Low Iron Bioavailability Research Articles

Effect of germination of finger millet on nutritional value of foods and effect of food supplement on nutrition and anaemia status in Tanzania children

Inadequate dietary intake, often combined with an infection can lead to malnutrition that often manifest as growth failure or deficiency of essentials nutrients including iron leading to iron deficiency anaemia. In an effort to investigate diet in relation to nutrition status of children, diet and dietary intake were investigated in rural Tanzania. The effect of germination of finger millet based food recipe on its nutritional value was evaluated. The food consisted of finger millet flour, kidney beans, ground peanuts and dried mangoes at predetermined proportions of 75:10:10:5 respectively. Dietary habits of young children were investigated and effects of a fortified food supplement and the cereal based recipe on nutrition status of children were investigated. The two diets were then supplemented to children for 6 months and changes on anaemia and anthropometrical indices of children were evaluated at follow up periods. To assess anaemia and iron status, haemoglobin (Hb), haematocrit (Hct), erythrocyte protoporphyrin (EP) and serum ferritin (SF); and weights and heights were measured to assess growth. A significant improvement in nutrient density was noted in processed cereals. Bioavailability of iron in cereal based diet increased from 0.75 +/- 18 to 1.25 +/- 41 mg/100 g (P = 008), viscosity was significantly raised by 12% and phytate concentration was reduced from 4.5 +/- 0.5 to 4.1 +/- 0.5 mg/g (P = 0.03). Significantly lower intake of iron was observed in schoolchildren with Hb < 11.5 g/dl) compared to those who were normal. Total iron intake was 22+/- 7 and 27 +/- 13 mg/day, respectively (P < 0.05). There was a significant correlation between iron intake and serum ferritin (r = 0.233, P < 0.05). After six months of supplementing children with the fortified beverage a significantly larger increase in haemoglobin concentration was shown in the fortified group than in the non-fortified group (a difference of 6.2 versus 3.2 g/dl respectively). Supplementing infants with the germinated cereal based food supplement showed a general improvement on Hb status and growth that was not significantly different to that in the control group (P > 0.05). In conclusion, consumption of foods with low iron bioavailability is a major cause of anaemia. Germination improves the nutritional value of foods however there is need to fortify such processed foods for infant feeding.

Efeito da fortificação de farinhas com ferro sobre anemia em pré-escolares, Pelotas, RS

Iron fortification of flour has been sanctioned by the Brazilian government since 2004. The objective of the study was to assess the impact of flour fortification on hemoglobin level in children under six. A time-series study was carried out in Pelotas, southern Brazil, consisting of three assessments at a 12-month interval. In May 2004, before flour fortification, hemoglobin measurements were obtained in a probabilistic sample of 453 children. Twelve and 24 months later, samples of 923 and 863 children were studied, respectively. The three groups studied were comparable in terms of demographic and socioeconomic characteristics. At baseline, mean hemoglobin was 11.3 +/- 2.8 g/dL. In the post-fortification period, means were 11.2 +/- 2.8 (at 12 months) and 11.3 +/- 2.5 g/dL (at 24 months), with no statistically significant difference among the three time periods studied (p=0.16). Fortification had no effect on hemoglobin levels of the children studied. This finding could be partially due to inadequate flour intake and/or low bioavailability of dietary iron.

From Harvest to Health: Challenges for Developing Biofortified Staple Foods and Determining Their Impact on Micronutrient Status

The use of conventional breeding techniques and biotechnology to improve the micronutrient quality of staple crops is a new strategy to address micronutrient deficiencies in developing countries. This strategy, referred to as "biofortification," is being developed and implemented through the international alliance of HarvestPlus to improve iron, zinc, and vitamin A status in low-income populations. The objective of this paper is to review the challenges faced by nutritionists to determine and demonstrate the ability of biofortified crops to have an impact on the nutritional and health status of target populations. We reviewed available published and unpublished information that is needed to design and evaluate this strategy, including issues related to micronutrient retention in staple foods, micronutrient bioavailability from plant foods, and evidence for the efficacy of high-micronutrient-content staple foods to improve micronutrient status. Further information is needed on the retention of micronutrients in staple foods, in particular of provitamin A carotenoids, when stored and prepared under different conditions. The low bioavailability of iron from staple foods and the ability to demonstrate an impact on zinc status are specific challenges that need to be addressed. In target countries, infections and other micronutrient deficiencies may confound the ability to affect micronutrient status, and this must be taken into account in community-based studies. Information to date suggests that biofortification has the potential to contribute to increased micronutrient intakes and improved micronutrient status. The success of this strategy will require the collaboration between health and agriculture sectors.

Fermentation and Lactic Acid Addition Enhance Iron Bioavailability of Maize

Maize is one of the most important cereal crops for human consumption, yet it is of concern due to its low iron bioavailability. The objective of this study was to determine the effects of processing on iron bioavailability in common maize products and elucidate better processing techniques for enhancing iron bioavailability. Maize products were processed to represent different processing techniques: heating (porridge), fermentation (ogi), nixtamalization (tortillas), and decortication (arepas). Iron and phytate contents were evaluated. Iron bioavailability was assessed using the Caco-2 cell model. Phytate content of maize products was significantly reduced by decortication (25.6%, p = 0.003) and nixtamalization (15%, p = 0.03), and iron content was reduced by decortication (29.1%, p = 0.002). The relative bioavailability (RBA, compared to 100% bioavailability of porridge with FeSO4) of ogi was significantly higher than that of other products when fortified with FeSO4 (p < 0.001) or reduced iron (p < 0.001). Addition of lactic acid (6 mg/g of maize) significantly increased iron solubility and increased bioavailability by about 2-fold (p < 0.01), especially in tortillas. The consumer panel results showed that lactic acid addition does not significantly affect the organoleptic characteristics of tortillas and arepas (p = 0.166 and 0.831, respectively). The results suggest that fermentation, or the addition of small amounts of lactic acid to unfermented maize products, may significantly improve iron bioavailability. Lactic acid addition may be more feasible than the addition of highly bioavailable but expensive fortificants. This approach may be a novel means to increase the iron bioavailability of maize products to reduce the incidence of iron deficiency anemia.

Kaempferol in Red and Pinto Bean Seed ( Phaseolus vulgaris L.) Coats Inhibits Iron Bioavailability Using an In Vitro Digestion/Human Caco‐2 Cell Model

Four different colored beans (white, red, pinto and black beans) were investigated for factors affecting iron bioavailability using an in vitro digestion/human Caco-2 cell model. Iron bioavailability from whole beans, de-hulled beans and their hulls was determined. The results show that white beans contained higher levels of bioavailable iron compared to red, pinto and black beans. These differences in bioavailable iron were not due to bean-iron and bean-phytate concentrations. Flavonoids in the colored bean hulls were found to be contributing to the low bioavailability of iron in the non-white colored beans. The flavonoids, kaempferol and astragalin (kaempferol-3-O-glucoside), were identified in red and pinto bean hulls via HPLC and mass spectrometry. Kaempferol, but not astragalin, was shown to inhibit iron bioavailability. Treating in vitro white bean digests with 40, 100, 200, 300, 400, 500, and 1000 μM kaempferol significantly inhibited iron bioavailability (e.g., 15.5%, 40 μM and 62.8%, 1000 μM) in a concentration dependent fashion. Thus, seed coat kaempferol was identified as a potent inhibitory factor affecting iron bioavailability in the red and pinto beans studied. Results comparing the inhibitory effects of kaempferol, quercitrin and astragalin on iron bioavailability suggest that the 3′,4′-dihydroxy group on the B-ring in flavonoids is contributing to the lower iron bioavailability.

Childhood anemia - A study in tribal area of Mohana block in Orissa

Background : Anemia is widely prevalent in India and affects both sexes and all age group. Although the National Anemia Prophylaxis Programme (NAPP) has been set up in all states of the country since 1970, the benefits have not yet been appreciated in the target population. Objective : 1. To assess the prevalence of anemia and its severity in tribal children. 2. To find out age & sex wise distribution of Hb level in these children. 3. To explore different underlying factors of development of anemia. Methods : The present study is a cross sectional study conducted in tribal villages of Mohana block in Gajapati district of Orissa. A total of 599 tribal children in the age group 6 month - 14 years were recruited from August 2004 to February 2005. The study variables included age, sex, Hb level, food consumption and clinicoepidemiological factors which were analysed by simple proportion and Z test. Results : About 94% of under five children were found to be anemic and 8.8% of them were severely anemic. Almost all children of age group 5-14 years were anemic, amongst them 59.4% were moderately anemic and 5. 4% were severely anemic. There is no significant difference in mean Hb level between male and female in both the age groups. It was significantly more in the age group of 5-14 years. About 94% were taking food of low iron bioavailability. Pallor was found in 33.6% and H/O irregular fever in 28.7% of children. 26.9% children had splenomegaly. Only 2.3% children had taken IFA supplementation in last one year. Conclusions : Anemia is a major health problem in tribal children. Reorientation of primary health care functionaries to cover the children under NNAPP with the help of ICDS workers and school authorities.

Kaempferol in Red and Pinto Bean Seed (Phaseolus vulgaris L.) Coats Inhibits Iron Bioavailability Using an in Vitro Digestion/Human Caco-2 Cell Model

Four different colored beans (white, red, pinto, and black beans) were investigated for factors affecting iron bioavailability using an in vitro digestion/human Caco-2 cell model. Iron bioavailability from whole beans, dehulled beans, and their hulls was determined. The results show that white beans contained higher levels of bioavailable iron compared to red, pinto, and black beans. These differences in bioavailable iron were not due to bean-iron and bean-phytate concentrations. Flavonoids in the colored bean hulls were found to be contributing to the low bioavailability of iron in the non-white colored beans. White bean hulls contained no detectable flavonoids but did contain an unknown factor that may promote iron bioavailability. The flavonoids, kaempferol and astragalin (kaempferol-3-O-glucoside), were identified in red and pinto bean hulls via HPLC and MS. Some unidentified anthocyanins were also detected in the black bean hulls but not in the other colored bean hulls. Kaempferol, but not astragalin, was shown to inhibit iron bioavailability. Treating in vitro bean digests with 40, 100, 200, 300, 400, 500, and 1000 microM kaempferol significantly inhibited iron bioavailability (e.g., 15.5% at 40 microM and 62.8% at 1000 microM) in a concentration-dependent fashion. Thus, seed coat kaempferol was identified as a potent inhibitory factor affecting iron bioavailability in the red and pinto beans studied. Results comparing the inhibitory effects of kaempferol, quercitrin, and astragalin on iron bioavailability suggest that the 3',4'-dihydroxy group on the B-ring in flavonoids contributes to the lower iron bioavailability.

Effect of retinol on iron bioavailability from Iranian bread in a Caco-2 cell culture model

Objective Iron and vitamin A deficiencies are among the most prevalent nutritional problems. There are no data on iron bioavailability in Iran. In addition, interaction of vitamin A with iron bioavailability is not well documented, so we determined iron bioavailability from the most widely consumed food in Iran, lavash bread, and the effect of vitamin A on this bioavailability. Methods In vivo human studies for determining iron bioavailability are cumbersome, time consuming, and costly to perform, so we used an in vitro model in Caco-2 cells. Bread samples were digested with or without vitamin A (10 μg/1.0 g of dried bread). We used an iron solution containing vitamin C as a positive control. Iron absorption was measured using 59FeCl 3. Bioavailability was defined as the percentage of radiolabeled iron taken up and transferred by Caco-2 cells after 1.5 h of incubation. Experiments were carried out two to four times. Results Mean ± standard deviations for iron bioavailability in bread samples digested without or with additional vitamin A and in controls were 2.53 ± 1.55%, 6.62 ± 3.40%, and 20.80 ± 2.30%, respectively ( P < 0.001). Vitamin A caused a 2.62-fold increase in iron absorption from bread samples. Conclusions Iranian lavash bread has low iron bioavailability, but this can be increased by vitamin A supplementation. Increasing vitamin A intake can be considered as a method for increasing iron bioavailability, thus combating iron and vitamin A deficiencies simultaneously.

Kaempferol and Quercitrin Effect on Iron Bioavailability in White and Colored Bean Seeds ( Phaseolus vulgaris L.) Using an In Vitro Digestion/Human Caco‐2 Cell Model

Four different colored commercial beans (white, red, pinto and black beans) were investigated for factors affecting iron bioavailability. An in vitro digestion/human Caco-2 cell model was used to study the polyphenols from whole beans, de-hulled beans and their hulls and assess iron bioavailability. The results show that white beans contained higher levels of bioavailable iron compared to colored beans. These differences in bioavailable iron were not due to bean-iron and bean-phytate levels. Flavonoids in the colored bean hulls were found to be contributing to the low bioavailability of iron in the colored beans. White bean hulls contained no detectible flavonoids. The flavonoids, kaempferol and quercitrin, were identified in red and pinto bean hulls via HPLC. Some unidentified anthocyanins were also detected in the black bean hulls but not in the other colored bean hulls. Kaempferol and quercitrin were shown to inhibit iron bioavailability, with quercitrin being more inhibitory than kaempferol. Treatment of in vitro digestates with kaempferol and quercitrin inhibited iron bioavailability in a concentration dependent fashion. Thus, these flavonoids were found to be the main inhibitory factors affecting iron bioavailability in the red and pinto beans studied.

Inhibitory effects of dietary calcium on the initial uptake and subsequent retention of heme and nonheme iron in humans: comparisons using an intestinal lavage method

Calcium is the only reported dietary inhibitor of both heme- and nonheme-iron absorption. It has been proposed that the 2 forms of iron enter a common pool in the enterocyte and that calcium inhibits the serosal transfer of iron into blood. We aimed to ascertain whether the inhibitory effect of calcium occurs during initial mucosal uptake or during serosal transfer and to compare the serosal transfer of heme and nonheme iron, which should not differ if the 2 forms have entered a common mucosal iron pool. Whole-gut lavage and whole-body counting were used to measure the initial uptake (8 h) and retention (2 wk) of heme and nonheme iron with and without a calcium supplement (450 mg). Two experiments tested basal meals with low iron bioavailability and 360 mg Ca (n = 15) or with high iron bioavailability and 60 mg Ca (n = 12). Added calcium reduced the initial uptake of heme iron by 20%, from 49% to approximately 40% from both meals (P = 0.02), and reduced the total iron absorbed from the low- and high-bioavailability meals by approximately 25% [from 0.033 to 0.025 mg (P = 0.06) and from 0.55 to 0.40 mg (P < 0.01), respectively]. Calcium did not affect the serosal transfer of either form of iron. Calcium supplementation reduced heme and total iron without significantly affecting nonheme-iron absorption, regardless of meal bioavailability. Calcium inhibited the initial mucosal uptake rather than the serosal transfer of heme iron. Differences in serosal transfer indicate that heme and nonheme iron did not enter a common absorptive pool within 8 h after a meal.

Biodisponibilidade de ferro do açaí (Euterpe oleracea Mart.) e da farinha de mandioca fortificada com ferro em ratos

OBJETIVO: Este estudo teve como objetivo avaliar a biodisponibilidade do ferro do açaí (Euterpe oleracea Mart.) e da farinha de mandioca fortificada com ferro, utilizando o método de depleção e repleção de hemoglobina em ratos. MÉTODOS: No período de depleção, durante a lactação, as ratas (Rattus novergicus) e seus filhotes receberam ração à base de caseína (American Institute of Nutrition - 93G), sem adição de ferro na mistura salina, sendo que os filhotes, quando desmamados, continuaram a receber a mesma ração por mais sete dias. Paralelamente, houve um grupo controle no qual ratas e filhotes receberam ração comercial. No período de repleção de catorze dias, os ratos machos (n=40) foram distribuídos aleatoriamente em cinco grupos de oito ratos cada um, os quais receberam rações experimentais (açaí e farinha de mandioca fortificada com ferro) e controles (do açaí e American Institute of Nutrition 93). A concentração de hemoglobina foi determinada semanalmente e a biodisponibilidade de ferro das rações foi determinada por meio de cálculos do ferro ingerido e do ferro hemoglobínico dos ratos dos diferentes grupos. RESULTADOS: Ao final do período de depleção, a concentração de hemoglobina dos ratos, de 4,7 ± 0,5g/dL, demonstrou a efetividade do método utilizado. A maior biodisponibilidade de ferro foi constatada na farinha de mandioca fortificada (44,6±3,6%), em contraste com a baixa biodisponibilidade do ferro do açaí (12,1±5,5%). CONCLUSÃO: O ferro presente no açaí não foi eficaz na recuperação da concentração de hemoglobina dos ratos. Portanto sugere-se cautela ao recomendar a utilização do açaí como fonte de ferro.

Iron deficiency due to consumption of a habitual diet low in bioavailable iron: a longitudinal cohort study in Moroccan children

In many developing countries, cereal and legume-based diets contain low amounts of bioavailable iron, which may increase the risk of iron deficiency. The objective was to measure change in iron status in Moroccan children who consumed their habitual diet containing low amounts of bioavailable iron. The design was a prospective, longitudinal, free-living cohort study in iron-replete, nonanemic 6-10-y-old children (n = 126). Hemoglobin, serum ferritin, and transferrin receptor were measured at baseline. The children then consumed their habitual cereal and legume-based diet for 15 mo, when their iron status was retested. We used weighed food records and direct food analysis to calculate dietary iron intake and iron bioavailability. On the basis of the change in hemoglobin and body iron stores calculated from the serum transferrin receptor-to-ferritin ratio, iron balance and iron absorption were estimated over the 15-mo period. Mean daily iron intake was 10.8 mg/d, 97% of which was nonheme iron. Estimated nonheme-iron bioavailability from algorithms was 1.0-4.3% adjusted for low body iron stores. Over 15 mo, the mean change in total body iron was -142 mg, and mean iron absorption was estimated to be 0.22 mg/d, or 2% of dietary iron. Mean hemoglobin concentration decreased 12 g/L. At 15 mo, 75% of the cohort had deficits in tissue iron, and one-third had mild iron deficiency anemia. Low iron bioavailability from legume and cereal-based diets is a cause of iron deficiency anemia in children in rural Africa.

Is there an association between the nutritional status of the mother and that of her 2-year-old to 5-year-old child?

The aim of this study was to determine whether there is an association between the nutritional status of the mother and that of her 2-year-old to 5-year-old child in a rural village in South Africa where there is a high prevalence of childhood malnutrition (in particular, deficiencies of vitamin A and iron) and of maternal obesity.A blood sample and anthropometric measurements were obtained for 118 child–mother pairs. There was a positive mother–child correlation for serum ferritin (R=0.2304, P<0.05) and haemoglobin (R=0.2664, P<0.01) concentrations, respectively. The child of an anaemic mother had a relative risk of 1.632 of also being anaemic. There was no mother–child association for either serum retinol concentration or anthropometric measurements. Serum retinol concentrations showed a positive correlation with both serum ferritin (mothers only; R=0.2161, P<0.01) and haemoglobin (R=0.2807, P<0.01 for mothers; and R=0.2710, P < 0.01 for children) concentrations.The mother–child association for iron status is probably because of an inadequate dietary intake and low bioavailability of dietary iron, which are major causes of iron deficiency. The lack of mother–child association for serum retinol concentration could probably be ascribed to the fact that children are more susceptible to vitamin A deficiency than adults because of childhood diseases.

Cultural and Environmental Barriers to Adequate Iron Intake among Northern Kenyan Schoolchildren

The purpose of this study was to examine the context of iron deficiency and feeding patterns of iron-rich foods among northern Kenyan school-aged children. A nutrition survey was conducted among 300 subjects in two Rendille communities, Korr and Karare. The objectives were to determine the prevalence of iron deficiency as it relates to parasitic infection, dietary intake, and sociodemographic factors, as well as cultural food proscriptions influencing child feeding. Sociodemographic and qualitative data on food beliefs and child-feeding practices were obtained from the primary caretaker of each subject. From pediatric subjects, 24-hour dietary recall data were obtained with the help of the primary caretaker, and capillary blood from a fingerstick was used to detect iron deficiency based on measures of hemoglobin, the zinc protoporphyrin-to-heme ratio, C-reactive protein, and transferrin receptor. With an overall prevalence of 31.2%, iron deficiency was found to be associated with dietary iron intakes constrained by diverse economic, cultural, and environmental factors among Rendille children. In Karare, where children's iron intake approached recommended levels, iron deficiency was found to be attributable to low bioavailability of iron (only 4.3% of total iron intake), rather than low dietary intake per se. By contrast, in Korr the average daily iron intake was estimated at only 65% of recommended allowances, indicating that iron deficiency was the outcome not merely of low bioavailability, but rather of overall inadequate iron intake. Sociodemographic analysis showed a significant interaction between sex and economic status, revealing that girls in economically sufficient households were 2.4 times as likely to have iron deficiency as boys. This difference in risk parallels culturally defined gender-based proscriptions for child feeding: girls are believed to benefit from "soft foods," including rice, maize porridge, and tea, whereas boys benefitfrom "hard foods," including meat, blood, and beans. Consequently, in households economically able to purchase iron-rich foods, these foods are being preferentially fed to boys. Economic development may result in improved iron status for boys, but it will be unlikely to benefit girls in the absence of a dietary modification intervention. A modification of culturally acceptable "soft foods" to include iron-rich foods may provide a sustainable approach to controlling and preventing iron deficiency in this population.

Impact of dietary iron intake on anaemia in Tanzanian schoolchildren

Objective. To investigate the nutritional relationship between dietary intake and prevalence of anaemia among Tanzanian schoolchildren. Methods. Dietary intakes of 101 schoolchildren aged 7 - 12 years were assessed using a pre-tested food frequency questionnaire. Haemoglobin (Hb), haematocrit, erythrocyte protoporphyrin (EP) and serum ferritin (SF) were used to determine their anaemia and iron status. Other socio-economic variables were collected using a profile questionnaire. Results. Significantly lower intake of iron was seen in 48% of schoolchildren with Hb < 11.5 g/dl (anaemic) compared with those who were normal. Total iron intake was 22 ± 7 and 27 ± 13 mg/day respectively (p < 0.05). There was a general poor intake of iron from animal sources in all children. A higher iron intake was found in schoolchildren with normal iron status (by EP and SF levels) than in those who were not normal (26 ± 11 mg/day v. 22 ± 9 mg/day, p < 0.05). Iron deficiency was found in 45% of schoolchildren (N = 80) and 31% were categorised as having iron deficiency anaemia. The mean energy intake in boys was higher than in girls (2 150 ± 770 v. 1 830 ± 895 kcal/day respectively). Boys also had a higher intake of ascorbic acid (50 ± 32 v. 31 ± 23 mg/day, p > 0.05). In stepwise multiple regression analysis, daily iron intake remained the most significant nutrient predicting for Hb status. There was a significant correlation between iron intake and serum ferritin (r = 0.233, p < 0.05). Conclusion. Iron intake in this Tanzanian community is inadequate for maintaining normal iron nutrition. The factors contributing to the inadequacy include consumption of foods with low iron bioavailability. Food-based intervention should be one of the important strategies for reducing the magnitude of the problem of anaemia in this community.

Iron absorption by heterozygous carriers of the HFE C282Y mutation associated with hemochromatosis

Research conducted before genotyping was possible suggested that subjects heterozygous for the genetic mutation associated with hemochromatosis absorbed nonheme iron more efficiently than did control subjects when tested with a fortified meal. Heme-iron absorption in these subjects has not been reported. We compared the absorption of heme and nonheme iron from minimally or highly fortified test meals between HFE C282Y-heterozygous and wild-type control subjects. After prospective genotyping of 256 healthy volunteers, 11 C282Y-heterozygous and 12 wild-type control subjects were recruited, and their iron absorption was compared by using a hamburger test meal with or without added iron and ascorbic acid. After retrospective genotyping of 103 participants in previous iron-absorption studies, 5 C282Y-heterozygous subjects were compared with 72 wild-type control subjects. HFE C282Y-heterozygous subjects did not differ significantly from wild-type control subjects in their absorption of either heme or nonheme iron from minimally or highly fortified test meals. No differences were detected in blood indexes of iron status (including serum ferritin, transferrin saturation, and non-transferrin-bound iron) or in blood lipids or transaminases, but heterozygotes had significantly greater, although normal, fasting glucose concentrations than did wild-type control subjects. Compound heterozygotes (those who had both HFE C282Y and H63D mutations) absorbed more nonheme (but not heme) iron from meals with high (but not low) iron bioavailability. HFE C282Y-heterozygous subjects did not absorb dietary iron more efficiently, even when foods were highly fortified with iron from ferrous sulfate and ascorbic acid, than did control subjects. Iron fortification of foods should not pose an additional health risk to HFE C282Y heterozygotes.

Effects of the benthic cyanobacterium Lyngbya majuscula on larval recruitment of the reef corals Acropora surculosa and Pocillopora damicornis

Coral reef degradation resulting from a multitude of stressors is occurring on a global scale (Hoegh-Guldberg 1999; Hughes et al. 2003). The outcome of reef degradation is often a decrease in live coral, followed by the proliferation of algae (termed a phase shift) (Hughes 1994; McCook 1999). Successful coral recruitment is critical to the regeneration of reefs, and recruitment failuremay be a major reason that reefs are not recovering from phase shifts (Hughes and Connell 1999; Hughes and Tanner 2000). When reefs become dominated by macroalgae, larval access to suitable settling habitat is decreased (McCook et al. 2001), and sediments trapped within algal turfs may reduce survival of coral spat (Sato 1985). Rates of coral recruitment are inversely correlated to algal biomass (Birkeland 1977; Rogers et al. 1984). Interactions between benthic cyanobacteria and corals have not been examined experimentally to date, but recent studies have documented cyanobacterial blooms on coral reefs in Guam (Nagle and Paul 1998; Thacker and Paul 2001), atoll islands across Micronesia and the Northwest Hawaiian Islands (especially near iron shipwrecks, J. Maragos, personal communication), and off Broward county, Florida (authors’ personal observations). Also, cyanobacteria are often dominant in the turfs that first colonize dead coral skeleton after mortality caused by coral bleaching (Diaz-Pulido and McCook 2002). The environmental factors that contribute to cyanobacterial bloom formation in the benthic marine environment have not been definitively identified, but low wave action (Thacker and Paul 2001), phosphate levels (Kuffner and Paul 2001), and iron bioavailability (J. Maragos, personal communication) may be worth examining in the field. There could be other mechanisms for reductions in coral recruitment rates besides the preemption of space by weedy primary producers. Many benthic species of algae (Hay et al. 1987; Schmitt et al. 1995) and cyanobacteria (Nagle and Paul 1998; 1999; Pennings et al. 1997) produce toxic secondary metabolites that act as anti-herbivory and anti-fouling agents (see Paul et al. 2001 for review). Lyngbya majuscula, in particular, has been shown to produce three bioactive compounds (malyngolide, malyngamide A and malyngamide B) that deter feeding in juvenile parrotfishes (Thacker et al. 1997). Given the generalized toxicity and multi-function nature of many secondary metabolites produced by marine algae and cyanobacteria (Paul et al. 2001), it would not be surprising if these or other chemicals perform allelopathic roles as well. In this study we examine the effects of Lyngbya majuscula on the larvae of two species of corals, Acropora surculosa (broadcast spawner) and Pocillopora damicornis (brooder), to test whether the presence of Lyngbya majuscula has a negative effect on coral larval survival or recruitment beyond levels that would be expected due to space preemption.

Transcriptional and Posttranscriptional Control of Cable Pilus Gene Expression in Burkholderia cenocepacia

Burkholderia cenocepacia is an important member of the Burkholderia cepacia complex, a group of closely related bacteria that inhabits a wide variety of environmental niches in nature and that also colonizes the lungs of compromised humans. Certain strains of B. cenocepacia express peritrichous adherence organelles known as cable pili, thought to be important in the colonization of the lower respiratory tract. The genetic locus required for cable pilus biogenesis is comprised of at least five genes, designated cblB, cblA, cblC, cblD, and cblS. In this study a transcriptional analysis of cbl gene expression was undertaken. The principal promoter, located upstream of the cbl locus, was identified and characterized. By using lacZ transcriptional fusions, the effects of multiple environmental cues on cbl gene expression were examined. High osmolarity, temperature of 37 degrees C, acidic pH, and low iron bioavailability were found to induce cbl gene expression. Northern hybridization analysis of the cbl locus identified a single, stable transcript corresponding to cblA, encoding the major pilin subunit. Transcriptional fusion studies combined with reverse transcription-PCR analysis indicated that the stable cblA transcript is the product of an mRNA processing event. This event may ensure high levels of expression of the major pilin, relative to other components of the assembly pathway. Our findings lend further insight into the control of cable pilus biogenesis in B. cenocepacia and provide evidence for regulation of cbl gene expression on both the transcriptional and posttranscriptional levels.

Anaemia in relation to low bioavailability of dietary iron among school-aged children in the Aral Sea region, Kazakhstan

This study investigates anaemia related to the sufficiency of dietary iron intake of school-aged children in the Kzyl-Orda region of Kazakhstan. We conducted a cross-sectional study of 97 school-aged children living in Kzyl-Orda. Blood samples were collected for measuring haemoglobin. Dietary intake data were obtained from 24-h dietary recalls. Iron bioavailability was estimated with algorithms adjusting for absorption enhancers (meat, fish and poultry, and vitamin C) and inhibitors (tea and phytates) consumed in the same meal. The median total iron intakes were adequate compared with the median basal iron requirement; however, the median bioavailable iron intakes were well below the median absorbed iron requirement. Available iron was 6.9–7.2% of the total iron intake after adjusting for the absorption enhancers, and was reduced by 3.1–4.4% after adjusting for both enhancers and inhibitors. After adjustment for energy intake, higher iron intake was significantly associated with a decreased prevalence of anaemia (odds ratio, 0.39; 95% confidence interval, 0.16–0.93; P=0.034). Some evidence suggested an association between bioavailable iron intake after adjustment of absorption enhancers and inhibitors (odds ratio, 0.43; 95% confidence interval, 0.18–1.01; P=0.053). In conclusion, low bioavailability of dietary iron seems related to anaemia in the region. Although iron fortification or supplementation programmes can be useful for promoting the anaemia prevention control programme, further efforts for nutritional education suited for family level dietary practice are necessary.

Iron Homeostasis in Plants: Sensing and Signaling Pathways

Since iron is both an essential element as well as a potential toxin, it is a nutrient which on the one hand fulfils many important functions in plants but on the other can cause severe cell damage as a consequence of the formation of reactive hydroxyl radicals. Uptake of iron, its concentrations within particular tissues, and its subcellular distribution is therefore subject to careful control. In addition, the low bioavailability of iron in most soils necessitates the mobilization of sparingly soluble iron compounds. This has led to the evolution of concerted responses that assist in maintaining an adequate supply of iron for plant roots. These responses comprise morphological changes, such as the development of extra root hairs, formation of rhizodermal transfer cells, and induction of cluster roots, as well as induction of genes coding for enzymes involved in the mobilization and uptake of nutrients. Investigations at the protein, mRNA, and structural level showed that both systemic responses, involving transmission of long distance signals, and external nutritional signals, inducing localized responses, are involved in the complex control of iron homeostasis. A number of components have been identified at the molecular level, but the interplay between these components and the signal transduction cascades leading to an iron status within an adequate range are largely unknown. This review summarizes the available data that explain how these processes are coordinated to maintain a continuous and acceptable Fe supply despite changing environmental conditions.