The isoflavone content of commercially-available feline diets in New Zealand

Abstract

Isoflavones are present in commercially-prepared feline diets sold in New Zealand at concentrations that have elicited physiological responses in the reproductive, endocrine, and immune systems of other mammalian species. Since isoflavones appear to be a common constituent of feline diets, further investigation of the biological activities of these dietary compounds in cats is warranted.

ANIMAL MODELS OF DISEASE: Feline hyperthyroidism: an animal model for toxic nodular goiter

“…Other dietary factors that have been implicated in the pathogenesis of the feline toxic nodular goiter include dietary flavonoids, which are found in high concentrations in many cat foods (Court & Freeman 2002, Bell et al 2006. Flavonoids can act to inhibit thyroid peroxidase and have known goitrogenic properties (Divi & Doerge 1996, Köhrle 2000, Doerge & Sheehan 2002.…”

Isoflavone metabolism in domestic cats (Felis catus): Comparison of plasma metabolites detected after ingestion of two different dietary forms of genistein and daidzein1

“…Food was withheld 18 h before oral administration of 1 soy extract tablet (approximately 0.218 g, Phytolife1 One a Day; Healthy Living, Palmerston North, New Zealand). Analysis by HPLC (Bell et al, 2006b) showed that on average, 1 tablet contained 10.17 mg genistein and 13.12 mg daidzein (as-fed) as aglycone equivalents. One-half of the daily allowance (293 kJ·kg BW -1 ·d -1 ; NRC 1986) of an isofl avone-free diet (Table 1) of each cat was offered 5 min before administering the tablet.…”

“…The diet was a nutritionally complete and balanced, moist commercial diet, which met the maintenance nutrient requirements of adult cats (AAFCO, 2009) and contained the following ingredients: selected meat byproducts and meat derived from beef, lamb, and chicken; fi sh byproduct; vegetable protein; gelling agents; calcium; coloring; and necessary vitamins. This diet was previously analyzed (Bell et al, 2006b), and no detectable isofl avones (genistein, daidzein, formononetin, and biochanin A) were found.…”

“…Four adult castrated male, domestic short-haired cats with a mean age of 4.80 ± 1.83 yr and BW of 4.55 ± 0.55 kg were gradually adapted over a 10-d period before the start of the trial to a moist, commercially prepared meat and gravy formula diet containing (as aglycone equivalents; Bell et al, 2006b) 151 μg genistein and 1,984 μg daidzein/g DM (Table 1). During the 10 d, cats were offered an amount of food in 2 distinct meals (0900 and 1700 h) to meet their maintenance energy requirements (293 kJ·kg BW -1 ·d -1 ; NRC, 1986).…”

“…Studies have shown that some domestic cat diets available in North America and New Zealand contain substantial concentrations of genistein and daidzein, with up to 249 μg genistein and 151 μg daidzein/g DM (Court and Freeman, 2002;Bell et al, 2006b). The isofl avone content of felid diets has been assumed to result primarily from the inclusion of soy products in the formulation of these diets (Setchell et al, 1987;Court and Freeman, 2002).…”