BIOAVAILABILITY OF ZINC TO RATS FROM SOY FLOUR AND CHICKEN BASED DIETS
Abstract
The bioavailability of intrinsic and extrinsic ('65)Zn to rats from chicken and soy protein based diets was investigated. Rats absorbed 72.5% of the ('65)Zn from an intrinsically labeled, defatted soy flour test meal, indicating that the flour was a suitable vehicle for delivering detectable quantities of the nuclide during bioavailability studies. Sequential post-dose measurements of whole body ('65)Zn retention by marginally depleted rats from either an oral or an injected dose indicated that approximately 1% of the retained dose was metabolized and excreted daily. As determined by whole body retention, availability of ('65)Zn from chicken protein diets (93%) was significantly higher than that from mixed chicken/soy protein diets (85%) or from soy flour diets (76%). If the individual protein in the diet was labeled prior to incorporation into the diet, there were no significant differences in ('65)Zn retention due to intrinsic or extrinsic labeling techniques, however, if the whole diet was labeled extrinsically, differences in ('65)Zn retention were significant. In another study, rats were adapted to a soy protein based diet for two or seven days in order to investigate the effect of this variable on absorption of ('65)Zn from a soy protein based test meal. Animals adapted to soy for seven days had a significantly lower ('65)Zn retention (73%) from the soy test meal than those adapted to chicken for seven days (82%). Retention by rats adapted to soy for two days (76%) was not significantly different than that of the other two groups. Preadaptation of rats to a soy protein based diet had a negative effect on ('65)Zn retention from a soy protein based test meal. Tibia zinc, weight gain, tibia ('65)Zn retention and small intestine ('65)Zn retention were not sensitive indicators of zinc bioavailability to rats subjected to subtle dietary changes. However, these parameters gave assessments similar to whole body ('65)Zn retention for bioavailability of zinc when dietary differences were more pronounced. Whole body ('65)Zn retention techniques provided the most sensitive indicator of zinc bioavailability from soy, chicken and mixed chicken/soy protein based diets.
Degree
Ph.D.
Subject Area
Nutrition
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