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TABLE 8-1 Concentration of Vitamins Lost in Sweat

Vitamin

Concentration (µg per 100 ml)

Thiamin

0–15

Riboflavin

0.5–12

Nicotinic acid (total)

8–14

Pantothenic acid

4–30

Ascorbic acid

0–50

Pyridoxine

7

Folic acid (plus metabolites)

0.26

 

SOURCE: Mitchell and Edman (1951). Data based on ranges reported from several studies completed in the 1940s.

This chapter addresses whether those individuals who expend greater amounts of energy in exercise training or work require greater amounts of vitamins and whether vitamin supplementation will enhance exercise performance. Some of this information has also been covered in a previous paper (Clarkson, 1991). This chapter also examines whether exercise in a hot environment will lead to an increased requirement for certain vitamins and whether vitamin supplements will reduce heat stress.

Vitamins are classified as either water soluble or fat soluble. Watersoluble vitamins are the B complex vitamins and vitamin C. These are stored in relatively small amounts in the body and cannot be retained for long periods. If blood levels of water-soluble vitamins exceed renal threshold, they are excreted into the urine. Most water-soluble vitamins serve major functions of either energy production or hematopoiesis. With the exception of vitamin K, fat-soluble vitamins are stored in greater amounts than the water-soluble vitamins. Fat-soluble vitamins are absorbed and transported in the body in close association with lipids and have roles that are largely independent of energy production.

WATER-SOLUBLE VITAMINS

Vitamin B complex consists of eight vitamins: vitamin B1 (thiamin), vitamin B2 (riboflavin), niacin, vitamin B6 (pyridoxine), vitamin B12 (cyanocobalamin), biotin, folic acid, and pantothenic acid. The quantity stored differs among the vitamins. For example, if an individual's diet is deficient in most of the B vitamins, clinical symptoms can sometimes occur in 3 to 7 days (Guyton, 1986). Vitamin B12 is an exception because it can be stored in the liver for a year or longer. The B vitamins, except B12 and folic acid, primarily serve as coenzymes in the metabolism of glucose and fatty



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