the vitamin that helps prevent osteoporosis is the vitamin D. Normally, vitamin D helps your body to effectively absorb calcium into your body. Vitamin D can be gained through adequate sunlight exposure, especially during the morning sunlight, but this may not still be a good source of vitamin D especially when you are a working person. when a person lacks of vitamin D, that person's body won't be able to absorb that calcium that he needs for his body, this would cause the body, especially the bone to reproduce new bones slower than normal as the person grows.