Vitamin D helps your body absorb calcium for healthy bones, and supports the immune system. It's also been linked to lowering the length and severity of respiratory infections.
Your skin makes vitamin D when it's exposed to ultraviolet light from the sun. People with darker skin need more time in the sun, and people who are obese (body mass index greater than 30) can have difficulty absorbing vitamin D through their diets.
Deficiency Signs
Known as the sunshine vitamin, it improves calcium absorption and helps create strong bones. It is also involved in regulating the brain and nervous system, helping with mental health, and reducing inflammation in the body.
A deficiency may develop if you don’t spend enough time outdoors or eat enough of certain foods. It can also be caused by specific medical conditions and some medications. Those at risk include people with darker skin (it takes longer for the skin to make vitamin D), those taking some types of medication (such as anti-convulsants and glucocorticoids) and those with obesity, as fat cells prevent the body from absorbing vitamin D.
In the case of children, a vitamin D deficiency can cause rickets if they don’t get enough sun or supplementation. It can have long-term psychological effects in later life, and has been linked with depression, schizophrenia and dementia. Children with low vitamin D levels in childhood also appear to have higher scores on tests that measure behavior problems in adolescence.
Health Risks
Vitamin D deficiency can cause a variety of health problems. In adults, the deficiency can lead to osteomalacia (soft bones) or to secondary hyperparathyroidism that increases risk of bone fractures. In children, the deficiency can cause rickets, a condition that causes bowed legs.
Severe vitamin D deficiency can also result in a buildup of calcium in the blood, which can lead to kidney and liver disease. It can also lead to a weakness of the heart muscle (cardiomyopathy). People with severe vitamin D deficiency may experience a general feeling of being unwell, along with bone pain, joint pain (arthralgias), fatigue and a tingling sensation in the muscles (fasciculations).
The Recommended Dietary Allowance for adults is 600 international units (IU) of vitamin D a day. However, some people may need higher doses of the nutrient because of medical conditions or other reasons. Vitamin D is available in a variety of foods, including some fish, fortified milk products and orange juice. It is also made naturally in your body when your skin is exposed to sunlight, and it's found in some dietary supplements. For example, many multivitamins contain vitamin D. Other supplemental sources include fatty fish and egg yolks.
Remedial Tips
Vitamin D, also known as the sunshine vitamin, is essential for good health and is responsible for calcium absorption that strengthens bones. It helps maintain a healthy immune system, regulates insulin levels and supports a strong heart and lungs.
But vitamin D is present in very few foods and often at low levels, meaning many people have a hard time achieving their daily recommended intake. In addition, some groups of people -- including those with a milk allergy or lactose intolerance, infants who receive only breast milk and those on a restricted diet such as an ovo-vegetarian or vegan diet -- have a higher risk for deficiency.
Experts recommend that adults get enough vitamin D by eating a variety of foods and spending some time outdoors every day, especially in the summer months when UV rays are strongest. They also suggest taking vitamin D supplements, ideally with the form D3 (the more active version). For example, UnityPoint Health's Molly Ropte, DO, says the typical adult should take 600 international units a day of the supplement. However, she cautions that you should always speak with your doctor before starting a new supplement. The best way to know if you need a higher or lower dose is by getting your blood level tested for 25-hydroxy vitamin D, which most doctors can do in a routine visit.