Vitamin D is a fat soluble vitamin that human body needs to absorb calcium. It also plays an important role in maintaining muscle strength. Vitamin D deficiency is associated with reduced calcium absorption, bone loss, reduced muscle strength, and increased risk of fractures.
Vitamin D requirements
The American Academy of Pediatrics recommends 400 IU of vitamin D each day for infants from birth to 12 months of age. Vitamin D is found in formula or given as prescription drops (necessary for all breast-fed infants. General recommendations for the healthy population are as follows: 600 IU of vitamin D for most people from age 1 to 70 years old and 800 IU for people age 71 years and older. Some people need more vitamin D, for instance, if you have osteoporosis or other chronic medical conditions.
Populations at higher risk for vitamin D deficiency
Some of the populations at higher risk for vitamin D deficiency than the general population include:
• Infants fed only breastmilk
• Older individuals who consume diets low in vitamin D and do not take supplements containing vitamin D
• Individuals who take total sun precautions, consume diets low in vitamin D and do not take a supplement containing vitamin D
• Homebound individuals who get little sun exposure, consume diets low in vitamin D and do not take a supplement containing vitamin D
• Individuals with malabsorption syndromes who are not able to absorb dietary vitamin D (examples include: some people with Crohn's disease or celiac disease)
• Individuals with liver or kidney diseases who may be less able to process vitamin D
• Individuals taking certain medications that interfere with vitamin D metabolism (Some of these medications include steroids taken for more than 3 months, certain medications used to control seizures such as dilantin or phenobarbitol and cholestryamine used to lower the cholesterol level)
• Obese individuals
What should I do if I am at high risk for vitamin D deficiency?
It is important to speak to your doctor or healthcare provider about vitamin D and your bone health. If you have risk factors for vitamin D deficiency, it does not mean that you actually have vitamin D deficiency. Only your doctor or healthcare provider can make that determination. If your doctor or health care provider feels that it is necessary, he or she will recommend a specific blood test to check your vitamin D level.
What are the sources of vitamin D?
Sun exposure is not a reliable way to get vitamin D. Vitamin D from food and dietary supplements offer the same health benefits as vitamin D from the sun- without the danger of sun exposure.
To get enough vitamin D, most people need supplements. Vitamin D rich foods include fatty fish and fish oils. Some foods are fortified with vitamin D.
Vitamin D content of foods is stated in international units (IU). The amount of vitamin D that is found in food varies depending on the feed given to animal sources of vitamin D, the brand purchased, as well as the amount of vitamin D added to fortified foods.
What is the difference between vitamin D3 and vitamin D2
The type of vitamin D added to fortified foods varies. Vitamin D3 (cholecalciferol) is found in animal products or made from the ultraviolet irradiation of lanolin. Vitamin D2 is more common in vegetarian food sources and manufactured through the ultraviolet irradiation of yeast. Foods fortified with vitamin D3 include cow's milk, some yogurts, vitamin D fortified orange juice, some breakfast cereals and some breakfast bars. Vitamin D3 and Vitamin D2 can also be obtained from multivitamins, in combination with some calcium supplements, or alone as a separate vitamin D supplement.
The nutrition fact labels of supplements can be useful to find out the type of vitamin D added. Individuals who follow vegan diets (strict vegetarian diets that exclude all animal products and by-products) will prefer the vegetarian source of vitamin D, vitamin D2. The most recent evaluation of scientific studies indicates that vitamin D2 and vitamin D3 are both used efficiently by most healthy people.
It's sensible to avoid sources of vitamin D that are high in retinol.
Vitamin D and vitamin A are both fat-soluble vitamins that may be present in some of the same foods or supplements. Cod liver oil, for example, contains high amounts of both vitamin D and a type of vitamin A called retinol. A large study found that postmenopausal women who consumed very high intakes of retinol (from food sources such as cod liver oil and liver, from certain multivitamins, or from vitamin A supplements) appeared to have an increased risk of hip fractures. However, there was no association between high intakes of another type of vitamin A, called beta-carotene and the risk of hip fracture. Beta-carotene is found in a wide variety of yellow and orange-colored fruits and vegetables, as well as green leafy vegetables. It is sensible to avoid foods and supplemental sources of vitamin D that are high in retinol. Until more information is available, this includes the avoidance of cod liver oil and vitamin D supplements that have vitamin A added.