Can Vitamin D Prevent Diabetes?

Recently, Vitamin D has gained a lot of interest for its potential to prevent chronic diseases. The latest article released this year by Mitri et al., linking the risk of diabetes to low levels of vitamin D in the body, has created media speculation about the potential of vitamin D to help prevent diabetes.

Vitamin D is the term given to a group of pre-hormones, called secosteroids, which the body requires in small quantities to function. One of the major roles of vitamin D is regulating calcium and phosphate levels in the blood and strengthening the bones. The major natural source of vitamin D is exposure to solar radiation; ultraviolet (UV) B rays are known to trigger its production in the skin. It is also available in a limited number of food products and as a dietary supplement; for more information, refer to Clinuvel’s article on vitamin D.

Extensive research has been done on vitamin D’s potential health benefits, especially in the case of preventing diabetes. In a recent study, Gagnon et al. (2011) noticed an association between the levels of vitamin D and the risk of diabetes in Australian men and women. This research involved measuring the levels of calcidiol (the inactive storage form of vitamin D measured in a blood sample) in the patients’ serum (fluid component of blood) to predict the risk of type 2 diabetes and insulin sensitivity. A few months later, Mitri et al. also presented a study which revealed that high levels of vitamin D improved the functions of beta cells. These beta cells, which are present in the pancreas, are responsible for insulin production and secretion. Insulin controls the levels of glucose in the blood, which would otherwise be toxic and result in the development of diabetes.

In 2005, Mathieu and Badenhoop released an article explaining the role of vitamin D in insulin regulation.  It was demonstrated that the pancreatic beta cells, which are responsible for insulin production and secretion, possess vitamin D receptors (VDRs). Normal insulin secretion is dependent on vitamin D binding to these receptors, and thus an adequate concentration of vitamin D in the body is considered to be essential for insulin regulation.  None of this research has, however, definitively linked low vitamin D levels to the development of diabetes.

Since studies linking vitamin D and disease prevention are considered to be important advancements in the prevention of chronic diseases, this research has received widespread media coverage. The tanning industry seems to have gained an impetus through these reports to aggressively market indoor tanning, as UV exposure is a natural source of vitamin D. A number of tanning industry websites contain articles with reference to the studies done on vitamin D.

These links have not gone unnoticed in dermatological circles. According to a 2010 study by Greenman and Jones in the Journal of American Academy of Dermatology, tanning companies influence consumers using advertising strategies which counter the health concerns associated with their products; in this instance, the known carcinogenic effects of tanning beds. Dr Michael Holick’s 2004 book ‘The UV Advantage’ is one of the most referenced resources in the advertising campaigns of tanning companies. This volume documents research linking vitamin D to various diseases and cancers, which are often overstated by the tanning industry to market their products.

Vitamin D has indeed been linked to both type 1 and 2 diabetes in studies conducted around the world, yet no conclusive evidence has been found to confirm that it can prevent diabetes. Furthermore, a report by Robinson et al. (2011), concluded that no association was found between the levels of vitamin D and the risk of type 2 diabetes in older women. Yet, many people, including some tanning companies, rely on the present studies to promote preventative measures which can be misleading.  A better understanding of the roles of vitamin D is required before formulating any kind of preventative strategy.

It is likely that more research will be published reporting associations between vitamin D and prevalent chronic diseases. This year alone there have been at least three articles which have examined the links between vitamin D and the risk of diabetes. Of these, two have reported positive links and one was unable to find any association.  All of these reports allude to the growing interest, among researchers around the world, in exploring the role of vitamin D in preventing chronic diseases. While it’s important that such research continues, it is far too early to make definitive statements or legitimately base aggressive marketing campaigns about the health benefits of UV on these reports. For now, the advice of the dermatology industry is best: if your vitamin D levels are low, take a supplement.

References

Boerner, LK 2011, ‘Low vitamin D levels linked to diabetes risk’, Reuters, 27 April, retrieved 25 July 2011, <http://www.reuters.com/article/2011/04/27/us-vitamind-diabetes-idUSTRE73Q6VH20110427>.

Gagnon, C, Lu, ZX, Magliano, DJ, Dunstan, DW, Shaw, JE, Zimmet, PZ, Sikaris, K, Grantham, N, Ebeling, PR,  2011 & Daly, RM, ‘Serum 25-Hydroxyvitamin D, Calcium Intake, and Risk of Type 2 Diabetes After 5 Years, Results from a national, population-based prospective study (The Australian Diabetes, Obesity and Lifestyle Study)’, Diabetes Care, 34(5): 1133-1138.

Greenman, J & Jones, DA 2010, ‘Comparison of advertising strategies between the indoor tanning and tobacco industries’, Journal of the American Academy of Dermatology, 62(4):685.e1-18.

Holick, M & Jenkins, M 2004, The UV Advantage, I Books, New York.

Mathieu, C & Badenhoop, K 2005, ‘Vitamin D and type 1 diabetes mellitus: state of the art’, Trends in Endocrinology and Metabolism, 16(6):261-266.

Penckofer, S, Kouba, J, Wallis, DE & Emanuele, MA 2008, ‘Vitamin D and Diabetes, Let the Sunshine In’, The Diabetes Educator, 34(6):939-954, retrieved 25 July 2011, <http://tde.sagepub.com/content/34/6/939.full.pdf+html>.

Mitri, J, Dawson-Hughes, B, Hu, FB & Pittas, AG 2011, ‘Effects of vitamin D and calcium supplementation on pancreatic β cell function, insulin sensitivity, and glycemia in adults at high risk of diabetes: the Calcium and Vitamin D for Diabetes Mellitus (CaDDM) randomized controlled trial1,2,3,4’, The American Journal of Clinical Nutrition, 94(2): 486-494.

Robinson, JG, Manson, JE, Larson, J, Liu, S, Song,Y, Howard, BV, Phillips, L, Shikany, JM, Allison, M, Curb, JD, Johnson, KC & Watts, N 2011, ‘Lack of Association Between 25(OH)D Levels and Incident Type 2 Diabetes in Older Women’, Diabetes Care, 34(3): 628-634.

SunSplash Tanning 2008, ‘“Sun Scare”: Twisted Sun Care’, retrieved 25 July 2011, <http://www.tanatsunsplash.com/id10.html>.

Image reference

‘Sequoia sempervirins’ uploaded to Wikimedia Commons on 23 March 2006 by H-stt <http://commons.wikimedia.org/wiki/File:Redwood_sunlight.jpg>

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