Nutrition has a greater impact on bone mass and strength than exercise, according to a study that looked at mineral supplementation and physical activity in mice.
Researchers at the University of Michigan in the US found that even after the exercise training stopped, the mice retained bone strength gains as long as they ate a mineral-supplemented diet.
"The longer-term mineral-supplemented diet leads to not only increases in bone mass and strength, but the ability to maintain those increases even after detraining," said David Kohn, a professor at the University of Michigan.
"This was done in mice, but if you think about the progression to humans, diet is easier for someone to carry on as they get older and stop exercising, rather than the continuation of exercise itself," Kohn said.
The second important finding is that the diet alone has beneficial effects on bone, even without exercising, according to the study published in the journal PLOS ONE.
This surprised Kohn, who expected exercise with a normal diet to fuel greater gains in bone strength, but that wasn't the case.
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"The data suggests the long-term consumption of the mineral-supplemented diet could be beneficial in preventing the loss of bone and strength with age, even if you don't do exercise training," he said.
Most other studies look at effects of increasing dietary calcium, Kohn said. The new study increased calcium and phosphorous, and found benefits to increasing both.
This is not to suggest that people run out and buy calcium and phosphorus supplements, Kohn said.
The findings do not translate directly from mice to humans, but they do give researchers a conceptual place to start.
It is known that humans achieve peak bone mass in their early 20s, and after that it declines.
The question becomes how to maximise the amount of bone when young, so that when declines do begin, people start from a better position, Kohn said.
In addition to testing bone mass and strength, Kohn and colleagues performed a full battery of mechanical assessments on the bone, which is important because the amount of bone does not always scale with or predict the mechanical quality of the tissue.