skin rash or chest pain.

Research: In several experiments, rodents given cordyceps swam for longer times than rodents without the boost. Although a few human studies suggested the fungus could increase energy levels in older adults, two studies published earlier this year failed to show any effect on exercise performance in young athletes from cordyceps supplements.

Dietary supplement makers are not required by the U.S. government to demonstrate that their products are safe or effective. Ask your healthcare provider for advice on selecting a brand.

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-- Elena Conis