Vitamin D

What is vitamin D?

What are the sources of vitamin D?

To get enough vitamin D, most people need supplements. Vitamin D rich foods tend to be high in fat and not eaten daily as part if the typical US diet. Sun exposure is another way to get vitamin D but there is concern about harmful ultraviolet rays that can damage the skin.

Vitamin D Sources

Why is vitamin D called the "sunshine vitamin" ?

Vitamin D is often referred to as the "sunshine vitamin". That is because the human body has the potential to make vitamin D from casual sun exposure of short duration. However unprotected sun exposure can put an individual at risk for skin cancer, cataracts, and premature aging. According to the American Academy of Dermatology, vitamin D from food and dietary supplements offer the same health benefits as vitamin D from the sun- without the danger of UV exposure. For more information, click on the American Academy of Dermatology Vitamin D Factsheet

For quick tips for sun protection, take the American Cancer Society's Sun Safety Quiz:

What foods and supplements contain vitamin D?

There are only a few naturally occurring food sources of vitamin D, such as fatty fish and fish oils. Some foods are fortified with vitamin D, meaning that although they do not naturally contain vitamin D, the vitamin is added to the food or beverage.

What are the sources of vitamin D?

What is the difference between vitamin D3 and vitamin D2

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. 

A 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.  Although further investigation is needed to study the relationship between retinol from various sources and fracture risk, it is sensible to avoid foods and supplemental sources of vitamin D that are high in retinol. This includes the avoidance of cod liver oil and vitamin D supplements that have vitamin A added until more information is available.

How much vitamin D do I need?

According to The National Osteoporosis Foundation, experts recommend that adults under age 50 consume a daily intake of 400 to 800 international units (IU) of vitamin D. People age 50 and older need between 800 and 1000 IU. Some people will need even more.Your doctor or healthcare provider may prescribe more Vitamin D than recommended for the general population, if you are at high risk for vitamin D deficiency or if you have been diagnosed with low serum vitamin D levels.

What populations are at higher risk for vitamin D deficiency?

The following populations are at higher risk for vitamin D deficiency than the general population:

• 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)

What should I do if I am at high risk for vitamin D deficiency?

If you happen to be at high risk 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 you think that you may be at risk for vitamin D deficiency, it is important to speak to their doctor or healthcare provider. If your doctor or health care provider feels that it is necessary, he or she may recommend a blood test to check your vitamin D level.

There is evidence that the intake of 800 IU/day of vitamin D (or more) along with adequate calcium may reduce the risk for falls (by increasing muscle strength) and reduce the risk for fracture in postmenopausal women and older adults. We know that as adults age, the need for vitamin D increases, however older adults are often not not meeting the recommended intake for vitamin D. In order for seniors to get enough vitamin D, a supplement is probably required.  It is a good idea for all adults to speak to their health care provider about their individual recommendations for vitamin D. 

Can too much vitamin D be harmful?

Since vitamin D can be stored in your body, it has been presumed that too much may be harmful. However, toxicity is rarely seen. It is important to follow the advice of your doctor or health care provider and not to exceed 2000 IU/day of vitamin D from diet and/or supplements without a prescription.