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Vitamin D: Part I

Quick Hit Summary

Emerging evidence indicates that vitamin D plays a much larger role in human health than what was originally believed. Ironically, despite the fact that one can naturally produce it (via sunlight exposure), many individuals have vitamin D insufficiency. Recent research indicates that low vitamin D levels are associated with various health issues including colon, prostrate and breast cancer.

Vitamin D

Have you ever found yourself staying flipping through the TV channels, for the umpteenth time, only to find an infomercial staring back at you upon finally putting the remote down? I know I have. It always fascinates me to learn about the next great supplement that will do everything from cure cancer to reversing that retreating hairline of yours. Although I say that tongue-in-cheek, I must admit that some legit supplements do have an amazing reach with respect to its health/performance benefits. For instance, look at fish oil…. What can’t that supplement do with respect to health and performance?!?!? The next product I feel is about to explode on the market, due to its far reaching health benefits is Vitamin D. What’s so special about vitamin D you ask? Read on and find out!

Figure 1 The molecular Structure of Vitamin D313

Vitamin D Sources

Vitamin D belongs to a group of vitamins known as the fat soluble vitamins. As with all fat soluble vitamins, the body can store vitamin D for extended periods of time. In the public arena, it has gained widespread notoriety for the beneficial role it plays in promoting bone strength. Vitamin D accomplishes this via increasing dietary calcium absorption (a mineral critical to healthy bone structure) from the digestive track into one’s bloodstream. In addition, recent research also indicates that other health conditions, such as cancer, diabetes, and pain management are influenced by one’s vitamin D status. This vitamin can be obtained in 2 ways:

1) Obtained via dietary sources which are measured in International Units (IU’s).

2) Produced by the skin via exposure to sunlight (UV-B rays)

In both circumstances, the vitamin is obtained in its inactive “pro-vitamin” form. After absorbed into the body it is metabolized by the liver and kidney (thus activating it) before binding to receptors throughout the body.

Vitamin D Status in the USA

Although one’s skin naturally produces the prerequisite molecules to form vitamin D via sunlight exposure, many factors inhibit this process. One’s age and the strength of the suns UV-B rays are just a couple variables that affect pro-vitamin D production. Exposed to the same amount of sunlight, an older individual (62-80 yrs) will produce 4x less vitamin D vs. a younger individual (20-30 yrs)1. In addition the strength of UV-B rays varies depending on fog, clouds, time of day and one’s geographic location. In most locations only, UV-B rays are only strong enough to significantly stimulate the skins production of vitamin D between the hours of 10am-2pm2. Furthermore, in the states north of Georgia, there is insufficient amounts of UV-B radiation to naturally synthesize vitamin D for 2-6 months of the year237. This occurs during the fall, winter and spring as the earth gets farther away from the sun.

Between lack of dietary intake and UV-B exposure, a surprisingly large percentage of individuals have a vitamin D inadequacy4. In a research study involving>18,000 participants (varying in age, demographics, etc) across the Unites States, between 25%–57% of the subjects had insufficient levels of Vitamin D. Interestingly enough, vitamin D inadequacy has even been found in southern states. In a recent study involving 637 individuals from Arizona, almost 50% were found to have inadequate vitamin D levels5. Similar results have been seen in Florida6.

Vitamin D inadequacy has also been reported in collegiate athletes. In a study completed by Halliday et al., researchers examined the vitamin D status of 41 collegiate athletes14. As aforementioned, one’s geographic location influences the ability to naturally manufacture vitamin D via sunlight237. Thus, to give you a frame of reference, the participants in this study were all members of various athletic teams at the University of Wyoming. Vitamin D status was assessed at the following 3 time points during the academic year:

  • Fall (late September – early October)
  • Winter (late February – early March)
  • Spring (late April – early May)

As seen in Table 1, the incidence of sub-optimal vitamin D status was alarmingly high during the winter months; only 15.2% of athletes had optimal blood levels at this time. Of even greater surprise was the percentage of athletes who lacked optimal vitamin D during the fall months. Despite being assessed following the summer months, when sunlight is optimal for synthesizing and storing pro-vitamin D, ~25% of all athletes still had less than optimal vitamin D stores.

Table 1. Vitamin D status of collegiate athletes when assessed 3 times during the academic year. Optimal vitamin D levels were defined as >40ng/ml \

Time Period % of Athletes with Optimal Vitamin D (> 40ng/ml) Mean Vitamin D Levels (ng/ml)
Fall 75.6% 49.0 ng/ml
Winter 15.2% 30.5 ng/ml
Spring 36.0% 41.9 ng/ml

Vitamin D & Cancer

Although more research is still needed in this area (most of the research currently involves epidemiology studies vs. true experimental designed studies), there appears to be an inverse association between vitamin D levels and colon, prostrate, and breast cancer. In other words, the higher one’s vitamin D status, the less likely they are to be diagnosed with these cancers.

For men, it was found that those taking a vitamin D supplement > 600 IU were 40% less likely to be diagnosed with prostrate cancer vs. those not taking any vitamin D supplement8. Similarly 16 year prospective study involving 827 premenopausal women, it was found that those who consumed > 500 IU were 28% less likely to develop breast cancer vs. those taking in < 150 IU9.

Of all the research looking at the association between vitamin D status and cancer, the strongest relationship is seen with colon cancer10. Numerous observational studies have provided evidence of this claim. In a meta-analysis study that combined data from 18 previously conducted studies, it was found that a 50% reduction in colon cancer was obtained with daily vitamin D intakes >1000 IU vs those getting < 80-150 IU11.

There are a couple of proposed physiological mechanisms to explain the relationship seen with vitamin D and cancer. Within the colon, breast and prostrate are receptors that bind with vitamin D10. Researchers believe that the binding of vitamin D to these receptors influences the growth of both normal and malignant cells. It achieves this by regulating the differentiation of cells, inducing “cellular suicide” in abnormal cells (in a process referred to as apoptosis), and reducing new blood vessel (angiogenesis) formation to cancerous tissue[1112.

Stay Tuned for Part II of this series when we explore the relationship between vitamin D, diabetes and cardiovascular health


1 Leavitt,SB. Vitamin D – A Neglected ‘Analgesic’ for Chronic Musculoskeletal Pain. June 2008, .Obtained September 23, 2009 from: http://Pain-Topics.org/VitaminD.

2 Holick MF. Vitamin D: the underappreciated D-lightful hormone that is important for skeletal and cellular health. Curr Opin Endocrinol Diabetes 2002;9:87-98.

3 Looker AC, Dawson-Hughes B, Calvo MS, Gunter EW, Sahyoun NR. Serum 25-hydroxyvitamin D status of adolescents and adults in two seasonal subpopulations from NHANES III. Bone 2002;30:771-7.

4 Sunlight, vitamin D and the prevention of cancer: a systematic review of epidemiological studies. Source: European journal of cancer prevention, [0959-8278] Rhee yr:2009.

5 Jacobs ET, Alberts DS, Foote JA, et al. Vitamin D insufficiency in southern Arizona. Am J Clin Nutr. 2008;87(3):608-613.

6 Bouillon R, Norman AW, Lips P. Vitamin D deficiency. N Engl J Med. 2007 Nov 8;357(19):1980-1; author reply 1981-2.

7 Holick MF. Vitamin D deficiency. N Engl J Med 2007;357:266-81.

8 Ahn J, Albanes D, Peters U, Schatzkin A, Lim U, Freedman M, et al. (2007). Dairy products, Calcium intake, and risk of prostate cancer in the prostate, lung, colorectal, and ovarian cancer screening trial. Cancer Epidemiol Biomarkers Prev 16:2623–2630.

9 Shin MH, Holmes MD, Hankinson SE, Wu K, Colditz GA, Willett WC (2002).Intake of dairy products, calcium, and vitamin d and risk of breast cancer. J Natl Cancer Inst 94:1301–1311.

10 Rhee HV, Coebergh JW, Vries ED. Sunlight, vitamin D and the prevention of cancer: a systematic review of epidemiological studies. Eur J Cancer Prev. 2009 Aug 26.

11 Gorham ED, Garland CF, Garland FC,et al. Vitamin D and prevention of colorectal cancer. J Steroid Biochem Mol Biol 2005;97:179-94.

12 Harris DM, Go VL (2004). Vitamin D and colon carcinogenesis. J Nutr 134:3463S–3471S.

13 Image was obtained on May 31, 2010 from: http://en.wikipedia.org/wiki/File:Cholecalciferol-3d.png

14 Halliday T, Peterson N, Thomas J, Kleppinger K, Hollis B, Larson-Meyer D. Vitamin D Status Relative to Diet, Lifestyle, Injury and Illness in College Athletes. Med Sci Sports Exerc. 2010 Jun 11. [Epub ahead of print]

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Written on September 27, 2009 by Sean Casey
Last Updated: July 06, 2010

This information is not intended to take the place of medical advice.Please check with your health care providers prior to starting any new dietary or exercise program. CasePerformance is not responsible for the outcome of any decision made based off the information presented in this article.

About the Author: Sean Casey is a graduate of the University of Wisconsin-Madison with degrees in both Nutritional Science-Dietetics and Kinesiology-Exercise Physiology. Sean graduated academically as one of the top students in both the Nutritional Science and Kinesiology departments.
Field Experience: During college, Sean was active with the UW-Badgers Strength and Conditioning Department. He has also spent time as an intern physical preparation coach at the International Performance Institute in Bradenton, FL. He also spent time as an intern and later worked at Athletes Performance in Tempe, AZ. While at these locations he had the opportunity to train football, soccer, baseball, golf and tennis athletes. Sean is also active in the field of sports nutrition where he has consulted with a wide variety of organizations including both elite (NFL’s Jacksonville Jaguars) and amateur athletic teams. His nutrition consultation services are avalable by clicking on the Nutrition Consultation tab.