How Are Calcium & Vitamin D Related?

Calcium is necessary for strong bones and teeth, normal muscle and nerve function, and normal blood clotting. Milk is fortified with vitamin D, and calcium supplements contain vitamin D as well. Calcium and vitamin D are put together because your body needs vitamin D to get the calcium from food and supplements into your body.

Calcium Absorption

Vitamin D facilitates the absorption of calcium in the duodenum, which is crucial when the intake of calcium is low. According to 2008 information from Colorado State University, vitamin D stimulates the small intestine to make proteins called calbindin that transport calcium through the walls of the small intestine and into the blood stream. The intestines cannot make calbindin without vitamin D.

Regulation

Vitamin D regulates calcium in the blood and in the bones. According to 2011 information from the Office of Dietary Supplements of the Institutes of Health, vitamin D is necessary for osteoclasts and osteoblasts to break down and build up bone tissue. Vitamin D also regulates calcium levels in the blood. You need a specific amount of calcium in the blood to enable bone mineralization and to avoid tetany caused by hypocalcemia.

Recommended Calcium Amounts

According to 2011 information from the Office of Dietary Supplements of the National Institutes of Health, adult males need 1,000 mg calcium each day until the age of 71, when the recommendation goes up to 1,200 mg. Adult females need 1,000 mg calcium per day until age 51, when the recommendation goes up to 1,200 mg. Toddlers need 700 mg per day, children age 4 to 8 need 1,000 mg per day, and children from 9 to 18 years old need 1,300 mg per day.

Recommended Vitamin D Amounts

The sun is a major source of vitamin D for some people. Five to 30 minutes of sun exposure two times per week is sufficient for vitamin D production, depending on time of year and weather conditions. Dietary recommendations are set based on little to no sun exposure. According to 2011 information from the Office of Dietary Supplements of the National Institutes of Health, children and adults need 600 IU vitamin D per day and adults over the age of 70 need 800 IU per day.