The incidence of diabetes was almost 8% lower in people with blood levels of vitamin D greater than 18.5 ng/mL, compared with levels lower than 18.5 ng/mL, according to results of a study with 961 people published in Clinical Nutrition​​.

While the results show correlation and not causation, researchers from the University Hospital Carlos Haya in Malaga note that it is biologically plausible that vitamin D may reduce the incidence of diabetes, including influencing the function of beta-cells, cells in the pancreas that control insulin production.

The vitamin may also affect sensitivity to insulin, said the researchers, while an anti-inflammatory role may also affect diabetes risk.

D and Diabetes​

This is not the first time that a potential anti-diabetic role for vitamin D has been reported. Last summer, researchers from Tufts and Harvard Universities reported​ in the American Journal of Clinical Nutrition​ that a daily 2,000 International Units (IU) dose of vitamin D3, also known as cholocalciferol, may boost the functioning of beta cells by 25%.

According to the World Health Organisation (WHO), diabetes affects over 220 million people globally and the consequences of high blood sugar kill 3.4 million every year. If such statistics weren’t scary enough, the WHO is predicting deaths to double between 2005 and 2030.

The total costs associated with the condition in the US alone are thought to be as much as $174 billion, with $116 billion being direct costs from medication, according to 2005-2007 American Diabetes Association figures.

Study details​

The new study, led by Inmaculada Gonzalez-Molero, included 1226 people, 961 of whom finished the study. Blood levels of vitamin D were taken – measured as 25-hydroxyvitamin D and oral glucose tolerance tests were performed at the start (1996-1998), during (2002-2004) and end of the study (2005-2007).

Results showed that the incidence of diabetes was less than 5% in people with 25-hydroxyvitamin D levels greater than 18.5 ng/mL, compared with an incidence of 12.4% in people with blood levels of the sunshine vitamin less than this.

In addition, the risk of developing diabetes was significantly lower in people with the higher vitamin D levels, with no diabetes recorded in people with blood levels of 25-hydroxyvitamin D higher than 30 ng/mL.

“It is important to note that this study was carried out in a population from southern Europe, where there is a high solar radiation (more than 1700 h/year) and a wide consumption of a Mediterranean diet,”​ wrote the researchers.

“Because of the nature of our study, we cannot elucidate the mechanisms underlying the relation between vitamin D levels and diabetes, for which further studies are needed,”​ they concluded.

Shining light on the sunshine vitamin​

While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.

Vitamin D deficiency in adults is reported to precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases. There is also some evidence that the vitamin may reduce the incidence of several types of cancer and type-1 and -2 diabetes.

Source : Clinical Nutrition​​

Published online ahead of print, doi:10.1016/j.clnu.2011.12.001

“Vitamin D and incidence of diabetes: A prospective cohort study Vitamin D and diabetes incidence”​

Authors: I. Gonzalez-Molero, G. Rojo-Martínez, S. Morcillo, C. Gutierrez-Repiso, E. Rubio-Martin, M.C. Almaraz, G. Olveira, F. Soriguer