The amount of vitamin D appropriate for a person, based on age, gender, and health, is mapped out by the Food and Drug Administration (FDA) in the United States and by similar regulating agencies around the world. Determining how much vitamin D is being processed in your body requires a blood test. Once you have the test results in hand, you can adjust your vitamin D intake to meet the FDA guidelines.
Determining appropriate vitamin D intake is important when assessing a person’s diet and use of supplements. This fat-soluble vitamin plays a basic role in the absorption of calcium, and it is known to regulate the important processes of gene expression and cell differentiation within the body. Research shows that the majority of healthy adults in westernized society have adequate vitamin D intake, though various populations need special consideration and frequently require supplemental vitamin D in their diets. Toxicity stemming from too much vitamin D is also a concern.
The blood test to figure out how your body is handling vitamin D, called the 25-hydroxyvitaminD test, can be ordered by a physician or purchased at a pharmacy, done at home, and sent to a lab for analysis. For most people, a reading above 50 ng/ml (125 nmol/L) is an indication that their present diet is providing them with sufficient vitamin D intake. In regard to the data supporting the case that most adults receive enough dietary D vitamin, the test is most appropriately administered if there are risk factors for deficiency or toxicity.
Special consideration should be given to people living in underdeveloped regions, young children who are developing, pregnant women, elderly people, and people with chronic illness. These populations require higher concentrations of vitamin D in their bodies. Other factors, such as geographical location and skin color, play a role in determining how much additional vitamin D intake, if any, is needed. Researchers have said ingesting too much vitamin D is both possible and detrimental, but it does not happen often and is usually not serious.
Vitamin D is easily obtained in a well-rounded diet, with eggs and milk having particularly high concentrations. The main source of vitamin D for the human body is from skin cell production stimulated by exposure to the sun, and a person who is exposed to sunlight at least 15 minutes three times a week is most likely producing enough vitamin D to supplement his dietary intake. The FDA says that, to prevent diseases such as rickets and osteomalacia, healthy adults in the U.S. should get at least 200 IU (5 mcg) of vitamin D a day. Using a vitamin D supplement in this amount is appropriate and safe for most of the population, regardless of intake from of other sources. Higher doses of oral vitamin D and even injection are common if a physician deems them necessary.