News & Research

Low Vitamin D Levels Are Linked to Higher Death Risks in Type 2 Diabetes Vitamin D levels and mortality in type 2 diabetes, by Christel Joergensen and colleagues. Diabetes Care 33:2238–2243, 2010

What is the problem and what is known about it so far?

The majority of people get most of their vitamin D from spending time in the sun. Vitamin D levels can vary greatly from one person to the next depending on their sun exposure, skin color, and other factors. Many people do not get enough vitamin D. Low levels of vitamin D have been linked to a higher chance of getting heart disease and death within the general public and among people with kidney disease. Studies have also shown that vitamin D deficiency may play a role in the development of kidney disease and eventually worsening and leading to kidney failure. Diabetes is the leading cause of kidney disease, and many people with diabetes also die from complications related to heart disease. It is important to find ways to identify early which people with diabetes are most likely to get kidney and heart disease, so they can get preventive treatment to help them avoid these life-threatening complications.

Why did the researchers do this particular study?

The researchers wanted to find out whether the vitamin D levels of people with type 2 diabetes can help to identify those who are most at risk for heart and kidney disease and early death.

Who was studied?

The study included 289 adult patients with type 2 diabetes whose average age was 54 years. Some of the patients had healthy kidneys, some had signs of early kidney disease, and some had signs of more advanced kidney disease.

How was the study done?

Researchers measured vitamin D levels at the start of the study to find out which participants had low levels. They then followed up with patients for about 15 years to see who developed kidney and heart disease or died from heart disease or other causes.

What did the researchers find?

Patients with severe vitamin D deficiency were more likely to die from heart disease or from any cause regardless of their glucose control, kidney function, and other heart disease risk factors. However, those with severe vitamin D deficiency were not more likely than those with higher vitamin D levels to get kidney disease or to have their kidney disease worsen.

What were the limitations of the study?

Because of the study design, the researchers could find links between vitamin D levels, heart disease, and death, but they could not find the causes of these links. Also, low levels of vitamin D could be linked to other conditions, such as thyroid problems, that can increase a person’s risk of death. In addition, the researchers did not take into account the time of year when they measured the participants’ vitamin D levels or how much outdoor exercise the participants routinely got. Because most vitamin D comes from sun exposure, there could be differences in a person’s vitamin D level based on the amount of time he or she spends outdoors or the season of the year.

What are the implications of the study?

People with type 2 diabetes and low levels of vitamin D are more likely to die from heart disease or another disease than those with higher vitamin D levels. Whether taking vitamin D supplements can lower their risk still needs to be studied.

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