The Effects of a Calcium-Rich Pre-Exercise Meal on Biomarkers of Calcium Homeostasis in Competitive Female Cyclists: A Randomised Crossover Trial

Abstract

Cycling is recognised as a sport in which there is a high incidence of poor bone health. Sweat calcium losses may contribute to this.PurposeTo examine whether a calcium-rich pre-exercise meal attenuates exercise-induced perturbations of bone calcium homeostasis caused by maintenance of sweat calcium losses.MethodsUsing a randomized, counterbalanced crossover design, 32 well-trained female cyclists completed two 90 min cycling trials separated by 1 day. Exercise trials were preceded 2 hours by either a calcium-rich (1352 ± 53 mg calcium) dairy based meal (CAL) or a control meal (CON; 46 ± 7 mg calcium). Blood was sampled pre-trial; pre-exercise; and immediately, 40 min, 100 min and 190 min post-exercise. Blood was analysed for ionized calcium and biomarkers of bone resorption (Cross Linked C-Telopeptide of Type I Collagen (CTX-I), Cross Linked C-Telopeptide of Type II Collagen (CTX-II), Parathyroid Hormone (PTH), and bone formation (Procollagen I N-Terminal Propeptide (PINP)) using the established enzyme-linked immunosorbent assay technique.ResultsPTH and CTX-I increased from pre-exercise to post-exercise in both conditions but was attenuated in CAL (p < 0.001). PTH was 1.55 [1.20, 2.01] times lower in CAL immediately post-exercise and 1.45 [1.12, 1.88] times lower at 40 min post-exercise. CTX-I was 1.40 [1.15, 1.70] times lower in CAL at immediately post-exercise, 1.30 [1.07, 1.57] times lower at 40 min post-exercise and 1.22 [1.00, 1.48] times lower at 190 min post-exercise (p < 0.05). There was no significant interaction between pre-exercise meal condition and time point for CTX-II (p = 0.732) or PINP (p = 0.819).ConclusionThis study showed that a calcium-rich pre-exercise breakfast meal containing ~1350 mg of calcium consumed ~90 min before a prolonged and high intensity bout of stationary cycling attenuates the exercise induced rise in markers of bone resorption – PTH and CTX-I.Trial RegistrationAustralian New Zealand Clinical Trials Registry ACTRN12614000675628

Calcium Supplementation Attenuates Disruptions in Calcium Homeostasis during Exercise

“…However, due to the low number of participants in this category, we did not analyze whether they responded differently than their peers with t-scores greater than −1.0. However, we think it is unlikely that the difference in BMD scores would influence the outcomes because of the consistent findings across multiple labs that endurance exercise stimulates PTH secretion (3, 7, 10). Our working hypothesis is that the repeated activation of PTH and CTX by exercise is the cause of the bone loss observed in this population, and we hope to address the impact of bone health status on these markers in a future clinical trial.…”

“…In contrast, starting Ca supplementation 60 minutes before exercise prevented the decrease in iCa, attenuated the increase in PTH by almost 70%, and also tended (p=0.08) to suppress the CTX response (11). In young female cyclists, a high Ca meal (1352 mg) 120 minutes before exercise attenuated the changes in iCa, PTH, and CTX in response to 90 minutes of moderate intensity exercise when compared with a low Ca meal (46 mg) (7). Collectively, these studies indicate that intestinal Ca absorption can play an important role in defending serum Ca during exercise.…”

“…Exercise can cause a decrease in serum total and ionized calcium (iCa) during prolonged moderate-to-vigorous endurance exercise, which is a trigger for parathyroid hormone (PTH) secretion (1, 2, 6, 7, 11). PTH defends serum calcium (Ca) by increasing intestinal Ca absorption, inhibiting renal Ca excretion, and stimulating the mobilization of skeletal Ca.…”

“…The decrease in iCa and increase in PTH were attenuated when a Ca-enriched beverage or meal was consumed before and/or during exercise (1, 6, 7, 11). This Ca supplementation was effective in attenuating the increase in bone resorption in some experiments (6, 7, 11), but not others (1, 11). The discordance may relate to the timing of Ca dosing.…”

“…Timing is also important for exercise planning. Most experiments have investigated pre-exercise supplementation beginning 60 minutes or more before the onset of exercise (7, 11). While this may be appropriate for a planned research exercise visit, this degree of advanced planning may be difficult for regular exercise.…”