When astronauts first began long-term space missions, something curious occurred: their bones became thinner. Without the stress of gravity and regular exercise, the bones became less dense.
Today, astronauts on missions work out hard to prevent long-term bone damage (osteoporosis).
Bones on Earth need exercise to stay strong, too. It also helps them store minerals and make blood cells. Diet also affects bone health. For instance, muscles and nerves need the mineral calcium, just as bones do. If they don’t get calcium from milk and green vegetables, they’ll take it right out of the bones, which then become brittle. This is a bad condition called rickets. Exercise and good food help us fight many threats to long-term bone health—but not all.
