Comment: It should be noted that this study group was small. It would be interesting to have the authors repeat this study with a larger sample size over a longer period of time. Until proven otherwise, the message to your patients should be: Whether you are in shape or not, if you eat more fat than your body needs, your body will most likely store it.
Creatine is a hot, new ergogenic aid. Like so many other miracle substances, companies marketing creatine have been very enthusiastic and have been very liberal with their claims. I wrote an article on creatine in the April 8, 1994 issue of Dynamic Chiropractic. At the time, I had not found any published data using creatine on healthy, weightlifting humans. This double-blind, placebo-controlled study involved five subjects who were given four, 5 gm servings of creatine orally or a placebo. Before and after each blinded administration, the subjects did five sets of 30 repetitions of single leg knee extensions. The results: Peak torque production was greater in those subjects who took creatine in the second, third, and fourth sets, as well as parts of the first and fifth sets. Creatine ingestion also lowered plasma ammonia levels. The authors concluded that oral creatine could reduce fatigue in repeated sets of an aerobic exercise. They postulated that the fatigue reduction could be due to one or a combination of the following: a) increase in pre-exercise phosphocreatine levels; b) increase in muscle buffering capacity (although no blood lactate changes were found in this study); c) increase in phosphocreatine resynthesis; d) all of the above could potentially stimulate ATP resynthesis.2
Comment: One small study is certainly not the final answer, but it does make it easier to recommend creatine on a trial basis to your patients involved in heavy weightlifting who are looking for a natural advantage. Remember too that the results in this study were with a whopping 20 gm per day dose -- an amount that challenges even your most compliant patients.
Magnesium is an amazing mineral. Some day I am going to write a series of articles on magnesium, but keeping with today's sports theme, we will focus on a study looking at its ergogenic effects. Twenty-six untrained people were put on a weightlifting program and given either 150 percent of the RDA of magnesium or 70 percent of the RDA of magnesium. After seven weeks of training, three times per week, the subjects were tested. Strength gains in the magnesium 150 percent group were significantly greater than in the group that received magnesium levels at 70 percent of RDA.3
Comment: My recommendation is if you have patients who are engaged in a rigorous exercise program, you should examine their nutrient intakes carefully and not be afraid to place them on levels greater than the RDAs. A logical follow-up to this study would be a repeat study using the same parameters but with well-trained individuals.
I will conclude our update by reviewing three studies that involve sports and protein. The first involved postexercise feeding for glycogen replacement. After endurance exercise, muscle glycogen levels are low. This study compared carbohydrate, protein, and a carbohydrate-protein mixture after exhaustive exercise to see which helped the body to restore muscle glycogen levels. Plasma analysis after supplementation showed higher glucose levels after carbohydrate ingestion. Plasma insulin was highest after the protein-carbohydrate combination. Plasma insulin, not glucose, is the metabolite we want to see elevated because of its strong stimulating effect on muscle glycogen storage. Muscle biopsies revealed that the carbohydrate-protein supplement combination had faster rates of muscle glycogen repletion than the carbohydrate group alone, which had significantly greater impact on glycogen repletion than the protein only group, which was a distant third.4
In the second study, researchers looked at plasma amino acid changes after endurance exercise to exhaustion in 11 triathletes. The diets included a level of protein that was 1.6 gm/kg of body weight, which is significantly higher than the RDA of 0.8 gm/kg of body weight. Carbohydrates made up 65 percent of the total caloric intake. After in-depth analysis (which will not be reviewed due to space requirements), the researchers concluded that protein requirements of athletes participating in exhaustive endurance activities should be substantially higher than the RDA. They stated that precise recommendations required further study.5
Our final protein study looked at protein requirements and muscle mass and strength changes during intensive training in novice male body builders. Using a double blind, crossover format, 12 men in their early 20s were put on a six-day-a-week, intensive, weight lifting program. Researchers found that to maintain nitrogen balance, protein needs were 1.6 to 1.7 gm/kg of body weight, which is more than double the RDA.6
Comment: It is interesting that for years athletes in the body building, Olympic lifting, and power lifting communities have ingested amounts of protein that traditional medical practitioners and dietitians have said was of no benefit to them. I expect that if studies of this nature continue, we will receive further evidence that athletes who train intensely, whether it be in aerobic or anaerobic sports, have protein requirements greater than the general public. The rule of thumb I use for my patients is as follows: In times of illness, injury, stress, or intense training, the requirements for nutrient-dense foods, macronutrients, and micronutrients all increase. I am confident we will continue to see research that validates this principle.
- Bennett, Reed, et al. Short-term effects of dietary fat ingestion on energy expenditure and nutrient balance. American Journal of Clinical Nutrition. 55:1071-1077, 1992.
- Greenhaff, Casey, et al. Influence of oral creatine supplementation on muscle torque during repeated bouts of maximal voluntary exercise in humans. Clinical Science. 84:555-571, 1993.
- Brilla and Haley. Effect of magnesium supplementation on strength training in humans. Journal of American College of Nutrition. 11:326-329, 1992.
- Zawadski, Yaspelkis, and Ivy. Carbohydrate-protein conflict increases rate of muscle glycogen storage after exercise. Journal of Applied Physiology. 72:1854-1859, 1992.
- Bazzare and Merdoch, et al. Plasma amino acid responses of trained athletes to successive exhaustion trials with and without interim carbohydrate feeding. Journal of the American College of Nutrition. 11:501-511, 1992.
- Lemon, et al. Protein requirements and muscle mass/strength changes during intensive training in novice body builders. Journal of Applied Physiology. 73:767-775, 1992.
G. Douglas Andersen, DC
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