Vitamin D and calcium: How does vitamin D help calcium absorption?
You probably already know that you need calcium for strong, healthy bones. Phosphorus is another mineral that helps build and repair bones. Did you know that your body needs vitamin D to help enhance phosphorus and calcium absorption? Vitamin D plays a key role in enhancing phosphorus entry as well as maintaining a healthy balance of calcium and phosphorus in the blood. That makes vitamin D a critical component to maintaining healthy and strong bones.
Both phosphorus and calcium absorption takes place in the intestinal tract, particularly in the lower segment of the small intestine, which is called the ileum. In fact, 70 to 80 per cent of calcium absorption occurs in this specific area of the intestines.  The entry of calcium and phosphorus into the digestive tract is positively enhanced by the presence of Vitamin D.  That means that vitamin D is the key to getting calcium and phosphorus to enter the bloodstream via the gut.
Low levels of vitamin D can result in insufficient levels of both calcium and phosphorus. Therefore, it is not surprising that low levels of vitamin D can also be associated with soft, brittle, or deformed bones. Maintaining proper levels of vitamin D has been associated with the prevention of softening and weakening of bones in children (known as rickets) as well as softening of the bones (known as osteomalasia) in adults. Vitamin D and calcium also help protect older adults from a reduction in bone mass and thinning of the bone which predisposes the bones to break at the slightest movement (known as osteoporosis). [2,3]
A simple comparison would be to consider vitamin D as a doorman in the gut. It is the one responsible for opening the door and allowing the minerals calcium and phosphorus to enter. Once in the gut, calcium and phosphorus are free to move throughout the body to do what they do best; strengthen, repair, and build bone and teeth. But without vitamin D, it would have been very difficult for either calcium or phosphorus to enter. The next time you take in vitamin D either via sunlight, food, or a supplement, like Ddrops®, know that calcium and phosphorus are also on the way to help maintain healthy and strong bones.
Originally published on February 21, 2016
 R.H. Wasserman. Vitamin D and the Dual Processes of Intestinal Calcium Absorption. J. Nutr. November 1, 2004 vol. 134 no. 11 3137-3139
 The National Academy of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
 “Health and Medical Information Produced by Doctors.” MedicineNet, https://www.medicinenet.com/script/main/hp.asp