Acute Effects of Milk vs Carbohydrate on Bone Turnover Biomarkers Following Exercise in Young Adult Females
J.L. Prowting Appl. Physiol. Nutr. Metab. Vol. 46, 2021 S70
Dairy products and impact exercise are known to be independently
beneficial for bone mineral properties. It is unknown however
whether combining these two osteogenic interventions can synergistically augment acute bone turnover and cellular responses. Using
a randomized crossover design, our objective was to compare the
acute effects of consuming milk vs an isoenergetic carbohydrate
control beverage on bone biomarkers following loading exercise.
Thirteen healthy female participants (Age=2062y; Weight=5765kg)
consumed either 555mL of skimmed milk (MILK) or 52.5g of maltodextrin within 500mL of water (CHO), both immediately and 1 hour
following completion of a combined plyometric and resistance
exercise bout. Venous blood samples were obtained pre-exercise,
and 15-min, 75-min, 24-h and 48-h post-exercise to assess serum
concentrations of bone resorption biomarkers, including carboxylterminal crosslinking telopeptide of type I collagen (CTX), receptor
activator nuclear factor kappa-b ligand (RANKL), and sclerostin,
as well as bone formation biomarkers, including osteoprotegerin
(OPG) and osteocalcin. There was a significant main effect for time
(p<0.05) for RANKL, OPG:RANKL ratio, osteocalcin and sclerostin,
but no condition or interaction effects were observed (p>0.05).
Post-hoc analysis revealed that at 75-min post-exercise, RANKL,
osteocalcin and sclerostin were lower and OPG:RANKL ratio was
higher compared to baseline in both conditions. There were no differences over time or between conditions for CTX or OPG (p>0.05).
The net post-exercise area-under-the-curve (AUC) response relative
to baseline (percentage change from 1-h to 48-h) was significantly
lower in the MILK vs CHO condition for CTX (paired t-test, p=0.03),
however there were no significant differences between conditions
for the other biomarkers (p>0.05).
These results suggest that milk
does not alter absolute post-exercise concentrations of bone biomarkers compared to CHO. However, the blunted relative exercise
response of the bone resorption biomarker CTX in the MILK condition compared with CHO suggests a less catabolic acute response
when milk is consumed following loading exercise. Further research
is required to determine whether this observation would result in
beneficial chronic bone outcomes.