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Warmer Weather Equals Stronger Bones in New Study

Thermometer sticking out of sand on beach and Showing High Temperature
Andrey_Popov/Shutterstock

In case you needed another reason to move to a warm climate: researchers from the University of Geneva (UNIGE) in Switzerland have just figured out that living in an environment around 93°F makes bones stronger and helps ward off osteoporosis. And it all starts in the gut.

Tropical Mouse Vacation

In conducting their research, the team placed mice in a 93°F environment when they were born. As their growth was monitored, they found that the mice had longer and stronger bones. To see if the effects would translate to adult mice, they put some in the warm environment while some were left at colder temperatures. Sure enough, the mice that were kept warm developed stronger and denser bones than those left at colder temps.

To take another step in the research, the team removed the ovaries of female mice to mimic what happens to females after menopause, a prime time for osteoporosis to set in thanks to bone loss from lack of estrogen. Once again, the benefits of heat were supported.

“The effect was very interesting,” says Claire Chevalier, the first author of the study. “The simple fact of warming the living environment of our mice protected them from the bone loss typical of osteoporosis!”

Going With the Gut

Perhaps most impressive of all, it wasn’t heat’s effect on the bones directly, but how heat changed the gut microbiota—the collection of bacteria living in the digestive tract—that made the difference. The team believes this was because hot climates can disrupt the creation and destruction of polyamines, organic compounds associated with aging, and bone health.

“With heat, the synthesis of polyamines increases, while their degradation is reduced,” said Chevalier. “They thus affect the activity of osteoblasts (the cells that build bones) and reduce the number of osteoclasts (the cells that degrade bones). With age and menopause, the exquisite balance between the osteoclast and osteoblast activity is disrupted. However, heat, by acting on the polyamines, which we found to be partly regulated by the microbiota, can maintain the balance between these two cell groups.”

To confirm the effect of the microbiota on bone health, the researchers transferred the microbiota of mice raised in warm environments to those with osteoporosis and saw significant and rapid improvement in bone health.

It Seems to be True for People Too

Finally, to see if warm environments also help humans build better bones, the researchers examined global data comparing osteoporosis rates to average temperatures and latitudes, as well as providing data on vitamin D levels and calcium intake. Once again, heat proved beneficial.

“We found a clear inverse correlation between geographical latitude and hip fractures, meaning that in the northern countries the incidence is higher compared to the warmer south,” said study leader Mirko Trajkovski. “Normalizing the analysis of the known players such as vitamin D or calcium did not modify this correlation. However, when we excluded the temperature as the determinant, the correlation was lost. This is not to say that calcium or vitamin D do not play a role, either alone or in combination. However, the determining factor is heat—or lack thereof.”

The research has been reported in the peer-reviewed journal Cell Metabolism.