Athletes and Minerals: A Zinc Focus
Zinc Overview:Researchers have surmised that the inadequate intake of some minerals by people engaged in strenuous exercise could lead to the lowering of endurance capacity, depressed immune function, and the development of a variety of disease states.
Additionally, certain athletes; female athletes in particular, have diets that are very low in some key minerals. The interest in this area has resulted in literally thousands of reported clinical trials, surveys, and epidemiological studies devoted to sports, exercise, and mineral nutrition.
The complexity of the roles that minerals play in the human body makes it a dynamic that does not allow for any simple conclusions. Additionally, the impact on the functioning of the human body has been seen to differ depending on the type of exercise or sport one engages in, as well as the environmental conditions that it takes place in.Anaerobic or aerobic exercise? Hot weather or cold? High elevation or at sea level? Effort level, along with exercise duration plays a role here, as well.
Despite all of these variables, certain trends can be seen for the interrelationship between mineral nutrition and exercise.
The minerals magnesium, zinc, copper, and iron appear to be the prominent minerals impacted by exercise with magnesium and zinc being the most prominent.
Long term endurance training gives rise to lowered resting serum zinc levels in both males and females as compared to sedentary controls. Severe zinc deficiency can affect muscle function, since zinc is required for the activity of several enzymes in energy metabolism in muscle.
A low muscle zinc will result in a reduction of endurance capacity. There have been many other studies which have taken a look at the effect of exercise on zinc status. There are several rationales proposed for the cause of the hypozincemia seen resulting from training in athletes. These include 1.) the expansion of plasma volume 2.) increase zinc excretion (urinary and sweat) 3.) redistribution of zinc.
Plasma zinc levels have been seen to decrease at a rate of from 12-33% during physical training, and only up to a 12% loss can be attributed to increase in plasma volume. Studies have found that urinary zinc loss increases by 10-45% after moderate exercise, and is higher in trained athletes than sedentary.
Sweat zinc losses have been seen in males (0.65mg/hour) and females (0.4mg/hr) after one hour of moderate intensity exercise. Normal dermal losses of zinc have been rated as 0.76mg/day. It has also been shown that exercise will cause zinc to be redistributed to counteract some of the physiological impact of exercise.
Zinc and Hormones:
It is of note that a study in 2006 (Kilic M, et al., Neuro Endocrinol Lett 2006;27(1-2): 247-252) examined the effect of exhaustive exercise in elite athletes, and its effect on thyroid and testosterone levels. The study determined that exhaustive exercise led to a significant inhibition of both thyroid and testosterone concentrations.
Further, the researchers found that a 4 week course of oral zinc supplementation prevented this inhibition, and they concluded that physiological doses of zinc may benefit athletic performance. The relationship here could be a real key.
Given the function of zinc in exercise, the zinc status of an individual prior to the start of exercise is an important element. To increase zinc levels you need to use one that is of good bioavailability and free of tolerance problems or adverse effects.
Zinc is an essential trace mineral involved in the function of many enzymes, zinc supplementation has been recommended to prevent or treat the adverse effects of zinc deficiency.
Zinc Chelate Absorption:
Based on a study performed at Ohio State University; the intestinal absorption rate of Zinc Bisglycinate Chelate as compared to the following three forms came to:
- Zinc Bisglycinate Chelate 3.2 times that of zinc picolinate
- Zinc Bisglycinate Chelate 1.67 times that of zinc glyconate
- Zinc Bisglycinate Chelate 3.22 times that of zinc oxide.
No question about the need for minerals and athletes. Exercise has been shown to increase the turnover of minerals in numerous studies.