The healthy body is an amazing machine, and if maintained properly, it is efficient at keeping itself in homeostasis. Calcium and phosphorus are vital minerals present in our daily diets that play key roles in homeostasis. Both are required to work together to maintain our bone health as well as organ systems. To properly utilize these minerals from food, your body processes them through the absorption process.
Absorption of calcium is initiated when our body senses a low plasma levels. The parathyroid hormone is secreted to stimulate bone resorption and prepare your body for absorption. In addition to calcium we absorb from bone breakdown, approximately 20 to 30 percent of it comes from dietary intake. Absorption then takes place in the small intestine of the gastrointestinal tract and requires the assistance of 1,25 dihydroxycholecalciferol, better known as the active form of vitamin D. Vitamin D forms a complex with the epithelial cells of the small intestine and binds with calcium to be absorbed into your body. Without the assistance of this vitamin, your body won't absorb calcium.
While vitamin D is a requirement for calcium absorption, other components can improve this process. Acidic environments create a favorable setting for absorption. If taking a calcium carbonate supplement, you should take it with a meal to promote stomach acid secretion. You can take calcium citrate supplements regardless of having eaten. The presence of lactose also enhances absorption. Puberty, growth spurts, lactation and pregnancy also allow your body to absorb calcium more readily as they are needed for growth and bone building.
Sources of Calcium
High calcium foods include milk, cheese, yogurt, soybeans, canned salmon and sardines, fortified breads and beverages. The recommended daily intake for a healthy male or female between the ages of 19 to 50 is 1,000 mg per day. Dietary needs increase to 1,200 mg for women over the age 50, while men's needs increase to 1,200 mg after age 71.
When your body absorbs phosphorus it goes through a very similar process; PTH is released in response to low phosphorus levels and requires the vitamin D binding complex for absorption in the small intestine. Phosphorus, which is often bound with other minerals in our food in the form of phosphate, must be in its free form to be absorbed properly in the intestine. Although we absorb about 70 to 80 percent of phosphorus from food, other components from our diet can interfere with the absorption process. Phytates often found in grains, magnesium, iron and other minerals compete for the same absorption site as phosphorus and can hinder the process.
Sources of Phosphorus
High phosphorus foods include meat, fish, poultry, milk products, whole grains, and dried peas and beans. Recommended dietary intake for healthy adults ages 19 and older is 700 mg per day.
- Mosby's Pocket Guide Series: Fluid, Electrolyte, and Acid-Base Balance. 5th Edition”; Ursula Heitz, et al.; 2001
- "Physiology, 3rd Edition"; Linda Costanzo; 2002
- Office of Dietary Supplements: Calcium
- Institute of Medicine: Dietary Reference Intakes: RDA and AI for Vitamins and Elements