Tell me about...
Vitamin D
What is
vitamin D?
Vitamin D is actually a term for a group of hormones that
are stored mainly in the liver, as well as fat and muscle
tissue. It is one of three vitamins naturally manufactured
by the body, and it is produced by a chemical reaction to
the ultraviolet radiation contained in sunlight.
Why do
we need it?
Vitamin D increases the body's absorption and metabolism
of calcium and phosphorus. This makes it essential to maintaining
strong, healthy bones and teeth.
How much
vitamin D should I take?
According to the National Academy of Sciences, the recommended
daily allowance (RDA) for vitamin D is as follows:
- Adult men: 200 international units (5 micrograms)/day
- Adult women: 200 international units (5 micrograms)/day
- Adults age 51-70: 400 international units (10 micrograms)/day
- Adults 71 and over: 600 international units (15 micrograms)/day
- Children aged 7-10: 200 international units (5 micrograms)/day
- Infants: 200 international units (5 micrograms)/day
- Pregnant/lactating women: 200 international units (5 micrograms)/day
What are
some good sources of vitamin D?
Exposure to sunlight is the easiest way to build up stores
of vitamin D. By exposing the face, hands and forearms for
between 15-20 minutes two or three times per week, most people
can manufacture all the vitamin D they need.
Vitamin D is also found in a number of food products, most
notably vitamin D-fortified milk. Other sources include egg
yolks, fish, cheese, fortified cereals and liver.
What can
happen if I don't get enough vitamin D?
Vitamin D deficiency can result in bone-related disorders
such as rickets in children and osteomalacia in adults. Vitamin
D deficiency also increases the risk of hip fractures in postmenopausal
women, and has been linked to higher incidences of prostate
cancer and breast cancer.
What can
happen if I take too much vitamin D?
High doses of vitamin D can be very toxic. In children, large
doses can cause mental retardation, stunted growth and kidney
failure. In older children and adults, too much vitamin D
can result in weakness, anorexia, nausea, diarrhea and changes
in a person's mental state. With the exception of kidney failure,
low-calcium diets and withdrawal of vitamin D from a person's
diet can usually reverse these side-effects.
Other Resources :
The
More You Know About Vitamins
The
More You Know About Nutrition
References
• Hypovitaminosis
D in medical patients. New England Journal of Medicine
March 19, 1998.
• Safe amounts of vitamins. Health News August
26, 1998.
• Vitamins, minerals, diet and prostate cancer. Harvard
Men's Health Watch May 1998.
• Vitamin D deficiency ups fracture risk. Reuters Health,
April 27, 1999.
• Vitamin D in infancy increases girls' bone density.
Reuters Health, December 28, 1999.
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