Vitamin D is one of the most important vitamins for overall health but more than half the world's population is deficient in the vital nutrient. Inadequate vitamin D absorption not only causes skeletal disorders, such as rickets and osteoporosis, but may contribute to chronic conditions such as cancers, diabetes and heart disease. Although vitamin D is produced by the body from exposure to sunshine, many health conditions, environmental issues and dietary concerns can contribute to insufficient vitamin D absorption.
Identification
Vitamin D, found in every cell in the body, works with phosphorus and calcium to sustain strong bones. Muscles need vitamin D to carry messages between the brain and every body part. Vitamin D helps the immune system destroy invading bacteria and viruses. Exposure to sunlight is the most reliable way for your body to generate adequate vitamin D. Consuming fish, mushrooms and fortified milk and cereal can add vitamin D to your diet. The recommended daily allowance, or RDA, for vitamin D is 600 IU. For adults 71 years of age and older, 800 IU are recommended.
Age
As you age, your skin reduces its ability to absorb and utilize the sun to make vitamin D. Compared with a 20-year old, by 70 years of age, 50 to 75 percent less vitamin D is made from the same amount of sun, according to the American Dietetic Association. In addition, the body may not absorb nutrients from food as well, including vitamin D. Many elderly people that are housebound or institutionalized are not exposed to the sun on a regular basis. As many as 60 percent of patients in hospitals are vitamin D deficient as are 80 percent of nursing home residents. Older people with lower blood levels of vitamin D and reduced muscle function may be more likely to lose their balance and fall.
Geography
Vitamin D production is most efficient during the summer months from 10 a.m. to 3 p.m. when the sun's rays are most intense. Many people work indoors and are not exposed to sunlight when it is most effective. Geography plays a role on vitamin D deficiencies. The further you live from the equator, the more sun exposure is necessary to generate vitamin D. People who live in latitudes above 42 degrees north, such as Chicago, Boston and Portland, may not receive the benefit of sufficient sun absorption from late October to early March. In areas with a latitude above 35 degrees north, as far south as Atlanta, vitamin D production may not occur from November to February, according to the "Vegetarian Journal."
Skin Color
Melanin is the pigment that gives skin its color. People with dark skin have a higher percentage of melanin, which protects against sun damage, but also blocks the ultraviolet rays necessary for the production of vitamin D. Dark skin may need twice the exposure to sunlight, as compared to fair-skin, in order to generate the same amount of vitamin D, according to Harvard School of Public Health.
Medical Issues
Because vitamin D is a fat-soluble, some health conditions that impair the body's ability to absorb fat, such as cystic fibrosis, celiac disease, pancreatitis or inflammatory bowel disease, may contribute to a vitamin D deficiency. Obesity, liver or kidney disease can also impair metabolism of vitamin D, according to Scientific American.
Sunscreen
People are becoming more aware of the damaging effects of the sun and its relationship to skin cancer. The wise decision to use sunscreen to block the UV rays makes it more difficult for the body to produce vitamin D. Even weak SPF 8 sunscreens block the body's ability to generate vitamin D by 95 percent. In addition, pollution can be a concern when it blocks the sun's rays.
References
- University of California: Population Gets Insufficient Amounts of Vitamin D, Says UC Riverside Biochemist; July 2010
- Scientific American: Vitamin D Deficiency Linked to Parkinson's Disease, Cognitive Decline; Nicholette Zeliadt; July 2010
- Office of Dietary Supplements: National Institutes of Health: Vitamin D
- American Dietetic Association Complete Food and Nutrition Guide; Roberta Larson Duyff; 2006
- Vitamin D Myths, Facts and Statistics; Mike Adams' January 2005
- Vegetarian Journal: The Vegetarian Resource Group; FAQs About Vitamin D; Reed Mangels; 2009
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