Here’s what you need to know about a few ergogenic aids in food and supplement form with scientific backup.

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To date, the following substances have been shown to improve athletic performance. Of course, this doesn’t mean you should start popping pills. In fact, scientists are constantly coming up with new information (good and bad), so stay on top of the current research if you decide to go with one of these supplements. Naturally, always check with your physician before embarking on anything new:

Antioxidants (C, E, beta-carotene, and selenium)Claim: Protects against the tissue damage from free radical formation induced by exercise.Fact: Might protect against tissue damage following prolonged endurance exercise, but doesn’t improve performance while you are actually exercising. Although the quantities of antioxidants found in food are somewhat small, they do help to stop the production and spread of harmful substances. CaffeineClaim: Improves endurance and overall athletic performance.Fact: Consuming as little as one hundred milligrams of caffeine an hour before a workout—the average amount of caffeine in a cup of coffee—has been shown to improve athletic performance of dedicated exercisers (casual exercisers may not experience the same boost). Researchers aren’t sure why, but it may be because caffeine signals your muscles to ignore fatigue and contract differently.Side effects of high caffeine consumption include nausea, muscle tremors, palpitations, and headaches. Not a good idea if you have a sensitive system. CreatineClaim: Increases the creatine phosphate content in muscles, improves high-power performance, and increases muscle mass.Fact: Research has suggested that consuming 20 grams of creatine per day (5 grams, four times daily) for five days might improve performance in brief, maximal exercise lasting less than 30 seconds. After this loading dose, a maintenance dose of 5 grams per day should suffice. However, not all studies have found that creatine improves strength, sprint performance, or lean muscle mass—so it might not improve all high-power activities.

The appeal of magic pills promising bigger muscles and faster speeds is tremendous. However, it’s important to know that very few supplements have credible research to back them up—in fact, most of the sport enhancers offer nothing but misleading labels. Without a doubt, the best investment for top performance is the old-fashioned mix—good eats and plenty of hard training.