Ever wonder how some folks exercise routinely with a bounce in their step, while others get to the gym and soon end up staggering to the first chair they see?

An answer may lie in the interrelationship between a common enzyme and tiny amounts of the mineral zinc it contains. Hundreds of zinc-dependent enzymes are thought to be involved in key metabolic responses that regulate energy expenditure. Lower-than-recommended levels of zinc could therefore take a toll on the body, particularly during exercise.

One such zinc-dependent enzyme, carbonic anhydrase, helps the body clear away byproducts of daily cellular activity. The enzyme transfers carbon dioxide from body tissues to blood, and then from blood to the lungs so it can be released.

A study in 2005 by Henry C. Lukaski, a physiologist with the U.S. Department of Agriculture's Agricultural Research Service in Grand Forks, N.D., showed that low dietary zinc impairs carbonic anhydrase activity in red-blood cells, thus making a person during exercise start panting as the heart struggles to pump blood to the lungs to expel byproducts.

Significant drops in exercise efficiency

In Lukaski's study, active men in their 20s and 30s experienced a significant drop in physiological efficiency while exercising after they took 3.5 milligrams of zinc daily - about a third of the recommended dietary allowance of 11 milligrams - for nine weeks.

After a six-week break, the men exercised the same way for nine more weeks while taking 15 milligram zinc supplements daily. During that time, their physiological response was normal while they exercised.

The study showed how low zinc intake affects activity in red-blood cells and heart function during exercise. During periods of low zinc intake, carbon dioxide backs up all the way to the muscle cell, resulting in acid-laden cells requiring more oxygen for clearing toxic byproducts, Lukaski said. 

Find out about your zinc levels

Nubella readers can assess their intake of nutrients, including zinc, by clicking here, and then keying in the foods they've eaten for two days or more up to a year. The website will generate the amount of daily zinc intake from foods and compare it with recommended intakes based on gender and age.

Good sources of zinc include oysters, fortified breakfast cereals, lean beef, beans, chicken, eggs and peanuts.

Zinc, an essential mineral found in almost every cell, stimulates the activity of approximately 100 enzymes and helps protect the immune system, heal wounds, maintain senses of taste and smell, push along DNA synthesis, and supports normal growth and development during pregnancy, childhood and adolescence.

For more information on zinc, click here.

Editor's Note: This article was written by Rosalie Marion Bliss with the Agricultural Research Service and appears in April's Agricultural Research magazine. For more information on the Agricultural Research Service's human nutrition projects, click here. Other information comes from Nubella News.

Source: U.S. Department of Agriculture Agricultural Research Service
Posted by: Steve Smith
Reference: Agricultural Research
Website: www.ars.uda.gov

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