Extra vitamin D can restore good bacteria in the gut, according to a study in mice, giving hope in the fight against risk factors for diabetes and heart disease. If these findings can be validated in humans, sun bathing and vitamin D supplements may be feasible and affordable approaches to improve or even prevent metabolic syndrome.

"Based on this study, we believe that keeping vitamin D levels high, either through sun exposure, diet or supplementation, is beneficial for prevention and treatment of metabolic syndrome," says Professor Stephen Pandol, at Cedars-Sinai Medical Center, USA, who collaborated with Yuan-Ping Han's research group at Sichuan University, China in the study.

Metabolic syndrome affects nearly a quarter of the world's adult population, and it is defined by a group of risk factors that put you on the road to diabetes and heart disease. The characteristic symptoms include obesity around the waistline and at least two of the following: high blood sugar levels, high blood pressure or high cholesterol. Sufferers usually also have excess fat in their liver. Vitamin D deficiency decreases the production of defensins, which are anti-microbial molecules essential to maintain healthy gut flora. As expected, an oral supply of a synthetic defensin recovers gut bacteria balance, decreases blood sugar levels and improves fatty liver.

In summary, a high fat diet alone is not enough to cause metabolic syndrome but it is needed in combination with vitamin D deficiency. Accordingly, vitamin D supplementation improves metabolic syndrome in mice. The next step would be to validate the results in humans. Han remains optimistic that the results of their study can be confirmed in humans. "We are planning a clinical study to confirm the link of vitamin D deficiency with gut bacteria disruption, and its association with metabolic syndrome," says Han.

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