Vitamin D is mentioned here and is worth discussing in more depth as we approach winter, which in northern climates, often brings weeks with little or no sunshine. Vitamin D is essential to building bone, in addition to calcium and exercise. This comprehensive fact sheet from the National Institutes of Health covers amount needed, recommended blood levels of Vitamin D, food, supplement and sunshine as sources, etc.
What you can do:
1. Get your vitamin D level checked. It should be between 50 and 100.
2. If you are deficient in Vitamin D, you can take up to 4,000 iu daily.