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Vitamin D is absolutely essential for good health.

Also known as the sunshine vitamin, it is made in your skin when exposed to sunlight.

Foods that do contain vitamin D include fatty fish like salmon, as well as fish liver oils.
Foods that do contain vitamin D include fatty fish like salmon, as well as fish liver oils. Photo credit: Shutterstock

In spite of that, vitamin D deficiency is one of the most common nutrient deficiencies in the world.

Up to 42 percent of the adult population in the U.S. has low vitamin D levels, which can cause health problems (1, 2, 3, 4, 5).

Vitamin D is particularly important for bone health and immune system function.

This article discusses how much vitamin D you need.

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that functions like a steroid hormone in the body.

There are two forms of vitamin D in the diet:

  • Vitamin D2 (ergocalciferol): found in some mushrooms.
  • Vitamin D3 (cholecalciferol): found in oily fish, fish liver oil and egg yolks.

D3 is the more powerful of the two types and raises blood levels of vitamin D almost twice as much as D2 (6, 7).

Large amounts of vitamin D can also be made in your skin when it is exposed to UV-rays from sunlight. Any excess vitamin D is stored in your body fat for later use.

Every cell in your body has a receptor for vitamin D. This vitamin is involved in many processes, including bone health, immune system function and protection against cancer (8, 9, 10, 11).

Bottom line: Vitamin D functions like a steroid hormone in your body. There are two forms in the diet, D2 and D3. It can also be produced in your skin when exposed to sunlight.

How Common is Vitamin D Deficiency?

Vitamin D deficiency is a problem all over the world.

However, it is especially common in young women, infants, the elderly and people who have dark skin (12, 13).

About 42 percent of the U.S. population is vitamin D deficient. However, this rate rises to 82 percent in African Americans and 70 percent in Hispanics (5).

If you have access to strong sun all year, then occasional sun exposure may be enough to fulfill your vitamin D requirements.

However, if you live far north or south of the equator then your vitamin D levels may fluctuate depending on the season. The levels may go down during the winter months, due to a lack of sufficient sunlight (14, 15, 16).

In that case, you need to rely on your diet (or supplements) for vitamin D, as well as on vitamin D that is stored in body fat during the summer (15).

In adults, a vitamin D deficiency may (17, 18, 19):

  • Cause muscle weakness.
  • Intensify bone loss.
  • Increase the risk of fractures.

In children, a severe vitamin D deficiency can cause delays in growth as well as rickets, a disease where the bones become soft.

Furthermore, vitamin D deficiency has been linked with several cancers, type 1 diabetes, multiple sclerosis, high blood pressure and thyroid problems (17, 20).

Bottom line: Vitamin D deficiency is very common worldwide, but occurs at higher rates in specific populations. A deficiency in vitamin D is linked to various health problems.

How Much Vitamin D Should You Take?

How much vitamin D you need depends on many factors. These include age, race, latitude, season, sun exposure, clothing and more.

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