Building and maintaining strong bones depends on calcium, vitamin D, and physical activity.
No matter what your age, strong bones help prevent osteoporosis, a disease in which bones become fragile and break easily. Often considered an "elderly" concern, osteoporosis prevention begins at an early age and continues throughout your lifetime.

Bone mass develops rapidly between the ages of 10 and 20 and peaks at age 30.

Your body uses vitamin D to help transport calcium to your bones. Foods such as milk, buttermilk, curds, paneer (cottage cheese) and eggs contain vitamin D. Your body also makes its own vitamin D when you are exposed to sunlight. Exposure to sunlight, three times a week, for 30 minutes, is the minimum sunlight required for younger people. However, many older people, who are not enough in the sun, need to take supplements to obtain their needed 400 to 600 IU of vitamin D per day.

Milk and nuts contains calcium as well as Vitamin D, which are essential for bone health.

Exercise keeps bones strong. It helps calcium deposition in the bones. It prevents calcium loss from bones. Weight-bearing exercise helps keep bones strong and prevents calcium loss. Calcium loss can take place at any age, even during childhood. For example, astronauts (weightlessness in space) and sedentary people are at greater risk for losing calcium from their bones.

Weight-bearing exercise includes walking, carrying groceries, carrying water, climbing stairs, dancing, skipping, hop-scotch, kho-kho, kasrat, playing other outdoor sports like gullidanda, volleyball, badminton, jogging, weight lifting, etc. Aim for at least 30 minutes of activity on most days of the week. You can add up the minutes throughout the day. It does not need to be all at one time.