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Identification and concentration of soy phytoestrogens in commercial dog foods

Rosario CerundoloDepartment of Clinical Studies-Philadelphia, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104.

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Michael H. CourtDepartment of Pharmacology and Experimental Therapeutics, School of Medicine, Tufts University, Boston, MA 02215.

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Qin HaoDepartment of Pharmacology and Experimental Therapeutics, School of Medicine, Tufts University, Boston, MA 02215.

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Kathryn E. MichelDepartment of Clinical Studies-Philadelphia, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104.

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Abstract

Objective—To identify and determine the concentrations of phytoestrogens in commercial dog foods.

Sample Population—24 commercial dog foods, including 12 moist or dry extruded commercial dog foods that contained soybeans or soybean fractions and 12 foods without any soybean–related ingredients listed on the label.

Procedure—Foods were analyzed for phytoestrogen content, including 4 isoflavones (genistein, glycitein, daidzein, and biochanin A), 1 coumestan (coumestrol), and 2 lignans (secoisolariciresinol and matairesinol) by use of acid-methanol hydrolysis and high-pressure liquid chromatography with UV-absorbance detection. Phytoestrogens were identified and quantified by reference to authentic standards.

Results—Isoflavones, coumestans, and lignans were undetectable in diets that did not list soybean–related ingredients on the label. Only 1 of the 12 diets that included soybean or soybean fractions had undetectable concentrations of phytoestrogens and that product contained soy fiber. The major phytoestrogens were the isoflavones daidzein (24 to 615 µg/g of dry matter) and genistein (4 to 238 µg/g of dry matter).

Conclusions and Clinical Relevance—Soybean and soybean fractions are commonly used ingredients in commercial dog foods. Dietary intake of phytoestrogens may have both beneficial and deleterious health effects. Our results indicated that certain commercial dog foods contain phytoestrogens in amounts that could have biological effects when ingested longterm. ( Am J Vet Res 2004;65:592–596)

Abstract

Objective—To identify and determine the concentrations of phytoestrogens in commercial dog foods.

Sample Population—24 commercial dog foods, including 12 moist or dry extruded commercial dog foods that contained soybeans or soybean fractions and 12 foods without any soybean–related ingredients listed on the label.

Procedure—Foods were analyzed for phytoestrogen content, including 4 isoflavones (genistein, glycitein, daidzein, and biochanin A), 1 coumestan (coumestrol), and 2 lignans (secoisolariciresinol and matairesinol) by use of acid-methanol hydrolysis and high-pressure liquid chromatography with UV-absorbance detection. Phytoestrogens were identified and quantified by reference to authentic standards.

Results—Isoflavones, coumestans, and lignans were undetectable in diets that did not list soybean–related ingredients on the label. Only 1 of the 12 diets that included soybean or soybean fractions had undetectable concentrations of phytoestrogens and that product contained soy fiber. The major phytoestrogens were the isoflavones daidzein (24 to 615 µg/g of dry matter) and genistein (4 to 238 µg/g of dry matter).

Conclusions and Clinical Relevance—Soybean and soybean fractions are commonly used ingredients in commercial dog foods. Dietary intake of phytoestrogens may have both beneficial and deleterious health effects. Our results indicated that certain commercial dog foods contain phytoestrogens in amounts that could have biological effects when ingested longterm. ( Am J Vet Res 2004;65:592–596)