Vitamin D is a fat-soluble vitamin that helps the body absorb calcium and promotes bone and immune system health. Most of your vitamin D needs can be met simply through exposure to the sun. As your skin is exposed to the sun's ultraviolet rays, it begins to produce thousands of units of vitamin D, which it then converts to steroid hormones that help maintain blood calcium levels. You can also find vitamin D in meat and dairy products, fortified cereals and supplements.
Infants and Children
The Institute of Medicine sets recommended daily allowances and adequate intake values for all nutrients. As with most vitamins, there is not enough scientific evidence to support an RDA for vitamin D for infants. The IOM does provide an AI, however, or an amount believed to be sufficient to satisfy infant's requirements: 10 micrograms per day from ages 0 to 12 months. The RDA for children ages 1 to 8 is 15 micrograms. One microgram is the equivalent of 40 international units, so infants need about 400 IUs of vitamin D, while children need 600.
Adults
The IOM's RDAs for vitamin D are set with the assumption that you achieve at least minimal sunlight. Males and females have the same vitamin D needs. From ages 9 to 70, males and females should consume 15 micrograms, or 600 IUs of vitamin D each day. After age 70, men and women need about 20 micrograms, or 800 IUs per day. Older individuals are often vitamin D-deficient, and need additional amounts to promote bone health and prevent diabetes and cardiovascular disease. Pregnant and nursing mothers have the same vitamin D needs as other adults.
Severe Side Effects
Vitamin D is interesting because once your skin produces about 20,000 units as a result of sunlight exposure, the ultraviolet rays then begin to destroy any excess amounts. Basically, the more vitamin D you make, the more is eliminated, and thus your body reaches a state of vitamin D homeostasis and you avoid vitamin D toxicity. Toxicity can occur, however, with excess supplement intake. Consuming more than 50,000 IUs of vitamin D each day may result in hypercalcemia, or an abnormally high level of blood calcium, which can result in bone loss, kidney stones and calcification of organs. Hypercalcemia is unlikely with dietary intake of less than 10,000 IUs a day, according to the Linus Pauling Institute at Oregon State University.
Mild Side Effects
Possible mild side effects with vitamin D supplements may include dry mouth and thirst, gastrointestinal disturbances, vomiting, itchiness, cognitive disturbances and fatigue, muscle problems and urinary irregularity. While you cannot get too much vitamin D from sunlight and it's almost impossible to get too much from food, scientists are still investigating the exact amount at which side effects from supplements occur. Vitamin D may interact with certain medications as well, so be sure to talk to your physician before taking a vitamin D supplement.
Sources
If you get plenty of sunlight, you will get more than enough vitamin D. Just a few minutes in the summer sun can produce up to 200 times the vitamin D your body needs, according to the Vitamin D Council. The highest dietary sources of vitamin D include pink salmon, sardines and other seafood products, fortified oatmeal, fortified milk, fortified orange juice and egg yolk.
References
- Vitamin D Council; Vitamin D Physiology; John Jacob Cannell; January 2006
- Institute of Medicine; Dietary Reference Intakes; Vitamins and Minerals; 2004
- Linus Pauling Institute at Oregon State University; Vitamin D; Jane Higdon; 2004
- BBC News; Elderly Need More 'Sun Vitamin'; May 2009
- University of Maryland Medical Center; Vitamin D; June 2010
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