Some of the ways to maintain bone density without medication are

Weight bearing exercise (more here),

Strength training (more here and here),

Whole body vibration,

Some Yoga positions,

Drinking green tea and practicing Tai Chi,

Getting enough calcium and vitamin D (more here and here, dosage here), as well as omega-3 fatty acids,, carotenoids, silicon, citrate, nitrates, magnesium, and manganese,

Eating tomatoes (more here)

Eating prunes (more here), and

Cuddling a purring cat.

And then there’s medication, if necessary.