What is Vitamin D?
Vitamin D is a fat soluble vitamin that your 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 may increase the risk of broken bones.
|Age||Vitamin D in IU IInternational Units)|
|Birth to 12 months||400|
|1 to 70 years old||600|
|71 years and older||800|
How much vitamin D do I need?
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). The Institute of Medicine recommends 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. These are general recommendations for the healthy population. Some people need more vitamin D. Your healthcare provider may tell you that you need more vitamin D if you have osteoporosis or other chronic medical conditions and/or if you have been diagnosed with low vitamin D levels. The National Osteoporosis Foundation recommends 800 IU to 1000 IU of vitamin D each day for people over age 50.
What populations are 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 breast milk and not receiving vitamin D drops
- Infants consuming less than 32 ounces (1 quart) of formula with or without vitamin D added and not receiving vitamin D drops
- Older individuals eating diets low in vitamin D and not taking supplements containing vitamin D
- Homebound individuals or people who take total sun precautions, eat diets low in vitamin D, and not taking a supplement
containing vitamin D
- Dark-skinned individuals less able to absorb vitamin D from sunlight
- People with conditions or diseases that reduce the ability to absorb vitamin D from foods (examples include: some people with Crohn’s disease, celiac disease, radiation enteritis, or after some bariatric surgery)
- People with liver or kidney diseases who may be less able to process vitamin D
- Individuals taking certain medications that interfere with the way the body uses vitamin D. Some of these medications include:
- steroids (examples: prednisone, cortisone) taken for more than 3 months
- certain medications used to treat seizure disorders or depression such as phenytoin (Brand name: Dilantin), valproic acid (brand name: Depakote), and others
- cholestryamine (Brand Name: Questron) used to lower cholesterol levels or reduce bile acid
- Obese individuals
What should I do if I am at high risk for vitamin D deficiency?
It is important to speak to your 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 healthcare provider can make that determination. If your health care provider feels that it is necessary, he or she will recommend a blood test called 25(OH) vitamin D level.
What are the sources of vitamin D?
Sun exposure is not a reliable way to get vitamin D and there is concern about harmful ultraviolet rays that can put an individual at risk for skin cancer, cataracts, and premature aging. Vitamin D from food and dietary supplements offer the same health benefits as vitamin D from the sun without the danger of sun exposure.
Vitamin D rich foods tend to be high in fat and not eaten as part of the typical daily American diet. Sources include fatty fish, fish oils, sun-dried shiitake mushrooms, and egg yolk. There are several foods that are fortified with vitamin D. Vitamin D fortified foods do not naturally contain vitamin D, but the vitamin is added to the food or beverage in the manufacturing process. Most fortified foods contain small amounts of vitamin D in a serving.
There is limited but growing information about the vitamin D content of foods. The vitamin D content of foods is stated in international units (IU). For example, milk is fortified with 100 IU of vitamin D in each 8-ounce cup. Most dairy products including yogurts and cheeses have not traditionally been made with fortified milk. However, recently some dairy products and other foods have been manufactured with vitamin D added. It is important to read food labels for vitamin D content.
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 separate vitamin D supplements.
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 well by most healthy people.
It is 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.
Another large population study also found an association between high intakes of retinol from supplements and hip fracture but reported no association between retinol from cod liver oil or other food sources and fracture risk.
Further research is needed to study the relationship between retinol from various sources and fracture risk. In the meantime, it is sensible to avoid foods and supplemental sources of vitamin D that are high in retinol. Until more information is available, it is wise to avoid cod liver oil and vitamin D supplements that have vitamin A added.