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)
Objective—To determine whether oral administration of metoclopramide or a commercially available powdered whole grapefruit (PWG) nutraceutical in combination with cyclosporine enhances systemic availability of cyclosporine in dogs.
Sample—8 healthy mixed-breed dogs in part 1 and 6 of these 8 dogs in part 2.
Procedures—Cyclosporine pharmacokinetics were determined over the course of 24 hours after oral administration of cyclosporine (5 mg/kg) alone, cyclosporine with metoclopramide (0.3 to 0.5 mg/kg), cyclosporine with 2 g of PWG, or cyclosporine combined with both metoclopramide and 2 g of PWG by use of a Latin square crossover study with a 14-day washout period between treatments. Sixty days later, 6 of the 8 dogs were given 10 g of PWG followed by cyclosporine, and pharmacokinetic parameters were compared with those previously obtained after administration of cyclosporine alone.
Results—Although metoclopramide or coadministration of metoclopramide and 2 g of PWG had no effect on the pharmacokinetic parameters of cyclosporine, compared with results for cyclosporine alone, the higher (10-g) dose of PWG resulted in 29% faster mean time to maximal plasma cyclosporine concentration, 54% larger area under the curve, and 38% lower apparent oral clearance.
Conclusions and Clinical Relevance—Adjustment of the cyclosporine dose may not be needed when metoclopramide is coadministered orally to prevent common adverse effects of cyclosporine. Powdered whole grapefruit has the potential to reduce the required orally administered dose of cyclosporine but only when PWG is used in an amount (at least 10 g) that is currently not cost-effective.
Objective—To evaluate the effect of a soy-based diet on general health and adrenocortical and thyroid gland function in dogs.
Animals—20 healthy privately owned adult dogs.
Procedures—In a randomized controlled clinical trial, dogs were fed a soy-based diet with high (HID; n = 10) or low (LID; 10) isoflavones content. General health of dogs, clinicopathologic variables, and serum concentrations of adrenal gland and thyroid gland hormones were assessed before treatment was initiated and up to 1 year later. Differences between groups with respect to changes in the values of variables after treatment were assessed by means of a Student t test (2 time points) and repeated-measures ANOVA (3 time points).
Results—No differences were detected between the 2 groups with respect to body condition and results of hematologic, serum biochemical, and urine analyses. Most serum concentrations of hormones did not change significantly after treatment, nor were they affected by diet. However, the mean change in serum concentration of total thyroxine was higher in the HID group (15.7 pmol/L) than that in the LID group (–1.9 pmol/L). The mean change in estradiol concentration after ACTH stimulation at 1 year after diets began was also higher in the HID group (19.0 pg/mL) than that in the LID group (–5.6 pg/mL).
Conclusions and Clinical Relevance—Phytoestrogens may influence endocrine function in dogs. Feeding soy to dogs on a long-term basis may influence results of studies in which endocrine function is evaluated, although larger studies are needed to confirm this supposition.