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Vitamin D2 may lead to muscle damage in athletes

Published on

12 February 2014

Vitamin D deficiency appears to be an independent risk factor for the development of type 2 diabetes, says a new study from Israel.
The observational study measured serum 25-hydroxyvitamin D concentrations and documented cases of impaired glucose control and type 2 diabetes in 83,526 adults between the ages of 40 and 70 with normal glucose control and 34,434 participants with impaired fasting glucose (IFG) over the course of two years (1). The study results showed that – after adjustment for confounders such as BMI, cholesterol levels, history of cardiovascular diseases and smoking – participants with vitamin D deficiency, especially at levels below
37.5 nmol/L, had a significantly increased risk of developing IFG and diabetes. The risk of IFG and diabetes was reduced in participants with initial low serum vitamin D concentrations and whose levels increased over time compared to those with consistently low levels.

The researchers concluded that these findings indicated that a low vitamin D level is an independent risk factor for diabetes and that increased intakes of the vitamin may reduce the risk. Vitamin D insufficiency has been linked to dysfunction of insulin-producing beta cells and insulin resistance, which may increase blood glucose at all stages of diabetes (2). Previous studies have already suggested that low vitamin D levels are associated with type 2 diabetes and the metabolic syndrome (3, 4).

A new US study reports that taking vitamin D2 supplements may result in higher muscle damage after intense weight lifting.

The randomized controlled trial measured blood vitamin D concentrations and muscle functions of 28 athletes who received a daily 3800 IU of vitamin D2 or placebo for six weeks and performed intense weight lifting (1). The study results showed that the participants who took vitamin D2 supplements had a significantly increased exercise-induced muscle damage compared to the placebo group. In addition, while blood vitamin D2 levels increased in the supplement group, their vitamin D3 levels decreased.

The researchers commented that high blood levels of vitamin D2 seem to cause something to occur at the muscle level that worsens muscle damage following stressful exercise, probably by lowering vitamin D3 levels. Initially, the scientists had hypothesized that taking the vitamin D2 supplement would improve per- formance by reducing inflammation and aiding in recovery from exercise-induced muscle damage, particu- larly as many athletes are deficient in vitamin D in the winter months.

There is an ongoing debate about the difference in effects of vitamin D3 versus vitamin D2 on human health. Vitamin D3 is the form of vitamin D that humans produce from sun exposure. Vitamin D2 is a form of vitamin D produced by certain organisms, like mushrooms.


  1. Tsur A. et al. Decreased serum concentrations of 25-hydroxycholecalciferol are associated with increased risk of progression to impaired fasting glucose and diabetes. Diabetes Care. 2013; 36(5):1361-1367.
  2. Pittas A. G. et al. The role of vitamin D and calcium in type 2 diabetes. A systematic review and meta-analysis. J Clin Endocrinol Metab. 2007; 92(6):2017-2029.
  3. Mitri J. et al. Vitamin D and type 2 diabetes: a systematic review. Eur J Clin Nutr. 2011; 65(9):1005-1015.
  4. Nieman D. C. et al. Vitamin D2 Supplementation Amplifies Eccentric Exercise-Induced Muscle Damage in NASCAR Pit Crew Athletes. Nutrients. 2014; 6(1):63-75.

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