High vitamin D levels linked to increased muscle strength in girls

High level of vitamin D is associated with increased muscle strength in girls, but the association was not found in boys, according to a new study published in the Journal of Clinical Endocrinology and Metabolism.

The study was conducted by Henrik Thybo Christesen, a professor at Hans Christian Andersen Children’s Hospital, Odense University Hospital, Odense, Denmark, and colleagues to determine the association of handgrip strength (HGS) in 5-year-old-children with serum 25-hydroxyvitamin D (s-25OHD) from pregnancy to five years.

Severe deficiency of vitamin D may lead to myopathy, a muscle disease characterized by improper functioning of muscle fibers, in adults. However, there is not much information about an association between muscle strength and vitamin D in children.

In the study, 881 5-year-old children in Odense Child Cohort got their muscle strength measured with a standardized test for hand grip strength meant for children. For 499 of the children, Vitamin D status analyses were done. Low Vitamin D levels were defined as serum 25OH-Vitamin D below 50 nmol/L. The statistical analyses were adjusted for height, weight and body fat percentage and were statistically highly significant. This means that the association wasn't due to being overweight and thereby having lower Vitamin D and lower muscle strength. It also means that it wasn't because girls liked to be more inside and were less physically active. The body fat percentage was calculated based on skinfold measurements.

Key Findings:

• Girls with low vitamin D had a 70 percent increased risk of being among the lowest 10 percent in a test for muscle strength.


• Girls were stronger if their Vitamin D level was more than 50 nmol/L, the difference was evident only in the girls and not in boys.


• There was no association with vitamin D levels in mothers during pregnancy or in the umbilical cord at birth.


• There is no prenatal programming effect of muscle strength.

According to Christesen, the study 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, which is a growth factor that increases muscle strength. Also, the IGF-I level is different in boys and girls which could be part of the explanation.

"Five-years-25OHD was independently associated with HGS and myopathy in girls, but not in boys. Muscle strength may be dependent on vitamin D status even in the higher range in preschool girls. The sex difference remains unexplained," concluded the authors.

For further information click on the link: https://doi.org/10.1210/jc.2018-00281