When astronauts started spending a long time in space, their bones got thinner. Without gravity and regular exercise, the bones became less dense.
Today, astronauts work out hard in space. They have to. If they don’t, they risk long-term bone damage, also known as osteoporosis.
Bones on Earth need exercise, too. It makes them stronger. It also helps them store minerals and make blood cells. Diet is a big part of bone health, too. For instance, muscles and nerves need the mineral calcium, just as bones do. If they don’t get it from milk and green vegetables, they pull calcium from the bones. That makes bones more brittle. This condition is called rickets. Exercise and good food help us fight many threats to long-term bone health—but not all.
