Vitamin D Overview

Vitamin D is a fat-soluble vitamin that plays an important role in your body’s ability to absorb calcium and maintain the right level of phosphorus in your blood. People who don’t get enough vitamin D can experience a range of health problems, such as rickets and osteoporosis.

Vitamin D is the only vitamin that your body can manufacture on its own. Your body makes vitamin D when your skin is exposed to direct sunlight. For many people, getting 5 to 30 minutes of sun exposure a few times a week is all it takes to get enough vitamin D.

What Vitamin D Does

Vitamin D is stored in your liver. Before your body can use vitamin D, it needs to convert it into a usable form. Vitamin D is first converted into a substance known as calcidiol, and then into calcitriol. Once vitamin D is transformed into calcitriol, it is able to help your body absorb both calcium and phosphorus. Calcium and phosphorus are two minerals that are essential to bone health. As a result, low vitamin D levels can lead to problems with bone health.

Why it’s Important

Vitamin D plays an important role in maintaining healthy bones. Children who don’t get enough vitamin D may suffer from rickets, a condition characterized by a softened or weakened bones. In adults, rickets is known as osteomalacia. Adults with chronically low vitamin D levels may also eventually develop osteoporosis, or brittle bones. There is also evidence that low vitamin D levels are connected to conditions such as rheumatoid arthritis, heart disease, diabetes, and breast and colon cancer.

Signs You’re Not Getting Enough Vitamin D

It’s not always easy to tell when you’re not getting enough vitamin D. However, groups that are at particular risk of vitamin D deficiency include breast-fed infants, people with dark skin, older adults, people who do not get a significant amount of sun exposure (particularly those that live in northern latitudes), individuals who suffer from fat malabsorption, and those who are obese or have had gastric bypass surgery.

Initial vitamin D deficiency symptoms include muscle aches, bone pain and weakness. Infants may have muscle spasms and a soft skull, and they may have trouble sitting or crawling. Those with a severe vitamin D deficiency may experience deformed bones, or bones that often fracture, and they may have trouble walking.

A doctor may suspect vitamin D deficiency based on a number of factors. Symptoms such as those described above, along with evidence of low levels of sun exposure or poor diet, may lead a doctor to suspect vitamin D deficiency. If your doctor thinks you are vitamin D deficient, X-rays or blood tests may be done to confirm the diagnosis. Usually, increased sun exposure, changes in diet or vitamin D supplements will resolve vitamin D deficiency.

Resources

Mayo Clinic Staff. (2007). Vitamin D. Retrieved December 10, 2009, from the Mayo Clinic website: http://www.mayoclinic.com/health/osteoporosis/DS00128.

MedlinePlus Staff. (2008). Rickets. Retrieved December 10, 2009, from the MedlinePlus website: http://www.nlm.nih.gov/medlineplus/ency/article/000344.htm.

MedlinePlus Staff. (2009). Vitamin D. Retrieved December 10, 2009, from the MedlinePlus website: http://www.nlm.nih.gov/medlineplus/ency/article/002405.htm.

Merck Home Manual Staff. (n.d.). Vitamin D. Retrieved December 10, 2009, from the Merck website: http://www.merck.com/mmhe/sec12/ch154/ch154j.html.

National Osteoporosis Foundation Staff. (n.d.). Vitamin D. Retrieved December 10, 2009, from the National Osteoporosis Foundation website: http://www.nof.org/prevention/vitaminD.htm.