Inhibition of the intestinal absorption of iron by sodium alginate and guar gum in rats

Na-alginate as well as guar gum inhibit the absorption of a 59Fe-labelled iron dose (360 nmol) from tied-off jejunal segments of either normal or iron-deficient rats. In order to inhibit the absorption of the iron dose by half as compared with normal rats to which ionized iron was administered 1.2--8 mg of guar gum and 8-30 mg Na-alginate was necessary. In iron-deficient rats the highest dose dose of Na-alginate tested, 100 mg, inhibited the absorption of iron by about 20%; the highest dose of guar gum, 30 mg, inhibited the amount of iron absorbed by about 25%. An artificial diet containing 10% of either guar gum and Na-alginate fed for 3 days inhibited the absorption of iron in normal but not in iron-deficient rats. Also, in these experiments guar gum proved to be more effective than Na-alginate.     

Effects of spinach leaf protein concentrate on the serum cholesterol and amino acid concentrations in rats fed a cholesterol-free diet

The effects of spinach leaf protein concentrate (SPPC) on serum and liver lipid concentrations and on serum free amino acid concentrations were examined in rats fed a cholesterol-free diet containing 2 and 10% fats. The serum total cholesterol, triacylglycerol and phospholipid concentrations in the rats fed an SPPC diet containing 2% corn oil were significantly lower than those of the rats fed a corresponding casein diet. When 10% corn oil or lard was used, the serum cholesterol-lowering effect of the SPPC became insignificant, but the serum and liver triacylglycerol concentrations were kept at significantly lower levels. Both the amounts of fecal neutral steroids and bile acids were significantly higher in the rats fed the SPPC than those of the casein-fed rats. The concentrations of serum threonine, serine, glutamine, glycine, cystine, and isoleucine were significantly higher in the rats fed the SPPC diet containing 2% corn oil compared with those of the control rats, but when the dietary fat was raised to 10%, only glycine showed a higher serum concentration. These results indicate that the SPPC has a stronger cholesterol-lowering effect at a lower dietary fat level, 2%, and the activity is partly due to the inhibition of intestinal absorption of cholesterol and bile acid, and partly due to an increase in the concentration of some of the serum amino acids.     

Pectin with low molecular weight and high degree of esterification increases absorption of 58Fe in growing rats

Effects of pectins with different degrees of esterification (DE) and molecular weights (MW) on iron bioavailability were investigated in healthy growing rats by following erythrocyte incorporation of a dose of 58Fe. Rats were fed a control diet for 8 d and then deprived of food for 16 h. Two hours after the start of feeding iron-deficient diets, with or without pectin (80 g/kg diet), a dose of FeSO4 rich in 58Fe (60.28%) was intubated into the stomach; rats were then allowed to feed for an additional 4 h before withdrawal of food for 10 h. Rats were then fed iron-adequate diets for 9 d. The pectins differed in DE and MW, respectively, as follows: P-A (73%, 860,000), P-B (75%, 89,000), P-C (22%, 1,260,000) and P-D (24%, 114,000). Rats fed pectin-free diet with free access to food or restricted to the same quantity consumed by a respective pectin group served as controls. Iron absorption was 48% in the control group and 57% in rats fed P-B. Rats fed P-B had higher (P 2 < or = 0.05) serum iron, transferrin saturation, hematocrit and liver and spleen iron than the control group or the group fed P-C. These indices, except for transferrin saturation, were also higher In rats fed P-A and P-D compared with those fed P-C and controls, but to a lesser extent than in rats fed P-B. The data indicate that bioavailability of dietary non-heme iron was enhanced when pectin of low MW and high DE was added to the diet. This improvement was not evident with pectins having high MW and/or low DE.     

Absorption of isomeric, palmitic acid-containing triacylglycerols resembling human milk fat in the adult rat

The effect of the positional distribution of palmitic acid (16:0) in triacylglycerols (TAG) on 16:0 apparent absorption in adult rats was investigated. The rats were fed two diets which contained 30 energy % as fat with identical total fatty acid compositions, both containing 30% 16:0. The Betapol diet contained TAG with 73% of total 16:0 in the sn-2 position, the control diet contained TAG with 6% of total 16:0 in the sn-2 position. After six weeks on these diets, the rats were killed two or six hours after the last meal, and the small intestine was removed, cut into 10-cm segments, and the fatty acid composition of the segment's contents was determined. At both time points the amount of 16:0 in the intestinal segments starting at 40 cm from the stomach was much lower in the animals fed Betapol than in the animals fed the control diet. Overall absorption of 16:0 and stearic acid was significantly greater in the Betapol group. Absorption of oleic and linoleic acid from the small intestine was similar in both groups, although the overall absorption was significantly greater in the animals fed Betapol. Total fat absorption was significantly higher in the Betapol-fed rats than in the control-fed rats. No effect on calcium and nitrogen absorption, on plasma total cholesterol and TAG levels, and on bodyweights (growth) was seen. The data demonstrate that the positional distribution of the fatty acids in the TAG molecule affects the site of absorption in the small intestine and particularly the net absorption of saturated fatty acids.     

Effect of calcium intake on nonheme-iron absorption from a complete diet

Recent studies based on radioiron measurements from single meals have suggested that calcium has a strongly inhibitory influence on nonheme-iron absorption. In view of evidence that the importance of various dietary enhancers and inhibitors of absorption is greatly diminished when assessed by labeling a complete diet, the present study evaluated the effect of variations in calcium intake on total dietary nonheme-iron absorption. Nonheme-iron absorption was measured in 14 healthy volunteers during three periods in which the diet was freely chosen or modified to decrease or increase dietary calcium intake maximally. The diet was labeled during each 5-d period by including with each of the two main meals of the day a small bread roll tagged extrinsically with radioiron. Carefully maintained dietary records indicated that 69-78% of the daily iron intake was labeled by this method. The basal calcium intake of 684 mg/d varied from 280 to 1281 mg/d when calcium intake was reduced or increased, respectively. Geometric mean iron-absorption values of 5.01%, 4.71%, and 5.83% for the three dietary periods were not significantly different from one another. No significant relation was observed between nonheme-iron absorption and dietary factors known to influence iron absorption. We conclude that calcium intake had no significant influence on nonheme-iron absorption from a varied diet.     

Effects of iron deficiency on the absorption and distribution of lead and cadmium in rats

In order to evaluate the effects of iron deficiency on the absorption of pollutant metals, an iron-deficient diet was fed to young rats until their tissue-iron stores were depleted. Prior to the development of anemia, the iron-deficient rats and littermate controls were administered an intragastric gavage of lead-210 or cadmium-109 and were killed 48 hr later. The body burden of lead was approximately 6 times greater, and that of cadmium approximately 7 times greater, in iron-deficient rats than in the controls. No consistent effects were observed on concentrations of serum total lipids or serum proteins nor on protein electrophoretic patterns in rats with a deficit in iron stores.     

Hepatotoxicity induced by iron overload and alcohol. Studies on the role of chelatable iron, cytochrome P450 2E1 and lipid peroxidation

BACKGROUND/AIMS: Clinical experience and studies with experimental animal models indicate a synergistic hepatotoxic effect of dietary iron overload and chronic alcohol ingestion. In order to elucidate the mechanism underlying this synergism, we examined the hepatic levels of ethanol-inducible cytochrome P450 2E1, glutathione and malondialdehyde, and the effect of iron chelation with desferrioxamine, in livers from rats treated with iron and/or ethanol. METHODS: Animals received diets with or without 2.5-3% carbonyl iron for 6-9 weeks, followed by an ethanol-containing diet or a liquid control diet for 5-9 weeks. Desferrioxamine was administered subcutaneously with mini-osmotic pumps. Alanine aminotransferase activity in serum and hepatic contents of glutathione and malondialdehyde were determined. The hepatic level of cytochrome P450 2E1 was determined with Western Blotting using a specific polyclonal antibody. RESULTS: The combination of iron and alcohol led to a marked increase in serum alanine aminotransferase activity as compared with all other treatment groups, and iron chelation with desferrioxamine reversed these increases. Treatment with alcohol alone led to slightly increased aminotransferases compared with controls. The level of cytochrome P450 2E1 was significantly elevated in microsomes isolated from ethanol-treated rats, but neither additional iron supplementation nor desferrioxamine influenced this level significantly. Glutathione contents were increased in the livers of animals treated with iron and/or ethanol. Malondialdehyde values were increased in iron-treated animals, whereas neither ethanol nor desferrioxamine altered malondialdehyde levels significantly. CONCLUSIONS: The toxic effects exerted by the combination of iron overload and chronic ethanol feeding on rat liver are dependent on a pool of chelatable iron. The hepatic level of cytochrome P450 2E1 is markedly induced by ethanol but not further altered by iron overload. Neither increased lipid peroxidation nor depletion of hepatic glutathione levels can explain the synergistic hepatotoxic effects of iron and ethanol in this model.     

Iron stores in man in relation to diet and iron requirements

OBJECTIVE: To calculate iron stores in man and their rates of changes in relation to iron requirements and dietary iron intake and bioavailability. METHOD: Newly established relationships between iron absorption from whole diets and serum ferritin (SF) and between SF and iron stores allow calculations of amounts of stored iron under different conditions (diets, losses) at stationary states when absorption equals losses. Rate of growth of stores can also be calculated. All calculations are based on observations and require no model assumptions. RESULTS: Present calculations of iron stores agree with previously observed phlebotomy values. Differences in intake and bioavailability of dietary iron and in iron requirements had marked effects on amounts of stored iron. A wide range of diets was studied, from a hypothetical high-meat diet typical for early man to diets in developing countries. A new equation is given for the translation of SF into iron stores. Analyses of growth rate of stores under different conditions showed a fast growth from zero iron stores during the first year (reaching about 80% of final amounts) followed by a much slower rate for 2-3 y. A marked inertia was seen in rate of changes in iron stores that was more marked the closer stores were to their stationary states making it difficult to use SF to estimate short term changes in iron absorption in iron replete subjects. CONCLUSIONS: Realistic Western-type diets with good bioavailability can cover iron requirements in most women and can restitute iron stores during lactation. The high prevalence of iron deficiency in menstruating Western women is thus mainly related to a further low bioavailability of iron in present diets. Present analyses also demonstrated an effective control of iron absorption preventing development of iron overload in otherwise healthy subjects even if the diet is fortified with iron and even if meat intake is high.     

Iron(III) chloride injection increases nigral uric acid in guinea-pig

The present study was carried out to determine if iron chloride (FeCl3) injections into the substantia nigra of guinea-pigs produced changes in nigro-striatal uric acid levels. Two-weeks following unilateral injection of FeCl3 (185 nmol Fe3+), ipsilateral uric acid levels were increased 176% over contralateral levels in the substantia nigra. No effect on striatal uric acid levels was observed. Iron chloride injection produced a 74% depletion of dopamine levels in the ipsilateral striatum. Ipsilateral/contralateral ratios were significantly decreased for striatal dopamine and significantly increased for nigral uric acid when compared with saline-injected controls. The results of this work indicate that FeCl3 injections into the substantia nigra of guinea-pigs produce a significant, localized increase in tissue uric acid levels two weeks after treatment.     

Involvement of vitamin E and protein thiols in the inhibition of microsomal lipid peroxidation by glutathione

Iron-ascorbate stimulated lipid peroxidation in rat liver microsomes can be inhibited by glutathione (GSH). The role of protein thiols and vitamin E in this process was studied in liver microsomes isolated from rats fed diets either sufficient or deficient in vitamin E and incubated at 37 degrees C under 100% O2. Lipid peroxidation was induced by adding 400 microM adenosine 5'-triphosphate, 2.5 to 20 microM FeCl3, and 450 microM ascorbic acid. One mL of the incubation mixture was removed at defined intervals for the measurement of thiobarbituric acid reactive substances (TBARS), protein thiols and vitamin E. In vitamin E sufficient microsomes, the addition of GSH enhanced the lag time prior to the onset of maximal TBARS accumulation and inhibited the loss of vitamin E. Treatment of these microsomes with the protein thiol oxidant diamide resulted in a 56% loss of protein thiols, but did not significantly change vitamin E levels. However, diamide treatment abolished the GSH-mediated protection against TBARS formation and loss of vitamin E during ascorbate-induced peroxidation. Liver microsomes isolated from rats fed a vitamin E deficient diet contained 40-fold less vitamin E and generated levels of TBARS similar to vitamin E sufficient microsomes at a 4-fold lower concentration of iron. GSH did not affect the lag time prior to the onset of maximal TBARS formation in vitamin E deficient microsomes although total TBARS accumulation was inhibited. Similar to what was previously found in vitamin E sufficient microsomes [Palamanda and Kehrer, (1992) Arch. Biochem. Biophys. 293, 103-109], GSH prevented the loss of protein thiols in vitamin E deficient microsomes.(ABSTRACT TRUNCATED AT 250 WORDS)     

An approach for studies of mediator-induced leukocyte rolling in the undisturbed microcirculation of the rat mesentery

To determine the absorption and biodistribution of iron from microencapsulated ferrous sulfate (SFE-171), used to fortify dairy products with iron, a comparative study in four groups of 30 mice each was carried out. In two of the groups, the absorption of iron from ferrous ascorbate in water (13.3 +/- 4.3%) and from ferrous sulfate in water (12.7 +/- 3.9%) was determined and taken as reference standards. In the third group the iron absorption from SFE-171 in milk was determined, giving a value of 12.1 +/- 4.2%, which statistically does not differ from the data obtained with either reference standard. In the fourth group, the absorption of iron from ferrous sulfate in milk showed a value of 7.7 +/- 3.4%, which statistically differs with a p < 0.01 from the data corresponding to the other three groups. The biodistribution studies showed that the iron from the SFE-171 follows the same metabolic pathway as the iron from the reference standards thus, giving a higher radioactivity percentage and radioactivity concentration in organs or systems, principally blood, that are closely related to iron metabolism. Our studies allow us to conclude that the iron from SFE-171 in milk follows the same behavior as the nonhemic iron, with a higher absorption than that of ferrous sulfate in milk.     

Brain iron, transferrin and ferritin concentrations are altered in developing iron-deficient rats

To study the iron, transferrin, and ferritin distribution at subcellular levels in response to acute dietary iron deficiency, we tested the hypothesis that early post-weaning iron deficiency can change iron and iron regulatory protein concentrations in rat brain. Male Sprague-Dawley rats were fed diets containing either 2 or 35 micrograms iron/g for 2, 3 or 4 wk starting at 21 d of age. Brain iron, transferrin and ferritin concentrations in cytosolic and microsomal fractions of either whole brain or pons and cerebellum were then determined. After 14 d of dietary iron restriction, brain iron concentrations were 50% lower in the microsomal fraction and 30% lower in cytosol compared with controls. Brain cytosolic transferrin concentration almost doubled in the same animals. Brain ferritin concentration in fractions from rats fed the iron-deficient diet for 14 d was lower than in controls, but then remained fairly constant. Absolute brain weight and total brain protein contents were unaffected by iron restriction. This study extends previous research by demonstrating that the brain responds to changes in body iron status with a change in transferrin concentration. If the dietary restriction is quite severe, this adaptation is insufficient. This study also notes that brain ferritin decreases with decreasing body iron status, though it was less responsive than nonheme iron in liver. The concept that iron enters the brain through a highly regulated endocytotic process at the blood brain barrier, that undoubtedly involves the regulation of transferrin receptors in capillary endothelial cell, is supported by our observation of elevated transferrin concentrations in brain of iron-deficient rats.     

Prevention of coprophagy modifies magnesium absorption in rats fed with fructo-oligosaccharides

We developed a new type of anal cup for prevention of coprophagy and determined whether the absorption of Ca and Mg and the stimulatory effects of feeding fructo-oligosaccharides (FO) on the absorption of Ca and Mg were altered by prevention of coprophagy in rats. Rats were fed on a FO-free diet or a diet containing 50 g FO/kg for 2 weeks with or without prevention of coprophagy. FO-feeding increased the apparent absorptive ratio of Ca and Mg in rats with or without prevention of coprophagy. However, in the FO-fed groups the absorptive ratio of Mg in rats with prevention of coprophagy was higher than in rats without prevention of coprophagy. The Ca content of the femur was higher in rats fed on the FO-diet than in rats fed on the FO-free diet both with and without coprophagy. In conclusion, FO-feeding increased the absorption of Ca and Mg in rats both with and without coprophagy. Moreover, prevention of coprophagy enhanced the absorption of Mg in rats fed with FO. Coprophagy has to be considered when the effects of luminal fermentation or mineral absorption are examined in rats.     

Effect of modified and unmodified tapioca starches on 59Fe retention in rats

The effects of a chemically-modified tapioca starch hydroxypropyl distarch phosphate (HDP), and unmodified tapioca starch (UMS) on 59Fe retention by rats were compared. Three experimental variables were evaluated: 1) the type of starch in the diet, 2) cooking of either the starch alone or the entire diet, and 3) the iron status of the rats. There were no significant differences in 59Re retention between iron-adequate rats fed either UMS or HDP. 59Fe retention by iron-deficient rats was not affected by the type of starch in the diet when uncooked starch was used. However, if the starch was cooked, substitution of HDP for UMS resulted in a significant depression in iron retention by iron-deficient rats. Cooking the entire diet produced a similar but less marked effect. The results of these experiments suggest that the inclusion of one particular type of modified tapioca starch in the diet may affect iron utilization.     

Sodium balance and jejunal ion and water absorption in Dahl salt-sensitive and salt-resistant rats

1. Apparent Na+ absorption and jejunal water, Na+, Cl- and K+ absorption in vivo was evaluated in young (prepubertal) and adult Dahl salt-sensitive (DS) and Dahl salt-resistant (DR) rats kept on a low-salt (low-salt rat chow + distilled water) or a high-salt diet (HS1 diet: NaCl-enriched rat chow + distilled water; HS2 diet: standard rat chow + 1% saline as drinking fluid). These two high-salt diets were chosen because the HS1 regimen has been shown to increase blood pressure (BP) in DS rats and the HS2 regimen decreases jejunal water and ion absorption in normotensive Wistar rats. 2. The HS1 or HS2 diet increased BP in young and adult DS rats but had no effect on the BP of young and adult DR rats. 3. Irrespective of dietary Na+ intake, no significant difference of apparent Na+ absorption (dietary Na+ intake minus faecal Na+ output) was observed between DS and DR rats both in prepuberty and in adulthood. Young DS rats kept on a low-salt diet had increased faecal Na+ output in comparison with young DR rats. This difference disappeared with increasing dietary Na+ intake. 4. There were no interstrain differences on the effect of a high-salt diet on jejunal Na+ and K+ absorption in young and adult DS and DR rats. However, high-salt diets stimulated jejunal water and Cl- absorption in young DS rats, but not in adult DS rats and young and adult DR rats. Interstrain differences of water and Cl- absorption were observed only in adulthood. Adult DR rats kept on an HS2 diet absorbed more water and Cl- than their DS counterparts. 5. Our results do not indicate any abnormalities of apparent Na+ absorption and jejunal water and electrolyte transport in DS and DR rats. We conclude that there is no relationship between intestinal Na+ absorption and sensitivity or resistance to induction of experimental salt hypertension.     

Milk inhibits and ascorbic acid favors ferrous bis-glycine chelate bioavailability in humans

The chemical properties of ferrous bis-glycine chelate allow for its use as a fortificant in fluid, high fat vehicles. This chemical form may also protect iron from the inhibitory or enhancing effects of the diet on iron absorption. Alternatively, iron bis-glycine chelate may be absorbed by a mechanism independent of an individual's iron stores. To test these hypotheses, the bioavailability of iron bis-glycine chelate added to water and milk was studied using a double-isotopic method in two groups of 14 women. Iron absorption from aqueous solutions of 0.27 mmol/L (15 mg/L) of elemental iron as either iron bis-glycine or ferrous ascorbate was not significantly different (34.6 and 29.9%, respectively). There were significant correlations between (log) iron absorption of iron bis-glycine with (log) serum ferritin (r = -0.60, P < 0.03) and with (log) iron absorption from ferrous ascorbate (r = 0.71, P < 0.006), suggesting that iron bis-glycine chelate bioavailability is indeed affected by iron stores. Iron absorption of iron bis-glycine given in milk was significantly lower (P < 0.002) than when given in water, with values of 11.1 and 46.3%, respectively (standardized to 40% absorption of the reference dose). With the addition of 0.57 mmol/L ascorbic acid (100 mg/L), iron absorption of iron bis-glycine given in milk increased significantly from 11.1 to 15.4% (P < 0.05). These findings show that milk and ascorbic acid affect iron bis-glycine chelate bioavailability and also demonstrate that iron stores may influence its bioavailability as well. The good bioavailability of iron bis-glycine makes this compound a suitable alternative to be considered in iron fortification programs.     

The effects of whole wheat, wheat bran and zinc in the diet on the absorption and accumulation of cadmium in rats

The purpose of the present study was to determine if the inclusion of whole-grain wheat or wheat bran in the diet or the addition of Zn to the diet affects the absorption and accumulation of Cd. Five groups of six rats each were fed deionized water and one of five diets composed of one part basic diet and one part wheat crispbread for 6 weeks. The accumulation of Cd in the liver and kidneys was measured using atomic absorption spectrometry and estimated by measuring the absorption and retention of 109Cd from a single meal after 3 weeks on the diets. The fractional accumulation of Cd in the liver and kidneys was lower in rats fed on whole-wheat and bran diets than in those fed on wheat-endosperm diets. As adding Zn or Cd to endosperm diets to approximate the bran and whole-wheat diet levels had no effect on the fractional Cd absorption, the reduced absorption from the whole-wheat and bran diets is probably not due to their higher Zn and Cd concentrations but may be due to their higher fibre or phytate concentrations. The amount of Cd accumulated in the liver and kidneys of the rats fed on whole-wheat and bran diets was higher than that in rats fed on the endosperm diet. Thus, the reduction in the fractional Cd accumulation from the whole-wheat and bran diets is not sufficient to compensate for their higher Cd concentrations.     

On the automaticity of ipsilateral response activation in the Simon effect

The purpose of this investigation was to establish whether plasma cholesterol and triacylglycerol(s) in copper deficiency can be increased or decreased by hepatic iron levels. Weanling male Sprague-Dawley rats were randomly divided into six dietary groups based on levels of dietary copper and iron. They were fed from weaning their respective diets for 6 wk. Forty percent of the copper-deficient rats fed a 15.7 mumol Fe/g diet died; 22% of those fed a diet containing 8.6 mumol Fe/g died; and there were no deaths in the 3.4 mumol Fe/g diet group. Rats belonging to the group fed the high-iron diet also exhibited the highest levels of liver iron, liver glutathione, and plasma cholesterol and triacylglycerol(s) compared with those fed either the adequate or low levels of dietary iron. There was a direct correlation (r = 0.82 and 0.77, respectively) between levels of cholesterol and triacylglycerol(s) in plasma and hepatic iron concentrations. These results provide strong evidence that points to a major involvement of iron in the lipemia of copper deficiency. These data may be important to those individuals who consume large quantities of fortified iron foods and supplement with iron but whose intake of copper is suboptimal.     

Transcriptional and translational regulation of photosystem I and II genes in light-dark- and continuous-light-grown cultures of the unicellular cyanobacterium Cyanothece sp. strain ATCC 51142

Formation of an iron chelate of glycated protein was demonstrated by the appearance of an absorption peak at approximately 270 nm after mixing glycated bovine serum albumin with FeCl3. This peak disappeared and a new peak appeared at approximately 420 nm to form an isosbestic point at approximately 340 nm by the addition of deferoxamine mesylate, an iron-chelating agent, to the mixture, thus confirming the formation of the iron chelate of the glycated protein in the mixture. The lipid peroxide level was increased markedly in endothelial cells and slightly in smooth muscle cells from bovine aorta incubated in the medium containing glycated fetal bovine serum-iron chelate. Morphological observation by phase-contrast microscopy and scanning electron microscopy revealed that the glycated fetal bovine serum-iron chelate caused intense damage to the endothelial cells. These results indicate that glycated protein-iron chelate provokes lipid peroxidation, which explains at least in part the mechanism of atherogenesis found in diabetic patients.     

PCR-RFLP pattern of three kinds of Metagonimus in Korea

Nicotinic acid has functional groups capable of forming complexes with trace metals. The present study examines the effect of nicotinic acid supplementation on absorption and utilization of zinc and iron. In vitro zinc uptake by human erythrocytes was studied using blood samples of 10 healthy subjects. It was found that 8 mumoles nicotinic acid or NADP increased 65Zn uptake by 38.9% and 43.1% in fasting, and by 70.9% and 28.1% in postprandial conditions. In animal experiments, nicotinic acid supplementation to finger millet based diet resulted in significant enhancement of percent zinc absorption, liver zinc and growth of weanling mice (P < 0.05). When mice were fed with nicotinic acid-deficient, -adequate and -excess synthetic diets for four weeks it was observed that, in comparison with the nicotinic acid-deficient diet, percent zinc absorption, intestinal zinc, percent haeomoglobin and liver iron increased significantly under nicotinic acid-adequate and -excess conditions. The results obtained suggested that nicotinic acid, in addition to its known effect on growth and metabolism, may be playing an important role in enhancing zinc and iron utilization.