Bioavailability Studies of Stabilized Iron (II) Sulfate by Means of the Prophylactic-preventive Method

The bioavailability of stabilized ferrous sulfate was studied by means of the prophylactic-preventive test in rats. For comparative purposes, ferrous sulfate was used as reference standard. The test was performed in male weaned rats during 3 weeks, which were randomized into three groups of ten animals each. A control group received a basal diet of low iron content while the other groups received the same diet added with iron at a dose of 15 mg/kg as FeSO₄ 7H₂O and stabilized ferrous sulfate, respectively. Individual hemoglobin concentrations and weights were determined at the beginning and at the end of the study, and food intake was daily registered. Iron bioavailability (BioFe) of each source was calculated as the ratio between the amount of iron incorporated into hemoglobin during the treatment and the total iron intake per animal. A relative biological value was obtained as the ratio between the BioFe of stabilized ferrous sulfate and the reference standard given a value of 96%. Stabilized ferrous sulfate showed a high bioavailability, and when it is used to fortify dairy products as cheese and fluid milk in a dose of 15–20 mg of iron per kilogram, it behaved inertly in relation to the sensorial properties of the fortified food. These results suggest that this iron compound is a promising source to be use in food fortification.     

Iron bioavailability from fortified petit suisse cheese determined by the prophylactic-preventive method

In this research, we measured the iron bioavailability of ferrous gluconate stabilized with glycine (SFG) when it is used to fortify petit suisse cheese using the prophylactic-preventive method in rats. Three groups of male, weaned rats received a basal diet (control diet; 5.2 ppm Fe), a reference standard diet (SO₄Fe; 9.2 ppm Fe), and a basal diet using iron-fortified petit suisse cheese as the iron source (cheese diet; 8.8 ppm Fe) for 22d. The iron bioavailability was calculated as the ratio between the mass of iron incorporated into hemoglobin and the total iron intake per animal during the treatment. These values (BioFe) were 68% and 72% for SFG and ferrous sulfate, respectively. The value of the Relative Biological Value (RBV) was 95% for SFG in petit suisse cheese. These results show that according to this method, the iron bioavailability from industrial fortified petit suisse cheese can be considered as a high bioavailability rate.     

Bioavailability study of dried microencapsulated ferrous sulfate — SFE 171 — by means of the prophylactic-preventive method

Microencapsulated ferrous sulfate with soy lecithin (SFE-171) has been used as an iron source for the fortification of milk and dairy products. With the purpose to extend the use of this agent to other kind of foods or even to pharmaceutical preparations for oral administration, the SFE-171 was turned into a fluid powder (SFE-171-P) by means of vacuum drying. The iron bioavailability (BioFe) of SFE-171-P was evaluated in this work by means of the prophylactic-preventive method in rats, using ferrous sulfate as reference standard. Both iron sources were separately added to a basal diet of low iron content in a concentration of 10 mg iron/kg diet. Two groups of 10 weaned rats 25 days old received the fortified diets during 28 days, while a third group of the same size received the basal diet without iron additions. The weights and haemoglobin concentrations (HbC) of every animal were determined before and after the treatment, thus allowing the calculation of the mass of iron incorporated into haemoglobin (HbFe) during this period. The BioFe of the iron sources were obtained as the percentage ratio between the HbFe and the mass of iron consumed by each animal. The results were also given as Relative Biological Value (RBV), which relates the BioFe of the studied source with that of the reference standard. The liver iron concentration (LIC) of each animal was determined at the end of the experiment in order to evaluate the influence of the studied iron sources on the liver iron stores. SFE-171-P presented BioFe, RBV and LIC values of (47 ± 7) %, 109% and (46.6 ± 3.4) mg/kg respectively, while the corresponding values for the reference standard were of (43 ± 7)%, 100% and (45.0 ± 4.7) mg/kg. These results show that the drying process used to produce the SFE-171-P does not affect its bioavailability, which is also adequate for the potential use of this product in food fortification or with pharmaceutical purposes.     

Stabilized–Solubilized Ferric Pyrophosphate as a New Iron Source for Food Fortification. Bioavailability Studies by Means of the Prophylactic–Preventive Method in Rats

The purpose of the present work was to evaluate the iron bioavailability of a new ferric pyrophosphate salt stabilized and solubilized with glycine. The prophylactic–preventive test in rats, using ferrous sulfate as the reference standard, was applied as the evaluating methodology both using water and yogurt as vehicles. Fifty female Sprague–Dawley rats weaned were randomized into five different groups (group 1: FeSO₄; group 2: pyr; group 3: FeSO₄ + yogurt; group 4: pyr + yogurt and group 5: control). The iron bioavailability (BioFe) of each compound was calculated using the formula proposed by Dutra-de-Oliveira et al. where BioFe % = (HbFef − HbFei) × 100/ToFeIn. Finally, the iron bioavailability results of each iron source were also given as relative biological value (RBV) using ferrous sulfate as the reference standard. The results showed that both BioFe % and RBV % of the new iron source tested is similar to that of the reference standard independently of the vehicle employed for the fortification procedure (FeSO₄ 49.46 ± 12.0% and 100%; Pyr 52.66 ± 15.02% and 106%; FeSO₄ + yogurth 54.39 ± 13.92% and 110%; Pyr + yogurt 61.97 ± 13.54% and 125%; Control 25.30 ± 6.60, p < 0.05). Therefore, the stabilized and soluble ferric pyrophosphate may be considered as an optimal iron source for food fortification.     

Iron bioavailability from fortified fluid milk and petit suisse cheese determined by the prophylactic-preventive method

In this research, we measure the iron bioavailability of micronized ferric orthophosphate when it is used to fortify low-fat fluid milk enriched with calcium and petit suisse cheese using the prophylactic-preventive method in rats. Four groups of male weaned rats received a basal diet (control diet; 6.5 ppm Fe), a reference standard diet (SO₄Fe; 18.2 ppm Fe), a basal diet using iron-fortified fluid milk as the iron source (milk diet; Fe ppm 17.9), and a basal diet using iron-fortified petit suisse cheese as the iron source (cheese diet; 18.0 ppm Fe) for 22 d. The iron bioavailability of the different sources was calculated as the ratio between the mass of iron incorporated into hemoglobin during the experiment and the total iron intake per animal. The relative biological values with regard to the reference standard (RBV%) were 61% and 69% for the milk and cheese diet, respectively. These results show that according to this method, the iron bioavailability in both fortified foods can be considered as medium bioavailability rates.     

Stabilized ferrous gluconate as iron source for food fortification

The iron bioavailability and acute oral toxicity in rats of a ferrous gluconate compound stabilized with glycine (SFG), designed for food fortification, was studied in this work by means of the prophylactic method and the Wilcoxon method, respectively. For the former studies, SFG was homogenously added to a basal diet of low iron content, reaching a final iron concentration of 20.1±2.4 mg Fe/kg diet. A reference standard diet using ferrous sulfate as an iron-fortifying source (19.0±2.1 mg Fe/kg diet) and a control diet without iron additions (9.3±1.4 mg Fe/kg diet) were prepared in the laboratory in a similar way. These diets were administered to three different groups of weaning rats during 23 d as the only type of solid nourishment. The iron bioavailability of SFG was calculated as the relationship between the mass of iron incorporated into hemoglobin during the treatment and the total iron intake per animal. This parameter resulted in 36.6±6.2% SFG, whereas a value of 35.4±8.0% was obtained for ferrous sulfate. The acute toxicological studies were performed in two groups of 70 female and 70 male Sprague-Dawley rats that were administered increasing doses of iron from SFG. The LD₅₀ values of 1775 and 1831 mg SFG/kg body wt were obtained for female and male rats, respectively, evidencing that SFG can be considered as a safe compound from a toxicological point of view.     

Stabilized ferrous gluconate as iron source for food fortification: bioavailability and toxicity studies in rats

The iron bioavailability and acute oral toxicity in rats of a ferrous gluconate compound stabilized with glycine (SFG), designed for food fortification, was studied in this work by means of the prophylactic method and the Wilcoxon method, respectively. For the former studies, SFG was homogeneously added to a basal diet of low iron content, reaching a final iron concentration of 20.1 +/- 2.4 mg Fe/kg diet. A reference standard diet using ferrous sulfate as an iron-fortifying source (19.0 +/- 2.1 mg Fe/kg diet) and a control diet without iron additions (9.3 +/- 1.4 mg Fe/kg diet) were prepared in the laboratory in a similar way. These diets were administered to three different groups of weaning rats during 23 d as the only type of solid nourishment. The iron bioavailability of SFG was calculated as the relationship between the mass of iron incorporated into hemoglobin during the treatment and the total iron intake per animal. This parameter resulted in 36.6 +/- 6.2% for SFG, whereas a value of 35.4 +/- 8.0% was obtained for ferrous sulfate. The acute toxicological studies were performed in two groups of 70 female and 70 male Sprague-Dawley rats that were administered increasing doses of iron from SFG. The LD50 values of 1775 and 1831 mg SFG/kg body wt were obtained for female and male rats, respectively, evidencing that SFG can be considered as a safe compound from a toxicological point of view.     

Bioavailability of Iron in the Regional Basic Diet (RBD) with Dietary Supplement in Brazil

The consumption of the regional basic diet (RBD) determines a state of malnutrition found in the low-income population of Northeastern Brazil. A dietary supplement known as multimixture has been used as an alternative source of iron in food for the prevention and/or treatment of anemia and for the recovery from malnutrition. The purpose of the present work was to evaluate the bioavailability of iron in the RBD supplemented with multimixture in iron-depleted and non-depleted Wistar rats. To produce iron depletion in the animals, pretest depletion diets without iron and the pretest control diet based on the AIN-93 diet were used for 8 weeks. This phase was followed by the test diets: control, AIN-93 extrinsically labeled with ⁵⁹FeCl₃; RBD, containing carioca beans intrinsically labeled with ⁵⁹Fe; and RBDMM, RBD plus multimixture, supplied in a single meal. Hemoglobin concentration, weight gain, and dietary intake were determined in the pretest phase. Iron bioavailability was determined by the determination of total-body radiation in the animals for 7 days, using a solid scintillation detector. The hemoglobin concentration, weight gain, and dietary intake were greater in the non-depleted animals than in the iron-depleted ones. The iron bioavailability of the diets did not differ significantly. It was concluded that the multimixture did not affect the bioavailability of Fe contained in the beans of the RBD.     

Availability and antiperoxidative effects of beta-carotene from Dunaliella bardawil in alcohol-drinking rats

The present study demonstrated the high bioavailability and antiperoxidative capacity of the natural beta-carotene isomer mixture of Dunaliella bardawil compared with synthetic beta-carotene under alcohol-induced oxidative stress. Weanling rats were adapted to ethanol by increasing ethanol levels in their drinking water to 30% at 5% intervals per week; other rats received water with no added ethanol. One water-drinking group and one alcohol-drinking group with no dietary carotene were used as controls. Two water-drinking groups were supplemented with 1 g/kg diet beta-carotene either from Dunaliella or a synthetic source, and due to reduced food intake, two ethanol-fed groups received 2 g beta-carotene per kilogram of diet from each source. Following 3 months of ethanol consumption, both carotene sources were found to prevent ethanol-induced lipid peroxidation as expressed by the hepatic conjugated oxidized dienes level. However, in the algal-fed rats, hepatic carotene and vitamin A levels were higher. In addition to a lower performance of the group fed ethanol and synthetic beta-carotene, there were three deaths in this group.     

Effect of Mineral Fortification on Plasma Biochemical Profile in Rats

This study aimed at investigating the changes in biochemical profile of male rats following 8 weeks administration of different concentration of elemental iron, sodium iron ethylenediaminetetraacetate (NaFeEDTA), zinc sulfate (ZnSO₄), and zinc oxide (ZnO) in whole wheat flour. Eight groups comprising five rats each were fed fortified whole wheat flour in the form of baked pallets, while one group served as control. Concentration of total cholesterol, high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), triglycerides, total proteins, albumin, globulin, plasma glucose, and blood urea nitrogen were assayed. Supplementing mineral-fortified diet to male rats did not indicate any significant (p ≤ 0.05) effect on total cholesterol concentration. Diets containing NaFeEDTA alone increased HDL-C and decreased LDL-C; however, the differences remained non significant. Likewise, plasma triglycerides content of male rats remained unchanged on feeding fortified diets. Diets containing iron as NaFeEDTA and elemental iron exerted little effect on total protein concentration in the plasma of rats. Plasma glucose and blood urea nitrogen levels did not exhibit any significant change as a result of ingesting mineral supplemented diets. The study concludes that the forms of fortificants and the fortification levels used in the current study are undamaging for lipid profile, renal function, and glucose levels in rats, suggesting that these may be safely used in wheat flour to combat iron and zinc deficiency in vulnerable groups.     

Beta-carotene from cassava (Manihot esculenta Crantz) leaves improves vitamin A status in rats

The bioavailability of beta-carotene from cassava (Manihot esculenta Crantz) leaves was assayed in vitamin A deficient Wistar rats (Rattus norvegicus). Rats were separated into three groups and fed with a modified AIN-93G--vitamin A deficient--diet. Deficient rat received this diet without any additional vitamin A source. Controls received the diet with 7200 microg of synthetic beta-carotene (control), while experimentals (test) received 19.5 g of cassava leaves powder per kg of diet. The cassava leaves with beta-carotene promotes similar growth and tissue weight in rats to the synthetic beta-carotene. The relative bioavailability, estimated as the Retinol Accumulation Factor (RAF), was 16.5 and 27.5 for control and test groups, respectively, indicating that control and test rats should have an intake of 16.5 microg or 27.5 microg of beta-carotene from synthetic form or cassava leaves powder for each 1 microg of hepatic retinol stored, respectively. The cassava leaves beta-carotene bioavailability was lower than the synthetic beta-carotene probably because the beta-carotene from the leaf matrix may be bounded to protein complex or inside organelles, which impair carotenoid absorption. Our findings showed that beside the hepatic retinol recovery, cassava leaf beta-carotene could maintain rat growth and avoid vitamin A deficient symptoms.     

Influence of diet on iron, copper, and zinc status in children under 24 months of age

The objective of the study was to determine whether iron and micronutrient status is improved with an increased amount of meat in the diet. To this end, a longitudinal prospective study with infants recruited at 4 mo and followed until 24 mo of age was undertaken. One hundred ninety-eight infants formed the original study cohort; 48 withdrew before the end of the study. Subjects were classified as nonmeat eaters or as mixed (red and white)-meat eaters subgrouped into tertiles depending on the meat content reported in diet diaries. Seven-day weighed food records were recorded at 4, 8, 12, 16, 20, and 24 mo. Blood samples taken at 4, 12, and 24 mo were analyzed for parameters of iron and micronutrient status. Iron intake increased during the first year, thereafter remaining constant. The percentages of subjects with hemoglobin values below 110 g/L were 34.1, 23.1, and 13.4 at 4, 12, and 24 mo, respectively. For parameters of iron status, the number of results below the reference range was determined for each diet group and a significant negative relationship between serum iron and meat intake at 12 mo of age was seen (p<0.023). There was a trend for hemoglobin concentrations to be inversely related to the meat intake, at the same age (p<0.068). No effects on zinc or copper status were seen. We conclude that a weak association between dietary meat and iron/Hb suggests a positive role for red meat. There was no disadvantage to the nonmeat-eating infants with respect to zinc or copper.     

The Effects of Dietary Iron and Capsaicin on Hemoglobin,Blood Glucose,Insulin Tolerance,Cholesterol, and Triglycerides,in Healthy and Diabetic Wistar Rats

ObjectiveOur aim was to assess the effects of dietary iron, and the compound capsaicin, on hemoglobin as well as metabolic indicators including blood glucose, cholesterol, triglycerides, insulin, and glucose tolerance.ResultsHealthy rats fed a low-iron diet exhibited significantly reduced total cholesterol and triglyceride levels, compared with rats fed a control diet. Significantly reduced blood lipid was also provoked by low dietary iron in diabetic rats, compared with those fed a control diet. Insulin, and glucose tolerance was only improved in healthy rats fed the low-iron diet. Significant increases in total cholesterol were found in diabetic rats fed a high-iron diet, compared with healthy rats fed the same diet, although no statistical differences were found for triglycerides. Hemoglobin levels, which were not statistically different in diabetic versus healthy rats fed the high-iron diet, fell when capsaicin was added. Capsaicin also provoked a fall in the level of cholesterol and triglycerides in diabetic animals, versus diabetics fed with the high iron diet alone. In conclusion, low levels of dietary iron reduced levels of serum triglycerides, hemoglobin, and cholesterol, and significantly improved insulin, and glucose tolerance in healthy rats. In contrast, a high-iron diet increased cholesterol significantly, with no significant changes to triglyceride concentrations. The addition of capsaicin to the high-iron diet (for diabetic rats) further reduced levels of hemoglobin, cholesterol, and triglycerides. These results suggest that capsaicin, may be suitable for the treatment of elevated hemoglobin, in patients.     

High intakes of tin lower iron status in rats

The effects of relatively low (1, 10, and 50 mg/kg) and high (100 and 200 mg/kg) dietary concentrations of tin (added as stannous chloride) on iron status of rats were determined. After feeding the diets for 28 d, feed intake and body weights were not significantly affected. Iron concentrations in plasma, spleen, and tibia as well as percentage transferrin saturation were decreased in rats fed the diets supplemented with 100 or 200 mg tin/kg. In rats fed the diet containing 200 mg tin/kg, group mean hemoglobin, hematocrit, and red blood cell count were slightly lowered but total iron binding capacity was not affected. Iron status was not influenced by dietary tin concentrations lower than 100 mg/kg. If these results can be extrapolated to humans, then it may be concluded that tin concentrations in the human diet, which range from 2 to 76 mg/kg dry diet, do not influence iron status in humans.     

Interaction between nickel and iron in the rat

The interaction between nickel and iron was confirmed in rat metabolism. In a fully-crossed, two-way, three by four, factorially designed experiment, female weanling rats were fed a basal diet supplemented with iron at 0, 25, 50, and 100 μg/g and with nickel at 0, 5, and 50 μg/g. The basal diet contained about 10 ng of nickel and 2.3 μg of iron/g. After nine weeks, dietary iron affected growth, hematocrit, hemoglobin, plasma cholesterol, and in liver affected total lipids, phospholipids, and the contents of copper, iron, manganese, and zinc. By manipulating the iron content of the diet, effects of dietary nickel were shown in rats that were not from dams fed a nickel-deprived diet. Nickel affected growth, hematocrit, hemoglobin, plasma alkaline phosphatase activity, plasma total lipids, and in liver affected total lipids, and the contents of copper, manganese, and nickel. The interaction between nickel and iron affected hematocrit, hemoglobin, plasma alkaline phosphatase activity, and plasma phospholipids, and in liver affected size, content of copper, and perhaps of manganese and nickel. In severely iron-deficient rats, the high level of dietary nickel partially alleviated the drastic depression of hematocrit and hemoglobin, and the elevation of copper in liver. Simultaneously, high dietary nickel did not increase the iron level in liver and was detrimental to growth and appearance of severely iron-deficient rats. In nickel-deprived rats fed the borderline iron-deficient diet (25 μg/g) hematocrit and hemoglobin also were depressed. However, 5 μg Ni/g of diet were just as effective as 50 μg Ni/g of diet in preventing those signs of nickel deprivation. The findings in the present study suggested that nickel and iron interact with each other at more than one locus.     

Metal chelates of 2-hydroxy-4-methylthiobutanoic acid in animal feeding. Part 2: Further characterizations, in vitro and in vivo investigations

The alpha-hydroxyacid 2-hydroxy-4-methylthiobutanoic acid (the so-called methionine hydroxy-analogue, MHA), largely used in animal nutrition as a source of methionine, forms stable metal chelates with divalent metals of formula [{CH(3)SCH(2) CH(2)CH(OH)COO}(2)M].nH(2)O. Protonation and iron(III) and copper(II) complex formation constants have been determined by potentiometry at 25 degrees C. Distribution diagrams show that no free Fe(3+) cations are present in solution at pH>2.5. ESI-MS (Electron-Spray Ionization Mass Spectrometry) investigations carried out both on iron and zinc complexes in solution have evidenced various species with different MHA/metal ratios. In vivo trials were carried out with rats. After receiving a zinc-deficient diet for 3 weeks, animals were fed the same diet added with zinc sulfate or zinc/MHA chelate; the zinc content of faeces was higher (+45%; P<0.05) in sulfate fed rats, whereas zinc retention was higher (+61%; P<0.05) in the Zn/MHA diet. Experiments in vitro with human intestinal Caco-2 cells indicated that the MHA/Fe chelate was taken up by the cells without any apparent toxic effect. The iron uptake was higher than that of iron nitrilotriacetate (Fe(3+)NTA), an effective chelate for delivering iron to milk diets. In conclusion, these data indicate that the use of MHA chelates could be a valuable tool to increase bioavailability of trace minerals and reduce the environmental impact of animal manure.     

The effect of various dietary zinc concentrations on the biological interactions of zinc,copper, and iron in rats

Three groups (14 rats each) were fed one of the following diets for 8 wks: a control purified basal diet containing 12 ppm zinc, 5 ppm copper, and 35 ppm iron; the basal diet with less than 2 ppm zinc; or the basal diet supplemented with 1000 ppm zinc. Rats fed the zinc-deficient diet had decreased weight gain, moderate polydipsia, and intermittent mild diarrhea. The zinc-supplemented rats had a cyclical pattern of food intake and weight loss from weeks 5 to 8. Tissue concentrations suggest that zinc and copper were not mutually antagonistic with chronic dietary imbalances. If tissue element concentrations reflected intestinal uptake, then competition and/or inhibition of intestinal uptake occurred between zinc and iron. The fluctuations in tissue element concentrations that occurred with increased duration of the study were at variance with previous studies of shorter time periods. The dietary proportions of zinc, copper, and iron appear to influence zinc, copper, and iron metabolism at the intestinal and cellular transport levels over a given period of time.     

Comparison of Osborne-Mendel and S5B/PL Strains of Rat: Central Effects of Galanin,NPY, β-Casomorphin and CRH on Intake of High-Fat and Low-Fat Diets

The effects of central administration of galanin, neuropeptide Y (NPY), β-casomorphin_(1–7) and corticotropin releasing hormone (CRH) on intake of either a high-fat or low-fat diet have been compared in two strains of rat, the dietary fat-sensitive Osborne-Mendel (OM) rat and the dietary fat-resistant S5B/Pl rat. Injection of galanin (0.1, 0.3 nmoles) into the 3rd cerebral ventricle stimulated the intake of both a high-fat and a low-fat diet in OM rats in a dose dependent manner but the response was significantly smaller in rats fed the low-fat diet. In S5B/Pl rats, galanin had a small stimulatory effect on food intake but only at a high dose (2 nmole). β-casomor-phin_(1–7) (5 nmoles), an opioid-like peptide, increased the intake of the high-fat but not the low-fat diet in OM rats, whereas S5B/Pl rats fed either a high-fat or a low-fat diet did not respond to β-caso-morphin/j.yy Both strains showed a similar stimulatory response to NPY (0.1, 0.5 nmoles) on the intake of the high-fat or the low-fat diet, but the magnitude of the response was attenuated in S5B/Pl rats. In contrast, the anorectic effects of CRH (0.26 nmoles) on food deprived animals was similar in both strains for both diets. We speculate that the regulatory system controlling the intake of fat activated by galanin and β-casomorphin_(1–7) may be defective in S5B/Pl rats.     

Patterns of food intake and self-selection of macronutrients in rats during short-term deprivation of dietary zinc

Although it has been known for more than 50 years that zinc (Zn) deficiency regularly and consistently causes anorexia in many animal species, the basic mechanism(s) that cause this phenomenon still remain(s) an enigma. The following studies describe feeding behavior in the early stages of zinc deficiency in the rat model. In one experiment, we used computerized feeding monitors that measured the intake of individual rats at 10-min intervals over 24-hr periods. Male rats were acclimated to the cages and fed a Zn-adequate egg-white-based diet, or a similar diet with <1.0 mg Zn/kg. Food intake was monitored for seven, consecutive 24-hr periods. The 24-hr food intake pattern of the Zn-deprived rats did not differ from the controls; they simply ate less food, mainly during the night hours, with no differences between groups during the day. Although Zn-deprived rats ate less food than controls, the percentage of total diet consumed during night and day did not differ between groups. In another experiment, we simultaneously offered male rats three isocaloric diets with different macronutrient compositions and with or without adequate Zn, and measured the amount of each diet selected during seven, 24-hr periods. The three diets contained either 57% protein from egg white, 30% fat from soybean oil, or 80% carbohydrate from a combination of starch, hydrolyzed starch, and sucrose. For the first four days on experiment, rats selected similar amounts of each diet. Then the Zn-deprived rats began to select only 50% as much of the protein diet as the controls. Similar results were obtained when the data were expressed on the basis of each macronutrient as a percentage of the total diet selected. Zn-deprived rats selected a diet that contained 8% protein, 73% carbohydrate, and 6% fat while the Zn-adequate rats selected 12% protein, 69% carbohydrate, and 6% fat. Fat intake was not affected by Zn-deprivation. The results confirm our previous findings, and are discussed in terms of Zn-deprivation blunting the pathways of signal transduction that involve the peptide hormones known to affect food intake regulation.     

Effects of type of fat in the diet on iron bioavailability assessed in suckling and weanling rats

Differences in iron bioavailability from human milk and milk formulas may in part be due to differences in lipid composition. We investigated the short and long term effects of diets based on different fats [corn, coconut, olive, or soy oil, human milk fat (HMF) and a formula fat blend (FF)] on iron absorption in rats. Suckling rat pups dosed with 59Fe-labeled diets containing different fat sources were killed after 6 h, and blood and individual tissues were counted. Iron availability was estimated by % 59Fe in blood. Pups dosed with a more saturated fat (coconut oil) had a higher % 59Fe in blood than those fed other fat sources. Weanling rats were used to determine iron bioavailability from fat sources using both the hemoglobin repletion method and whole body counting. Hemoglobin regeneration was significantly higher for rats fed the HMF diet (8.4 +/- 0.5 g/dl) than from the FF diet (6.5+/-0.6 g/dl) or the corn oil diet (less saturated) (6.4 +/- 0.3 g/dl). Rats fed diets based on coconut oil (more saturated) had significantly higher % 59Fe retention (61.6 +/- 1.4) than rats fed diets based on FF (49.8 +/- 3.4). There was a significant positive association between oleic acid in the diet and oleic acid in the intestinal mucosa (r = 0.95, p < 0.05) and between linoleic acid in the diet and linoleic acid in the intestinal mucosa (r = 0.97, p < 0.05) suggesting that the dietary treatment altered the fatty acid composition of the brush border membrane. Our results suggest that saturated fats may increase iron absorption and that part of this may be achieved by changes in the fatty acid composition of the intestinal mucosa. Hemoglobin regeneration and % 59Fe retention data suggest that differences in iron absorption from infant diets may in part be due to differences in fat composition. Therefore, lipid composition of infant formulas should also be taken into consideration as a factor influencing iron bioavailability.