Tuesday, June 1, 2010

Air pollution, sunlight, vitamin D and type-two diabetes

Does air pollution cause diabetes, or does pollution cause vitamin D deficiency, which then leads to diabetes?

New research from Germany showed that women who lived in heavily air-polluted areas were at greater risk for type-two diabetes than those who lived in less-polluted areas. Those who lived within 100 meters of busy roadways doubled the diabetes risk. http://www.newswise.com/articles/study-suggests-link-between-air-pollution-and-type-2-diabetes-in-women

The authors assumed that the inhalation of pollutants was responsible for the increased risk of diabetes among those living in heavily-polluted areas, but I suggest another possibility: It is well-known that air pollution filters out sunlight and correlates to profoundly lower vitamin D levels. [1] [2] [3]

But do vitamin D levels have an influence on type-two diabetes? Research shows that Vitamin D levels correlate closely to insulin sensitivity; the higher the vitamin D levels, the more receptive the body is to the action of insulin, which makes carbohydrates easier to metabolize.[4] This same study shows that the higher the vitamin D levels are, the lower are the blood sugar levels. Other research shows that men with the highest vitamin D levels had a 30% reduced risk of type-2 diabetes compared to those with low levels,[5] probably because the beta cells of the pancreas (the insulin producing cells) have vitamin D receptors[6] and function more efficiently when vitamin D levels are higher.[7]

It is highly likely that the reason for the increased risk for diabetes was not the inhalation of air pollutants, but rather the lack of sunlight and subsequent vitamin D deficiency. It is time to leave the pollution and return to the sun.

[1] Mims FM., 3rd Significant reduction of UVB caused by smoke from biomass burning in Brazil. Photochem Photobiol. 1996 Nov;64(5):814–816.
[2] Agarwal, K et al. The impact of atmospheric pollution on vitamin D status of infants and toddlers in Delhi, India. Arch Dis Child 2002;87:111-113
[3] Holick MF. Environmental factors that influence the cutaneous production of vitamin D. Am J Clin Nutr 1995;61:(Suppl):638S-645S.
[4] Chiu K. et al. Hypovitaminosis D is associated with insulin resistance and beta cell dysfunction. Am J Clin Nutr 2004;79:820-25.
[5] Mattila, C. Serum 25-hydroxyvitamin D concentration and subsequent risk of type-2 diabetes. Diabetes Care 2007;30:2569-70.
[6] Brown, A. et al. Vitamin D. American J of Physiol 1999;277(2 Pt 2):F157-75.
[7] Norman, A. et al. Vitamin D deficiency inhibits pancreatic secretion of insulin. Science 1980;209:823-25.

1 comment:

PeterVermont said...

I think that vitamin D serum levels should always considered as a possible confounding variable in human epidemiological disease studies.