High Vitamin D linked with strong muscles in girls

Surprisingly, the same link was not true for boys. 

"We also found that girls were stronger if their Vitamin D level was more than 50 nanomoles per litre. The most surprising finding was that this difference was only evident in girls and not in boys," said lead author Rada Faris Al-Jwadi from the University of Southern Denmark.

However, the study reported in the Journal of Clinical Endocrinology and Metabolism, offers no explanation for the difference between boys and girls.

But other studies on children and adults have shown that vitamin D increases the levels of IGF-I -- a growth factor that increases muscle strength.

However, the IGF-I level is different in boys and girls which could be part of the explanation. 

"We can't, based on our data, conclude that girls will get stronger muscles if they got more vitamin D through their food, as supplement pills or because of more sun exposure which are some of the most important sources of Vitamin D. Even though, our association could mean exactly that," said Henrik Thybo Christesen, Professor at the varsity.

The study, published in Journal of Clinical Endocrinology and Metabolism, included 499 children aged five years. 

In a hand grip strength test meant for children, girls with low vitamin D have a 70 per cent increased risk of being among the lowest 10 per cent.

The study showed no association with vitamin D levels in mothers during pregnancy or in the umbilical cord at birth. This leads to the conclusion that there is no prenatal programming effect of muscle strength.

"We are talking about a more immediate effect of Vitamin D," Jwadi said.