Two questions relevant to the safety of phosphate additives have been raised in the literature: 1) Is the dietary ratio of calcium to phosphorus clinically significant in humans? Specifically, can a high-phosphorus, low-calcium diet cause hypocalcemia and/or secondary hyperparathyroidism in humans? 2) Does the growing use of phosphate-containing food additives increase the risk of low bone density and/or fracture in humans? In 1999, the Institute of Medicine published a monograph which addressed these two questions. This article critically reviews the findings and conclusions of the Institute of Medicine in the light of recent research.