If you shun the sun, suffer from milk
adhere to a strict vegetarian diet, you may be at risk for
vitamin D deficiency.
Known as the sunshine vitamin, vitamin D is produced by the body in response to
sunlight. It is also occurs naturally in a few foods -- including
some fish, fish
liver oils, and egg yolks -- and in fortified dairy and grain products.
Vitamin D is essential for strong bones because it helps the body use
from the diet. Traditionally, vitamin D deficiency has been associated with
rickets, a disease in which the bone tissue doesn't properly mineralize, leading
to soft bones and skeletal deformities. But increasingly, research is revealing
the importance of vitamin D in protecting against a host of health problems.
Symptoms and Health Risks of Vitamin D Deficiency
Symptoms of bone pain and
muscle weakness can mean you have a vitamin D deficiency. However, for many
people, the symptoms are subtle. Yet even without symptoms, too little vitamin D
can pose health risks. Low blood levels of the vitamin have been associated with
- Increased risk of death from cardiovascular disease
- Cognitive impairment in
- Severe asthma in children
Research suggests that vitamin D
could play a role in the prevention and treatment of a number of different
conditions, including type1 and type 2 diabetes,
intolerance, and multiple sclerosis.
Causes of Vitamin D Deficiency
Vitamin D deficiency can occur for a number of
You don't consume the recommended levels of the vitamin over time. This is
likely if you follow a strict vegetarian diet, because most of the natural
sources are animal-based, including fish and fish oils, egg yolks, cheese,
fortified milk, and
Your exposure to sunlight is limited. Because the body makes vitamin D when
your skin is exposed to sunlight, you may be at risk of deficiency if you are
homebound, live in northern latitudes, wear long robes or head coverings for
religious reasons, or have an occupation that prevents sun exposure.
You have dark skin. The pigment melanin reduces the skin's ability to make
vitamin D in response to sunlight exposure. Some studies show that older adults
with darker skin are at high risk of vitamin D deficiency.
Your kidneys cannot convert vitamin D to its active form. As people age their
kidneys are less able to convert vitamin D to its active form, thus increasing
their risk of vitamin D deficiency.
Your digestive tract cannot adequately absorb vitamin D. Certain medical
problems, including Crohn's disease, cystic fibrosis, and celiac disease, can
affect your intestine's ability to absorb vitamin D from the food you eat.
You are obese. Vitamin D is extracted from the blood by fat cells, altering
its release into the circulation. People with a body mass index of 30 or greater
often have low blood levels of vitamin D.
Tests for Vitamin D Deficiency
The most accurate way to measure how much vitamin D is in your body is the 25-hydroxy vitamin D blood test. A level of 20 nanograms/milliliter to 50 ng/mL is considered adequate for healthy people. A level less than 12 ng/mL indicates vitamin D deficiency.
Treatment for Vitamin D Deficiency
Treatment for vitamin D deficiency
involves getting more vitamin D -- through diet and supplements. Although there is no consensus on vitamin D
levels required for optimal health -- and it likely differs depending on age and
health conditions -- a concentration of less than 20 nanograms per milliliter is
generally considered inadequate, requiring treatment.
Guidelines from the Institute of Medicine increased the recommended dietary allowance (RDA) of vitamin D to 600 international units (IU) for everyone aged 1-70, and raised it to 800 IU for adults older than 70 to optimize bone health. The safe upper limit was also raised to 4,000 IUs.
Institute of Medicine: "Dietary Reference Intakes for Calcium and vitamin D."
Office of Dietary Supplements, National Institutes of Health; "Dietary
Supplement Sheet: Vitamin D."
Melamed M. Archives of Internal Medicine, August 2008.
News release, Peninsula Medical School News.
WebMD Health News: "Low Vitamin D Linked to Severe Asthma."
Garland C.F. Annals of Epidemiology, July 2009.
"25-hydroxy Vitamin D Test."
Harvard School of Public Health: "Vitamin D: How Much Is Enough?"
Reviewed by Kathleen M. Zelman, MPH, RD, LD on May 04, 2012