CYCLING PERFORMANCE TIPS
Vitamins are naturally occuring compounds which act as catalysts in the various metabolic pathways that convert fats, carbohydrates, and proteins into the Calories power the muscles and other cellular activities. They do not directly supply energy or serve as structural components of body cells. They facilitate these energy producing reactions, but are consumed by them. Thus the recommended daily requirements, which are supplied by a niormal, balanced diet, are independent of body size or daily energy expenditures.
Can a strenous physical training program lead to vitamin or mineral deficiencies? It is generally agreed that the vitamin needs of an athlete are no greater than those of sedentary individuals. However occasional papers do suggest that imbalances might occur among athletes. Thus many trainers and athletes, hoping to avoid even a small risk of a deficiency that might impair performance, add a supplement as a form of insurance. And the placebo effect is so strong that some athletes have actually been reported to become psychologically dependent on high dose supplements.
Vitamins are classified as water soluble or fat soluble. The fat soluble vitamins (A,D,E, and K) are primarily stored in the liver and fatty tissues. And when high dose supplements are used, this group of vitamins can accumulate to toxic levels. Water soluble vitamins (B and C) are not stored in the body to any appreciable extent, are eliminated in the urine, and must be replenished on a regular basis (by a balanced diet).
Mega-vitamin supplements can be harmful, especially with the fat soluble vitamins which are not eliminated in the urine. And there have been occasional reports that even the water soluble vitamins (B complex, and C which are excreted in the urine) can be harmful at doses of 10 to 100 times the recommended daily requirements (RDA).
RDAs have been determined by numerous governmental and professional organizations, and are not always identical. Thus they tend to be expressed as ranges. Dietary surveys indicate that athletes, replacing their daily training Calories with a balanced diet easily exceed these RDAs. The exceptions are athletes on weight loss diets or those participating in sports that glamorize unrealistically low body fat levels.
The real question is whether the "normal" blood levels of various vitamins and minerals, determined from large groups of individuals, are actually on the low side as the populations studied actually contain small numbers of marginally deficient individuals. Thus it is this comparison number that is in error, and might explain why athletes in a "low normal" range show benefits in some studies.
VITAMIN SUPPLEMENTS AND EXERCISE PERFORMANCE
There is no question that vitamin supplements improve performance in athletes with preexisting vitamin deficiencies. And it has been speculated that the improvement of performance noted in several papers was the result of treating unidentified, preexisting vitamin deficiencies (see the comment on "normal values" above).
Studies designed to avoid the weaknesses of these past papers, assessing the effect of vitamin supplementation in both male and female athletes consuming their RDA of vitamins through diet alone, have shown no benefit from the use of high potency multivitamin formulations. In addition, they have emphasized their potential toxicity as well as the fact that the use of supplements often support poor nutrition as these athletes feel their supplements eliminate the need to eat a balanced diet.
One study covered a 6 to 7 month training period. While an increase in blood and tissue levels of multiple vitamins was demonstrated, there was no evidence of an effect on athletic performance. A second studied 22 men over a 90 day period, measuring maximal oxygen uptake, endurance capacity, and isokinetic strength. This double blinded, placebo controlled study failed to demonstrate any performance advantage of vitamin supplements. It appears that it is the perceived need for vitamin supplements, based on anecdotal reports, not firm scientific evidence, that continues this overuse.
Although they may not help improve maximum levels of performance, there may be a training benefit. There is intriguing data suggesting that antioxidant vitamins can minimize free radical damage to cells. Exercising muscles generate oxygen centered free radicals which in turn can harm cell mitochondria. Vitamin E, beta Carotene, and vitamin C are all nutritional antioxidants with Vitamin E appearing to be the most effective against these exercise induced free radicals. Two studies, one using 330 mg of Vit E for 5 months during extreme endurance training in cyclists, and another using 800 IU daily for 48 days demonstrated a significant reduction in serum creatine kinase (a muscle enzyme) and microscopic cellular injury (but alas, no change in physical performance).
MINERAL SUPPLEMENTS AND EXERCISE PERFORMANCE
Minerals are chemical elements essential for normal cell functioning Calcium and phosphorus are major components of bones while sodium and potassium are found in all tissue fluids - both within and around cells. The trace elements magnesium, chloride, sulfur, and zinc play a key role in cell function while iron, manganese, cobalt, selenium copper, and iodine are found in much smaller quantities and play essential roles as catalysts in cellular chemical processes.
These minerals, found in all foods, are kept in balance through internal regulation of absorption and excretion. As a result, adequate tissue levels are once again easily provided by a balanced diet. And as with vitamins, multiple studies of body tissue mineral status in athletes failed to identify any deficiencies in those ON A BALANCED DIET compared to people engaged in normal daily activities. Athletes who are restricting energy intake to achieve a lower body weight (endurance runners for example) are the exception, and may need supplements.
Sodium has been proposed as beneficial in endurance performance by preventing hyponatremia (a low blood sodium concentration). However recent evidence suggests that it is the excess consumption of pure water that is the problem, not a lack of sodium. Aside from sodium, there is no evidence that using any single or combination of electrolyte supplements enhances physical performance. And except for iron deficiency (with documented low hemoglobin levels) the same holds true for all of the well advertised trace minerals supplements.
As with vitamins, there have been several well controlled, blinded studies on the effect of trace mineral supplements on performance. These have looked at such parameters as muscle glycogen depletion, serum free fatty acids, maximal aerobic capacity, and endurance abilities. Absolutely no benefits were identified in the group using the supplements. And side effects were even more common than with vitamins including such non specific complaints as nausea, malaise, and easy fatiguability.
The bottom line is that an athlete's vitamin and nutritional needs are readily and easily met with a balanced, isocaloric diet that meets daily Caloric expenditures. If there are special dietary considerations (a negative Caloric balance to attempt to lose weight while training for example), or a concern about how well balanced your diet may be, there is little risk (other than to the wallet) in using a common over the counter multiple vitamin once a day. Vitamin and mineral supplements are not the easy answer to increased performance.
For more details on individual vitamins and minerals, follow this link.