Calcium is vital to muscle contraction, and vitamin D has been shown to reverse myopathy in osteomalacia, suggesting the latter may have beneficial effects on skeletal muscle strength.
Based on this, researchers at the All India Institute of Medical Sciences in New Delhi conducted an RCT to determine the impact calcium or cholecalciferol had on skeletal muscle strength and serum testosterone in young men with vitamin D deficiency.
Testing for testosterone…and more
They recruited 180 male subjects between the ages of 18 and 22, and randomly assigned them to four groups: a double-placebo group, a group given calcium and a placebo, a group given cholecalciferol and a placebo, and finally, a group given cholecalciferol and calcium.
They stated that the cholecalciferol doses were 60,000 IU a week for eight weeks, followed by 60,000 IU every fortnight. Doses for elemental calcium, on the other hand, were 500mg, taken twice daily for six months.
They then measured the subjects’ handgrip, pinch-grip strength, distance walked in six minutes, dyspnoea score, serum vitamin D levels, total testosterone, and free androgen index (FAI).
After the intervention period, they observed that in the cholecalciferol groups, the subjects’ serum vitamin D levels had risen from between 12nmol/L and 31nmol/L at baseline to above 75nmol/L.
No significant effect
They added, however, that the change in handgrip strength was comparable across all four groups, before and after adjustment for delta testosterone and FAI, and that mean serum testosterone had in fact “decreased significantly at six months”.
They wrote that six months of supplementation with calcium and vitamin D had “no significant effect” on the serum testosterone levels and skeletal muscle strength in young men aged 18 to 22.
Still, this was the first RCT to assess serum testosterone and skeletal muscle strength following six months of vitamin D and calcium supplementation, and they said the lack of any significant impact of vitamin D on skeletal muscle strength in young men “needs caution” because of serum testosterone’s complex photoperiodicity (physiological reaction to the length of day or night).
They alluded to a pilot study conducted on older male subjects — up to 40 years old — who were reassessed in November and December, saying they were likely on an “upward trajectory of serum testosterone”, unlike the current study, which reassessed its subjects in April and May, when they were said to have less serum testosterone.
Because of this, the researchers concluded: “More studies are required to confirm the results of the present study.
“Also, a meta-analysis may help to resolve the issue of vitamin D supplementation and its axis with testosterone and muscle strength.”
Source: Clinical Endocrinology
“Vitamin D and calcium supplementation, skeletal muscle strength and serum testosterone in young healthy adult males: Randomized control trial”
Authors: Soma Saha, et al.