Charlotte N. Armah

Establishing optimal selenium status: results of a randomized, double-blind, placebo-controlled trial

BACKGROUND Dietary recommendations for selenium differ between countries, mainly because of uncertainties over the definition of optimal selenium status. OBJECTIVE The objective was to examine the dose-response relations for different forms of selenium. DESIGN A randomized, double-blind, placebo-controlled dietary intervention was carried out in 119 healthy men and women aged 50-64 y living in the United Kingdom. Daily placebo or selenium-enriched yeast tablets containing 50, 100, or 200 microg Se ( approximately 60% selenomethionine), selenium-enriched onion meals ( approximately 66% gamma-glutamyl-methylselenocysteine, providing the equivalent of 50 microg Se/d), or unenriched onion meals were consumed for 12 wk. Changes in platelet glutathione peroxidase activity and in plasma selenium and selenoprotein P concentrations were measured. RESULTS The mean baseline plasma selenium concentration for all subjects was 95.7 +/- 11.5 ng/mL, which increased significantly by 10 wk to steady state concentrations of 118.3 +/- 13.1, 152.0 +/- 24.3, and 177.4 +/- 26.3 ng/mL in those who consumed 50, 100, or 200 microg Se-yeast/d, respectively. Platelet glutathione peroxidase activity did not change significantly in response to either dose or form of selenium. Selenoprotein P increased significantly in all selenium intervention groups from an overall baseline mean of 4.99 +/- 0.80 microg/mL to 6.17 +/- 0.85, 6.73 +/- 1.01, 6.59 +/- 0.64, and 5.72 +/- 0.75 microg/mL in those who consumed 50, 100, or 200 microg Se-yeast/d and 50 microg Se-enriched onions/d, respectively. CONCLUSIONS Plasma selenoprotein P is a useful biomarker of status in populations with relatively low selenium intakes because it responds to different dietary forms of selenium. To optimize the plasma selenoprotein P concentration in this study, 50 microg Se/d was required in addition to the habitual intake of approximately 55 microg/d. In the context of established relations between plasma selenium and risk of cancer and mortality, and recognizing the important functions of selenoprotein P, these results provide important evidence for deriving estimated average requirements for selenium in adults. This trial was registered at clinicaltrials.gov as NCT00279812.

Impact of menstrual blood loss and diet on iron deficiency among women in the UK

Women of childbearing age are at risk of Fe deficiency if insufficient dietary Fe is available to replace menstrual and other Fe losses. Haem Fe represents 10-15 % of dietary Fe intake in meat-rich diets but may contribute 40 % of the total absorbed Fe. The aim of the present study was to determine the relative effects of type of diet and menstrual Fe loss on Fe status in women. Ninety healthy premenopausal women were recruited according to their habitual diet: red meat, poultry/fish or lacto-ovo-vegetarian. Intake of Fe was determined by analysing 7 d duplicate diets, and menstrual Fe loss was measured using the alkaline haematin method. A substantial proportion of women (60 % red meat, 40 % lacto-ovo-vegetarian, 20 % poultry/fish) had low Fe stores (serum ferritin <10 microg/l), but the median serum ferritin concentration was significantly lower in the red meat group (6.8 microg/l (interquartile range 3.3, 16.25)) than in the poultry/fish group (17.5 microg/l (interquartile range 11.3, 22.4) (P<0.01). The mean and standard deviation of dietary Fe intake were significantly different between the groups (P=0.025); the red meat group had a significantly lower intake (10.9 (sd 4.3) mg/d) than the lacto-ovo-vegetarians (14.5 (sd 5.5) mg/d), whereas that of the poultry/fish group (12.8 (sd 5.1) mg/d) was not significantly different from the other groups. There was no relationship between total Fe intake and Fe status, but menstrual Fe loss (P=0.001) and dietary group (P=0.040) were significant predictors of Fe status: poultry/fish diets were associated with higher Fe stores than lacto-ovo-vegetarian diets. Identifying individuals with high menstrual losses should be a key component of strategies to prevent Fe deficiency.

A diet rich in high-glucoraphanin broccoli interacts with genotype to reduce discordance in plasma metabolite profiles by modulating mitochondrial function

Background: Observational and experimental studies suggest that diets rich in cruciferous vegetables and glucosinolates may reduce the risk of cancer and cardiovascular disease (CVD). Objective: We tested the hypothesis that a 12-wk dietary intervention with high-glucoraphanin (HG) broccoli would modify biomarkers of CVD risk and plasma metabolite profiles to a greater extent than interventions with standard broccoli or peas. Design: Subjects were randomly assigned to consume 400 g standard broccoli, 400 g HG broccoli, or 400 g peas each week for 12 wk, with no other dietary restrictions. Biomarkers of CVD risk and 347 plasma metabolites were quantified before and after the intervention. Results: No significant differences in the effects of the diets on biomarkers of CVD risk were found. Multivariate analyses of plasma metabolites identified 2 discrete phenotypic responses to diet in individuals within the HG broccoli arm, differentiated by single nucleotide polymorphisms associated with the PAPOLG gene. Univariate analysis showed effects of sex (P < 0.001), PAPOLG genotype (P < 0.001), and PAPOLG genotype × diet (P < 0.001) on the plasma metabolic profile. In the HG broccoli arm, the consequence of the intervention was to reduce variation in lipid and amino acid metabolites, tricarboxylic acid (TCA) cycle intermediates, and acylcarnitines between the 2 PAPOLG genotypes. Conclusions: The metabolic changes observed with the HG broccoli diet are consistent with a rebalancing of anaplerotic and cataplerotic reactions and enhanced integration of fatty acid β-oxidation with TCA cycle activity. These modifications may contribute to the reduction in cancer risk associated with diets that are rich in cruciferous vegetables. This trial was registered at clinicaltrials.gov as NCT01114399.

Diet rich in high glucoraphanin broccoli reduces plasma LDL cholesterol: Evidence from randomised controlled trials.

Scope Cruciferous-rich diets have been associated with reduction in plasma LDL-cholesterol (LDL-C), which may be due to the action of isothiocyanates derived from glucosinolates that accumulate in these vegetables. This study tests the hypothesis that a diet rich in high glucoraphanin (HG) broccoli will reduce plasma LDL-C. Methods and results One hundred and thirty volunteers were recruited to two independent double-blind, randomly allocated parallel dietary intervention studies, and were assigned to consume either 400 g standard broccoli or 400 g HG broccoli per week for 12 weeks. Plasma lipids were quantified before and after the intervention. In study 1 (37 volunteers), the HG broccoli diet reduced plasma LDL-C by 7.1% (95% CI: –1.8%, –12.3%, p = 0.011), whereas standard broccoli reduced LDL-C by 1.8% (95% CI +3.9%, –7.5%, ns). In study 2 (93 volunteers), the HG broccoli diet resulted in a reduction of 5.1% (95% CI: –2.1%, –8.1%, p = 0.001), whereas standard broccoli reduced LDL-C by 2.5% (95% CI: +0.8%, –5.7%, ns). When data from the two studies were combined the reduction in LDL-C by the HG broccoli was significantly greater than standard broccoli (p = 0.031). Conclusion Evidence from two independent human studies indicates that consumption of high glucoraphanin broccoli significantly reduces plasma LDL-C.

Development of a high-resolution ICP-MS method, suitable for the measurement of iron and iron isotope ratios in acid digests of faecal samples from a human nutrition study

High-resolution ICP-MS has been used to determine iron concentrations and isotope ratios in acid digests of faecal material from a human nutritional study (designed to investigate the absorption of iron from different types of diet). A resolution setting of 4000 was employed to separate the analyte isotopes from argon-based spectral interferences. Accurate correction of chromium and nickel isobaric overlaps required a correction for mass bias between the monitor isotopes 53Cr+ and 60Ni+, and the interfering isotopes 54Cr+and 58Ni+. Control faecal samples collected from each volunteer, and known to contain natural isotopic abundance iron, were used to calculate the mass bias correction factor, which was then applied to the remaining samples. The method was validated through the measurement of 190 separate acid digests of the certified reference material NIST 1577b (Bovine Liver), measured over a seven month period. The mean iron concentration of all 190 digests was 182 ± 16 µg g−1 compared to the certified value of 184 ± 15 µg g−1. Good agreement with the published natural 57Fe/58Fe isotope ratio was also observed, with a typical ‘in-batch’ precision of 1% RSD for the three replicates of NIST 1577b that were routinely analysed as part of each sample digestion batch. No significant difference was found between isotope ratios measured by ICP-MS (acid digested faecal samples) and by TIMS (fully cleaned up solutions originating from the same set of faecal samples). The preparation and analysis of samples by the ICP-MS method allowed a single analyst to digest, dilute and analyse 120 samples in duplicate in a period of 10 working days.

An ICP-MS methodology using a combined high-resolution/multi-collector detector system for the measurement of total zinc and zinc isotope ratios in faecal samples from a human nutrition study

Inductively coupled plasma (ICP), using a novel combination of high-resolution and multi-collector mass spectrometric detectors, was used for the determination of zinc totals and zinc isotope ratios in nitric acid digests of freeze dried faecal material. The samples were collected as part of a human study investigating the absorption of iron, copper and zinc from three different diet types. A solution of 70Zn was administered to each volunteer and its absorption monitored by measuring the changes to the natural isotopic ratio as the non-absorbed dose appeared in the faeces. 70Zn was measured, at a resolution of 2350, on an electron multiplier in the axial channel of the multi-collector array, whilst 67Zn, 68Zn, 69Ga and 71Ga were simultaneously measured at low resolution (400), using Faraday collectors. Internal and external standardisation procedures were compared for the correction of instrumental drift, but the effectiveness of internal standardisation was limited due to the use of the two different types of detector (electron multiplier and Faraday). Mass bias was corrected for, using the isotope ratio measured in the first faecal sample from each volunteer on the study (t = 0), known to contain only zinc of natural isotopic abundance. The method was validated through the measurement of 190 separate digests of the reference material NIST 1577b, analysed over a seven month period. The mean of all 190 replicates was 125 ± 14 µg g−1, compared to the certified value of 127 ± 16 µg g−1. Zinc isotope ratios measured in the reference material digests showed excellent agreement with published natural isotopic abundance data. Within-sample precision was approximately 0.1 % RSD for 67Zn/70Zn, 68Zn/70Zn and 67Zn/68Zn, and was well inside the requirements of this human study. Good agreement was also found between the isotope ratios measured by TIMS analysis of fully cleaned up samples and by ICP-MS analysis of acid digested solutions of the same set of faecal samples. The preparation and analysis of samples by the ICP-MS method developed allowed a single analyst to digest, dilute and analyse 120 samples in duplicate in a period of 10 working days.

Selenium supplementation has beneficial and detrimental effects on immunity to influenza vaccine in older adults

Summary Background & aims Mortality resulting from influenza (flu) virus infections occurs primarily in the elderly through declining immunity. Studies in mice have suggested beneficial effects of selenium (Se) supplementation on immunity to flu but similar evidence is lacking in humans. A dietary intervention study was therefore designed to test the effects of Se-supplementation on a variety of parameters of anti-flu immunity in healthy subjects aged 50–64 years. Methods A 12-week randomized, double-blinded, placebo-controlled clinical trial (ClinicalTrials.govNCT00279812) was undertaken in six groups of individuals with plasma Se levels <110 ng/mL. Four groups were given daily capsules of yeast enriched with 0 μg Se/day (SeY-0/d; n = 20), 50 μg Se/d (SeY-50/d; n = 18), 100 μg Se/d (SeY-100/d; n = 21) or 200 μg Se/d (SeY-200/d; n = 23). Two groups were given onion-containing meals with either <1 μg Se/d (SeO-0/d; n = 17) or 50 μg Se/d (SeO-50/d; n = 18). Flu vaccine was administrated at week 10 and immune parameters were assessed until week 12. Results Primary study endpoints were changes in cellular and humoral immune responses. Supplementation with SeY and SeO affected different aspects of cellular immunity. SeY increased Tctx-ADCC cell counts in blood (214%, SeY-100/d) before flu vaccination and a dose-dependent increase in T cell proliferation (500%, SeY-50/100/200/d), IL-8 (169%, SeY-100/d) and IL-10 (317%, SeY-200/d) secretion after in vivo flu challenge. Positive effects were contrasted by lower granzyme B content of CD8 cells (55%, SeY-200/d). SeO (Se 50 μg/d) also enhanced T cell proliferation after vaccination (650%), IFN-γ (289%), and IL-8 secretion (139%), granzyme (209%) and perforin (190%) content of CD8 cells but inhibited TNF-α synthesis (42%). Onion on its own reduced the number of NKT cells in blood (38%). These effects were determined by comparison to group-specific baseline yeast or onion control groups. Mucosal flu-specific antibody responses were unaffected by Se-supplementation. Conclusion Se-supplementation in healthy human adults with marginal Se status resulted in both beneficial and detrimental effects on cellular immunity to flu that was affected by the form of Se, supplemental dose and delivery matrix. These observations call for a thorough evaluation of the risks and benefits associated with Se-supplementation.

Cruciferous Vegetables – and Biological Activity of Isothiocyanates and Indoles

Epidemiological studies correlate diets that are relatively rich in cruciferous vegetables with a reduction in the incidence and progression of cancer at various sites. These vegetables are characterised by their accumulation of sulphur-containing glycoisdes know as glucosinolates. In this chapter, we initially review the epidemiological evidence and comment upon the potential interaction between diet and polymorphisms at GST loci. We then discuss the biological activity of isothiocyanates and indoles that are derived from glucosinolates following ingestion of cruciferous vegetables, and which may underlie their protective effects.

416 EFFECT OF A HIGH GLUCORAPHANIN BROCCOLI DIET ON BLOOD PRESSURE AND THE CARDIOVASCULAR RISK PROFILE OF AN AT RISK GROUP: A RANDOMISED CONTROLLED STUDY

Objectives and Background: To quantify the effect of a 12 week dietary intervention with a high glucoraphanin (HG) broccoli on blood pressure (BP), cardiovascular disease (CVD) risk and biomarkers. In the UK, CVD affects more than five million people with estimated annual costs exceeding £30bn(1). A novel HG cultivar of broccoli has been developed by conventional plant breeding that has a threefold greater level of glucoraphanin than the standard variety, subsequently delivering a threefold greater level of the sulforaphane to the systemic circulation (2, 3). Our aim was to explore the potential role of this novel broccoli in reducing CV risk factors. Design and Methods: A twelve week intervention was undertaken where 48 subjects consumed 400 g of either a standard or HG broccoli or garden peas each week. Outcome measures included biochemical and vascular measurements. Results: The HG broccoli intervention resulted in a significant reduction in absolute 10 year CVD risk, total and LDL cholesterol, acylcarnitines and lysophosphatidylcholines concentrations. When the results were stratified by GSTM1 genotype, a more significant reduction in CVD risk, systolic BP and lysophosphatidylcholine concentration was observed in subjects with a non-null GSTM1 homozygous deletion. The standard broccoli interventions did not result in any significant changes in CVD risk or associated biomarkers. The pea intervention resulted in a significant reduction in systolic BP. Conclusions: Consuming HG broccoli for 12 weeks led to a significant reduction in the cardiovascular risk due primarily to modifications in lipid metabolism. References:Luengo-Fernandez R, Leal J, Gray A, Petersen S, Rayner M. Heart. 2006 Oct;92(10):1384–9.Mithen R, Faulkner K, Magrath R, Rose P, Williamson G, Marquez J. Theor Appl Genet. 2003 Feb;106(4):727–34.Gasper AV, Al-Janobi A, Smith JA, Bacon JR, Fortun P, Atherton C, et al. Am J Clin Nutr. 2005 Dec;82(6):1283–91.