Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2005
Publication Date: 5/25/2005
Citation: Al-Wahsh, I.A., Horner, H.T., Palmer, R.G., Reddy, M.B., Massey, L.K. 2005. Oxalate and phytate of soy foods. Journal of Agricultural and Food Chemistry. 53:670-674. Interpretive Summary: Human consumption of soy products is increasing. Soy foods have high nutritional value and also have been reported to have health benefits. However, high concentrations of oxalate in soy foods increase the risk of kidney stones. These are calcium oxalate kidney stones. Soy foods also contain phytate. Studies suggest that phytate exhibits effective anticarcinogenic action against many types of cancer. Phytate is also a potential inhibitor of calcium oxalate kidney stone formation. Our objective was to test 30 commercial soy foods for oxalate and phytate content. There was a wide range of concentrations of oxalate and phytate in the soy foods tested. Soy food containing low concentrations of oxalate and high concentrations of phytate may be advantageous for kidney stone patients or persons with high risk of kidney stones.
Technical Abstract: Consumption of foods made from soybeans is increasing because of their desirable nutritional value. However, some soy foods contain large concentrations of oxalate and/or phytate. Oxalate is a component of calcium oxalate kidney stones, whereas phytate is an inhibitor of calcium kidney stone formation. Thirty tested commercial soy foods exhibited ranges of 0.02 to 2.06 mg oxalate /g and 0.80 to 18.79 mg phytate/g. Commercial soy foods contained ranges of 2 to 58 mg of total oxalate per serving and 76 to 528 mg phytate per serving. Eighteen of 19 selected tofu brands and two soymilk brands contained less than 10 mg oxalate per serving. Soy flour, textured vegetable soy protein, vegetable soybeans, soy nuts, tempeh, and soynut butter exhibited large oxalate amounts, defined as greater than 10 mg per serving. The correlation between oxalate and phytate in the soy foods was significant (r = 0.71, P < 0.001) indicating that oxalate-rich soy foods also contain large concentrations of phytate. There also was a significant correlation, based on molar basis, between the divalent ion binding potential of oxalate plus phytate and calcium plus magnesium (r = 0.90, P < 0.001) in soy foods. Soy foods containing small concentrations of oxalate and large concentrations of phytate may be advantageous for kidney stone patients or persons with high risk of kidney stones.