Dennis D. Miller

The pig as an experimental model for elucidating the mechanisms governing dietary influence on mineral absorption.

This review highlights the similarities between pigs and humans and thereby the value of the porcine human nutritional model, and reviews some of the more recent applications of this model for nutritional research.

Iron absorption and bioavailability: An updated review

Regulation of iron absorption operates at the level of duodenal mucosal cells. Despite much research, the specific biochemical pathways of iron absorption and the regulatory mechanisms controlling it remain unknown. This review summarizes current knowledge of and hypotheses on each of the three steps of iron absorption: uptake from the intestinal lumen into mucosal cells, transit through the cell, and release from the cells into the body. Absorption may be defined as the movement of iron from the intestinal lumen across the epithelial cells of the digestive tract into the circulation, while bioavailability generally refers to the proportion of iron in a given food or diet that the body can actually utilize. The most common technique of measuring iron absorption and bioavailability, extrinsic radiolabeling of a single meal, is discussed in the context of the latest studies using this methodology.

Enhancing the absorption of fortification iron. A SUSTAIN Task Force report.

Iron deficiency remains a major global health problem affecting an estimated 2 billion people. The World Health Organization ranked it as the seventh most important preventable risk for disease, disability, and death in 2002. Since an important factor in its causation is the poor bioavailability of iron in the cereal-based diets of many developing countries, SUSTAIN set up a Task Force, consisting of nutritional, medical, industry, and government experts to consider strategies for enhancing the absorption of fortification iron. This paper summarizes the findings of this Task Force. Detailed reviews of each strategy follow this overview. Highly soluble compounds of iron like ferrous sulfate are desirable food fortificants but cannot be used in many food vehicles because of sensory issues. Thus, potentially less well-absorbed forms of iron commonly are used in food fortification. The bioavailability of iron fortificants can, however, be enhanced with innovative ingredient technologies. Ascorbic acid, NaFeEDTA, ferrous bisglycinate, and dephytinization all enhance the absorption of fortification iron, but add to the overall costs of fortification. While all strategies cannot be recommended for all food fortification vehicles, individual strategies can be recommended for specific foods. For example, the addition of ascorbic acid is appropriate for dry blended foods such as infant foods and other dry products made for reconstitution that are packaged, stored, and prepared in a way that maximizes retention of this vitamin. NaFeEDTA can be recommended for fortification of fish sauce and soy sauce, whereas amino acid chelates may be more useful in milk products and beverages. With further development, dephytinization may be possible for low-cost, cereal-based complementary foods in developing countries. Encapsulation of iron salts in lipid coatings, while not an iron absorption-enhancing strategy per se, can prevent soluble forms of iron from interacting undesirably with some food vehicles and hence broaden the application of some fortificants. Research relevant to each of these strategies for enhancing the bioavailability or utility of iron food fortificants is reviewed. Individual strategies are evaluated in terms of enhancing effect and stability, organoleptic qualities, cost, and regulatory issues of interest to the nutrition community, industry, and consumers. Recommendations are made on potential usages and further research needs. Effective fortification depends on the selection of technically feasible and efficacious strategies. Once suitable strategies have been identified, cost becomes very important in selecting the best approach to implement. However it is essential to calculate cost in relation to the amount of bioavailable iron delivered. An approach to the calculation of cost using a conservative estimate of the enhancing effects of the innovative technologies discussed in the supplement is given in the final section.

Dietary inulin affects the expression of intestinal enterocyte iron transporters, receptors and storage protein and alters the microbiota in the pig intestine.

Inulin, a linear beta fructan, is present in a variety of plants including chicory root and wheat. It exhibits prebiotic properties and has been shown to enhance mineral absorption and increase beneficial bacteria in the colon. The aim of the present study was to assess the effect of dietary inulin on the gene expression of selected intestinal Fe transporters and binding proteins. Anaemic piglets at age 5 weeks were allocated to a standard maize-soya diet (control) or the same diet supplemented with inulin at a level of 4 %. After 6 weeks, the animals were killed and caecum contents and sections of the duodenum and colon were removed. Segments of the genes encoding for the pig divalent metal transporter 1 (DMT1) and duodenal cytochrome-b reductase (Dcytb) were isolated and sequenced. Semi-quantitative RT-PCR analyses were performed to evaluate the expression of DMT1, Dcytb, ferroportin, ferritin, transferrin receptor (TfR) and mucin genes. DMT1, Dcytb, ferroportin, ferritin and TfR mRNA levels in duodenal samples were significantly higher in the inulin group (P < or = 0.05) compared with the control. In colon, DMT1, TfR and ferritin mRNA levels significantly increased in the inulin group. Additionally, the caecal content microflora was examined using 16S rDNA targeted probes from bacterial DNA. The Lactobacillus and Bifidobacterium populations were significantly increased in the inulin group (P < or = 0.05) compared with the control group. These results indicate that dietary inulin might trigger an up regulation of genes encoding for Fe transporters in the enterocyte. The specific mechanism for this effect remains to be elucidated.

Nicotianamine, a Novel Enhancer of Rice Iron Bioavailability to Humans

Background Polished rice is a staple food for over 50% of the worlds population, but contains little bioavailable iron (Fe) to meet human needs. Thus, biofortifying the rice grain with novel promoters or enhancers of Fe utilization would be one of the most effective strategies to prevent the high prevalence of Fe deficiency and iron deficiency anemia in the developing world. Methodology/Principal Findings We transformed an elite rice line cultivated in Southern China with the rice nicotianamine synthase gene (OsNAS1) fused to a rice glutelin promoter. Endosperm overexpression of OsNAS1 resulted in a significant increase in nicotianamine (NA) concentrations in both unpolished and polished grain. Bioavailability of Fe from the high NA grain, as measured by ferritin synthesis in an in vitro Caco-2 cell model that simulates the human digestive system, was twice as much as that of the control line. When added at 1∶1 molar ratio to ferrous Fe in the cell system, NA was twice as effective when compared to ascorbic acid (one of the most potent known enhancers of Fe bioavailability) in promoting more ferritin synthesis. Conclusions Our data demonstrated that NA is a novel and effective promoter of iron utilization. Biofortifying polished rice with this compound has great potential in combating global human iron deficiency in people dependent on rice for their sustenance.

Calcium in the Diet: Food Sources, Recommended Intakes, and Nutritional Bioavailability

Calcium nutritional status among some groups in the United States is suboptimal when judged by calcium intakes and the high prevalence of osteoporosis. Unfortunately, however, it is not clear that increases in calcium intake will have a significant impact on osteoporosis or other chronic diseases that have been linked to calcium nutriture. There is still considerable controversy surrounding the issue of calcium RDAs. The bodys ability to adapt to varying levels of calcium intakes, the lack of sensitive indicators of calcium status, and the complexity and slow progression of chronic diseases such as osteoporosis make it very difficult to establish the role of diet in this regard. Great progress has been made in the study of calcium absorption. Much is known about the mechanisms involved in calcium absorption and its regulation. Thus, a rapidly advancing field and further developments will be invaluable to our understanding of the role of diet in calcium nutrition. Calcium bioavailability is affected by diet composition and the chemical form of calcium in foods. The calcium in dairy products is readily absorbed in the intestine. Lactose enhances calcium absorption efficiency under some conditions. Components of plants such as fiber, phytate, and oxalic acid may depress calcium absorption. High intakes of protein increase urinary losses of calcium but this effect may be partially offset by the phosphate association with most high-protein foods. Calcium absorption from salts used in supplement tablets is generally good. Absorption from salts such as calcium carbonate which require acid for dissolution may be poor in persons with achlorhydria unless the tablets are consumed with a meal. The practical significance of factors that may alter calcium bioavailability in normal mixed diets is difficult to assess. It may be a significant factor when calcium intakes are marginal or when absorption by the active transport, vitamin D-dependent process is impaired or not fully developed, i.e., it may be significant when vitamin D status is poor, in the elderly, and in young infants.

Iron binding by tannic acid: Effects of selected ligands

Abstract Foods with high tannin content inhibit Fe absorption from meals. Presumably, tannins form complexes with Fe in the intestinal lumen reducing Fe bioavailability. Our objective was to assess the influence of various ligands on Fe binding by tannic acid in vitro . Different mixing sequences were employed to determine whether the ligands could prevent Fe from binding to the tannin or could remove Fe already bound. Solutions of Fe +3 (FeC 3 in 0.1 n HCl), ligand (ethylenediamine-tetraacetic acid (EDTA), ascorbic acid, nitrilotriacetic acid (NTA) or citric acid) and tannic acid (200 μg ml −1 ) in pH 4.4 acetate buffer were combined to obtain a final ligand:Fe molar ratio of 1:1 (89 μ m ). Three mixing sequences were followed: sequence I (Fe and ligand combined and added to tannin); sequence II (tannin and ligand combined and added to Fe); and sequence III (Fe and tannin combined and added to ligand). Fe-tannin binding was assessed by measuring absorbance at 560 nm (visible absorbance maximum) at 15 s intervals for 5 min. An Fe-tannin mixture without ligand served as the control. With EDTA, sequence I resulted in no binding. In sequence II and III, there was some binding initially, but it decreased with time. With ascorbic acid, sequence I resulted in no binding. In sequence II and III, initial binding was slightly lower than the control. Binding did not change with time. With NTA, initial binding varied with the sequence, but converged with time to a value slightly lower than the control. Citric acid did not affect binding regardless of addition sequence. These findings suggest that ligands with high affinity for Fe (e.g. EDTA) can prevent Fe from binding tannin and can remove Fe already bound. Ligands with lower affinity (e.g. citric acid) have little effect. The implications are that EDTA, ascorbic acid and NTA may affect Fe bioavailability from meals containing tannins.

Production and supply of high‐quality food protein for human consumption: sustainability, challenges, and innovations

The Food and Agriculture Organization of the United Nations estimates that 843 million people worldwide are hungry and a greater number suffer from nutrient deficiencies. Approximately one billion people have inadequate protein intake. The challenge of preventing hunger and malnutrition will become even greater as the global population grows from the current 7.2 billion people to 9.6 billion by 2050. With increases in income, population, and demand for more nutrient‐dense foods, global meat production is projected to increase by 206 million tons per year during the next 35 years. These changes in population and dietary practices have led to a tremendous rise in the demand for food protein, especially animal‐source protein. Consuming the required amounts of protein is fundamental to human growth and health. Protein needs can be met through intakes of animal and plant‐source foods. Increased consumption of food proteins is associated with increased greenhouse gas emissions and overutilization of water. Consequently, concerns exist regarding impacts of agricultural production, processing and distribution of food protein on the environment, ecosystem, and sustainability. To address these challenging issues, the New York Academy of Sciences organized the conference “Frontiers in Agricultural Sustainability: Studying the Protein Supply Chain to Improve Dietary Quality” to explore sustainable innovations in food science and programming aimed at producing the required quality and quantity of protein through improved supply chains worldwide. This report provides an extensive discussion of these issues and summaries of the presentations from the conference.

Toward a comprehensive approach to the collection and analysis of pica substances, with emphasis on geophagic materials.

Background Pica, the craving and subsequent consumption of non-food substances such as earth, charcoal, and raw starch, has been an enigma for more than 2000 years. Currently, there are little available data for testing major hypotheses about pica because of methodological limitations and lack of attention to the problem. Methodology In this paper we critically review procedures and guidelines for interviews and sample collection that are appropriate for a wide variety of pica substances. In addition, we outline methodologies for the physical, mineralogical, and chemical characterization of these substances, with particular focus on geophagic soils and clays. Many of these methods are standard procedures in anthropological, soil, or nutritional sciences, but have rarely or never been applied to the study of pica. Principal Findings Physical properties of geophagic materials including color, particle size distribution, consistency and dispersion/flocculation (coagulation) should be assessed by appropriate methods. Quantitative mineralogical analyses by X-ray diffraction should be made on bulk material as well as on separated clay fractions, and the various clay minerals should be characterized by a variety of supplementary tests. Concentrations of minerals should be determined using X-ray fluorescence for non-food substances and inductively coupled plasma–atomic emission spectroscopy for food-like substances. pH, salt content, cation exchange capacity, organic carbon content and labile forms of iron oxide should also be determined. Finally, analyses relating to biological interactions are recommended, including determination of the bioavailability of nutrients and other bioactive components from pica substances, as well as their detoxification capacities and parasitological profiles. Significance This is the first review of appropriate methodologies for the study of human pica. The comprehensive and multi-disciplinary approach to the collection and analysis of pica substances detailed here is a necessary preliminary step to understanding the nutritional enigma of non-food consumption.

Biofortified black beans in a maize and bean diet provide more bioavailable iron to piglets than standard black beans.

Our objective was to compare the capacities of biofortified and standard black beans (Phaseolus vulgaris L.) to deliver iron (Fe) for hemoglobin (Hb) synthesis. Two lines of black beans, one standard and the other biofortified (high) in Fe (71 and 106 microg Fe/g, respectively), were used. Maize-based diets containing the beans were formulated to meet the nutrient requirements for swine except for Fe (Fe concentrations in the 2 diets were 42.9 +/- 1.2 and 54.6 +/- 0.9 mg/kg). At birth, pigs were injected with 50 mg of Fe as Fe dextran. At age 28 d, pigs were allocated to the experimental diets (n = 10). They were fed 2 times per day for 5 wk and given free access to water at all times. Body weights and Hb concentrations were measured weekly. Hb repletion efficiencies (means +/- SEM) did not differ between groups and, after 5 wk, were 20.8 +/- 2.1% for the standard Fe group and 20.9 +/- 2.1% for the high Fe group. Final total body Hb Fe contents did not differ between the standard [539 +/- 39 mg (9.7 +/- 0.7 micromol)] and high Fe [592 +/- 28 mg (10.6 +/- 0.5 micromol)] bean groups (P = 0.15). The increase in total body Hb Fe over the 5-wk feeding period was greater in the high Fe bean group [429 +/- 24 mg (7.7 +/- 0.4 micromol)] than in the standard Fe bean group [361 +/- 23 mg (6.4 +/- 0.4 micromol)] (P = 0.034). We conclude that the biofortified beans are a promising vehicle for increasing intakes of bioavailable Fe in human populations that consume beans as a dietary staple.