Vitamin D3 is beneficial for maintaining bone health throughout the aging process, according to WebMD. It is needed by the body to regulate calcium and phosphorous, which together largely compose bones.
Deficiency of vitamin D can result in osteomalacia or rickets, both diseases characterized by a softening of the bones, states the Mayo Clinic. There is also evidence that supplementation with vitamin D3 can reduce the risk of certain types of cancer as well as multiple sclerosis and even seasonal colds, according to WebMD. It is safe to orally supplement with up to 4,000 IUs of vitamin D daily, says the Mayo Clinic.