of water every 15 to 20 min of exercise (Convertino et al,
1996). If the activity lasts less than 1 h, water is gener-
ally the recommended fluid. When the exercise lasts
more than 1 h, addition of 4–8% carbohydrate (glucose,
sucrose, fructose, glucose polymers, and the like) and/or
electrolytes can be beneficial (Murray et al, 1989). This
amount of carbohydrate with the addition of electrolytes
ensures maximal stimulation of fluid absorption because
of increased palatability and aids in gastric emptying.- Fluid intake after exercise is necessary to replace
losses incurred during the activity. Body weight
changes are the best method of determining fluid
replacement amounts after exercise. Five hundred
milliliters of fluid should be consumed for every 1 lb
of weight lost (Shirreffs et al, 1996). Foods consumed
should be rich sources of sodium and potassium, such
as fruits and vegetables, particularly if the sweat loss
was high (Burke, 1997).
VITAMINS
- Most sedentary adults in the United States meet the
Dietary Reference Intakes (DRIs) for the B vitamins
involved in energy metabolism (vitamin B 12 , folate,
niacin, riboflavin, and thiamin) (Alaimo et al, 1994)
(see Table 14-2).- Active individuals expend energy in exercise that ele-
vates both caloric and nutrient needs; however, for the
most part, increased nutrient needs are met when ath-
letes consume more calories. Athletes who restrict
their intake for the purpose of maintaining a lower
body weight may be at increased risk for nutrient defi-
ciencies and may not be meeting DRI recommenda-
tions (Janelle and Barr, 1995). - The majority of research has indicated that athletes
are consuming adequate amounts of these micronutri-
ents; however, more research is necessary to ade-
quately evaluate the B 12 and folate status of athletes
(Fogelholm, 1995). - Deficiencies of the B vitamins have been shown to
compromise performance, and when individuals with
documented deficiencies are provided supplemental B
vitamins, noted increases in performance are observed
(van der Beek et al, 1988; 1994).
MINERALS- Active individuals are encouraged to consume cal-
cium in amounts consistent with the DRI for their age
86 SECTION 1 • GENERAL CONSIDERATIONS IN SPORTS MEDICINE
TABLE 14-2 Dietary Reference Intakes for Selected Vitamins
NUTRIENT LIFE STAGE GROUP RDA∗ UL† SELECTED FOOD SOURCES
Folate Male Enriched cereal grains, dark leafy vegetables, enriched and whole-grain
19–50 y 400 μg/d 1000 μg/d breads and bread products, fortified ready-to-eat cereals
Female
19–50 y 400 μg/d 1000 μg/d
Niacin Male Meat, fish, poultry, enriched and whole-grain breads and bread products,
19–50 y 16 mg/d 35 mg/d fortified ready-to-eat cereals
Female
19–50 y 14 mg/d 35 mg/d
Riboflavin Male Organ meats, milk, bread products and fortified cereals
19–50 y 1.3 mg/d ND
Female
19–50 y mg/d ND
Thiamin Male Enriched, fortified, or whole-grain products, bread products and
19–50 y 1.2 mg/d ND ready-to-eat cereals
Female
19–50 y 1.1 mg/d ND
Vitamin B 6 Male Fortified cereals, organ meats
19–50 y 1.3 mg/d 100 mg/d
Female
19–50 y 1.3 mg/d 100 mg/d
Vitamin B 12 Male Meat, fish, poultry, fortified cereals
19–50 y 2.4 μg/d ND
Female
19–50 y 2.4 μg/d ND
SOURCE: National Academy of Sciences (1998).
ABBREVIATION: ND = not determined.
*Recommended dietary allowances are set to meet the needs of most (97%) individuals in an age and gender group.
†Tolerable upper intake level is the maximum level of daily nutrient intake that is likely to pose no risk of adverse effects.