Bones feel solid, but the inside of a bone is actually filled with holes like a honeycomb. Bone tissues are broken down and rebuilt all the time. While some cells build new bone tissue, others dissolve bone and release the minerals inside, according to experts at NIH in Health.

As we get older, we begin to lose more bone than we build. The tiny holes within bones get bigger, and the solid outer layer becomes thinner. In other words, our bones get less dense. Hard bones turn spongy, and spongy bones turn spongier. If this loss of bone density goes too far, it’s called osteoporosis. Over 10 million people nationwide are estimated to have osteoporosis.

In bad accidents, it’s normal for bones to break. But if your bones are dense enough, they should be able to withstand most falls. Bones weakened by osteoporosis, though, are more likely to break.

You can lower your risk of osteoporosis.

Getting plenty of calcium, vitamin D, and exercise is a good start.

•  Calcium is a mineral that helps bones stay strong. It can come from the foods you eat—including milk and milk products, dark green leafy vegetables like kale and collard greens—or from dietary supplements.

•  Vitamin D helps your body absorb calcium. As you grow older, your body needs more vitamin D, which is made by your skin when you’re in the sun. You can also get vitamin D from dietary supplements and from certain foods, such as milk, egg yolks, saltwater fish, fortified milks and cereals, and cod liver oil.

•  Exercise, especially weight-bearing exercise, helps bones too. Weight-bearing exercises include jogging, walking, tennis, and dancing. The pull of muscles is a reminder to the cells in your bones that they need to keep the tissue dense.

Smoking, in contrast, weakens bones. Heavy drinking does too—and makes people more likely to fall. Certain drugs may also increase the risk of osteoporosis. Having family members with osteoporosis can raise your risk for the condition as well.

The good news

Even if you already have osteoporosis, it’s not too late to start taking care of your bones. Since your bones are rebuilding themselves all the time, you can help push the balance toward more bone growth by giving them exercise, calcium, and vitamin D.