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Good Question: Why Do We Shrink As We Age?

MINNEAPOLIS (WCCO) -- Over the course of their lifetimes, people can get shorter. Men can lose about an inch on average as they get older. For women, it's more than two. So, why do we shrink as we age? Good Question.

"It has to do with gravity, the ravages of gravity," says Dr. Kjell Lindgren, a NASA astronaut.

When he spent 141 days on the International Space Station, he stretched an inch.

"For the longest time, we thought that was because of the intervertebral discs -- those cushions in between our vertebrae that those kind of inflated and hydrated, and that's where that came from," says Lindgren. "Recently results show that's not the case, that is really is kind of a posture change."

He says without gravity, people lose some of the curves in their upper and lower back.

With gravity – which is how everyone else on Earth lives – the opposite happens and people will get shorter. As people age, they lose muscle tone, which is mostly responsible for posture. Bones also lose mineral density and can cause some of the vertebrae to compress along with the discs in between.

"The cartilage becomes less spongy and starts to compress as well," says Lindgren.

People can start shrinking in their 40s. On average, women lose about a half-inch every decade after age 40.

Experts say it's not entirely possible to prevent a person from getting shorter as they age, but exercise, especially resistance training, and a balanced diet with calcium can help.

"It's the prescription for good health in general and the prescription we follow at the astronaut office," says Lindgren.

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