William A. House

Tea consumption does not affect iron absorption in rats unless tea and iron are consumed together

Abstract Phenolic compounds may influence iron absorption by complexing iron in the intestinal lumen or by altering intestinal permeability. We assessed the effects of tea on iron absorption and intestinal permeability in rats in two experiments. In experiment 1, rats maintained on a commercial rat diet were fasted overnight with free access to water and then gavaged with 1.0 ml of 59 Fe labeled FeCl 3 (0.1 mM or 1.0 mM) and lactulose (0.5 M) in water or black tea. Iron absorption was estimated from 59 Fe retention. Intestinal permeability was evaluated by lactulose excretion in the urine. Iron absorption was lower when given with tea at both iron concentrations but tea did not affect lactulose excretion. In experiment 2, rats maintained on a commercial rat diet were divided into two groups. One group was given black tea as the only source of water for 3 d. The other group was given water. Both groups were fasted overnight with free access to water and then gavaged with 1.0 ml of water or black tea containing 59 Fe labeled FeCl 3 (0.1 mM) and lactulose (0.5 M). Iron absorption was not affected by 3 d of tea consumption but was decreased when delivered in tea. Lactulose excretion was not affected by 3 d tea consumption or by delivery in tea. These data suggest that tea affects iron absorption by forming iron complexes in the lumen.

Testing Iron and Zinc Bioavailability in Genetically Enriched Beans (Phaseolus Vulgaris L.) and Rice (Oryza Sativa L.) in a Rat Model

A rat model was used to determine the bioavailability of iron and zinc in bean seeds and rice grain from enriched genotypes of these globally important staple foods. Seed and grain from the genotypes tested (intrinsically radiolabelled with either 59Fe or 65Zn) were cooked, homogenized in water, and lyophilized to dryness. The dried, radiolabelled powder was fed to young male rats in single meals. Bioavailability was calculated from the amount of radiolabelled iron and zinc retained in the rats over a 10-day period as determined each day by whole-body gamma spectrometry assay. The data collected demonstrate that increasing the amount of iron or zinc in enriched rice grain and bean seed significantly increases the amount of iron or zinc bioavailable to rats. Although a rat model is not ideal for determining iron and zinc bioavailability to humans, because rats are much more efficient at absorbing iron and zinc from plant foods than humans, rats can be used to give relative estimates of bioavailable iron and zinc in plant foods. These estimates can be used to rank promising genotypes of staple foods for use in later feeding trials with humans, greatly reducing the numbers of genotypes that would have to be tested in humans without use of the rat model. Ultimately, because of the complexities of determining the bioavailability to humans of iron and zinc in plant foods, human feeding trials performed under free-living conditions should be conducted with the most promising genotypes before these genotypes are released for distribution to breeding programmes worldwide

Changes in meal frequency alter iron absorption efficiency in rats

Abstract There is no standard procedure in regard to the type or feeding pattern of prestudy diet in studies on determinations of iron bioavailability. The objective of this study was to determine the influence of meal frequency on the absorptive capacity of mucosal cells. Male Wistar rats were assigned to three groups of ten rats each and fed 12 g of diet daily for three days. The food allotment was provided in either one meal (M1) daily (70 mg Fe / kg diet), four meals (M4) daily (70 mg Fe / kg diet), or a single meal for one day (210 mg Fe / kg diet) followed by single low-iron meals (9.4 mg Fe / kg diet) for two days (MX). The rats were then deprived of food for 18 hours, administered 59 Fe by gavage, and killed ten hours later. Absorption was estimated as the 59 Fe retained in carcass without the gastrointestinal tract. Mucosal cells from the duodenum were isolated by mechanical vibration and mucosal ferritin determined by an immunoassay method. The effect of meal frequency on absorption efficiency of 59 Fe was significant and independent of liver iron stores. Absorption of 59 Fe dose was higher in rats fed four meals daily (42.2 ± 5.2%) than those fed one meal daily (27.1 ± 2.7%), but rats fed a single meal for one day then iron-deficient meals for two days absorbed significantly more 59 Fe (64.8 ± 4.8%) than did rats in the other groups. These data indicate that the frequency of iron consumed in a short-term period alter the efficiency of iron absorption in rats. Iron status of mucosal cells alone, as determined by mucosal ferritin, cannot explain the variations in iron absorption.

Influence of meal frequency on iron absorption as assessed by hemoglobin repletion in rats

Abstract The effects of short periods of fasting, characteristic of a human eating pattern consisting of one, two, or four meals daily, on iron absorption were investigated in anemic rats by hemoglobin repletion assay. Sixty weanling rats were fed a lowiron diet (8 mg Fe / kg diet) for 13 days. The anemic rats were then fed ferrous sulfate- or ferric phosphate-fortified diets (35 mg Fe / kg diet) for 11 days under three feeding regimens: one, two, or four meals daily. Hemoglobin regeneration efficiency (hemoglobin iron gain / Fe intake) was the indicator of iron absorption. Greater hemoglobin regeneration efficiency was found in rats fed a FeSO 4 diet with four (82.5 ± 4.8%) or two (78.8 ± 4.1%) meals daily than those pair-fed one (63.4 ± 3.4%) meal daily. No significant difference among the groups fed one, two, or four meals of the FePO 4 diet was observed. Both iron source and meal frequency significantly affected iron absorption but the interaction effect was not significant. We conclude under the conditions of this study that periods of fasting as long as 24 hours in the context of a diet do not enhance iron absorption and that feeding patterns are a factor to consider in iron bioavailability determinations.

Enhancing Beans (Phaseolus Vulgaris L.) as Sources of Bioavailable Iron through Genetic Selection

Iron (Fe) deficiency is the most prevalent nutrient deficiency in humans. Globally, this disorder adversely affecting the health, well being, and livelihood of over 2 billion people, especially those living in developing countries. Significantly increasing the bioavailable amount of Fe in staple plant foods could contribute greatly to reducing the incidence of Fe deficiency, particularly among those at greatest risk (i.e., poor women, infants and children). Fe-enriched genotypes of beans could be selected for in plant breeding programs to improve human nutrition and thereby enhance nutritional health in a sustainable manner.

Zinc Accumulation by Hepatocytes Isolated from Male Rats of Different Zinc Nutritional Status

Some characteristics of Zn uptake and effects of various multivalent cations, metabolic inhibitors, hormones, and sulfhydryl-blocking agents on Zn accumulation by rat hepatocytes in monolayer culturel or in suspensions2 have been reported. Hepatocytes used in these studies were isolated from rats fed Zn-adequate (ZA) diets. The study reported here was conducted to evaluate the effect of rat Zn status on Zn uptake by isolated hepatocytes.