Calcium is the most abundant mineral in the human body. Over 99% of total body calcium is found in the bones and teeth. The remaining 1% is found throughout the body in blood, muscle and the intracellular fluid. Calcium is used for muscle contraction, blood vessel constriction and relaxation, the secretion of hormones and enzymes, and nervous system signaling. A constant level of calcium is needed to be maintained in the body in order for these processes to function properly. The body gets the calcium it needs through food and by being extracted from bones. Calcium-rich foods include dairy products and dark, leafy greens. For dietary calcium, vitamin D is important and recommended for optimal calcium absorption through the intestine. Calcium extraction from bones occurs when dietary calcium is insufficient and can lead to weakened bone structure 1.
Many individuals in the U.S. consume inadequate amounts of calcium. The U.S. Food and Drug Administration (FDA) has established a Reference Daily Intake (RDI) of 1,000 mg calcium for adults and children 4 or more years of age (21CFR101.9). RDIs are a set of dietary references for essential vitamins and minerals that are considered amounts sufficient to meet the daily requirements of healthy individuals. RDIs serve as the basis for calculating the percent daily value (%DV) amounts found on dietary supplement and food labels.
Calcium carbonate is an organic compound used as a source of the essential mineral calcium in dietary supplements. It is considered generally recognized as safe (GRAS) for use in foods by the U.S. Food and Drug Administration (FDA) 2.
Calcium citrate/malate/glycinate is a mixture of calcium salts and chelates that are commonly used as sources of the essential mineral calcium in dietary supplements.