Vitamin D Summary

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Vitamin D Summary

 

Vitamin D, calciferol, is a fat-soluble vitamin. It is found in food,

but also can be made in your body after exposure to ultraviolet rays

from the sun (1,2). Vitamin D exists in several forms, each with a

different activity. Some forms are relatively inactive in the body,

and have limited ability to function as a vitamin. The liver and

kidney help convert vitamin D to its active hormone form. (3).

The major biologic function of vitamin D is to maintain normal blood

levels of calcium and phosphorus (4). Vitamin D assists in the

absorption of calcium, helping to form and maintain strong bones. It

promotes bone mineralization in concert with a number of other

vitamins, minerals, and hormones. Without vitamin D, bones can become

thin, brittle or soft. Vitamin D prevents rickets in children and

osteomalacia in adults, which are skeletal diseases that result in

defects that weaken bones (5,6).

 

Fortified foods are the major dietary sources of vitamin D (4). Prior

to the fortification of milk products in the 1930s, rickets (a bone

disease seen in children) was a major public health problem in the

United States. Milk in the United States is fortified with 10

micrograms (400 IU) of vitamin D per quart, and rickets is now

uncommon in the US (7).

 

One cup of vitamin D fortified milk supplies about one-fourth of the

estimated daily need for this vitamin for adults. Although milk is

fortified with vitamin D, dairy products made from milk such as

cheese, yogurt, and ice cream are generally not fortified with

vitamin D. Only a few foods naturally contain significant amounts of

vitamin D, including fatty fish and fish oils (4). The table of

selected food sources of vitamin D suggests dietary sources of

vitamin D.

 

Exposure to sunlight is an important source of vitamin D. Ultraviolet

(UV) rays from sunlight trigger vitamin D synthesis in the skin

(7,8). Season, latitude, time of day, cloud cover, smog, and

suncreens affect UV ray exposure (8). For example, in Boston the

average amount of sunlight is insufficient to produce significant

vitamin D synthesis in the skin from November through February.

Sunscreens with a sun protection factor of 8 or greater will block UV

rays that produce vitamin D, but it is still important to routinely

use sunscreen whenever sun exposure is longer than 10 to 15 minutes.

It is especially important for individuals with limited sun exposure

to include good sources of vitamin D in their diet.

 

Life-Stage Men Women

Ages 19-50 5 mcg* or 200 IU 5 mcg* or 200 IU

Ages 51-69 10 mcg* or 400 IU 10 mcg* or 400 IU

Ages 70 + 15 mcg* or 600 IU 15 mcg* or 600 IU

 

*1 mcg vitamin D = 40 International Units (IU)

 

 

Cancer Prevention

 

A large daily dose of vitamin D can dramatically lower the risk of

developing common cancers, scientists say.

 

The " natural " form of the vitamin, known as D3, could dramatically

reduce the chances of developing breast, ovarian and colon cancer, as

well as others, by up to 50 per cent, according to the research

published in the American Journal of Public Health. The findings are

based on a review of 63 studies that looked at the relationship

between blood levels of vitamin D and cancer risk

 

The research concluded that 1,000 international units (IU) of vitamin

D were required daily could to lower an individual's cancer risk.

Such large doses of vitamin D must be treated with caution as more

than 2,000 IU a day can lead to the body absorbing too much calcium,

and possible damage to the liver and kidneys.

 

D3 is normally produced in the skin by the action of sunlight, but is

also obtained from certain foods. Dietary sources are limited, a

glass of milk, for instance, contains only 100 IU of the vitamin. The

researchers suggest that supplements may be one of the best ways to

take the vitamin.

 

 

 

References

 

1-8. Office of Dietary Supplements, National Institutes of Health,

6100 Executive Blvd., Room 3B01, MSC 7517, Bethesda, MD 20892-7517

 

http://www.timesonline.co.uk/article/0,,1-1961302,00.html

 

 

 

Andrew Pacholyk, MS, L.Ac.

Peacefulmind.com

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