What vitamin D doesVitamin D is one of several substances called vitamins, which the body needs to grow and develop normally. Vitamin D is famous for its role in helping the body absorb the calcium needed for strong bones and in maintaining an adequate level of calcium in the blood. A deficiency of vitamin D leads to a softening of the bones that in children is called rickets and in adults osteomalacia.
Vitamin D also plays a role in promoting cell growth, in building our immune function, and in reducing inflammation. New research is studying the role these activities may play in the development of several chronic diseases, including heart disease, multiple sclerosis, and diabetes. Checking the patient’s vitamin D status is becoming a common laboratory test ordered by doctors, and levels less than 30 nanomoles per liter (nmol/l) of blood indicates a deficiency.
How can we get this vitamin?Food sources of vitamin D are mainly fatty fish like salmon, trout, and sardines, as well as foods fortified with the vitamin, such as milk, cereal, and a variety of snack bars. Food sources, however, may only provide about 200 international units (IU) per day, and the recommended intake for adult ages 51 to 70 years old is 400 IU/day—so people usually have to take supplements. A daily supplement of the active form of vitamin D (D3) of from 800 IU to 1000 IU is often recommended and is considered safe.
Vitamin D’s links to diabetesVitamin D’s connection to diabetes is still being studied, but we do know that this vitamin is found in the beta cells that make insulin and that insulin secretion is dependent on calcium—which, as was stated above, is dependent on vitamin D. Providing adequate vitamin D has improved insulin secretion in animals, but more research is definitely needed to confirm this in humans.
While we wait for more study results, we must do what we can to maintain an adequate level of vitamin D in the blood. Food sources, supplements, or a little sunshine (just 15 to 20 minutes exposure three times a week) is necessary.
Who’s at risk of a deficiency?Those at greatest risk for vitamin-D deficiency are:
- breast-fed babies
- older adults
- people who are obese, because their increased fat stores interfere with how vitamin D is released into the blood stream
- others with limited sun exposure
- people with darker skin color, who have greater amounts of melanin in their skin, a substance that acts as a natural sun blocker
- people who wear clothing that covers most of their skin