Exercise is an integral part of building strong bones, but it goes hand in hand with nutrition. The foods we eat (or don't eat) have just as much impact on our future bone health as our activity level and can help add to our bone bank for later on. When most people are asked about how they think strong bones are built, the first answer given is usually related to calcium intake. Dairy products like milk, cheese and yogurt, white beans, kale and spinach are excellent sources of calcium. However, while this mineral is essential for the proper development of bones, the body is unable to absorb it without the addition of vitamin D. Many foods today, like cereal and orange juice, come fortified with vitamin D, but shrimp and tuna are excellent sources as well. And let's not forget sunlight. Just 10 minutes of direct sunlight exposure three times a week provides what the body needs to produce enough vitamin D. Another contributor is vitamin K, which is essential in helping the body build the proteins necessary for healthy bones. Vitamin K also stimulates calcium absorption and reduces its excretion. You can fill up on it with kale, spinach and broccoli. And one thing to reduce is caffeine (especially for young people). It's not necessary to cut it out altogether, but consuming too much (more than the equivalent of two cups of coffee per day) can interfere with the body's ability to absorb enough calcium.
Source : https://health.usnews.com/health-care/for-better/articles/2018-09-14/why-maintaining-bone-health-starts-in-youth264