Low Vitamin D Not Tied to Diabetes Risk

Low levels of vitamin D were common among people with type 2 diabetes but probably not the cause of the disease

(RxWiki News) Past studies have suggested that low vitamin D may be tied to an increased risk for type 2 diabetes. But new research challenges that notion.

Researchers recently found that type 2 diabetes patients often had low levels of vitamin D, but these vitamin D levels did not appear to be the cause of the patients' diabetes.

Type 2 diabetes is a condition in which the body becomes resistant to insulin. Insulin is a hormone that helps the body process and use glucose (blood sugar).

For this study, the research team, led by Dr. Nita G. Forouhi, of the University of Cambridge in the UK, used data from more than 100,000 people who took part in past studies. The authors looked at four genes in a DNA sequence variation that affects vitamin D levels in the body. The genes were responsible for some people having lower vitamin D levels in the blood than other people without those sequences.

The authors then studied whether those gene sequences were also more common in people with type 2 diabetes.

The study authors discovered that diabetes patients did not have those genes more often than others.

They also also found no evidence that having too little vitamin D caused changes to blood sugar levels.

"Low vitamin D levels are usually associated with poor health. This is why you see a correlation of low vitamin D with many chronic disease states," said Dr. Barry Sears, President of the non-profit Inflammation Research Foundation in Marblehead, MA and creator of The Zone Diet.

"However, intervention studies with vitamin D have demonstrated rather unimpressive benefits in treating those chronic disease conditions, indicating that low vitamin D may not have any causal relationship with the chronic disease," said Dr. Sears, who was not involved in this study.

"This article confirms those poor clinical outcomes using genetic analysis to indicate little relationship between vitamin D levels and type 2 diabetes," Dr. Sears said.

Dr. Forouhi and team noted that there may be many explanations for why people with type 2 diabetes have lower vitamin D levels. The study authors suggested one: People who exercised a lot were less likely to develop diabetes, the authors wrote. People who exercised outside were exposed to the sun, which is a source of vitamin D, and so these people had more vitamin D in their bodies. Therefore, more vitamin D was once thought to prevent diabetes, the authors concluded.

Researchers are not sure how vitamin D exerts its effects on blood sugar, but it does regulate calcium, which plays a role in managing blood sugar. Most people get their vitamin D through foods or by sun exposure, which allows the body to make more vitamin D.

There may be other reasons that will come to light with more research explaining the association between low vitamin D levels and diabetes.

The study authors had hoped they could recommend vitamin D supplements as a way to prevent diabetes, but they found this was not the case.

“While our current findings do not provide support for a causal role of vitamin D in the development of type 2 diabetes, we are far from done with this topic,” Dr. Forouhi said in a press release.

She said more research is needed, but "until then, we need to be cautious about vitamin D’s potential role in the prevention of type 2 diabetes and stick to things that are proven to work — diet and exercise.”

Dr. Brian Buijsse, of the German Institute of Human Nutrition in Nuthetal, wrote an editorial about this study's findings. He agreed that more research is needed, but that “the sky is becoming rather clouded for vitamin D in the context of preventing type 2 diabetes.”

This study and editorial were published Oct. 1 in The Lancet Diabetes & Endocrinology.

The UK Medical Research Council funded the study. The authors declared no conflicts of interest.

Review Date: 
September 30, 2014