Jack R. Dainty

Background: The functional significance of moderate riboflavin deficiency as it is currently assessed is not well understood. Animal and human studies have suggested a role for riboflavin in the absorption and mobilisation of iron and as such may be important in maintaining haematological status. Recent National Diet and Nutrition Surveys in the United Kingdom have shown that young women in particular are at risk of moderate riboflavin deficiency and low iron status. Methods/Design: A randomised placebo controlled intervention trial was conducted to investigate the effect of riboflavin supplementation on various measures of haematological status in a group of moderately riboflavin deficient young women aged 19 to 25 years. Women who were low milk consumers were initially screened for riboflavin status as assessed by the erythrocyte glutathione reductase activation coefficient assay (EGRAC). One hundred and twenty three women with EGRAC values >1.40 were randomised to receive 2 mg, 4 mg riboflavin or placebo for 8 weeks. In addition 36 of these women were randomly allocated to an iron bioavailability study to investigate the effect of the intervention on the absorption or utilisation of iron using an established red cell incorporation technique. Discussion: One hundred and nineteen women completed the intervention study, of whom 36 completed the bioavailability arm. Compliance was 96 ± 6% (mean ± SD). The most effective recruitment strategy for this gender and age group was e-communication (e-mail and website). The results of this study will clarify the functional significance of the current biochemical deficiency threshold for riboflavin status and will inform a re-evaluation of this biochemical threshold. Trial Registration: Current Controlled Trials Registration No. ISRCTN35811298

The post-genomic technologies are generating vast quantities of data but many nutritional scientists are not trained or equipped to analyse it. In high-resolution NMR spectra of urine, for example, the number and complexity of spectral features mean that computational techniques are required to interrogate and display the data in a manner intelligible to the researcher. In addition, there are often multiple underlying biological factors influencing the data and it is difficult to pinpoint which are having the most significant effect. This is especially true in nutritional studies, where small variations in diet can trigger multiple changes in gene expression and metabolite concentration. One class of computational tools that are useful for analysing this highly multivariate data include the well-known ‘whole spectrum’ methods of principal component analysis and partial least squares. In this work, we present a nutritional case study in which NMR data generated from a human dietary Cu intervention study is analysed using multivariate methods and the advantages and disadvantages of each technique are discussed. It is concluded that an alternative approach, called feature subset selection, will be important in this type of work; here we have used a genetic algorithm to identify the small peaks (arising from metabolites of low concentration) that have been altered significantly following a dietary intervention.

Background: An improved understanding of copper metabolism is needed to derive more precise estimates of dietary requirements. Objectives: The objectives were to validate a method for estimating endogenous losses of copper, test whether a simple model can predict true absorption from the plasma appearance of labeled copper, and develop a compartmental model for copper metabolism by using stable isotopes. Design: A stable isotope of copper was intravenously administered to 6 men, and fecal samples were collected for 14 d. Four weeks later the study was repeated, but with an oral dose, and blood samples were collected for 7 d and fecal samples for 14 d. Results: There was no significant difference (P = 0.48) in the estimated endogenous loss of copper calculated by using either the excreted intravenous dose (x̄ ± SD: 32 ± 5%) or the absorbed and excreted oral dose (35 ± 2%). A simple mathematical model fitted to plasma isotope appearance data estimated true absorption to be 8 ± 2% compared with 48–49% measured by fecal monitoring. A more complicated compartmental model predicted that, when newly absorbed copper first enters the blood, 74% is removed by the liver and 99% is bound to ceruloplasmin in the plasma. The exchangeable pool of copper was estimated to be 43 ± 30 mg. Daily endogenous losses were predicted to be 2.4 mg. Conclusions: The results showed that fecal monitoring is the only method that can reliably measure labeled copper absorption, and it is not necessary to administer an intravenous dose of copper to estimate endogenous losses. The compartmental model provides new insights into human copper metabolism.

Objective: To evaluate whether a compartmental model could estimate iron absorption as accurately as the well-validated technique of plasma area under the curve using labelled test meals. Design: The study is a randomised cross-sectional intervention. Setting: The study was carried out at the Human Nutrition Unit at the Institute of Food Research, Norwich, UK. Subjects: A total of nine female volunteers, aged 338 y. Interventions: Volunteers were given an oral dose (approximately 5 mg) of Fe-57 as iron sulphate in an orange juice test drink and simultaneously infused Fe-58 (approximately 200 g) as iron citrate over 90 min. Multiple blood samples were taken for the following 6 h. The samples were analysed by mass spectrometry and iron absorption was estimated using a mathematical model based on the appearance of Fe isotopes in plasma and the area under the curve technique. Results: The geometric mean (-1 s.d., +1 s.d.) absorption of the model estimate is 16% (9, 31) and the area under curve estimate is 18% (8, 29). Conclusions: Results indicate that a compartmental model can be used to estimate labelled iron absorption although it is unlikely that this new method will be used in favour of an existing one. Further studies are now needed with unlabelled iron to assess whether the technique could have application in the assessment of total (haem+nonhaem) iron absorption from food. Sponsorship: European Union Marie Curie Fellowship and Biotechnology and Biological Sciences Research Council (BBSRC), UK.

A method for measuring unlabelled Fe absorption has been investigated in a pilot study using a simple mathematical model. The metabolism of newly absorbed Fe can be approximated as a single-compartment model with the sampled compartment being the plasma pool. Five female volunteers (aged 30–55 years) were recruited to participate in the pilot study. After a 10 mg oral dose of unlabelled ferrous sulfate, the change in plasma Fe concentration over the following 6 h was used to estimate the quantity of absorbed Fe from the mathematical model. To assess the accuracy of the new technique, a 1 mg oral dose of 57Fe-labelled iron sulfate was given simultaneously with a 225 μg intravenous dose of 58Fe as iron citrate. The plasma appearance of the labelled Fe was used to estimate the absorption of the oral label from the traditional area under the curve method. There was no significant difference (P=0·61) between the geometric mean absorption of the unlabelled (19 (- 1 sd 12, +1 sd 28) %) and the labelled Fe (17 (- 1 sd 10, +1 sd 29) %). These initial results are encouraging, but further work needs to be undertaken with smaller doses, as typically found in meals. The effect of diurnal variation in serum Fe concentration on the estimation of unlabelled Fe absorption needs further assessment.