Iron, copper and zinc metabolism of rats fed various levels and types of tea

The effects of tea and components in tea on mineral metabolism were investigated in a series of studies. In studies A and B weanling rats were fed diets containing various levels (0, 0.35, 1.17 or 3.50%) of a commercially prepared instant tea and diets containing 0 or 1.17% catechin. In study C anemic rats were fed diets containing 0 or 2.31% desiccated green or black tea infusions for 23 d. In study D rats were fed a diet containing 2.31% desiccated black tea infusions for 16 d, were fed the tea-containing diet in a single meal labeled with 59Fe or were given black tea infusions as their sole fluids. Rats fed diets containing 2.31% green or black tea or given fluid tea had elevated hematocrits but experienced minimal changes in tissue iron levels or in iron absorption; this is counter to conclusions from studies in which iron absorption was monitored indirectly. Ingestion of instant or black tea consistently elevated liver copper levels; this may be part of the mechanism by which hematological variables were affected. Although the green tea contained significant amounts of aluminum, rats fed the tea did not accumulate aluminum in their bones.     

Iron retention by rats from casein-legume test meals: effect of tannin level and previous diet

The effect of tannin content on iron (Fe) bioavailability from several legumes was evaluated. Absorption of Fe from a casein (C), isolated soy protein (ISP), chickpea (CP) or red kidney bean (RKB) test meal was tested in marginally Fe-deficient rats [9.9 +/- 0.2 g Hb/100 mL (mean +/- SD)] using the extrinsic tag technique. Also, the effects of a casein habitual diet or of one of three casein-legume habitual diets fed before and after the test meal were investigated. Weanling male rats were fed the habitual diets containing 23 +/- 4 mg Fe/kg of diet (range 17-28) for 13 d. On d 14, after an overnight fast, rats were fed the test meal (1.5 g + 0.1 microCi 59Fe), and whole-body radioactivity was determined. The same habitual diet was refed for seven additional days, and whole-body radioactivity was determined again. Rats retained more iron from C (86%) than from ISP, CP or RKB test meals (73%, 75% and 67%, respectively) when the respective casein-legume habitual diets were fed before and after the test meals. With the casein habitual diet, there was no difference in retained iron from C, ISP, CP or RKB test meals (86%, 87%, 83% and 82%, respectively). Retention of iron from an RKB test meal was increased from 69.6 to 73% when about 90% of the extractable tannins were removed, but the difference was not statistically significant. Thus, feeding a casein-legume diet but not a casein diet prior to a test meal apparently predisposes the rat to lower iron absorption. However, in these studies, tannins per se did not significantly depress iron bioavailability.     

Iron, zinc and copper interactions: chronic versus acute responses of rats

Several methodologies were evaluated to study iron, zinc and copper interactions. In three studies, rats were fed diets containing adequate levels of iron (33-35 micrograms Fe/g diet) and zinc (15-25 micrograms Zn/g diet) and diets with excessive levels of zinc (2441-2470 micrograms Zn/g diet) or iron (1408-3042 micrograms Fe/g diet). Consumption of excess iron for several weeks or in one test meal did not alter tissue levels of zinc or apparent absorption of 65Zn. In contrast rats fed excess zinc throughout the three studies had depressed hematocrits and serum copper levels, apparently absorbed 59Fe less efficiently and retained less 59Fe in livers and tibias than control animals. Nutritional status with regard to iron or zinc, not just the intakes of iron and zinc, also influenced the interactions between zinc and iron. Rats fed excess iron for several weeks retained less 65Zn from a test meal in their tibias than rats fed excessive iron in only the test meal. Although chronic ingestion of excess zinc depressed apparent absorption of 59Fe from a test meal, the ingestion of one test meal with excess zinc did not. Investigators studying nutrient interactions should not rely solely on studies in which unadjusted humans or animals are given a single dose of test substances because acute responses do not reflect all the changes induced by chronic feeding.     

Calcium does not inhibit iron absorption or alter iron status in infant piglets adapted to a high calcium diet

The purpose of this study was to investigate whether a dietary calcium:iron ratio similar to that often consumed by premature human infants inhibits iron absorption in infant piglets adapted to a high calcium diet. Male Yorkshire piglets were randomized at 3 to 4 d of age to a high calcium diet (4.67 g/L = HC) or a normal calcium diet (2.0 g/L = NC) and fed for 2 to 2.5 wk. An iron dextran injection was administered in amounts to achieve a marginal state of iron repletion to simulate iron status of premature infants. In vivo iron absorption from the diet was determined using the radiotracers 55Fe and 59Fe and whole body counting. Calcium:iron interactions at absorption sites in piglets fed HC and NC were investigated by measurements of time-dependent 59Fe uptake in response to different calcium:iron ratios in vitro in brush border membrane vesicles (BBMV). In vivo iron absorption from the diet did not differ between NC and HC diet groups [57 +/- 8% versus 55 +/- 17% (mean +/- SD), respectively]. Iron status and iron contencentrations in spleen, liver, intestine, kidney and heart did not differ between diet groups. Iron uptake in BBMV was significantly reduced by calcium in both HC and NC (P < 0.001); but there were no significant differences in iron uptake in response to different calcium:iron ratios between HC and NC. With feeding a HC diet for 2 wk there may be an adaptive response to counteract the inhibitory effects of calcium on iron absorption, thus resulting in similar in vivo iron absorption and iron status irrespective of the 1.3-fold difference in dietary calcium:iron ratio between piglet groups. However, future studies are needed to determine the specific sites of calcium:iron interactions and adaptation mechanisms. Since the calcium:iron ratios used in this study reflect the usual calcium:iron ratios in diets for premature infants, it is unlikely that interactive effects of calcium with iron will compromise iron status in this infant population when diets are supplemented with calcium.     

Effect of dietary phytate on bioavailability of iron

Experiments were carried out on iron-chelating capacity of phytic acid in fortified and unfortified diets of whole wheat, white flour and wheat bran using albino rats in a 10-day balance study. The results revealed that gross digestibility was highest in control diet (93.25%), least in the wheat brain diet with added ferrous sulfate (86.70%) and intermediate in other diets. Among the unfortified and fortified diets, the highest amount of phytate was present in the diet having wheat bran (2.69–4.99 mg/g). Phytate concentration of the rat faeces followed the pattern of dietary phytate content of test diets. The data indicated high values for iron (200.00–236.64 mg/g) in fortified diets while in the unfortified diets, the value was the same (16.67 mg/g) except the casein diet, which contained 69.99 mg/g of iron. Iron concentration of the fat faeces ranged 16.25–23.50 mg/g; the higher value being in the excreta of animals given fortified diets. The casein diet had iron 46.75 mg/g. The overall results showed that the phytate absorption was relatively higher in groups fed fortified diets. Iron absorption almost followed the pattern of phytate absorption. Correlation co-efficient analysis showed insignificant relationship between iron and phytate absorption indicating little effect of dietary phytate on the biovailability of iron.     

Aqueous ethanol extraction of dietary soy protein isolate improves 59Fe absorption by the rat from a casein-based test meal

A commercial soy protein isolate (SPI) was further processed in an attempt to understand how a diet based on SPI can cause decreased iron retention by the rat from a separately administered casein-based test meal. Groups of eight rats were fed either a casein-based diet or a diet based on SPI. The acid-precipitated SPI was incorporated into diets as such, after neutralization, after 60% (v/v) ethanol extraction and neutralization, or after 60% ethanol exposure and neutralization. All dietary SPI was heat-treated by exposure to steam at 108 degrees C for 30 min. Rats were fed their respective diets, each containing 25 mg Fe/kg, for 13 d, and then all rats were fed a 59Fe-radiolabeled 2.5-g casein test meal containing 64 micrograms of iron. Ingested radioactivity was determined following the meal, and retained radioactivity over the subsequent 10-d period. Absorption was not distinguishable for groups fed the casein-based (78.3 +/- 3.6%) and the ethanol-extracted, SPI-based diet (80.2 +/- 5.4%). Absorption was lower (P less than 0.01) for groups fed each of the other SPI-based diets: SPI as such (68.3 +/- 8.9%), neutralized SPI (69.8 +/- 5.0%) and ethanol-exposed SPI (67.6 +/- 4.8%). An ethanol-extractable component of SPI may be responsible for decreased iron absorption by animals fed SPI prior to a radiolabeled test meal.     

Effects of iron status and soy protein on iron absorption by rats

The effects of iron nutrition and soy protein on iron absorption by rats was studied. Rats were fed semipurified diets containing either 0, 5, or 20 micrograms of added iron per gram of diet to obtain groups with different iron status. After 3 weeks the rats had mean hemoglobin concentrations of 7.0, 10.7 and 13.2 g/dl, respectively. As the rats became more anemic, percent iron absorption from casein and soy protein diets increased. The relative availability of iron from soy compared with casein-based diets was 70 to 90%. Iron status did not affect the relative iron availability among treatments. The rat trials did not indicate any significant differences between iron absorption from meals containing soy flour (SF), soy protein concentrate (SC) or soy protein isolate (SI) regardless of the iron status of the rat. These studies do not support the hypothesis that the subject's iron status will affect the relative availability of iron from foods. Recent human iron absorption studies suggest that relative iron availability from meals containing soy proteins is lower than expected based on rat studies. Furthermore, differences in iron availability between soy flour and soy isolate observed in human studies are not apparent in these rat studies.     

The effect of dietary iron levels on changes in iron status and zinc-dependent enzyme activities in rats fed two levels of dietary zinc

In order to determine the interrelationship between dietary iron and zinc levels, the effects of dietary iron levels (2, 10, 20, and 40 microg/g) on changes in iron and zinc status and zinc enzyme activities (aminolevulinic acid dehydratase ALA-D EC 4.2.1.24 and alkaline phosphatase ALK-P EC 3.1.3.1) in male Wistar rats were investigated using adequate and marginally deficient zinc diets (25 and 5 microg/g). When rats were fed 5 microg Zn/g diets, body weight gain and food intake remained unchanged at a Fe diet intake of 20 microg/g or greater. Similar tendencies were obtained for hemoglobin, hematocrit, plasma iron, and transferrin saturation. In contrast, liver, spleen, and femur iron concentrations increased gradually with increased iron intake. Feeding diets containing 25 microg Zn/g did not alter these parameters. The percentages of apparent iron absorption in both dietary zinc groups tended to increase with decreasing dietary iron and attained maximum levels at an Fe intake of 10 microg/g. However, In the case of rats fed Fe at concentrations of 2 microg/g Iron absorption decreased. Regardless of the dietary zinc level, rats fed diets with an Fe concentration of 2 microg/g had decreased zinc absorption and plasma ALK-P activity. However, ALA-D activity was not influenced by dietary iron.     

Effect of dietary pectin on iron absorption and turnover in the rat

The influence of dietary pectin on iron absorption and retention was studied in rats. Basal diet with low and normal iron levels were fed with and without addition of 2% citrus pectin. After 40 days rats were fasted for 24 hours and were given 59Fe in dilute HCl with or without 2% pectin by gavage. Whole-body counting techniques were employed to monitor 59Fe absorption and turnover. Rats maintained on low iron diet absorbed and retained a much higher proportion of 59Fe than rats maintained on normal level of iron. Dietary pectin at the level fed in this study had no influence on iron uptake and/or turnover in rats.     

Intestinal Fe distribution and absorption in rats with different iron status and given wheat bran or ferrous sulfate as dietary iron sources

Distribution of intestinal iron and absorption were studied in rats with high hemoglobin (Hb) levels of >7.5 g/dL or low-Hb, ≤7.5 g/dL, which were fasted overnight and fed a single 2-gram meal of diet containing either wheat bran or FeSO₄. One hour later they were gavaged with 2 μCi of ⁵⁹FeCl₃ in 0.5M HCl. Low-Hb rats absorbed similar amounts of iron from the bran and FeSO₄ diets. Both groups of rats absorbed similar amounts of iron from FeSO₄, but the high-Hb rats absorbed less iron from bran than did the low-Hb ones. Gastric ⁵⁹Fe clearance was slower in the high-Hb than in the low-Hb rats. Gastric ⁵⁹Fe clearance was faster from FeSO₄ diet, regardless of iron status. About 10–20% of the ⁵⁹Fe was in the ileum and about 1.3–3.3% of the ⁵⁹Fe was in the colon after gavaging; the distal intestines of the rats fed the bran diet contained the least ⁵⁹Fe. During the first 24 h, whole blood ⁵⁹Fe activity was similar for both diets; but after 24 h, ⁵⁹Fe activity was lower in the rats fed the bran diet. During the first 48 h, plasma clearance of i.v. injected ⁵⁵Fe transferrin was greater in the low-Hb rats than in the high-Hb ones but plasma clearance was not affected by iron source. However, beginning at 36 h, clearance was reduced in rats fed the bran diet. Thus, the high-Hb rats (but not the low-Hb rats) differed in the mechanisms of their absorption of wheat bran and FeSO₄ iron.     

Partially hydrolyzed guar gum increases intestinal absorption of iron in growing rats with iron deficiency anemia

OBJECTIVE: The objective of this study was to evaluate the effect of partially hydrolyzed guar gum (PHGG) dietary fiber towards intestinal iron absorption, for dietary intake and on the growth of rats with iron deficiency anemia in comparison to those fed on a diet with cellulose and without dietary fiber. MATERIALS AND METHODS: Male Wistar rats (n=24) weaned at 21 days were fed with AIN93-G diet without iron for 2 weeks in order to induce iron deficiency anemia. At 36 days old, the anemic rats were divided into three groups: (1) PHGG group-100g of PHGG per kg of diet; (2) Cellulose group-100g of cellulose per kg of diet; (3) Control group-diet without dietary fiber. All the diets had 25mg of elemental iron/kg of diet added to lead to recovery from iron deficiency anemia. RESULTS: The final hemoglobin values in g/dl, for the PHGG group, the cellulose group and the control group were, respectively: 11.3+/-1.2, 8.6+/-0.7 and 8.1+/-0.9 (P<0.001). The levels of hepatic iron, in mug/g of dry tissue, in the same order, were: 322.2+/-66.6, 217.2+/-59.1 and 203.7+/-42.4 (P<0.001). Apparent iron intestinal absorption was, respectively: 67.5+/-8.9%, 35.4+/-15.3% and 31.3+/-24.9% (P<0.001). The three groups consumed similar quantities of diet. The changes in weight and in body length were similar in the three groups studied. CONCLUSION: PHGG led to greater intestinal absorption of iron, regeneration of hemoglobin and hepatic levels of iron than diet with cellulose and diet control.     

Absorption and tissue distribution of zinc, iron and copper by rats fed diets containing lactalbumin, soy and supplemental sulfur-containing amino acids

Zinc, copper and iron utilization was examined in rats fed diets containing 30% lactalbumin (L); 30% soy assay protein (S) or 30% soy assay protein supplemented with 0.26% cysteine (SC), 0.45% methionine (SM), 0.26% cysteine and 0.45% methionine (SCM) or 0.71% cysteine (SXC). Diets L, SC and SCM contained equal amounts of cysteine; diets L, SM and SCM contained equal amounts of methionine; diets L, SCM, SXC contained equal amounts of sulfur-containing amino acids. Rats fed diet L had significantly higher levels of zinc in tibias, kidneys and plasma; higher levels of copper in kidneys; and higher levels of iron in tibias than rats fed diet S. Rats fed diet L also absorbed (apparent and true) significantly more zinc; excreted significantly more zinc of endogenous origin in the feces; and absorbed (apparent) significantly less copper than rats fed diet S. Rats fed the soy diets supplemented with sulfur-containing amino acids, especially diet SXC, tended to have elevated levels of zinc in their tibias and kidneys and greater apparent and true absorptions of zinc than rats fed diet S. Rats fed diet SXC still had significantly lower zinc levels in tissue than rats fed diet L. Apparent absorption of zinc was similar among rats fed diets L, SCM and SXC.     

The effect of tea on iron and aluminium metabolism in the rat

Weanling male Wistar rats were fed for 28 d on a semi-synthetic diet containing normal (38 micrograms/g) or low (9 micrograms/g) levels of iron. They were given water or tea infusion (20 g leaves/l water) to drink. Two further groups were given a normal- or low-Fe diet containing added tea leaves (20 g/kg diet). At the end of the study period, all rats given the low-Fe diet were severely anaemic, as assessed by haemoglobin, packed cell volume and liver Fe. Those given tea or the diet with added tea leaves showed a greater degree of Fe depletion. The blood and liver aluminium levels were not increased as a result of consuming tea or tea leaves, despite the higher Al intakes. Fe deficiency per se had no effect on Al absorption or retention from tea. It was concluded that the Al in tea was very poorly absorbed but that tea, either in the form of an infusion or as tea leaves, had an adverse effect on Fe status.     

High dietary iron concentrations enhance the formation of cholesterol oxidation products in the liver of adult rats fed salmon oil with minimal effects on antioxidant status

The aim of this study was to investigate the effect of high dietary iron concentrations on the antioxidant status of rats fed two different types of fat. Four groups of male adult Sprague-Dawley rats were fed diets with adequate (50 mg iron supplemented per kg diet) or high (500 mg iron supplemented per kg diet) iron concentrations with either lard or salmon oil as dietary fat at 100 g/kg for 12 wk. The antioxidant status of the rats was profoundly influenced by the type of fat. Rats fed salmon oil diets had higher concentrations of thiobarbituric acid-reactive substances (TBARS) (P < 0.001), various cholesterol oxidation products (COP) (P < 0.001), total and oxidized glutathione (P < 0.05) and a lower concentration of alpha-tocopherol (P < 0.05) in liver and plasma than rats fed lard diets. The iron concentration of the diet did not influence the concentrations of TBARS, the activities of superoxide dismutase and glutathione peroxidase or the concentration of alpha-tocopherol in plasma or liver. The activity of catalase (P < 0.01) and the concentrations of total, oxidized and reduced glutathione (P < 0.05) in liver were slightly but significantly higher in rats fed high iron diets than in rats fed adequate iron diets, irrespective of the dietary fat. Rats fed the high iron diets with salmon oil, moreover, had higher concentrations of various COP in the liver (P < 0.001) than rats fed adequate iron diets with salmon oil. These results suggest that feeding a high iron diet does not generally affect the antioxidant status of rats but enhances the formation of COP, particularly if the diet is rich in polyunsaturated fatty acids.     

Sugar as a vehicle for iron fortification: further studies.

The data presented confirm the advantages of sugar as a vehicle for iron fortification over other vehicles used in the past. The absorption comparison between ferric and ferrous salts added to sugar demonstrated that Fe(III)-EDTA Complex and ferrous sulfate exhibited the highest absorption, while ferric ammonium citrate was poorly absorbed. It was also found that Fe(III)-EDTA reacts slowly with the tannin contained in tea; the color of the tea changes slightly in the first 2 hr after the addition of the fortified sugar. Iron absorption of sugar fortified with ferrous sulfate was tested in seven beverages. The mean absorption ratio from fortified sugar given with beverages to reference dose of iron ascorbate ranged between 0.42 and 0.70, that is, more than 4 times the absorption from fortified sugar when it is administered with a meal containing one or more vegetals. An absorption of between 0.25 and 0.80 mg of iron/soft drink sugar fortified with 3 mg of iron as ferrous sulfate can be expected in subjects with various degrees of iron deficiency. Thus, two soft drinks per day between meals would be enough to meet the iron requirement in more than 95% of menstruating women, even though the daily iron absorption from the diet is about 0.8 to 1.0 mg.     

Iron overload in hypercholesterolemic rats affects iron homeostasis and serum lipids but not blood pressure

Epidemiologic and experimental data suggest that excess iron may contribute to the development of cardiovascular diseases (CVD). Because increased LDL cholesterol, decreased HDL cholesterol and alteration of systolic blood pressure (SBP) have all been implicated as risk factors for atherosclerosis and related CVD, the present study was designed to determine whether excess iron alters serum lipids and SBP in control and hypercholesterolemic rats. Female Fischer rats were divided into four groups. The control group (C) was fed the control diet, the CI group was fed the control diet and given iron dextran injections, the hypercholesterolemic group (H) was fed a 1 g/100 g cholesterol diet, and the HI group was fed the cholesterol diet and given iron dextran injections. The rats were fed the diets for 8 wk and iron dextran injections were given during wk 6 at doses of 10 mg/d for 5 d. Excess iron reduced (P < 0.01) plasma total cholesterol in rats fed the cholesterol diet (5.31 +/- 0.83 and 3.17 +/- 0.31 mmol/L for H and HI, respectively). Excess iron also resulted in a redistribution of cholesterol among the various lipoprotein fractions, with an increase (P < 0.01) in HDL cholesterol (0.56 +/- 0.12 and 0.85 +/- 0.16 mmol/L for H and HI, respectively) and a decrease (P < 0.01) in LDL cholesterol (4.49 +/- 0.77 and 2.09 +/- 0.26 mmol/L for H and HI, respectively). This redistribution also occurred in the rats fed the control diet. The treatments did not affect SBP or heart rate. The high cholesterol diet affected iron homeostasis; group H had lower transferrin saturation than group C (P < 0.01); group HI had a lower serum iron concentration than group CI but did not differ from group H (P < 0.05). Therefore, we conclude that if iron has any effect on CVD, it is not through its influence on serum lipids and blood pressure.     

Pork meat increases iron absorption from a 5-day fully controlled diet when compared to a vegetarian diet with similar vitamin C and phytic acid content

Meat increases absorption of non-haem iron in single-meal studies. The aim of the present study was to investigate, over a 5 d period, the potential increasing effect of consumption of pork meat in a whole diet on the fractional absorption of non-haem iron and the total absorption of iron, when compared to a vegetarian diet. A randomised cross-over design with 3 x 5 d whole-diet periods with diets containing Danish-produced meat, Polish-produced meat or a vegetarian diet was conducted. Nineteen healthy female subjects completed the study. All main meals in the meat diets contained 60 g of pork meat and all diets had high phytic acid content (1250 mumol/d). All main meals were extrinsically labelled with the radioactive isotope (59)Fe and absorption of iron was measured in a whole body counter. The non-haem iron absorption from the Danish meat diet was significantly higher compared to the vegetarian diet (P=0.031). The mean fractional absorption of non-haem iron was 7.9 (se1.1), 6.8 (se 1.0) and 5.3 (se 0.6) % for the Danish and Polish meat diets and vegetarian diet, respectively. Total absorption of iron was higher for both meat diets compared to the vegetarian diet (Danish meat diet: P=0.006, Polish meat diet: P=0.003). The absorption ratios of the present study were well in accordance with absorption ratios estimated using algorithms on iron bioavailability. Neither the meat diets nor the vegetarian diets fulfilled the estimated daily requirements of absorbed iron in spite of a meat intake of 180 g/d in the meat diets.     

The effect of combined dietary iron, calcium and folic acid supplementation on apparent 65Zn absorption and zinc status in pregnant rats

In the present study the effect of combined iron, calcium and folic acid supplementation of the diet on 65Zn retention and zinc status was studied in the pregnant rat. Female Wistar rats were fed on a low- (8 micrograms/g) or high- (60 micrograms/g) Zn diet for 14 d and then mated overnight. After mating, half the rats were fed on the low- or high-Zn diet as before, whilst the other half were fed on similar diets supplemented with Fe, Ca and folic acid. The level of supplementation was chosen to reflect proportionately the possible increase in daily intakes of these nutrients by pregnant women. Rats which did not mate successfully were used as non-pregnant controls. On day 18 of pregnancy, each animal was given a meal of the appropriate diet labelled extrinsically with 65Zn, and on day 20 rats were killed. Carcass 65Zn retention was lower in pregnant and non-pregnant rats fed on the supplemented diets compared with those fed on the unsupplemented diets. Rats which consumed the supplemented diets throughout pregnancy had reduced plasma Zn concentrations but femur and fetal Zn concentrations were unaffected. Maternal femur Ca and fetal Fe concentrations were lower in the high-Zn groups compared with rats fed on low-Zn diets. It was concluded that the risk of inducing fetal Zn depletion as a consequence of Fe, Ca and folic acid supplementation during pregnancy appeared to be slight.(ABSTRACT TRUNCATED AT 250 WORDS)     

Iron status in Swedish teenage girls: impact of low dietary iron bioavailability

OBJECTIVE: Although it is well known that bioavailability of iron in the diet is important, it has not been fully elucidated in practice. We investigated iron intake and iron absorption in the ordinary diet of free-living individuals in relation to iron status and assessed iron requirements. METHODS: From a total of 1245 adolescent boys and girls included in the G?teborg Adolescence Study of food habits, 28 adolescent girls registered their food intake during 7 d. Iron intake was assessed on the basis of these 7-d dietary records. Iron absorption was calculated using an algorithm including enhancing and inhibiting dietary factors on iron absorption in relation to individual iron status. RESULTS: Available iron intake was 11.5 +/- 2.8 mg/d (mean +/- SD). The proportion of girls with an iron intake below the Nordic nutrition recommendations was 85% (n = 24). Calculated iron absorption was 1.09 +/- 0.59 mg/d (mean +/- SD). Only four girls satisfied their estimated individual iron requirement concerning the absorbed amount of iron. Iron depletion (serum ferritin concentration < or = 15 microg/L) was present in 10 girls (36%), 2 of whom were also anemic (hemoglobin concentration < or = 120 g/L). CONCLUSION: Swedish adolescent girls seemed to have difficulties satisfying their iron requirement in terms of absorbed amount. The data support the view that iron intake and bioavailability of dietary iron is important when evaluating whether iron requirements have been met.     

Ferric citrate is half as effective as ferrous sulfate in meeting the iron requirement of juvenile tilapia,Oreochromis niloticus x O. aureus

Two growth experiments were conducted to estimate the minimum dietary iron requirement for juvenile hybrid tilapia, Oreochromis niloticus x O. aureus. Purified diets containing 0, 10, 30, 50, 100, 150, 200 and 400 mg Fe/kg from ferric citrate (Experiment 1) and 0, 10, 30, 50, 100, 150 and 200 mg Fe/kg from ferrous sulfate (Experiment 2) were fed to tilapia (mean initial weight: 0.63 +/- 0.01 g, Experiment 1; 0.64 +/- 0.01 g, Experiment 2) for 8 wk. In Experiment 2, 150 mg Fe/kg from ferric citrate was also included for comparison. The rearing water contained 1.07 micro mol/L iron, and supplemental levels were confirmed by analysis. Each diet was fed to three replicate groups of fish. In Experiment 1, weight gain and feed efficiency (FE) were highest (P < 0.05) in fish fed the diet supplemented with 150 mg Fe/kg, followed by fish fed diets with 50, 100 and 200 mg Fe/kg and lowest in fish fed the unsupplemented control diet. Hepatic iron concentration was highest in fish fed diets supplemented with >150 mg Fe/kg, followed by fish fed the diet with 100 mg Fe/kg and lowest in fish fed diets with /=100 mg Fe/kg and mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were higher in fish fed diets with >/=150 mg Fe/kg than in fish fed the diet without iron supplementation. In Experiment 2, weight gain was higher in fish fed the diet with 50 mg Fe/kg than in fish fed diets with 150, 200 and /=50 mg Fe/kg and the ferric citrate comparison diet than fish fed diets with /=50 mg Fe/kg than in fish fed the unsupplemented control diet. Analyses by polynomial regression of weight gain and by broken-line regression of hepatic iron and blood Hb concentrations indicated that the dietary iron requirement for tilapia is approximately 150-160 mg Fe/kg and 85 mg Fe/kg with ferric citrate and ferrous sulfate as the iron source, respectively; it also appears that ferric citrate was approximately 50% as effective as ferrous sulfate in meeting the iron requirement.