For almost all vitamins and minerals, doses beyond the RDA
cause side effects that not only
can decrease performance, but also
can cause disability or death. •^
Vitamin A
excess can cause headache, loss of appetite, vomiting,
hair loss, itching, bone pain,
and kidney and liver damage. Long-
term use is associated with osteoporosis and hip fractures.
-^
Vitamin B
3 (niacin)
prevents the release of fatty acids. This can
adversely affect endurance performance. Excess B
3 can release
histamine, causing flushing, itching, asthma, and gastrointestinal problems. Vitamin B
3 can cause gout, diabetes, and liver
damage.
-^
Vitamin B
6 (pyridoxine)
can cause depletion of glycogen stores.
An excess can cause neurologic problems, including clumsiness and gait disturbance. It can interfere with the action of prescribed medicines.
-^
Folic acid
excess can camouflage vitamin B
12 deficiency,
allowing neurologic problems associated with B
12 deficiency to
progress unchecked.
-^
Vitamin C
excess can cause decreased levels of vitamin B
12
,
increase estrogen levels, and cause diarrhea and kidney stones.
-^
Vitamin D
excess can cause increased calcium in the blood and
kidney stones.
-^
Vitamin E
excess can cause malaise, gastrointestinal problems,
blurred vision, headache, bleeding tendencies, and possibly hypertension.
-^
Vitamin K
excess can interfere with the action of prescribed
medicines and cause jaundice in a newborn infant.
-^
Calcium
excess can cause kidney and neurologic disease.
-^
Chromium
excess can cause kidney failure and lung cancer.
-^
Copper
excess can cause liver and kidney disease, anemia, and
mental deterioration.
-^
Fluoride
excess can cause mottled t
eeth, gastrointestinal
problems, muscle contractions, and heart disease.
-^
Iron
excess can cause liver failure; diabetes; testicular atrophy;
arthritis; and heart, skin and neurologic disease.
-^
Magnesium
excess can cause tremor, spasm, rapid heart rate, and
high blood pressure.
-^
Manganese
excess can cause headaches, weakness, cramps,
impotence, Parkinson-like symptoms, and psychosis.
-^
Molybdenum
excess can cause gout.
-^
Selenium
excess can cause hair loss, fingernail abnormalities,
emotional problems, and fatigue.
-^
Sodium
excess can cause fluid retention and high blood pressure.
Weight gain can limit performan
ce in weight-dependant sports.
-^
Zinc
excess can cause stomach ulcers, pancreatitis, lethargy,
anemia, fever, nausea, and lung problems. Zinc excess reduces “good” cholesterol (HDL) and increases “bad” cholesterol (LDL). It is also associated with impaired immune function and decreased copper absorption.
Conclusion
The functions, increased requirements, and ergogenic and
ergolytic effects of vitamins and minerals are summarized in
Table
26
, below. In athletes without nutritional deficiencies, nutritional
supplements do not exhibit an ergogenic effect.
Ideally, get the recommended daily allowance from food. If your
diet is not ideal and you wish to supplement, do so only up to the RDA.
Megadoses not only may fail to improve performance but also
may be toxic.
Nutrition for Sports, Essentials of 128