Non-haem Iron Absorption Research Articles

Clinical trial on the effect of regular tea drinking on iron accumulation in genetic haemochromatosis

Background: Black tea is known to be a potent inhibitor of intestinal absorption of non-haem iron at least in healthy subjects. Aims: To investigate this effect in patients with genetic haernochromatosis, and, more importantly, the effect of regular tea drinking on the accumulation of storage iron in these patients over one year. Patients: Investigations were carried out on 18 patients with clinically proven genetic haemochromatosis. For the study of storage iron accumulation, they were separated into a group instructed to drink a particularly tannin rich tea regularly with meals and a control group. Methods: Intestinal iron absorption from a test meal was measured using whole body counting. Body iron stores were evaluated quantitatively by exhaustive phlebotomy, using haemoglobin, saturation of serum iron binding capacity, and serum ferritin for the assessment of body iron status. Results: A significant reduction in iron absorption was observed when the test meal was accompanied by drinks of tea instead of water. In the tea drinking group, the increase in storage iron was reduced by about one third compared with that of the control group. Conclusions: Regular tea drinking with meals reduces the frequency of phlebotomies required in the management of patients with haemochromatosis.

Clinical trial on the effect of regular tea drinking on iron accumulation in genetic haemochromatosis

Background—Black tea is known to be a potent inhibitor of intestinal absorption of non-haem iron at least in healthy subjects.Aims—To investigate this effect in patients with genetic haemochromatosis, and, more...

Evaluation of iron bioavailability in infant weaning foods fortified with haem concentrate.

Nutritional iron deficiency in infants over 4 months of age is one of the most common deficiency disorders. Dietary iron is comprised of non-haem and haem iron, the latter being absorbed by a separate pathway and more efficiently than non-haem iron. Fortification of infant weaning foods is one of the strategies adopted for preventing iron deficiency and the aim of this project was to examine the potential use of haem iron concentrate as a fortificant. Sixteen non-anaemic 6-month old infants were recruited and allocated to two groups of 8. Each infant consumed 2 meals/day of a commercial weaning food (100 g) for 7 consecutive days containing 40 mg ascorbic acid and 2.5 mg haem iron/100 g (Group 1) or the same quantity of iron as ferrous sulphate plus 40 mg ascorbic acid (Group 2). Bioavailability was assessed by chemical balance using carmine to mark the beginning and end of the faecal collection. The effect of haem iron concentrate (as a candidate for the factor in meat that enhances iron absorption) was examined by measuring its effect on 57Fe-labelled non-haem iron absorption. There was no difference in iron balance between the two groups. Mean iron retention was 3.5 (SD 2.1) mg/day in Group 1 (haem iron) and 3.0 (SD 2.4) mg/day in Group 2 (ferrous sulphate). Haem concentrate did not enhance the absorption of 57Fe-labelled non-haem iron, Group 1: 1710 (SD 11.1)%, Group 2: 28.4 (SD 17.7)%. Haem iron concentrate appears to be a highly bioavailable form of iron when added to infant weaning foods. This protein is not, however, responsible for the enhancing effect of animal protein on non-haem iron absorption.

Kinetic analysis of the intestinal iron absorption process in situ. The potential of vascularly autoperfused intestinal loops.

1 Blood sampling from mesenteric venules during absorption in situ is a useful tool to analyse intestinal absorption kinetics and prehepatic metabolism in different sections of the rat small intestine. By use of a micromanipulator, the method can be applied to the duodenum. This part of the small intestine shows the strongest adaptation of non-haem iron absorption to the demand for iron. 2 Iron absorption kinetics was linear in duodenal and jejunal segments. In iron-deficient animals, intestinal iron absorption capacity was increased in the duodenum, while simultaneously determined galactose absorption showed no change. 3 In situ perfusion and cannulation of mesenteric venules in duodenal segments are described. The use of a micromanipulator permits varying the blood volume collected by changing the vertical angle between the cannula and the mesenteric vessel. 4 Intestinal iron absorption rates remained close to constant when blood flow rates were varied by a factor of about ten. Plasma concentrations of absorbed iron vs mesenteric blood flow rates followed a hyperbolic function, as the plasma concentration of absorbed iron in mesenteric venules increased to the same extent as the blood flow decreased. 5 As the plasma transferrin concentration did not change over the experimental period, the concentration of absorbed iron in the mesenteric plasma exceeded the iron-binding capacity of plasma transferrin at low blood flow rates. This observation shows that enhancement of intestinal iron absorption does not require a corresponding increase in plasma iron-binding capacity in the intestinal tissue. 6 Vascularly perfused gut loops were also used to measure prehepatic metabolism, which may influence organotropism of carcinogenic metabolites. Therefore, this type of preparation is likely to find a variety of toxicological applications.

Regulation of intestinal non-haem iron absorption.

Regulation of intestinal non-haem iron absorption.

Absorption of Non-Haem Iron From Food During Normal Pregnancy

Abstract Objective: To determine whether the increased iron demands of pregnancy could be met by increased absorption from dietary sources. Design and setting: Longitudinal prospective study in the research unit of a maternity hospital. Subjects: 12 normal pregnant women. Interventions—At 12, 24, and 36 weeks9 gestation (within one week) and 16-24 weeks after delivery women ate a breakfast of meat, bread, and orange juice (3.2 mg iron), extrinsically labelled with the stable isotope iron-54 (2.8 mg); the stable isotope iron-57 (200 µg) was given intravenously. Main outcome measures: Serum samples were taken for 10 hours after administration of the isotopes; ratios of the isotopes were measured by inductively coupled plasma mass spectrometry, and the absorption of oral iron was calculated. Results: The geometric mean (95% confidence interval) absorption of iron at 12, 24, and 36 weeks9 gestation was 7% (5% to 11%), 36% (28% to 47%), and 66% (57% to 76%) respectively. At 16-24 weeks after delivery the absorption was 11% (6% to 21%). The mean increase in absorption at 36 weeks (compared with that at 12 weeks) was 9.1 times (6.0 to 13.7). One pregnant woman developed iron deficiency anaemia but was otherwise indistinguishable from the others. Conclusions: An increase in the absorption of iron from food is a physiological consequence of normal pregnancy, not the result of developing anaemia during pregnancy, and such an increase is large enough to meet the increased requirements of pregnancy provided that the dietary intake is adequate.

Absorption of non-haem iron from food during normal pregnancy.

To determine whether the increased iron demands of pregnancy could be met by increased absorption from dietary sources. Longitudinal prospective study in the research unit of a maternity hospital. 12 normal pregnant women. At 12, 24, and 36 weeks' gestation (within one week) and 16-24 weeks after delivery women ate a breakfast of meat, bread, and orange juice (3.2 mg iron), extrinsically labelled with the stable isotope iron-54 (2.8 mg); the stable isotope iron-57 (200 micrograms) was given intravenously. Serum samples were taken for 10 hours after administration of the isotopes; ratios of the isotopes were measured by inductively coupled plasma mass spectrometry, and the absorption of oral iron was calculated. The geometric mean (95% confidence interval) absorption of iron at 12, 24, and 36 weeks' gestation was 7% (5% to 11%), 36% (28% to 47%), and 66% (57% to 76%) respectively. At 16-24 weeks after delivery the absorption was 11% (6% to 21%). The mean increase in absorption at 36 weeks (compared with that at 12 weeks) was 9.1 times (6.0 to 13.7). One pregnant woman developed iron deficiency anaemia but was otherwise indistinguishable from the others. An increase in the absorption of iron from food is a physiological consequence of normal pregnancy, not the result of developing anaemia during pregnancy, and such an increase is large enough to meet the increased requirements of pregnancy provided that the dietary intake is adequate.

Absorption of non-haem iron in normal women measured by the incorporation of two stable isotopes into erythrocytes.

1. Iron absorption has been quantitatively measured as the incorporation of physiological doses of stable iron isotopes into erythrocytes. Five milligrams of 57Fe (orally) and 250 micrograms of 58Fe (intravenously) were given to five healthy women on 2 consecutive days. Fourteen days later the changes in the 57Fe/56Fe and 58Fe/56Fe ratios in the erythrocytes of each subject were measured using an inductively coupled plasma mass spectrometer. Isotope ratios were also measured in two subjects who were not given any enriched isotope. Concomitant measurements of plasma volume using a dye-dilution technique enabled the estimation of body iron mass and the calculation of iron absorption. 2. The mean coefficients of variation for the 57Fe/56Fe ratio and the 58Fe/56Fe ratio were 0.22% and 0.47%, respectively. This precision allowed enrichments of basal ratios to be reliably detected in all cases. The mean change in the 57Fe/56Fe ratio was 0.00116 (SD 0.00052, P < 0.001) and the mean change in the 58Fe/56Fe ratio was 0.00035 (SD 0.00004, P < 0.001). Control subjects showed no enrichment. 3. The calculated iron absorption ranged from 10% to 34%, and the amount of absorption was related to the iron stores of the subjects. Percentage iron absorption was identical when estimates of the plasma volume (derived from a body mass equation) were used instead of the plasma volume determined by dye-dilution measurements. Incorporation of intravenous iron into erythrocytes was on average 81% (range 68-93%). 4. The method is especially applicable to the study of iron absorption during pregnancy when incorporation into erythrocytes cannot be predicted.

Nutritional iron requirements and food iron absorption.

To prevent nutritional iron deficiency, sufficient iron must be absorbed from the diet to meet the normal physiological requirements. Daily iron losses in males are about 1 mg (14 micrograms kg-1), while the average additional requirements incurred in women include menstruation (0.6 mg), pregnancy (2.7 mg) and lactation (less than 0.3 mg). Requirements during pregnancy are not evenly distributed and increase to between 5-6 mg in the last trimester of pregnancy, which is more than can be absorbed from even an optimal diet. While the amounts absorbed are affected by the iron content of the diet, the composition of the latter is even more relevant. About one-quarter of the iron in haem proteins is absorbed regardless of the other components in the diet, while non-haem iron absorption is subject to the interplay of promoting and inhibiting substances in the diet. Thus diets rich in enhancers of non-haem iron absorption, chiefly meat and/or ascorbic acid, have high iron bioavailability (about 3 mg d-1) while diets in which inhibitors, such as polyphenols and phytates, predominate are poor sources of iron (less than 1 mg d-1). Examination of the relative proportions of promoters and inhibitors of iron absorption in individual foodstuffs and the measured iron absorption from them may be useful in predicting the overall iron bioavailability from mixed diets.

Measurement of non-haem iron absorption in non-anaemic rats using 59Fe: can the Fe content of duodenal mucosal cells cause lumen or mucosal radioisotope dilution, or both, thus resulting in the underestimation of Fe absorption?

Male Wistar rats (188 g) were fed on a semi-synthetic (SS) diet (38 mg iron/kg) ad lib. for 7 d and then meal-fed for 1 d. After a 21 h fast each rat was given one meal (10 g) of high-Fe SS (500 mg Fe/kg; high-Fe group) or control (38 mg Fe/kg; control group) diet. After 16 h 2 ml of an 59Fe-labelled ferrous sulphate solution (18 kBq 59Fe; 120 micrograms Fe) was administrated by gavage and equal numbers of rats from each group were killed 6 or 24 h after dosing. Mucosal uptake of 59Fe from the gut lumen and transfer of 59Fe from mucosa into the carcass were measured. Total Fe content of the duodenum was also determined. Mucosal 59Fe uptake and transfer were markedly lower in the high-Fe group compared with the control group. The Fe content of the duodenum, the major region of Fe absorption, was significantly greater in the high-Fe group than in the controls. A larger amount of Fe may thus have been released into the lumen of the high-Fe rats, via mucosal cell turnover, resulting in a greater lumen dilution of the 59Fe dose in this group compared with the controls. Calculations are presented which demonstrate that such an effect could not possibly account for the observed difference in mucosal 59Fe uptake between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of organic acids, phytates and polyphenols on the absorption of iron from vegetables.

1. Non-haem iron absorption from a variety of vegetable meals was studied in parous Indian Women, using the erythrocyte utilization of radioactive Fe method.2. The studies were undertaken to establish whether Fe absorption could be correlatedwith the chemical composition of the foodstuff.3. Addition of the following organic acids commonly found in vegetables, improved the geometric mean Fe absorption from a basic rice meal as follows: from 0·028 to 0·085 with 1 g citric acid, from 0·031 to 0·081 with 15 mg ascorbic acid, from 0·048 to 0·095 with 1 g L-malic acid, from 0·041 to 0·096 with 1 g tartaric acid. The only exception was oxalic acid; the addition of 1 g calciumoxalate to cabbage (Brassica oleraceae) was associated with some depression in Fe absorption from 0·320 to 0·195.4. There was a marked inhibition of the geometric mean absorption when 500 mg tannic acid was added to a broccoli (Brassica oleraceae) meal (0·015v. 0·297). Sodium phytate (2 g) caused a similar, though less profound inhibition (0·035 to 0·152).5. When 3 mg ferrous sulphate was added to different vegetables the geometric mean absorption varied widely. Vegetables of low Fe bioavailability were wheat germ (Triticum aestivum) 0·007, aubergine (Solanum melongena) 0·007, butter beans (Phaseolus lunatus) 0·012, spinach (Spinacea oleraceae) 0·014, brown lentils (Lens culinaris) 0·024, beetroot greens (Beta vulgaris) 0·024 and green lentils (Lens culinaris) 0·032. In contrast, bioavailability was moderate or good with carrot (Daucus carota) 0·098, potato (Solanum tuberosum) 0·115, beetroot (Beta vulgaris) 0·185, pumpkin (Cucurbita mixta) 0·206, broccoli 0·260, tomato (Lycopersicon esculentum) 0·224, cauliflower (Brassica oleraceae) 0·263, cabbage 0·320, turnip (Brassica rapa) 0·327 and sauerkraut 0·327.6. All the vegetables associated with moderate or good Fe bioavailability contained appreciable amounts of one or more of the organic acids, malic, citric and ascorbic acids.7. Poor Fe bioavailability was noted in vegetables with high phytate contents (e.g. wheat germ 0·007, butter beans 0·012, brown lentils 0·024 and green lentils 0·032).8. The fact that a number of vegetables associated with low Fe-absorption turned bluish-black when Fe was added to them, suggested that the total polyphenol content in them was high. The vegetables included aubergine spinach, brown lentils, green lentils and beetroot greens. When the total polyphenol content in all the vegetables tested was formally measured, there was a significant inverse correlation (r 0·859, P &lt; 0·001) between it and Fe absorption. The inverse correlation between the non-hydrolysable polyphenol content and Fe absorption wasr0·901 (P &lt; 0·001).9. The major relevance of these findings is the fact that the total absorption of non-haem-Fe from a mixed diet may be profoundly influenced by the presence of single vegetables with either marked enhancing or inhibiting effects on Fe bioavailability.

The effect of tea on iron absorption.

The effect of tea on iron absorption was studied in human volunteers. Absorption from solutions of FeCl3 and FeSO4, bread, a meal of rice with potato and onion soup, and uncooked haemoglobin was inhibited whether ascorbic acid was present or not. No inhibition was noted if the haemoglobin was cooked. The effect on the absorption of non-haem iron was ascribed to the formation of insoluble iron tannate complexes. Drinking tannin-containing beverages such as tea with meals may contribute to the pathogenesis of iron deficiency if the diet consists largely of vegetable foodstuffs.