In a , published in Plos One, researchers at the U.K.'s University of Birmingham have found that increased levels of active vitamin D can help optimize muscle strength.
Previous studies have highlighted the importance of vitamin D in the prevention of heart disease, cognitive decline, autoimmune disease and cancer. It also plays a key role in bone health and preventing osteoporosis. This new study, published in Plos One, suggests that muscles may also benefit from vitamin D, which could help increase muscle mass.
Researchers at the University of Birmingham used a cutting-edge technique to assess both active and inactive forms of vitamin D, as well as their impact on various muscle functions.
The scientists studied 116 healthy volunteers aged between 20 and 74 years old. Participants' active and inactive vitamin D levels were measured, as well as physical parameters such as body fat and lean mass, which measures muscle bulk.
Women with healthy body compositions and lower body fat were less likely to have high levels of inactive vitamin D, which is a marker for vitamin D deficiency.
No correlation in men
Similarly, lower inactive vitamin D levels were found in women with higher levels of body fat, suggesting a relationship between vitamin D and body composition.
However, the active form of vitamin D was associated with lean mass but not body fat. Participants with increased lean mass, and muscle bulk, had a higher level of active vitamin D in their bloodstreams.
"By looking at multiple forms in the same study, we can say that it is a more complex relationship that previously thought. It may be that body fat is linked to increased levels of inactive vitamin D, but lean mass is the key for elevated levels of active vitamin D," explains Dr. Zaki Hassan-Smith, from the University of Birmingham.
Still, some of the study's positive correlations between vitamin D and muscle bulk were not seen in men. The scientists envisage further research to explore this biological difference between men and women.
In conclusion, "It is vital to understand the complete picture, and the causal mechanisms at work, so we can learn how to supplement vitamin D intake to enhance muscle strength," said Hassan-Smith.
Produced by exposure to sunlight, vitamin D helps the body absorb calcium. Dietary sources include oily fish (salmon, trout, tuna, sardines and mackerel), calf's liver, soy and egg yolks.
Doctors often prescribe vitamin D supplements as vials to take every six months, while vitamin D3 drops can be taken every day. The healthy range for vitamin D levels is considered to be between 40 to 45 ng/ml (100 to 112.5 nmol/l).
