Protein is an important nutrient, essential for the growth and repair of body cells. But diets high in protein can cause increased calcium excretion. Some suggest taking magnesium to facilitate calcium absorption. Evidence, however, is scant. High magnesium intakes actually increase calcium loss in urine.
Vitamin D is needed for proper absorption of calcium.
Regular exposure to sunlight, along with drinking vitamin D-fortified milk, will meet the vitamin D needs of most young people. This may not be sufficient for some older people. Supplementation of vitamin D to provide 600 to 800 IU per day has been shown to improve calcium balance in elderly people. It is important to take vitamin D supplements under the supervision of a physician or dietitian. If you are not able to consume sufficient levels of calcium through diet, your doctor or dietitian may recommend calcium supplements.