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ARS Home » Plains Area » Grand Forks, North Dakota » Grand Forks Human Nutrition Research Center » Dietary Prevention of Obesity-related Disease Research » Research » Publications at this Location » Publication #65260
Title: QUANTITATIVE ASSESSMENT OF THE EFFECTS OF VARIABILITY IN DIETARY ZINC DOSE-RATE IDIORRHYTHMS UPON ZINC DEPOSITION IN BONE OF WEANLING RATS BY USING A SLOPE-RATIO ASSAY

Author
item MOMCILOVIC, BERISLAV - UNIV OF CROATIA
item Reeves, Phillip

Submitted to: Journal of Nutritional Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: This report provides a clue for overcoming the methodological difficulties in dealing with the effects of variability in nutrient intake. Although we know that our nutrient intake over time is subject to a lot of variability, almost all of current nutritional knowledge stems from research models in which animals are fed nutrients on a continuous basis. To deal with the real-life periodicity, we used a new experimental paradigm called idiorrhythm. This means that the experimental animals are fed so that the size of the dose of the nutrient in question is coupled to the frequency at which the dose is given over time. This is done in order to deliver the same total amount of nutrient, but, at different rates. The nutrient we studied in this report was the trace element zinc. Our study showed that idiorrhythmic feeding made a significant difference in the metabolic uptake of zinc when compared to continuous feeding. It showed that none of the various dose-time equivalents tested was superior to that of daily intake of zinc when the amount of zinc in the diet was adequate for growth and maximal zinc deposition in bone. Therefore, meaningful interpretation of supplemental feeding programs may not be possible unless the variability in nutrient intake with respect to dose- rate is considered.

Technical Abstract: We quantitatively assessed the effect of the idiorrhythmic dose-rate variability in dietary zinc intake on zinc deposition in the femur and incisor of weanling rats by the slope-ratio analysis of analogous idiorrhythms. In idiorrhythmic feeding the dose (x) is viewed over the period of the entire experimental epoch as a dose-time equivalent modulo (Mx) that can be divided into a series of equal products of different doses with different frequency (idiorrhythm, I). Each I is administered in a regularly recurring pattern to deliver the same dose as that from a standard daily regimen of zinc, albeit at a different rate; Ix = [dnth(Mx)]/dnth, where dnth is the sequential number of zinc dosing day separated by 1 to 7 days of feeding the diet without zinc when dnth>1. Four different Mx were tested, M3, M6, M12, and M24 providing 3, 6, 12, and 24 mg Zn kg**-1, diet d**-1 respectively over a 24 day epoch; each Mx had seven analogous Ix of different dose magnitudes but the same dosing frequency (dnth). The slopes for the M3, M6, and M12 analogous idiorrhythms showed that zinc deposition in the femur and incisor, as a measure of metabolic availability, varied considerably with spacing of the dose with time. Metabolic availability of zinc progressively decreased by 50% from I = Mx/1 to I = 4Mx/4. Then it rose to the initial I = Mx/1 values of animals fed zinc daily for I = 5Mx/5 and I = 6Mx/6, before it finally dropped again to the bottom level for I = 8Mx/8. The results showed that the impact of zinc dose-rate in dietary zinc intake is an important determinant of an adequate supply of metabolic zinc.