12 January - 20 June 2016

Which is best for bone strength? Nutrition vs exercise

Scientists from the University of Michigan have investigated whether exercise or nutrition has the bigger positive impact on bone strength. Bone mass continually declines with age and as people get older weight bearing exercise become more difficult. The mouse study published in PLOS one investigates combining exercise with a calcium and phosphorus supplemented diet.

Scientists from the University of Michigan have investigated whether exercise or nutrition has the bigger positive impact on bone strength. Bone mass continually declines with age and as people get older weight bearing exercise become more difficult.  The mouse study published in PLOS one investigates combining exercise with a calcium and phosphorus supplemented diet.

Kohn et al. split 176 male mice into 9 groups.  A no exercise and control diet, no exercise and supplemented diet for 8 week, exercise and control diet for 8 weeks, exercise and supplemented diet for 8 weeks, no exercise and control diet for 16 weeks, no exercise and supplement diet for 16 week, exercise and detraining and control diet for 16 weeks, exercise and detraining and supplement diet for 16 weeks and a baseline group.  The control diet contained 0.5% calcium and 0.5% phosphorus, whilst the supplemented diet contained 5% calcium and 1% phosphorus.  The exercise consisted of running an incline treadmill at 12 m/min, 30 min/day for 56 consecutive days.

Kohn et al sacrificed the mice and carried out tibial scans analysing bone volume, bone volume fraction, volumetric bone mineral density, trabecular number, trabecular thickness amongst others. The also measured structural and tissue level mechanical properties. 

They report that after intervention there was no significant difference in mean body weight between any of the groups. Even after detraining, Kohn et al report that the supplemented mice maintained bone mass and bone strength.  The 8 weeks of exercise along with the supplement “led to significantly greater tibial cortical BMC, area and movement of inertia” in the mice who exercised and consumed the supplemented diet compared to the no exercise and supplemented diet mice and the no exercise and control diet mice. The study states “data suggest combining exercise with the supplemented diet leads to peak cortisol bone mass at a faster rate than with the supplemented diet without exercise.  Exercise had little effect on cortical bone mass in mice fed the control diet.  There was no difference between control diet mice who had exercised and hadn’t exercised after 8 or 16 weeks. 

Kohn et al report that in previous studies they have used 10 times the amount of calcium of the control diet used in this study and found no negative health effects.  They do acknowledge that there are major difference between human and mouse calcium requirements and consumption. The study states that “in our studies, there appears to have been some added benefits to bone mass and strength from increasing both calcium and phosphorus that was not seen in other studies that only increased calcium.”

In conclusion Kohn et al reiterate their findings and note that “exercise was also beneficial as it allowed mice on the supplemented diet to achieve peak cortical bone mass in less time and prevented loss of trabecular bone and loss of bone strength from 8 to 16 weeks in mice on the control diet.  Long-term use of dietary mineral supplements may help increase and maintain bone mass with weight gain and/or ageing in adult mice.”

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