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12.3: Phosphorus

We have already talked about how blood phosphate levels are regulated in the body by PTH, calcitonin, and 1,25(OH)2D. Animal products are rich sources of phosphate. Plant products contain phosphorus, but some are in the form of phytic acid (phytate). In grains, over 80% of the phosphorus is phytate. This structure is shown below1.

Figure 12.31 Structure of phytic acid2

The bioavailability of phosphorus from phytate is poor (~50%) because we lack the enzyme phytase3. Nevertheless, ~50-70% of phosphorus is estimated to be absorbed from our diet1. Another source of phosphorus is phosphoric acid that is used to acidify colas. Colas are caramel-colored, carbonated soft drinks that contain caffeine, such as Coca-Cola, Pepsi, etc. Epidemiological studies have found that soft drink consumption is associated with decreased bone mineral densities, particularly in females4,5. It has been hypothesized that phosphoric acid plays some role in this effect, but there is limited evidence to support this belief.

Most phosphorus is excreted in the urine.

Phosphorus deficiency is rare but can hinder bone and teeth development. Other symptoms include muscle weakness, rickets, and bone pain6. Toxicity is also rare, but it causes low blood calcium concentrations and tetany1.

References & Links

1. Gropper SS, Smith JL, Groff JL. (2008) Advanced nutrition and human metabolism. Belmont, CA: Wadsworth Publishing.

2. http://en.wikipedia.org/wiki/File:Phytic_acid.png

3. Phosphorus. Linus Pauling Institute Micronutrient Information Center. http://lpi.oregonstate.edu/mic/miner...us#reference10

4. Tucker K, Morita K, Qiao N, Hannan M, Cupples LA, et al. (2006) Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The framingham osteoporosis study. Am J Clin Nutr 84(4): 936-942.

5. Libuda L, Alexy U, Remer T, Stehle P, Schoenau E, et al. (2008) Association between long-term consumption of soft drinks and variables of bone modeling and remodeling in a sample of healthy german children and adolescents. Am J Clin Nutr 88(6): 1670-1677.

6. Byrd-Bredbenner C, Moe G, Beshgetoor D, Berning J. (2009) Wardlaw's perspectives in nutrition. New York, NY: McGraw-Hill.