“The timing of calcium supplementation, and not just the amount of supplementation, may be an important factor in how the skeleton adapts to exercise training,” study lead author Vanessa D. Sherk, PhD, postdoctoral research fellow at the University of Colorado Anschutz Medical Campus, said in a press release. “Further research, however, is needed to determine whether the timing of calcium supplementation affects the skeletal adaptations to exercise training.”
Past studies revealed that a year of intense training resulted in substantial decreases in bone mineral density among competitive road cyclists. Experts believe that this kind of exercise-induced bone loss could be related to the loss of calcium during exercise. Researchers explain that as blood calcium levels drop, the parathyroid gland produces excess parathyroid hormone, which can mobilize calcium from the skeleton.
The latest study included 52 men aged 18 to 45 years. Participants were randomly assigned to take 1,000 milligrams of calcium and 1,000 international units of vitamin D either 30 minutes before or one hour after exercise. The exercise part of the study consisted of a simulated 35-kilometer time trial and participants wore skin patches to absorb sweat. Researchers measured blood levels of calcium and parathyroid hormone before and immediately after exercise. The study also measured participants’ collagen type-1 C-telopeptide (CTX) levels before and 30 minutes after exercise. Researchers estimated to amount of calcium lost through the skin during exercise by calculating pre- and post-body weight and measuring the calcium in the sweat from the skin patches.
In the latest study, researchers found that an exercise-induced decrease in blood calcium occurred whether calcium supplements were taken before or after exercising.
However, the findings revealed that pre-exercise supplementation resulted in less of a decrease in blood calcium levels and a slight increase in parathyroid hormone levels.
“These findings are relevant to individuals who engage in vigorous exercise and may lose a substantial amount of calcium through sweating,” Sherk said. “Taking calcium before exercise may help keep blood levels more stable during exercise, compared to taking the supplement afterwards, but we do not yet know the long-term effects of this on bone density.”
Researchers noted that the timing of calcium supplementation did not cause a difference in blood levels of a compound that is a biological indicator of bone loss. The study found that both the before-and after-exercise groups exhibited 50 percent increases in the level of collagen type-1 C- telopeptide (CTX).
The study was presented Tuesday at The Endocrine Society’s 95th Annual Meeting in San Francisco.
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source: Counsel & Heal By Christine Hsu