Healthy bones
The way to keep bones healthy is a blend of exercise, especially weight bearing exercise, and eating sufficient calcium and vitamin D. With all three in the right amounts, bones are likely to reach their maximum mass during childhood and early adulthood. Bone formation is a constant flux between bone formation and bone loss. Up until age 30 bone formation is more than bone loss so bones grow in size and density, providing the condition are right on the activity and food side. After 30 years bone mass tends to decrease, but that can be kept to a very slow rate by remaining active and eating well.
From a food aspect, you need both calcium and vitamin D together. You might eat enough calcium-containing foods, but without vitamin D you won’t be able to effectively absorb that calcium. This is the reason that you need vitamin D each day, whether from the sunshine or from food. This is where mushrooms can help.