Vitamin D

Function

The major biologic function of Vitamin D is to maintain normal blood levels of both calcium and phosphorous.  It aids in the absorption of calcium from food and supplements as well as the assimilation of calcium into the bone. It is important in both forming and maintaining strong bones. 

Sources

It is known as the “Sunshine Vitamin” because it is produced through the skin after exposure to ultraviolet rays from the sun.   Although it is very possible to get enough Vitamin D through exposure to sun, the amount varies greatly due to time of year (winter vs. summer), amount of sunscreen, and color of skin.   

The average American diet contains only small amounts of Vitamin D.  Vitamin D-fortified milk and yogurt as well as fatty fish like salmon and mackerel are the best dietary sources, but few people can manage to get enough through these foods.

Supplements are often needed to maintain adequate Vitamin D levels in the blood.

Deficiencies

The classic vitamin D deficiency diseases are rickets and osteomalacia (softening of the bones). 

NOTE: In patients receiving statin medications, when the vitamin D level in blood is low, it can interact with the statins and produce muscle pain, tenderness, cramping, and weakness.  When the serum vitamin D level is normalized by taking supplemental Vitamin D, statin therapy can be resumed without muscle problems.

Vitamin D deficiencies have also been linked to gum disease, insulin resistance, certain types of cancers and autoimmune diseases.

New Guidelines

In November 2010, the Institute of Medicine's (IOM) expert committee set a new "dietary reference intake" for vitamin D.  These Vitamin D recommendations are in International Units per Day. 

Recommended Intake	Safety Level
Infant 0-6 months	-	1,000
Infant 6-12 months	-	1,500
1-3 years old	600	2,500
4-8 years old	600	3,000
9-70 years old	600	4,000
> 70 years old	800	4,000

Recommendations

Although these are the “official” recommendation of the IOM, recent research shows that higher intakes are both safe and desirable, especially in patients with diabetes or who are on statins.

Many health professionals recommend taking a vitamin D supplement of at least 1000 IU every day to insure maintaining adequate levels. 

Patients who are found to have low levels of serum Vitamin D will be given much higher doses of Vitamin D in order to get their levels to a normal range and reach optimum health benefits.  In some cases, 50,000 – 100,000 IUs per week may be prescribed to normalize serum vitamin D.