Issue: 15.04 May/June 2005

Nutrition Roundup

This issue's Roundup reviews two recent studies on supplements that purport to decrease muscle damage and new research on the effects of green tea for endurance athletes.

By Christopher Mohr

Christopher Mohr, MS, RD, LDN, is a doctoral candidate in Exercise Physiology at the University of Pittsburgh. He is a registered and licensed dietitian and was a sports nutritionist at the University of Massachusetts for two years.

Antioxidants & Women
It is well established that exercise—specifically eccentric exercise—increases the production of reactive oxygen species (ROS). ROS have been associated with muscular fatigue and muscular damage. Subsequently, it is theorized that having increased levels of antioxidants in the blood may attenuate this normal increase in ROS, thereby reducing muscle damage.

In this study, 18 nontrained women 19 to 31 years of age participated in a double-blind, placebo-controlled trial in which researchers provided participants an antioxidant supplement or a placebo. Subjects were asked to consume the supplement three times per day for 14 days prior to the protocol and for two days post-protocol. Those who took the supplements were consuming 400 IU of vitamin E, 1 gram of vitamin C, and 90 micrograms of selenium a day.

The protocol consisted of four sets of 12 reps using non-dominant arm elbow flexors (biceps) over a full range of motion to elicit greater muscle damage. Subjects were also instructed to take five seconds to complete the eccentric portion of the exercise to ensure adequate muscle damage.

The researchers then used a number of known plasma markers of muscle damage to determine what, if any, effects the antioxidant combination product provided. As expected, the exercises did in fact elicit biomarkers of oxidative stress. The antioxidant therapy used in this study significantly reduced the normal rise in protein oxidation, which is one marker of oxidative stress, and had a modest but significant effect on another biomarker as well.

Considering this was the first study to date in women, and very few studies have been done at all in this area, more research is clearly necessary. It is also important to note that these were untrained women. It would be interesting to see if the same results would be seen in trained individuals, who are more accustomed to exercise stressors.

While it is not clear whether consuming additional antioxidants will boost performance, many nutritionists recommend that everyone—athlete and nonathlete—consume antioxidants for their overall health benefits. The first choice should be foods that are high in antioxidants: fruits and vegetables are great sources of vitamins C and A, almonds and wheat germ are great sources of vitamin E, and fish and meat are great sources of selenium. In addition, recommending a complete multivitamin that has sufficient doses of vitamins C, E, and selenium may also prove helpful.

Study Specs: "Combine Antioxidant Treatment Effects on Blood Oxidative Stress after Eccentric Exercise," in Medicine and Science in Sports and Exercise, by A. Goldfarb, R. Bloomer, and M. McKenzie. 37(2), 234-239, 2005.


Football Players Test HMB
There is some evidence that in untrained individuals HMB (beta-hydroxy beta-methylbutyrate) possesses anti-catabolic properties, meaning it prevents muscle breakdown. However, the research is still very limited on this supplement.

Most recently, HMB was put to the test in a population of highly trained competitive athletes. Researchers felt that if a product could enhance recovery and act as an anticatabolic agent with athletes who participate in high-volume, high-intensity training, it would be very useful.

Twenty-six NCAA Division III football players from various field positions were involved in this single blind experiment. Players were randomly assigned to either 3 grams of HMB or a placebo. The researchers tested the players before and after 10 days of preseason training, during which subjects participated in 19 practices and three resistance training sessions.

Various blood measures were taken, including testosterone and cortisol levels (anabolic and catabolic hormones, respectively), and the athletes' performance was measured. Finally, the athletes completed questionnaires asking about intensity, soreness, and fatigue.

In the end, there were no significant changes in levels of intensity, soreness, or fatigue. There were also no significant differences in the hormone levels measured between groups, and there were no significant differences in any of the performance measurements completed. This study does not support the use of HMB for its purported anticatabolic or improved strength gain claims.

Study Specs: "Effects of beta-Hydroxy beta-Methylbutyrate on Power Performance and Indices of Muscle Damage and Stress During High-Intensity Training," in The Journal of Strength and Conditioning Research, by J. Hoffman, J. Cooper, M. Wendell, J. Im, J. Kang. 18(4), 747-752, 2004.


Does Green Tea Affect Endurance Capacity?
The effects of green tea on endurance capacity, energy metabolism, and fat oxidation were studied over a 10-week period in mice. After consuming green tea extract the mice had higher rates of fat oxidation and their swimming times increased by 8 to 24 percent.

The mechanisms utilized by the researchers allowed them to determine that the increased effects in endurance performance and increased fat oxidation were mediated in part by epigallocatechin (EGCG), which is the primary catechin in green tea. Basically, catecholamines trigger our "fight or flight" response, which are released in times of cold, fear, and exercise. These cause an increase in heart rate and, subsequently, thermogenesis. This is normally a transient process because the enzymes in this reaction are quickly hydrolyzed. However, EGCG inhibits this hydrolysis and allows the process to continue beyond the otherwise short period.

Although this small study was conducted in mice, these findings support previous work with similar outcomes in both rats and humans. Green tea, therefore, shows serious promise for enhancing endurance performance and increasing endurance capacity.

Drinking several cups of green tea has numerous other health benefits. Green tea has been shown to increase thermogenesis, acts as a powerful antioxidant, has numerous properties that may help fight cancer, and has been correlated with overall decreased bodyweight and bodyfat in regular consumers. Green tea is the number two beverage consumed in the world (water is first), and I recommend that athletes drink at least a couple cups of it a day. (Note that one cup contains about 50 mg of caffeine.)

Study Specs: "Tea Extract Improves Endurance Capacity and Increases Muscle Lipid Oxidation in Mice," in American Journal of Physiology-Regulatory, Integrative and Comparitive Physiology, by T. Murase, S. Haramizu, A. Shimotoyodome, A. Nagasawa, and I. Tokmitsu. 288:708-715, 2005.

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