Natural Sources of Vitamin D

Vitamin D plays an important role in several bodily functions.  This vitamin is fat soluble and has been at the center of attention in recent years.

Vitamin D helps absorb calcium in the small intestines and is essential for bone growth and maintaining bone density. This vitamin is believed to have some role in the prevention of cancer, autoimmune conditions, heart disease, infections, and a number of other conditions.

Natural sources of vitamin D

1)   Vitamin D2 (ergocalciferol): Is synthesized in plants and fungi following the exposure to ultraviolet light.

2)   Vitamin D3 (cholecalciferol): Ultraviolet-B radiation from the sun prompts the production of vitamin D₃ from 7-dehydrocholesterol (7-DHC) in the skin.

Which kind is better?

Several studies suggest that vitamin D 3 is absorbed better and is more efficient in increasing and maintaining the blood vitamin D level.

U.S. consumption:

Most Americans, according to statistics, consume between 272-396 IU of Vitamin D daily.

Foods with the highest content of vitamin D in IU

Adapted from United States Department of Agriculture

Vitamin D content in breast milk

The breast milk of a healthy mother does not provide the suggested daily amount of Vitamin D.

Amount of body necessary to be exposed to sun

Studies suggest that UV-B radiation from the sun should cover at least 20% of the body’s surface. Sunlight is one of the most controversial (e.g. skin damage, cancer) natural sources of vitamin D.

Wearing white cotton transmits more UV-B to the body than black wool and allows for blood vitamin D concentrations to increase. Additionally, sunscreen could reduce the absorption of UV-B and consequently cause lower blood levels of this vitamin. For instance, sunscreen with a sun protection factor (SPF) of 8 can decrease vitamin D3 absorption by 95%, and SPF 15 can decrease it by 98%.

 How much daily intake is required?

T h e  E n d o c r i n e  S o c i e t y’s- Clinical Guidelines

Institute of Medicine Guidelines

Summary

Vitamin D shown to be an important part of many bodily functions and therefore, a healthy level is essential.

There is a limited accuracy of vitamin D level measurement throughout the country and is a cause of concern. Hopefully, with usage of better techniques the accuracy and reliability of these tests will also improve.

There have been confusing recommendations from different organizations about the amount of Vitamin D necessary to prevent deficiency in recent years, including the recent U.S. Preventive Services Task Force’s conclusion that the benefits and harms of daily supplementation with greater than 400 IU of vitamin D3 and greater than 1,000 mg of calcium to prevent fractures are not clearly understood.

In my opinion, the guidelines from the Endocrine Society and Institute of Medicine are not very different from each other.  The Endocrine Society’s recommendations are slightly more specific. Therefore, I would suggest following these recommendations at this time until more data is available.

Let’s review the recommendations one more time,

Infant and children 0-1year                            400 IU/ daily

Children 1 year and older                                 600 IU/ daily

Adults 18-50 year                                                600 IU/ daily

Adults 50-70 year                                               600-800 IU/daily

Pregnant women                                                  At least 600 IU/daily

It is also important to mention that overuse of this vitamin may cause more harm than good.

Are you on any vitamin D supplements?

Make sure that you discuss the appropriate daily dosage of this vitamin with your doctor next time.

Please read this article and share it with your friends and family members!

Reference

1.  Holick MF2007 Vitamin D deficiency. N Engl J Med 357:266–281 CrossRefMedline
2. Trang HM, Cole DE, Rubin LA, Pierratos A, Siu S, Vieth R. Evidence that vitamin D₃ increases serum 25-hydroxyvitamin D more efficiently than does vitamin D₂. Am J Clin Nutr. 1998;68 (4):854– 858 Abstract
3. Leerbeck E, Sondergaard H. The total content of vitamin D in human milk and cow’s milk. Br J Nutr. 1980;44 (1):7– 12 CrossRefMedlineWeb of Science