Here's the lowdown on four well-known supplements

Liz Applegate, Ph.D.

When it comes to nutritional supplements, there's always something new purported to do such-and-such. This supplement improves your 5-K time. That one improves your sex life. Another one improves your 5-K time and your sex life. (Hmm. Now we're getting somewhere.)

Should you believe these claims? Oftentimes, no. Let's set the record straight on four of the most popular supplements on the shelves: ginseng, sodium bicarbonate, creatine and branched-chain amino acids.

Ginseng
Ginseng is everywhere: in New Age beverages, herb supplements, sportsdrinks and energy gels. Used for thousands of years by the Chinese, ginseng is an herb traditionally taken for chronic fatigue, forgetfulness, nervous disorders, low sex drive and forgetfulness (did I mention that already?). More recently, in terms of exercise, ginseng has been said to boost energy levels and performance and to speed workout recovery. But aside from anecdotes and testimonials, there is no research supporting ginseng's performance-boosting effects.

And recent research has been done. Wayne State University exercise physiologist H. J. Engels, Ph.D., tested ginseng on a group of female athletes. Each athlete took either a placebo or 200 milligrams of ginseng extract daily for eight weeks. The women then pedaled to exhaustion on a stationary bike while being monitored for performance factors during and immediately after exercise. Result: Ginseng provided no performance benefit, nor did recovery rate improve.

In another study, Engels looked at whether ginseng improved mood state and whether it had a positive effect on perceived exertion. Again, researchers used an eight-week supplementation period and the same bike test. Study #2 result: The herb provided no mood benefit, nor did the subjects feel they were pedaling more easily.

My recommendation: Granted, ginseng has a long history as a medicinal herb, but it hasn't been scientifically shown to provide any performance benefit.

Sodium Bicarbonate
There may be something here--if you're a sprinter. Taking a few spoonfuls of sodium bicarbonate (commonly known as baking soda) several hours before intense bouts of exercise may improve staying power. That's because sodium bicarbonate acts as a buffer in the body, so it decreases lactic acid levels.

What happens is that during high-intensity exercise--like sprinting--only carbohydrate is used as a fuel source. A by-product of carbohydrate-only anaerobic exercise is lactic acid, which is normally cleared away and subsequently used as an energy source itself. However, a problem results if lactic acid is produced faster than it is cleared. As it accumulates, it begins to hamper muscle contractions, and you soon get that heavy feeling in your legs.

Several recent studies have shown that a dose of sodium bicarbonate can delay that feeling, thus improving performance during short exercise bouts. The question is, would a shot of sodium bicarbonate before a longer, yet still intense, session of exercise--a 5-K, for instance--give you an edge?

Researchers from the University of Kansas tested this hypothesis on runners. Each was given 20 grams of sodium bicarbonate 2 hours before an intense, 30-minute treadmill run. At the end of the run, the subjects sprinted to exhaustion, simulating a finishing kick in a race. Turns out the runners gained no benefit from the supplementation, as they sprinted for the same amount of time as did a placebo group. Note: One thing this experiment showed was that something other than lactic acid buildup contributes to end-of-race fatigue.

My recommendation: Sodium bicarbonate's fatigue-busting powers come into play only for short-duration, high-intensity exercise, such as sprinting. And beware: large doses (20 grams or more) may cause severe intestinal cramping, bloating and diarrhea.

Creatine
Creatine is found in the muscles and is crucial for high-intensity muscle contractions. During short, intense activities, such as sprinting or weight lifting, creatine (as creatine phosphate) regenerates the energy necessary to maintain muscle contractions. Like sodium bicarbonate, creatine also helps buffer the lactic acid that accumulates during high-intensity exercise. Further, research shows that loading up on creatine boosts creatine levels in the muscles, which should mean higher energy levels, faster running and delayed fatigue.

But is that what happens? Researchers from the U.K. and Sweden sought the answer. Sure enough, they showed that five days of creatine supplementation at 25 grams a day in trained runners improved 1000-meter run times. Creatine supplementation also improved 300-meter sprint times.

So far, so good. But creatine "loading" doesn't always work. Witness a recent study led by Melvin Williams, Ph.D., at Old Dominion University in Virginia, wherein athletes took either a placebo or 25 grams of creatine a day for seven days. Williams then videotaped the athletes during a 60-meter sprint. The result was that creatine supplementation had no effect on running velocity at any point during the sprint.

Creatine supplementation does seem to hold promise for vegetarians, who get little or no dietary creatine, since it is only obtained from meat. Realize, however, that one side effect of creatine supplementation is weight gain, most likely from water retention or from muscle-tissue gain.

My recommendation: Research results on creatine supplementation are mixed. Future research may show that supplementation is appropriate for non-meat eaters.

Branched-Chain Amino Acids
Branched-chain amino acids, or BCAAs, have been a hot topic for years now. One reason for this is that they do show promise for endurance athletes. Several well-designed studies suggest that supplemental branched-chain amino acids may improve performance and help prevent the muscle degradation that occurs during endurance training.

BCAAs, along with 17 other amino acids, are the "building blocks" that form all of the protein in our bodies. The three BCAAs are found primarily in muscle, and during long sessions of exercise (2 hours or more), these amino acids are broken down and burned for energy. If this happens often enough, muscle protein begins to dwindle.

That's when BCAA supplementation may come into play. Researchers from the University of Tasmania in Australia investigated the effects of BCAA supplementation on muscle damage in a group of cyclists. Subjects were given either a placebo or 12 grams of BCAAs daily for six days. (This amount is about double what you normally get from dietary sources--mostly meats and beans.) Immediately following the supplementation period, subjects cycled hard for 2 hours. After this exercise bout, blood samples were taken every hour for several hours, then once a day for four days. The researchers then measured muscle-tissue damage based on various enzyme levels in the blood.

Compared to the placebo group, those receiving BCAA supplementation showed decreased muscle damage, leading researchers to believe that supplementation may have helped replace the BCAAs lost during exercise. But before you try BCAA supplementation, remember that by far the best way to maintain adequate muscle tissue is by getting enough calories and protein. And while the subjects in this study had no adverse side effects from BCAA supplementation, we don't yet know the long-term effects of supplementation.

My recommendation: Of the four supplements reviewed here, branched-chain amino acids show the most promise for distance runners. Nevertheless, wait for more research before trying them.

Liz Applegate, Ph.D., is the Nutrition Editor for Runner's World. She is a member of The National Triathlon Training Camp Elite Team, and teaches at the University of California at Davis.