Type II Diabetes and Vitamin D

What role does vitamin D play in weight loss and type II diabetes?


A recent randomized controlled trial found that vitamin D supplementation decreased waist circumference, body weight and systolic blood pressure in Thai adults with prediabetes.

Prediabetes occurs when a person has a higher blood sugar level than normal, but not high enough to be considered type II diabetes. This is a sign that the body is not using insulin properly, known as insulin resistance. When an individual is affected by insulin resistance, glucose (sugar) builds up in the blood rather than being absorbed by the cells.

Prediabetes has become more prevalent in the U.S., affecting over 86 million adults ages 20 or older. Once someone has been diagnosed with prediabetes, it’s crucial to begin making changes to their lifestyle, such as increasing physical activity, limiting alcohol consumption and eating a more balanced diet. Without implementing these changes, approximately 15% to 30% of people with prediabetes will develop type II diabetes within five years.

Recently, researchers have begun to question whether vitamin D supplementation might also be an intervention to prevent the development of type II diabetes. Though, research on this topic has been conflicting. Some research has provided evidence that vitamin D supplementation improves insulin sensitivity, while others show that vitamin D doesn’t help control blood sugar. Now, researchers sought to gather more insight regarding the role vitamin D plays in the prevention of type II diabetes.

Researchers from Thailand enrolled 47 adults with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT). The participants were randomized into three groups: control, vitamin D2 or vitamin D3. The participants in the vitamin D2 and D3 groups received 20,000 IU and 15,000 IU weekly, respectively. The control group did not receive any vitamin D. After three months, the researchers assessed anthropometric measurements, insulin resistance and insulin secretion.

The researchers found that both vitamin D2 and D3 groups significantly increased vitamin D levels. (Though, as expected, vitamin D3 supplementation was more effective in raising vitamin D levels than D2.) Thus, the researchers combined the vitamin D groups into one for the analysis. Here is what they found:

  • Waist circumference, body weight and systolic blood pressure significantly decreased in the vitamin D group (p = 0.05).
  • Both body mass index and insulin resistance were reduced in the vitamin D group but did not reach statistical significance (p = 0.06, 0.09).

Participants who had an increase of vitamin D status over 10 ng/ml experienced a significant decrease in insulin resistance and a significant increase in disposition index. Disposition index is used to predict the risk for type II diabetes. The study presented significant results, suggesting that vitamin D may not only play a role in the prevention of type II diabetes, but it may also aid in weight loss. In the past couple of years, there have been two major studies regarding vitamin D and weight loss, both of which were clinical trials.

A study led by Dr. Luisella Vigna of the University of Milan investigated the role of vitamin D on weight loss in 400 obese or overweight adults. Vigna and colleagues divided the participants into three groups: those who did not take supplements, those who took 25,000 IU of vitamin D per month and those who took 100,000 IU of vitamin D per month. All participants were put on the same low-calorie diet. After six months, those who supplemented with 25,000 IU and 100,000 IU lost an average of 8.4 and 11.9 pounds, respectively, compared to the average 2.6 pounds lost of those who did not supplement with vitamin D.

A study published in the American Journal of Clinical Nutrition compared the effects of vitamin D on weight loss by dividing the participants into two groups. The first group followed a weight loss program and were given 2000 IU of vitamin D3 daily. The second group also followed the weight loss program, but instead, received a daily placebo. The study concluded that vitamin D3 supplementation with 2000 IU daily did not significantly increase weight loss in comparison to those who took a daily placebo. However, when the researchers conducted an analysis of women who became replete in vitamin D to women who remained insufficient (> 32 ng/ml vs < 32 ng/ml), they found that women with sufficient vitamin D levels had a greater waist circumference reduction than the deficient women (-6.6 cm vs 2.5 cm).

The current literature suggests that vitamin D likely helps with weight loss and possibly helps decrease the risk of developing type II diabetes. Though, further clinical trials investigating vitamin D’s effects on weight loss and type II diabetes are warranted.


Tovey, A. & Cannell, JJ. What role does vitamin D play in weight loss and type II diabetes? The Vitamin D Council Blog & Newsletter, 2016.


Nimitphong, H. et al. The Effect of Vitamin D Supplementation on Metabolic Phenotypes in Thais with Prediabetes. Journal of the Medical Association of Thailand, 2016.

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