Supplements: The Good and the Bad

There’s scant evidence for the effectiveness of most supplements. But here are a few to consider—and a few to shy away from.

THE GOOD

• Antioxidants: Regular use can interfere with training adaptations, but a regimen lasting no more than a week can help your body cope with added stress like recovering from a race or a trip to altitude.
• Caffeine: The most versatile and powerful performance enhancer out there, boosting both brain and muscle function.
• Creatine: The one (legal) weight-room powder that does result in muscle-mass gains.
• Vitamin D: Good diet alone often won’t meet your D needs. Get tested to confirm a deficiency, then consider adding up to 600 IUs per day.

THE BAD

• Calcium: It’s an effective way to strengthen bones, but in high doses it may also harden arteries. Get your fill through dietary sources like yogurt and broccoli.
• Vitamins A, C, and E: Taken over extended periods and at high doses, beta-carotene and vitamins A, C, and E have all been linked to increased cancer risk and higher death rates, and they may get in the way of exercise adaptations.
• Workout boosters: If a product claims to increase energy or enhance muscle growth, it’s almost certainly misleading you or contains an unlabeled stimulant or steroid.