Clinical Conditions


A condition that results when serum calcium decreases, tetany is characterized by very spastic contractions of the muscle and muscle pain. This can also be caused by an increase in serum phosphorous, which decreases serum calcium.


A loss of bone mineral causing a thinning of the bone; although osteoporosis usually occurs in the elderly and postmenopausal women, people of any age can be affected if their intake of calcium is too low.

Conditions of the Parathyroid Gland

The parathyroid hormone, produced by the parathyroid gland, is involved in the control of plasma calcium levels. When the plasma calcium level drops, the parathyroid gland reacts to restore normal levels. This is achieved three ways: 1) a stimulation in the mucosa of the intestine to absorb more calcium; 2) rapid mobilization of calcium form the bone; 3) renal excretion of phosphate. This last method means that parathyroid hormone also controls phosphorous levels.

Recommended Intake

The Recommended Dietary Allowance (RDA) of Calcium, set by the Food and Nutrition Board of the National Academy of Sciences, varies between 800 and 1200 mg for adults. Pregnant and lactating women require 1200 mg/day. Infants require 300-500 mg/day and 800 mg/day is recommended for children.

Food Sources

Dairy products are the main sources of calcium in the diet. Calcium is also obtained in smaller amounts from eggs, green leafy vegetables, broccoli, legumes, nuts, and whole grains.

Figure %: Calcium Content of Selected Foods


The recommended dosage for supplemental calcium is the RDA. Some forms of calcium supplements may contain high levels of lead and should be avoided. These include calcium in bone meal, dolomite, and unrefined calcium carbonate from limestone or oyster shells.