Total Heme Iron Research Articles

Technological properties and selected safety aspects of different cuts of organic and conventional pork

SummaryThe present study aimed at evaluating and comparing technological quality and selected safety aspects of commercial organic and conventional pork cuts. The technological value was determined on the basis of pH value, centrifugation loss, cooking loss, drip loss, colour parameters (as measured with L*a*b* system), total heme pigments and total heme iron. The meat safety was verified based on the content of nitrate, nitrite, cadmium, lead, total microbial count, number of Listeria monocytogenes and Salmonella. The results indicated that organic meat had higher content of heme pigments and heme iron than conventional meat. The rearing system had no effect on the lightness. The organic loins and shoulders were redder and yellower than conventional ones. Neither organic nor conventional meat cuts were contaminated by pathogenic bacteria and nitrite/nitrate residues. Legal requirements concerning cadmium content were met for all the tested samples, whereas concerning lead only for organic loins.

Onboard Evaluation of Variable Water Flow and Recirculation Effects on Bleeding of Atlantic Cod (Gadus morhua).

The aim of the study was to explore the effects of different design variables in the onboard bleeding process of cod on bleeding efficiency and the resulting product quality. A time- and flow-controlled process was used to create variable bleeding conditions for whole gutted cod onboard a wet-fish trawler. Two main design variables influencing the bleeding process are the pump flow recirculation (PFR) and the water replacement ratio (WRR); they were studied in five different combinations (groups). The effects of different bleeding conditions were evaluated by measurements of free fatty acids (FFAs), phospholipids (PLs), and total heme iron (HI) content during freezer storage for up to four months. The results for PL content and the regression model indicate that the enzyme activity in the fish muscle is lower in cases where PFR exerts greater influence in the bleeding process than WRR. The effects of successful blood removal also seem to be most noticeable after one month of freezer storage, rather than in fresh cod after seven days or after four months of simulated frozen food-chain storage. The study indicates that, with the bleeding medium to fish ratio of around 3:1 and enough WRR (over 100% replacement in 20 min), the PFR becomes the limiting design parameter regarding efficient blood removal and should be at least 10% of the tank volume per minute to ensure enough recirculation and flow of water in the bleed-out tanks.

Statistical Considerations Are Necessary in Assessing Associations between Micronutrient Intake and Times to Clinical Events

Dear Editor, Recently, de Oliveira Otto et al. (1) studied the associations of incidence of three clinical conditions with intake of certain micronutrients. The authors used Cox regression analysis to model times to metabolic syndrome (MetS), Type 2 diabetes, and cardiovascular disease (CVD) given baseline characteristics, including nutrient intake based on responses to an FFQ. To test for linear trends between nutrient intake and the outcomes, they treated intakes as continuous variables using the medians for each quintile. However, the baseline nutrient intake and follow-up biological measurements may be subject to substantial error. Mismeasured covariates in Cox models may lead to biased estimates, and hence, misleading inference (2,3). Statistical literature considers traditional methods that fail to account for covariate error as “naive” and recommends several methods for modeling of time-to-event data and covariates measured with error (4). Two-stage joint-modeling methods such as those used by Dafni and Tsiatis (3) model the covariate process using a mixed effects model and the time-to-event outcome by a Cox model based on the predicted covariate values. Many are approximate, requiring regression calibration (RC). Tsiatis and Davidian (5) propose a conditional score estimator that relaxes the assumption of normal random effects. Others capture extraneous variability via latent variables or latent classes, which may be useful for heterogeneous populations with potentially different baseline hazards. In the Nutrition Prevention of Cancer trials, Lin et al. (6) use latent class joint-modeling to investigate the association between selenium and prostate cancer. Simulation extrapolation (SIMEX) has also been used recently. RC is preferable to SIMEX when there is substantial measurement error, but it is not robust to misspecification of the measurement error distribution (7,8). When measurement error is understated, RC underestimates risk; when measurement error is overstated, RC overestimates risk (7). Two-stage joint models may be implemented in software such as SAS using standard procedures for mixed models and Cox models (4). Lin et al. (6) are willing to provide code in S Plus. Joint models are generally less biased and more powerful than naive approaches (3,5). Therefore, some conclusions by de Oliveira Otto et al. (1) may be suspect. Random measurement error, which biases estimates toward the null, is especially acute in nutritional epidemiological studies. Joint modeling may illuminate significant associations that were biased toward the null in the study by de Oliveira Otto et al. (1). Examples include the associations in model 2 of MetS with vitamin E and zinc as well as of CVD with zinc from red meat, adjusted for total heme iron. There may also be bias away from the null. A covariate that should be highly predictive of the event may carry residual error that artificially inflates the effect of another covariate. Consequently, the reported significant associations in the study by de Oliveira Otto et al. (1) may in fact be spurious and nonsignificant in a joint model. Dafni and Tsiatis (3) simulated an HIV treatment independent of AIDS progression after adjusting for CD4 counts, a highly variable biomarker predictive of the event time. Estimates ignoring error in CD4 counts were biased away from the null, incorrectly highlighting a treatment effect. Analyzing the data in the study by de Oliveira Otto et al. (1) with methodology that accounts for covariate measurement error constitutes better statistical practice and would strengthen the validity of the study.

Non-heme Iron as Ferrous Sulfate Does Not Interact with Heme Iron Absorption in Humans

The absorption of heme iron has been described as distinctly different from that of non-heme iron. Moreover, whether heme and non-heme iron compete for absorption has not been well established. Our objective was to investigate the potential competition between heme and non-heme iron as ferrous sulfate for absorption, when both iron forms are ingested on an empty stomach. Twenty-six healthy nonpregnant women were selected to participate in two iron absorption studies using iron radioactive tracers. We obtained the dose-response curve for absorption of 0.5, 10, 20, and 50mg heme iron doses, as concentrated red blood cells. Then, we evaluated the absorption of the same doses, but additionally we added non-heme iron, as ferrous sulfate, at constant heme/non-heme iron molar ratio (1:1). Finally, we compare the two curves by a two-way ANOVA. Iron sources were administered on an empty stomach. One factor analysis showed that heme iron absorption was diminished just by increasing total heme iron (P < 0.0001). The addition of non-heme iron as ferrous sulfate did not have any effect on heme iron absorption (P = NS). We reported evidence that heme and non-heme iron as ferrous sulfate does not compete for absorption. The mechanism behind the absorption of these iron sources is not clear.

Changes in the forms of iron and in concentrations of taurine, carnosine, coenzyme Q 10, and creatine in beef longissimus muscle with cooking and simulated stomach and duodenal digestion

Longissimus muscle samples from 31 Angus-cross heifers finished on either a high-concentrate feedlot diet or pasture were used to evaluate the effects of cooking (71 °C) on the concentration and forms of iron in the meat, and also on concentrations of the bioactive compounds taurine, carnosine, coenzyme Q 10, creatine and creatinine. For a sub-sample of 15 the effects of pepsin and pancreatin digestion were assessed. For iron, cooking resulted in some overall loss together with a major change from soluble haem and non-haem iron to the insoluble forms, but solubility was regained to a significant extent following digestion. Total haem iron percentage, however, decreased at each step from an initial 88% to a final 61% of total iron. For the bioactive compounds, cooking led to a reduction in taurine, carnosine, coenzyme Q 10, and creatine. The effects of digestion on the bioactive compounds varied. No clear differences were shown in the way in which beef from pasture-finished and feedlot-finished cattle responded to cooking and digestion.

Muscle profiling: Characterizing the muscles of the beef chuck and round

To fully characterize properties of the muscles of the beef chuck and round, and to reveal potential opportunities to upgrade the value, 39 different muscles were dissected from 142 beef carcasses differing in carcass weight, yield grade, and quality grade. Numerous physical and chemical properties of the muscles were determined. Muscle effects were observed for all traits (objective color, expressible moisture, proximate composition, emulsion capacity, pH, total collagen content, total heme-iron concentration, and Warner–Bratzler shear force). USDA quality grade generally had the most effect on muscle traits, with carcass weight and yield grade having lesser effects. These muscle profile data will allow for more informed decisions to be made in the selection of individual muscles from the beef chuck and round for the production of value-added products.

Dietary iron intake and blood donations in relation to risk of type 2 diabetes in men: a prospective cohort study

Excessive iron stores may promote insulin resistance and lead to the development of type 2 diabetes. However, prospective data relating iron intake and blood donations (determinants of body iron stores) to diabetes incidence are limited. We examined iron intake and blood donations in relation to the incidence of type 2 diabetes. We followed men aged 40-75 y who participated in the Health Professionals' Follow-up Study; were free of diabetes, cardiovascular disease, and cancer in 1986; and provided dietary data (n = 38 394). Of those participants, 33 541 also provided a history of blood donation during the past 30 y in 1992. During 12 y of follow-up, we ascertained 1168 new cases of type 2 diabetes. After adjustment for age, body mass index, and other diabetes risk factors, total iron intake was not associated with the risk of type 2 diabetes. Intakes of total heme iron [multivariate relative risk (RR) for extreme quintiles: 1.28; 95% CI: 1.02, 1.61; P for trend = 0.045] and of heme iron from red meat (RR: 1.63; 1.26, 2.10; P for trend < 0.001) were associated with an increased risk. However, heme-iron intake from sources other than red meat was not associated with diabetes risk (RR: 0.99; 0.81, 1.22). No significant associations were found between blood donation and the risk of type 2 diabetes. Heme-iron intake from red meat sources is positively associated with the risk of type 2 diabetes. Total iron intake, heme-iron intake from non-red meat sources, and blood donations are not related to the risk of type 2 diabetes.

High specific activity heme-Fe and its application for studying heme-Fe metabolism in Caco-2 cell monolayers.

Heme-Fe is an important source of dietary iron in humans. Caco-2 cells have been used extensively to study human iron absorption with an emphasis on factors affecting nonheme iron absorption. Therefore, we examined several factors known to affect heme iron absorption. Cells grown in bicameral chambers were incubated with high specific activity [59Fe]heme alone or with 1% globin, BSA, or fatty acid-free BSA (BSA-FA) to examine the effect of protein source on absorption. Heme iron absorption was enhanced by globin and inhibited by BSA and BSA-FA. Absorption of heme iron in cells pretreated for 7 days with serum-free medium containing 1, 25, 50, or 100 microM Fe was higher in the 1-microM-Fe pretreatment group than in all other groups (P < 0.05), showing an effect of iron status. Increased heme concentrations resulted in decreased percent absorbed but increased total heme iron absorption and increased transport rate across the basolateral membrane. Finally, cells treated with 10 microM CdCl2, which induces heme oxygenase, demonstrated higher absorption of [59Fe]heme than control cells (P < 0.05). Our results from Caco-2 cells are in agreement with human studies and make this a promising model for examining intestinal heme iron absorption.

Haematology and iron status of the egyptian fruit bat, rousettus aegyptiacus

1. 1. Haematological values and iron status of wild and captive fruit bats ( Rousettus aegyptiacus) were determined. 2. 2. Plasma iron concentrations were 175μg/dl in wild males, and 286–316 μg/dl in captive bats. 3. 3. Total splenic stores were small (around 100 μg) in relation to hepatic stores (3 mg) and total haem iron (2.6 mg). 4. 4. Haemoglobin levels, red cell counts and haematocrits were unusually high and mean corpuscular volumes low. 5. 5. Lactating wild bats showed no deficits in iron status or in haematological values. 6. 6. It is concluded that the ascorbic acid content of fruit, together with the bats' high food requirement, has ensured an ample iron supply in this vegetarian species.