New studies show the importance of vitamin D in the diet for type 2 diabetics

by Barbara Hewitt on February 11, 2016

Vitamin D supplements are unlikely to prevent prediabetes developing into type 2 diabetes, new research has found but those with the condition need to keep up their levels.

Vitamin D is generally known to reduce the risk of insulin resistance, which is often a precursor to type 2 diabetes and research has indicated that people who are deficient in vitamin D have a higher risk of type 2 diabetes.

But the vitamin is still important for those with type 2 diabetes and another piece of new research indicates that taking it as a supplement it not the best approach and that eating more eggs is a more efficient way to get enough.


Researchers from the Arctic University of Norway, carried out a small study of 511 people with prediabetes. Some 256 participants were given vitamin D supplements for five years and 255 a placebo.type

Oral glucose tolerance tests were carried out annually and 116 in the vitamin D group completed the study, while this figure was 111 in the placebo group.

The primary aim of the researchers was to assess the progression to type 2 diabetes. Secondary outcomes included glucose levels, insulin resistance, serum lipids and blood pressure.

Levels of vitamin D nearly doubled from baseline after five years in the vitamin D group, but remained largely stable in the placebo group. However, type 2 diabetes developed in 40.2% of the vitamin D group and 43.9% of the placebo group.

No significant differences in secondary outcomes were observed between the groups, with normal blood glucose levels found in 55 vitamin D group participants and 41 participants in the placebo group.

“Our study does not support giving vitamin D for the prevention of type 2 diabetes or for improvement of insulin resistance or hyperglycaemia. If there is a positive effect of vitamin D in this regard, the effect must be small. Very large studies with inclusion of vitamin D deficient subjects will be needed to show such a putative effect,” the study report said.

But vitamin D is important for those who go on to develop type 2 diabetes as new research from Iowa State University in the United States has found that a simple change in diet could boost levels of the vitamin.

Diabetics have trouble retaining vitamin D and other nutrients because of poor kidney function. The researchers, working with rats in the laboratory found that those on an egg based diet had higher concentrations of vitamin D, improved blood glucose levels and gained less weight.

“Eggs are the richest source of 25-hydroxyvitamin D-3 in the diet, and there isn’t any conversion required to make it into the blood. If you take it in a supplement or food fortified with vitamin D, it has to be converted to that form,” said Matthew Rowling, an associate professor of food science and human nutrition.

The variation in results was significant. Blood glucose levels dropped nearly 50% for diabetic rats on an egg based diet compared to diabetic rats fed a standard diet. Concentrations of 25D were 148% higher for the egg fed group.

Rowling and colleague Kevin Schalinske, professor of food science and human nutrition, and Samantha Jones, a graduate research assistant, are still working to understand why more vitamin D is retained from eggs than supplements. They say it may be related to other components found in eggs.

The next step is to determine the minimal amount of eggs needed in the diet to yield a benefit. The study was designed to replace protein in the diet, so the rats were fed the equivalent of 17 to 18 eggs daily. However, based on the results and the severity of the rats’ diabetes, researchers expect a much lower dosage will be effective in humans.

They also want to know if health benefits are enhanced when additional dietary constituents that promote the maintenance of vitamin D status and reduction of diabetic symptoms, such as fibre, are added to the diet.

“You may need even less egg if you combine it with something else that does not provide vitamin D per se, but rather protects the kidney and prevents loss of vitamin D. We want to make sure we understand what’s going on with egg consumption and promoting vitamin D balance and make sure there’s a linkage to outcomes whether it’s bone health or kidney health,” said Schalinske.