The phrase "to keep bones strong" means to take actions or do things that help maintain and improve the strength and health of our bones. Full definition
Milk is an excellent source of calcium, which helps keeps your bones strong. (verywellfit.com)
The kidneys help regulate calcium and vitamin D which keep bones strong. (kerryblues.org)
K2 goes straight to your blood vessel walls, bones, and tissues other than your liver, and is really critical for keeping your bones strong and arteries clear. (articles.mercola.com)