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Vitamin D, the Right Stuff

Vitamin D is a fat-soluble vitamin that your body makes after exposure to ultraviolet (UV) rays from the sun. Vitamin D functions as a hormone because it sends a message to the intestines to increase the absorption of calcium and phosphorus. By promoting calcium absorption, vitamin D helps to form and maintain strong bones.

Because vitamin D increases the absorption of calcium in the gastrointestinal tract and stimulates osteoblastic (bone-building cells) activity, vitamin D has been generating lots of interest lately in the medical literature. Borderline low levels of vitamin D have been found to be very common in the United States and Canada.

It is estimated that over 25 million adults in the United States have, or are at risk of developing, osteoporosis. Adequate storage levels of vitamin D help keep bones strong and help prevent osteoporosis in older adults. Vitamin D deficiency results in diminished calcium absorption, and has been linked to a higher incidence of osteoporosis-related bone fractures seen in post menopausal women and older Americans.

It is extremely important for individuals with limited sun exposure to ingest supplemental vitamin D.

Vitamin D is more effective than calcium for protecting and building bone.  Most people do not have adequate levels of vitamin D. Often a multi-vitamin containing the RDA for D is simply not sufficient to bring blood levels up to the ideal range, especially as we age.

Up to now, much of the public attention on vitamin D has been related to its protective effects on bone health, via increasing calcium absorption.  But it is now known that vitamin D has several other critical functions. 

Vitamin D insufficiency is thought to be a key contributor to many human diseases including several cancers, diabetes, cardiovascular disease, depression, and autoimmune diseases.1,2  

Scientists have found that Vitamin D has biological actions in almost every cell and tissue in the human body.  What is troublesome is that vitamin D deficiency is now recognized as a pandemic, affecting 30-50% of the population.2,3

Vitamin D regulates several genes and cellular processes related to cancer progression.  Some of the most groundbreaking findings in nutrition science in recent years have been evidence of the powerful protection provided by vitamin D against common cancers:

  • Breast cancer: About 75% of women with breast cancer are vitamin D deficient.4 A 2009 meta-analysis of 19 studies established a strong inverse relationship between circulating vitamin D levels and breast cancer – women in the highest vitamin D range reduced their risk of breast cancer by 45%.5 read more
  • Colorectal cancer: A 2009 review of 25 studies found that sufficient vitamin D levels were consistently associated with reduced risk of colorectal cancer.6 Even after diagnosis with colorectal cancer, higher vitamin D levels are associated with reduced mortality.7
  • Cancers of the prostate, pancreas, lung, and endometrium are also associated with vitamin D insufficiency.2,8

For most people, the principal source of vitamin D is production by the skin in response to sunlight. Very few foods naturally contain vitamin D, and achieving adequate vitamin D levels via sun exposure is difficult, considering that most of us work indoors, and cover our body with clothing, especially in the winter months. Plus, sun exposure to assure optimal Vitamin D status may damage and age the skin increasing wrinkling and the risk of skin cancer.

To maintain adequate blood levels of vitamin D, it is extremely important for individuals with limited sun exposure to ingest supplemental vitamin D.


References

1. Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr 2004;80(suppl):1678S- 88S

2. Holick MF and Chen TC. Vitamin D deficiency: a worldwide problem with health consequences. Am J Clin Nutr 2008;87(suppl):1080S- 6S.

3. Lee JH et al. Vitamin D deficiency an important, common, and easily treatable cardiovascular risk factor? J Am Coll Cardiol. 2008 Dec 9;52(24):1949-56.

4. Hines SL et al. Breast cancer survivors and vitamin D: A review. Nutrition. [Epub ahead of print]

5. Chen P et al. Meta-analysis of vitamin D, calcium and the prevention of breast cancer. Breast Cancer Res Treat. 2009 Oct 23. [Epub ahead of print]

6. Zhou G et al. Optimizing vitamin D status to reduce colorectal cancer risk: an evidentiary review. Clin J Oncol Nurs. 2009 Aug;13(4):E3-E17.

7. Ng K et al. Prospective study of predictors of vitamin D status and survival in patients with colorectal cancer. Br J Cancer. 2009 Sep 15;101(6):916-23. Epub 2009 Aug 18.

8. Peterlik M et al. Calcium, vitamin D and cancer. Anticancer Res. 2009 Sep;29(9):3687-98.
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