Sherin

Here is one of the studies:

http://www.hsph.harvard.edu/nutritionsource/calcium.html

Getting enough vitamin D

Vitamin D plays a critical role in maintaining bone health. When blood levels of calcium begin to drop, the body responds in several ways. It promotes the conversion of vitamin D into its active form, which then travels to the intestines (to encourage greater calcium absorption into the blood) and to the kidneys (to minimize calcium loss in the urine).

For bone health, an adequate intake of vitamin D is no less important than calcium. Vitamin D is found in milk and vitamin supplements, and it can be made by the skin when it is exposed to sunlight in the summertime. But not all sunlight is created equal. Above 40 degrees latitude (north of San Francisco, Denver, Indianapolis, and Philadelphia), the winter sunlight isn't strong enough to promote vitamin D formation. Sunscreens also prevent the formation of vitamin D, although they are still recommended to reduce risk of sun-induced skin cancer and skin damage.

An examination of clinical trials of vitamin D for the prevention of osteoporosis found that the vitamin decreases vertebral fractures and may decrease nonvertebral fractures.(4) A similar analysis of the effect of vitamin D on falls indicated that supplementation with vitamin D reduces the risk of falls among ambulatory or institutionalized older individuals with stable health by more than 20%.(5)

mr belvedere

Ahem, vitamin D is added to milk but doesn't metabolize efficiently in the body through this method or supplements. But it can't hurt, right? Good luck with your bones.