Human Feeding Trials Research Articles

Polymerase Chain Reaction and Denaturing Gradient Gel Electrophoresis Monitoring of Fecal Bifidobacterium Populations in a Prebiotic and Probiotic Feeding Trial

A culture-independent approach based on genus-specific PCR and denaturing gradient gel electrophoresis (DGGE) was used to monitor qualitative changes in fecal bifidobacterial communities in a human feeding trial. DNA was extracted directly from feces and bifidobacterial 16S rDNA sequences were amplified using genus-specific PCR. The PCR fragments were subsequently separated in a sequence-specific manner by DGGE in order to obtain a profile of bifidobacterial fragments. The DGGE profiles revealed that in general, administration for two weeks of galactooligosaccharide and/or Bifidobacterium lactis Bb-12 (8 g and 3 x 10(10) cfu per day, respectively) did not affect the qualitative composition of the indigenous Bifidobacterium population, while B. lactis Bb-12 transiently colonised the gut.

Breeding for Trace Mineral Density in Rice

In 1992 the International Rice Research Institute (IRRI) began to examine the effect of certain soil characteristics on the iron content of rice grains. As part of the Consultative Group for International Agricultural Research (CGIAR) Micronutrients Project, this effort was expanded in 1995 to include analysis of both iron and zinc, in collaboration with the University of Adelaide in Australia. Since then, germplasm screening has shown large genetic variation for iron and zinc concentrations in brown rice. Common cultivars contain about 12 mg of iron and 25 mg of zinc per kilogram. Some traditional varieties have double these amounts. Genetic-by-environmental interactions are sufficiently moderate that breeding for higher iron and zinc content is considered worthwhile. The next major research step will be to further study the genetics of trace mineral accumulation in the grain to determine the best selection techniques for use in breeding. High iron and zinc traits can be combined with improved agronomic traits. This has already been demonstrated in the serendipitous discovery in the IRRI testing programme of an aromatic variety (IR68144-3B-2-2-3) that has a high concentration of grain iron, about 21 mg/kg in brown rice. This elite line has good tolerance to rice tungro virus and to mineral-deficient soils and has excellent grain qualities. The yields are about 10% below those of IR72, but in partial compensation, maturity is earlier. After 15 minutes of polishing, IR68144-4B-2-2-3 had about 80% more iron than IR64, a widely grown commercial variety. It remains to be shown that this extra iron can improve the iron status of iron-deficient human subjects. A human feeding trial is being planned.

A Human Feeding Trial of Iron-enhanced Rice

A key unknown in the strategy of breeding for micronutrient-dense staple food crops is the bioavailability of the additional trace minerals in nutritionally improved lines. This paper describes a feeding trial to be undertaken in the Philippines during 2001 using human subjects that will examine the effect on iron status of long-term consumption of IR68-144, a high-yielding, aromatic, iron-dense rice that is currently undergoing agronomic testing at the International Rice Research Institute (IRRI). The subjects will be religious sisters-in-training who live year-round in convents in Greater Manila. This population was selected because they represent a sex and age segment of the population at high risk for iron deficiency. The iron status of the sample of 27 sisters indicates that 74% were anaemic (haemoglobin <120 g/L) and 48% iron deficient (serum ferritin <12 μg/L). These subjects consume large quantities of rice (400 g/day), and all their meals are prepared in common kitchens where different varieties of rice can be easily introduced to the menu. A pilot study found that the introduction of IR68-144 rice was highly tolerated by the kitchen staff who prepared the rice and the sisters who consumed it. There were no perceived differences in taste, texture, colour, or other properties compared with the commercial variety normally consumed. The high prevalence of iron deficiency, the considerable amount of rice consumed, the high level of cooperation of the subjects, and the structured routine of the convent make this an ideal research setting to investigate the effect of improving iron intakes through a staple food.

Testing Iron and Zinc Bioavailability in Genetically Enriched Beans (Phaseolus Vulgaris L.) and Rice (Oryza Sativa L.) in a Rat Model

A rat model was used to determine the bioavailability of iron and zinc in bean seeds and rice grain from enriched genotypes of these globally important staple foods. Seed and grain from the genotypes tested (intrinsically radiolabelled with either 59Fe or 65Zn) were cooked, homogenized in water, and lyophilized to dryness. The dried, radiolabelled powder was fed to young male rats in single meals. Bioavailability was calculated from the amount of radiolabelled iron and zinc retained in the rats over a 10-day period as determined each day by whole-body gamma spectrometry assay. The data collected demonstrate that increasing the amount of iron or zinc in enriched rice grain and bean seed significantly increases the amount of iron or zinc bioavailable to rats. Although a rat model is not ideal for determining iron and zinc bioavailability to humans, because rats are much more efficient at absorbing iron and zinc from plant foods than humans, rats can be used to give relative estimates of bioavailable iron and zinc in plant foods. These estimates can be used to rank promising genotypes of staple foods for use in later feeding trials with humans, greatly reducing the numbers of genotypes that would have to be tested in humans without use of the rat model. Ultimately, because of the complexities of determining the bioavailability to humans of iron and zinc in plant foods, human feeding trials performed under free-living conditions should be conducted with the most promising genotypes before these genotypes are released for distribution to breeding programmes worldwide

Probiotics: from myth to reality. Demonstration of functionality in animal models of disease and in human clinical trials.

The enteric flora comprise approximately 95% of the total number of cells in the human body and are capable of eliciting immune responses while also protecting against microbial pathogens. However, the resident bacterial flora of the gastrointestinal tract (GIT) may also be implicated in the pathogenesis of several chronic conditions such as inflammatory bowel disease (IBD). The University College Cork-based Probiotic Research Group has successfully isolated and identified lactic acid bacteria (LAB) which exhibit beneficial probiotic traits. These characteristics include the demonstration of bile tolerance; acid resistance; adherence to host epithelial tissue; and in vitro antagonism of potentially-pathogenic micro-organisms or those which have been implicated in promoting inflammation. The primary objective of this report is to describe the strategy adopted for the selection of potentially effective probiotic bacteria. The study further describes the evaluation of two members of the resulting panel of micro-organisms (Lactobacillus salivarius subsp. salivarius UCC118 and Bifidobacterium longum infantis 35624) under in vitro conditions and throughout in vivo murine and human feeding trials. Specifically, an initial feeding study completed in Balb/c mice focused upon (i) effective delivery of the probiotic micro-organisms to the GIT and evaluation of the ability of the introduced strains to survive transit through, and possibly colonise, the murine GIT; (ii) accepting the complexity of the hostile GIT and faecal environments, development of a method of enumerating the introduced bacterial strains using conventional microbiological techniques; and (iii) assessment of the effects of administered bacterial strains on the numbers of specific recoverable indigenous bacteria in the murine GIT and faeces. Additional research, exploiting the availability of murine models of inflammatory bowel disease, demonstrated the beneficial effects of administering probiotic combinations of Lactobacillus salivarius UCC118 and Bifidobacterium longum infantis 35624 in prevention of illness-related weight loss. A further ethically-approved feeding trial, successfully conducted in 80 healthy volunteers, demonstrated that yoghurt can be used as a vehicle for delivery of Lactobacillus salivarius strain UCC118 to the human GIT with considerable efficacy in influencing gut flora and colonisation.

Potential Uses of Caseinophosphopeptides

Abstract Caseinophosphopeptides (CPPs) are phosphorylated casein-derived peptides which possess the ability to bind and solubilise minerals, such as Ca2+. Consumption of high concentrations of Ca2+ in early life contributes to the development of maximal bone density, which in turn can prevent osteoporosis in later life. Furthermore, a recent report has shown a positive correlation between Ca2+ intake and the prevention of hypertension. The high bioavailability of Ca2+ from milk and dairy products has, in part, been attributed to the production of CPPs which have different levels of phosphorylation and are produced in vivo following digestion of α s 1 -, α s 2 - and β-casein by the action of gastrointestinal proteinases. CPPs which appear to be resistant to extensive proteolytic degradation, accumulate in the distal small intestine where they are purported to play a role in enhancing the passive absorption of Ca2+ and other trace elements. CPPs have also been produced in vitro using a range of commercially available proteinases of pancreatic origin. Several CPP enrichment procedures from casein hydrolysates have been reported, generally involving Ca2+ induced aggregation followed by ultrafiltration. These CPP enriched preparations have been used to characterise their interaction with Ca2+ and trace elements and to determine their effect on the bioavailability of dietary Ca2+ during animal and human feeding trials. There are conflicting reports, arising from the results of animal feeding studies, on the effectiveness of CPPs in enhancing Ca2+ bioavailability. However, a recent human feeding trial reported improved Ca2+ and Zn2+ absorption following CPP incorporation into a rice-based infant food. In vitro produced CPPs may also find application in the prevention and treatment of dental calculus. This review summarises the production, characterisation and potential applications of CPPs.

Quality and consumption of oxidized lipids from deep‐frying fats and oils in New Zealand

AbstractSamples of beef dripping and plant oil‐based deep‐frying fat were obtained from fast‐food premises in Christchurch, New Zealand, as well as samples of deep‐fried battered fish and potato chips. The fat in these samples was analyzed for level of oxidation by measuring acid value, peroxide value, polar compounds, thiobarbituric acid‐reactive substances (TBARS), and conjugated dienes. The acid and peroxide value results were contradictory when compared with limits set in the New Zealand Food Regulations 1984, but the levels of polar compounds were generally below 25%, indicating that the fats were well maintained. The TBARS and conjugated diene levels were compared with those for oxidized corn oil used in a feeding trial and indicated a similar oxidation level, although the amount of fat consumed in the feeding trial would be 30–50% higher. These results show that well‐maintained deep‐frying fat has oxidation levels sufficient to cause elevation of plasma lipid oxidation levels as observed in a human feeding trial.

Leaf Protein: Production and Use

Protein extracted from leafy crops is potentially the most abundant protein concentrate. It is an acceptable complement to green vegetables cooked in the normal manner, and it replaces oil-seed products and fishmeal in animal feeds. It is so easy to make, and its value as a source of protein and vitamin A is so obvious in human feeding trials, that it is surprising that it seems not to have become part of the culinary tradition anywhere. It is now slowly gaining recognition as an animal feed.

Leaf Protein: Production and Use

AbstractProtein extracted from leafy crops is potentially the most abundant protein concentrate. It is an acceptable complement to green vegetables cooked in the normal manner, and it replaces oil-seed products and fishmeal in animal feeds. It is so easy to make, and its value as a source of protein and vitamin A is so obvious in human feeding trials, that it is surprising that it seems not to have become part of the culinary tradition anywhere. It is now slowly gaining recognition as an animal feed.

Labeling of Soybeans with the Stable Isotope 70Zn for Use in Human Metabolic Studies

Radiozinc (65Zn) was used to assess the efficiency of incorporation of the label into soybean seeds by means of a noncycling hydroponic system. It was found that 21.3 and 27.6% of the applied dose was incorporated into the mature seeds when the tracer was applied during vegetative or flowering stages of growth cycle, respectively. The latter method was adapted to labeling with the stable isotope 70Zn, and quantitative incorporation of this isotope was investigated within and among hydroponic culture pots each containing four plants. It was found that on the average 17.7% ± 3.0% of the applied dose was recovered in the mature seeds harvested from each pot. The mass isotope enrichment ratio for 70Zn:68Zn in these seeds was 2.93 ± 0.38 (mean ± SD) compared with the natural ratio of 0.0343, indicating a high degree of stable isotope enrichment. Results of soybean fractionation studies showed that the enrichment was somewhat higher in the defatted meal fraction as compared with the full-fat, the hull, and the whole seed, indicating somewhat preferential translocation of the applied stable isotope in the protein. Despite this small but observable difference, all fractions were highly enriched with 70Zn. The data from this study indicated that noncycling hydroponic culture may be effectively employed to intrinsically label soybeans with the stable isotopes of zinc for use in human feeding trials dealing with the issues of zinc availability. A 100-g portion of such labeled seeds provided 38–43 g protein and 490–620 µg 70Zn in various processed products for use in human feeding studies.

Nullisonmic‐Tetrasomic Wheat for Agronomic and Nutritional Studies1

Chromosomes of Triticum aestivum L. homoeologous groups 1 and 6 have genes coding for synthesis of the endosperm gliadin components. A‐gliadin, coded by genes on chromosome 6A, and possibly other gliadins, produce symptoms in humans with celiac disease. It may be possible to eliminate toxic proteins through breeding. As a first attempt, nullisomic 6A‐tetrasomic 6B (N6AT6B) and N6A‐T6D limes of cultivar ‘Chinese Spring,’ which do not produce A‐gliadin, were grown in sufficient quantities for human feeding trials. Both lines produced satisfactory yields of grain for specialty uses. N6A‐T6B was more desirable agronomically and produced less agliadins than N6A‐T6D. Fertility of the N‐T lines was only slightly lower than that of Chinese Spring.

Human intolerance to bacteria as food.

DEMANDS for new means to solve man's nutritional needs when the pressure of population intensifies or when he attempts to travel in space have suggested the use of single cell organisms as food. Hydrogenomonas eutropha, a hydrogen-fixing bacterium, could effectively control the atmosphere of a space cabin as well as providing nourishment1. The protein is of high biological value2 and is well tolerated even in high concentrations in rat diets3. Human feeding trials seemed warranted and were attempted.