Michael Hoppe

The validation of using serum iron increase to measure iron absorption in human subjects

The objectives of the present study were to study the correlation between the change in serum Fe and Fe absorption when administering 100 mg Fe (as FeSO4) orally, and to study the correlation between the absorption from a 3 mg and a 100 mg Fe (as FeSO4) dose. The study was conducted in a group of eleven male blood donors, without any evident infection, who had given blood 8 weeks before the study. On three consecutive mornings the subjects were served a wheat roll fortified with Fe. On the first 2 d the roll was fortified with 3 mg Fe labelled with 59Fe; on day 3 the roll was fortified with 100 mg Fe labelled with 55Fe. The serum Fe response to the 100 mg dose was followed for 6 h. Fe absorption was measured by whole-body counting. High correlations were seen between the absorption of Fe and the change in serum Fe after 100 mg Fe (r2 0.94, P<0.001), between the absorption from 3 mg and 100 mg Fe (r2 0.88, P<0.001), and between the absorption from 3 mg Fe and change in serum Fe after 100 mg Fe (r2 0.90, P<0.001). This strengthens the evidence that it is possible to use the change in serum Fe as a measure of Fe absorption, e.g. when establishing the relative bioavailability for Fe powders. The results also imply that the induced serum Fe increase following 100 mg Fe added to a food could predict the Fe absorption of a small dose of Fe added to the same meal.

Hepcidin, interleukin-6 and hematological iron markers in males before and after heart surgery.

Anemia of inflammation in patients with acute or chronic acute-phase activation is a common clinical problem. Hepcidin is a peptide shown to be the principal regulator of the absorption and systemic distribution of iron. Main inducers of hepcidin are iron overload, hypoxia and inflammation, where the latter has been linked to hepcidin via increased interleukin-6 (IL-6). This article addresses the impact and time course of postoperative acute-phase reaction in humans following heart surgery on prohepcidin, hepcidin, hematological markers and IL-6 concentrations. Serum concentrations of prohepcidin, hepcidin, IL-6 and hematological iron parameters were studied in five male patients without infection before and after heart surgery. This study, which is the first to report the impact on serum hepcidin and serum prohepcidin concentrations in patients following surgery, clearly demonstrates the induction of hypoferremia due to the postoperative acute-phase reaction. Significant changes were seen for serum iron concentration, transferrin saturation, total iron binding capacity and hemoglobin concentration. A significant increase in ferritin concentration was seen 96-144 h postoperatively. Additionally, there were significant alterations in both serum hepcidin after 96-144 h and serum prohepcidin after 48 h compared with preoperative values. Serum prohepcidin decreased, whereas serum hepcidin increased. In conclusion, changes in serum prohepcidin were followed by an increase in serum hepcidin. This speaks in favor of a chain of action where proteolytic trimming of serum prohepcidin results in increased serum hepcidin. However, hypoferremia appeared prior to the changes in serum prohepcidin and serum hepcidin.

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 Göteborg 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.

The importance of bioavailability of dietary iron in relation to the expected effect from iron fortification

Background:The most common method of combating iron deficiency is iron fortification, especially in developing countries. However, few studies have shown a significant effect on iron status following iron fortification of low bioavailability diets.Objective:To investigate how iron fortification and dietary modifications affect iron absorption and rates of changes in iron stores.Methods:Research has made it possible to predict both iron absorption and the effects of iron fortification and diet modifications on iron stores using recently developed algorithms. Iron absorption and rate of change in iron stores were calculated from nine diets representing a broad range of iron bioavailability and iron contents. The calculations were related to the main target group for iron fortification, that is, women of reproductive age having empty stores but normal haemoglobin concentrations.Results:As the only measure, iron fortification has practically no effect on iron status if the original diet has low bioavailability. However, after dietary modifications such a diet shows a positive effect on iron stores. The combined action of fortification (6 mg/day) and modest bioavailability changes in a low bioavailability diet results approximately in 40 and 70% greater increases in iron stores than through iron fortification or dietary modification alone.Conclusions:It is difficult to achieve good effects on iron status from iron fortification as the only measure if the diet has low bioavailability. Both dietary modifications as well as iron fortification are required to improve effectively the iron status of a population.

Serum iron concentration as a tool to measure relative iron absorption from elemental iron powders in man.

Objective: To present a new method for measuring the relative bioavailability (RBV) of commercial elemental iron powders by investigating induced changes of serum iron concentration (S‐Fe) in relation to ferrous sulphate (FeSO4). Earlier studies have shown that in a group of subjects there is good agreement between the increase in S‐Fe and the amount of iron absorbed from a simple iron salt as FeSO4. Methods: The study included two groups of male blood donors (n=2×16 subjects) who were served three meals with an interval of approximately nine weeks between each one. In one group the meal was fortified with reduced iron, ferrous sulphate or no iron at all. In the other group the meal was fortified with electrolytic iron, ferrous sulphate or no iron. The S‐Fe increase was followed for 6 h. Studying the non‐iron meals was necessary so that the basal diurnal variation in the S‐Fe during the six hours could be measured and subtracted. Results: The mean S‐Fe increase calculated as the area under the curve (AUC) from the reduced iron (RBV=0.43) and the electrolytic iron (RBV=0.73) differed significantly from the AUC following FeSO4 (p=0.002 and p=0.021, respectively). The difference between the reduced and the electrolytic iron was also statistically significant (p=0.036). Conclusion: Measuring increases in S‐Fe could be a reliable and simple method to determine the RBV in comparative studies of elemental iron powders in relation to FeSO4.

Heme iron-based dietary intervention for improvement of iron status in young women.

OBJECTIVE Conventional iron deficiency treatment with pharmacologic iron doses often causes side effects. Heme iron has high bioavailability and a low capacity to cause gastrointestinal side effects. This study investigated the possibility of using heme iron in the form of blood-based crisp bread as a diet-based treatment program to improve the iron status of women of reproductive age. METHODS In a 12-wk intervention study, 77 women (mean age 24 y) were assigned to one of four groups: blood-based crisp bread (35 mg of iron [Fe], 27 mg of which was heme Fe), iron supplementation consisting of 35 mg of non-heme iron/day (Fe35), iron supplementation consisting of 60 mg of non-heme iron/day (Fe60), and controls (iron-free tablets). RESULTS Body iron increased significantly in the crisp bread group by a median of 2.7 mg/kg (interquartile range 3.1, n = 18), in the Fe35 group by 2.7 mg/kg (interquartile range 2.8, n = 11), and in the Fe60 group by 4.1 mg/kg (interquartile range 3.6, n = 13), whereas no change was observed in the control group. No statistically significant difference in iron status increase was observed between the crisp bread group compared with the two iron-supplemented groups. CONCLUSION Dietary-based treatment containing heme iron has few side effects and can be used efficiently to improve the iron status of women of reproductive age.

Probiotic strain Lactobacillus plantarum 299v increases iron absorption from an iron-supplemented fruit drink: a double-isotope cross-over single-blind study in women of reproductive age.

Iron deficiency is common, especially among young women. Adding probiotics to foods could be one way to increase iron absorption. The aim of this study was to test the hypothesis that non-haem iron absorption from a fruit drink is improved by adding Lactobacillus plantarum 299v (Lp299v). Iron absorption was studied in healthy women of reproductive age using a single-blind cross-over design in two trials applying the double-isotope (55Fe and 59Fe) technique. In Trial 1, iron absorption from a fruit drink containing 109 colony-forming units (CFU) Lp299v was compared with that from a control drink without Lp299v. Trial 2 had the same design but 1010 CFU were used. The test and control drinks contained approximately 5 mg of iron as ferrous lactate and were labelled with 59Fe (B) and 55Fe (A), respectively, and consumed on 4 consecutive days in the order AABB. Retention of the isotopes was measured with whole-body counting and in blood. Mean iron absorption from the drink containing 109 CFU Lp299v (28·6(sd 12·5) %) was significantly higher than from the control drink (18·5(sd 5·8) %), n 10, P<0·028). The fruit drink with 1010 CFU Lp299v gave a mean iron absorption of 29·1(sd 17·0) %, whereas the control drink gave an absorption of (20·1(sd 6·4) %) (n 11, P<0·080). The difference in iron absorption between the 109 CFU Lp299v and the 1010 CFU Lp299v drinks was not significant (P=0·941). In conclusion, intake of probiotics can increase iron absorption by approximately 50 % from a fruit drink having an already relatively high iron bioavailability.

The interaction between calcium and iron: choice of methodology is crucial for outcome and conclusions.

The following comments relate to the interesting article by Gaitán et al. (1) in which they conclude that calcium does not inhibit the absorption of nonheme iron at single doses <800 mg Ca. This dose-response study reports on a very important topic, since, as also pointed out by the authors, both iron and calcium are essential nutrients. However, the study’s results are compromised by a methodological weakness that may affect the interpretation of the results. In their study design Gaitán et al. (1) assessed iron absorption from single servings using radioisotope-labeled iron (5 mg) administered with increasing doses of calcium. Our comment is based on the fact that there is a well-known and considerable dayto-day variation in iron absorption within the same subject, which compromises assessment of iron absorption from single-servings (2, 3). As a consequence, the majority of studies using iron radioisotopes in the evaluation of iron absorption assess the mean value following the administering of the study meal (or drink) on two consecutive days. Nevertheless, Gaitán et al. (1) assessed iron absorption from single servings.When administering the iron dose on two consecutive days and calculating the mean absorption from those days, the influence of the day-to-day variation in iron absorption is markedly reduced. Björn-Rasmussen et al. (3) observed that nonheme iron absorption from two identical meals (total iron content 3.0 mg/meal) served on two consecutive days and labeled with two different iron isotopes (Fe and Fe) had a coefficient of variation (CV) of 36%between the two absorption measurements. Also Brise et al. (2) reported a CV of 35%, when using a similar design. The day-to-day variation stresses the importance of giving iron in repeated doses. Otherwise it is difficult to detect an actual difference in iron absorption from two different servings, as was the case in Gaitán et al. (1) where despite a mean difference of 30% in iron absorption when serving no calcium vs. serving 800 mg Ca, the difference was not significant (P 5 0.09). The inability to statistically confirm such a clinically important difference displays a methodological weakness, which most likely can be attributed to the known day-to-day variation in iron absorption and the fact that only single servings were studied. The choice of research method is crucial in determining the conclusions that can be drawn from the study. Thus, Gaitán et al. (1) should have considered the known variation in iron absorption. To draw accurate conclusions, in this case about dose-dependent inhibition of absorption, it is necessary to use the methods that have the necessary precision and accuracy.

Freeze-dried Lactobacillus plantarum 299v increases iron absorption in young females—Double isotope sequential single-blind studies in menstruating women

Background The probiotic strain Lactobacillus plantarum 299v has earlier been shown to increase iron absorption when added to foods. However, it is not known if the same probiotic strain in a freeze-dried format included in a capsule increases the iron absorption. Objective The aim of this study was to test the hypotheses that non-heme iron absorption from a light meal is promoted by a simultaneous intake of freeze-dried Lactobacillus plantarum 299v (Lp299v, DSM 9843). Study design With a single blinded placebo controlled sequential design, iron absorption from a light breakfast meal administered with or without capsules containing 1010 cfu freeze-dried Lp299v was studied in healthy female volunteers of fertile age. The methodology used was a double isotope technique (59Fe and 55Fe). Two studies were performed using the same protocol. Results In study 1, the absorption of iron from a meal without Lp299v was found to be 17.4 ± 13.4%, and from an identical meal with Lp299v was found to be 22.4 ± 17.3% (mean ± SD). This difference was statistically significant (p = 0.040, n = 14). In study 2, the absorption of iron from a meal without Lp299v was found to be 20.9 ± 13.1%, and from an identical meal with Lp299v found to be 24.5 ± 12.0% (mean ± SD, n = 28), which again was statistically significant (p = 0.003). Conclusion Freeze-dried Lp299v enhances the absorption of iron when administered together with a meal with a high iron bioavailability. Trial registration ClinicalTrials.gov Identifier: NCT02131870

Is cord blood hepcidin influenced by the low-grade acute-phase response occurring during delivery? : A small-scale longitudinal study

Abstract Aim: To measure serum hepcidin in late pregnancy and in cord blood, and to analyze relationship between hepcidin, interleukin-6, and biomarkers of fetal iron status. Materials and methods: Data from 15 uncomplicated singleton pregnancies were analyzed longitudinally in trimester 3 (T3) and at birth. Results: In T3, S-ferritin (median 14 µg/L) and transferrin (median 4.0 g/L) indicated low iron status, whereas the median soluble transferrin receptor (sTfR) was 4.0 mg/L, i.e. within the reference interval. Median T3 S-hepcidin was 7.8 ng/mL. Later on in cord blood, ferritin concentration (180 µg/L) were significantly higher, transferrin concentration (1.8 g/L) were significantly lower, and both sTfR (4.7 mg/L) and S-hepcidin concentrations (30.5 ng/mL) were significantly higher than maternal T3 concentrations. At the same time, cord blood interleukin-6 indicated an activated acute-phase reaction. In T3, after logarithmic transformation, there was a significant correlation between S-hepcidin and both S-ferritin (r = 0.691) and sTfR (r = −0.825). There was also a significant correlation between S-ferritin and both sTfR (r = −0.729) and transferrin (r = 0.549) in T3. Conclusions: Although S-ferritin, S-hepcidin, and sTfR were correlated during pregnancy, these relationships were not apparent in umbilical cord blood. Further, cord blood interleukin-6 indicated an activated acute-phase response, and sTfR, which is known to be unaffected by inflammation, indicated a low iron status in cord blood. Thus, instead of representing an enhanced iron status, the data appear to suggest that hepcidin and ferritin in cord blood may be influenced by the low-grade acute-phase response that occurs during delivery.