The aim of the work described in this thesis was to evaluate the potential for using stable isotope <SUP>13</SUP>C labelled tracer, 1-<SUP>13</SUP>C -AA, in studies of AA kinetics in humans. To this end a method of measuring AA isotope enrichment in plasma samples using gas chromatography and mass spectrometry, (GC/MS), was developed. Derivatisation of AA was required for gas chromatographic separation, and the trimethylsilyl, (TMS), ether derivative, AA-tetra-TMS, was found to be the most compatible with subsequent mass spectrometric quantitation of isotope enrichment. A method was developed to prepare lyophilized plasma samples for TMS derivatisation. Two studies of AA kinetics in human volunteers were than carried out in which a dose of stable isotope labelled 1-<SUP>13</SUP>C-AA was administered orally. The enrichment of AA was measured in plasma samples collected for 24 and 48 hours after dosing. In the second study, investigation of isoascorbic acid, (IAA), kinetics was also undertaken. IAA concentration in plasma samples was measured by high performance liquid chromatography, HPLC. Compartment models of AA and IAA handling in man were constructed and described as a series of mathematical expressions containing kinetic parameters. Kinetic analysis was achieved by fitting theoretical values calculated from the mathematical expressions describing the models to the observed (time course) data. This produced estimates of kinetic parameters, (flow constants and pool sizes), describing AA and IAA handing in man. These were compared with those obtained in other studies. The method is now being applied to further studies into the bioavailability, metabolism and utilization of AA in humans and has the potential to be a useful non-invasive technique which may provide an invaluable insight into the vitamin C status of individuals in a variety of populations.

No description available.

To investigate whether phytoestrogens had an antioestrogenic effect, a large double blind, randomised, placebo controlled trial was conducted for approximately one year. Mammographic breast density, hormone levels, menopausal symptoms, cardiovascular risk factors, bone density, and body composition were assessed. When compared with the effects of placebo, 40mg daily dose of isoflavones did not significantly alter mammographic breast density when assessed by several different methods. Mean change in estimated percent density determined from the mammogram comparison data was - 1.35% (SD 5.16) in the isoflavone group, and -1.79% (SD 7.41) in the placebo group. There was also no significant effect on levels of oestradiol, FSH, or LH. Menopausal symptoms, and hot flushes specifically, were not significantly altered by clover isoflavones. Cardiovascular risk factors (blood pressure, blood lipids, and blood clotting factors) were also not significantly altered. However, the isoflavones did affect bone density. Spine bone mineral density (BMD) decreased to a significantly lower extent in the isoflavone group compared with that seen in the placebo group (p<0.01). The effect on BMD was mainly seen in the pre- and peri-menopausal women, and isoflavones also had a significant effect on BMC in this group. Levels of the bone resorption marker, deoxypyridinoline (Dpd) increased in both the isoflavone and placebo pre- and peri-menopausal groups. However, the increase was significantly lower in the isoflavone group compared with placebo (p=0.03), supporting the finding of a beneficial effect of isoflavones on bone as judged by BMD and BMC. Similar trends (not significant) regarding BMC and BMD were seen in the hip in pre-and peri-menopausal women, and there was a significant increase in body fat with the isoflavone supplement in this group (p<0.01).

Chapter 1 provides a general introduction while Chapter 2 investigates the relationships between dietary iron intake, disease activity and quality of life (QOL) in patients with IBD. Results indicated that non-haem iron intake was significantly associated with iron requirements for IBD patients but not healthy controls. Interestingly, for iron replete IBD patients, a significant positive correlation between iron intake and disease activity was noted. Correlation between QOL and iron intake was also observed. Chapter 3 investigated the acute effects of a single oral dose of ferrous sulphate on (i) iron absorption into serum and (ii) systemic nontransferrin bound iron (NTBI) generation. It also investigated whether baseline haematinics are an appropriate indicator of iron requirements in IBD subjects. Overall, iron absorption did not differ between IBD patients and healthy controls and both groups showed a similarly significant rise in NTBI following supplementation. However, in healthy controls baseline haematinics predicted iron absorption (i.e. iron requirements) but not in patients with IBD. Chapter 4 reports a laboratory-based investigation on the ability of different organic acids (OA) to alter the precipitation and redissolution properties of insoluble ferric hydroxide. The aim being to identify potential OA’s for use in a novel ferric iron supplement. Results showed that malic acid had significant effects on the precipitation and redissolution of ferric iron and may be efficacious as an iron supplement. Finally, in Chapter 5, <i>in vivo</i> testing of selected iron-organic acid mixtures was undertaken in human volunteers comparing the absorption to ferrous sulphate. Results showed that these were reasonably absorbed, albeit to a lesser extent than ferrous sulphate. Further work could trial these in IBD as side effects should be minimised while at least some iron would be absorbed.

No description available.

This thesis investigates the dietary determinants of fat mass in children using prospective data on diet, fat mass and a range of important confounders (including maternal BMI and education, child’s baseline weight status and TV watching) from a random sub-sample (N ~ 600) of children in the Avon Longitudinal Study of Parents and Children. <br> Investigation I assessed bias in the reporting of energy intake (EI) and found that under-reporting was more common among fatter children. Controlling for misreporting allowed the expected direct effect of EI on fat mass to be observed. Investigation 2 modelled the impact of dietary energy density (DED) on fatness and found that, after controlling for confounders, each 1 kJ/g increase in DED at age 7 y increased the odds of having excess adiposity at age 9 y by 36%. There was no evidence of an effect of DED at age 5 y on having excess adiposity at age 9 y. Investigation 3 found the consumption of sugar-sweetened beverages was low in this sample. There was no evidence that sugar-sweetened beverages were related to fat mass or excess adiposity and therefore are not a significant driver of obesity in this sample of children. Investigation 4 characterised an energy-dense, low-fibre, high-fat dietary pattern score using reduced rank regression. After adjusting for confounding, children in the highest quintile of dietary pattern score (consuming the most energy dense, lowest fibre and highest fat diets) and age 5 and 7 y were 2.5 (95% CI 1.1 to 6.1) and 4.2 (95% CI 2.1 to 9.4) times more likely to have excess adiposity at age 9 y respectively compared to children with the lowest quintile of dietary pattern score. Dietary patterns appear to have a bigger impact on obesity risk than single dietary factors suggesting that the prevention of obesity should take a whole-diet approach.

The aim of this thesis was to investigate the role of dietary fat in the aetiology of type 2 diabetes. The associations of dietary fat and fish consumption with two intermediates in the development of diabetes, insulin resistance and glycaemia, and with the risk of developing diabetes, were examined. The analyses were based on data collected by the Ely and EPIC-Norfolk cohort studies. The cross-sectional associations of dietary fat and fish consumption with fasting insulin, a measure of insulin resistance, were investigated in 815 men and women aged 30-64 years. The dietary polyunsaturated:saturated fat ratio (P:S ratio) was independently related to (log<SUB>e</SUB>) fasting insulin (b = -0.231, p = 0.004). There was no evidence that total fat, saturated, monounsaturated and polyunsaturated fats, and fish consumption were associated with fasting insulin. Body mass index (BMI), waist:hip ratio (WHR), and physical activity were associated with fasting insulin. The cross-sectional associations of dietary fat and fish consumption with glycosylated haemoglobin (HbA<SUB>1c</SUB>), a measure of average blood glucose, were examined in 6414 men and women aged 40-79 years. Total fat, the P:S ratio and saturated fat were independently associated with HbA<SUB>1c</SUB> (b = 0.00726, p < 0.001; b = -0.0919, p = 0.013; and b = 0.0143, p < 0.001 respectively). Oily fish consumption was related to HbA<SUB>1c</SUB> in women (b = -0.0504, p = 0.016). There was no evidence that monounsaturated and polyunsaturated fats were related to HbA<SUB>1c</SUB>. BMI and WHR were related to HbAlc. The evidence for an effect of physical activity was weak. Incident cases of type 2 diabetes were identified for a case-control study nested within EPIC-Norfolk. Capture-recapture analysis suggested that 98-99% of cases were identified. The risk of developing diabetes was analysed in a study of .417 cases and matched controls. There were no statistically significant associations with any dietary factors. BMI, WHR and physical activity were associated with the risk of diabetes. The findings confirm the importance of obesity and physical activity as risk factors for diabetes and suggest that, despite attenuation by measurement error, the quantity and composition of dietary fat have a role in the aetiology of diabetes.

No description available.

In this Thesis a non-invasive, reliable and reproducible technique for the isolation of exfoliated colonocytes from human stool was developed. Exfoliated colonocytes were shown histologically and immunocytochemically to be gut derived although the exact area of the large bowel from which they were derived was not clear. To investigate factors determining the numbers of recovered exfoliated cells, cells were obtained from three studies in which diet was carefully controlled in human volunteers over periods of 10-15 days. On analysis of variance, there was a significant individual effect (<i>p </i>< 0.001), indicating that the recovery technique was reliable. High polyunsaturated diets supplemented with vitamin E, and low starch high sugar diets were probably associated with increased cell recoveries (<i>p</i> < 0.002). In a fourth study, there was a clear effect of alcohol on increasing the numbers of cells recovered (<i>p</i> = 0.004). Transit time and stool weight were not reliably associated with increased cell recovery, but stool consistency was a significant (<i>p</i> < 0.010) factor influencing cell recovery in all three studies investigated. Exfoliated cells are a source of genomic DNA which was successfully isolated from 93.3% of samples, but only 11.7% of these extractions produced DNA yields of 3μg or more, so that quantification of adduct levels could not be determined by a sensitive immunoslot blot analysis. However, direct visualization of diet related adduct formation was possible, and could be quantified as percentages of cells staining positive for the <i>N-</i>nitroso compound (NOC) related adduct, O⁶ carboxymethyl guanine. A red meat diet significantly (<i>p</i> = 0.001) increased percentages of isolated cells staining positive for this adduct compared with a vegetarian diet, and there was a significant correlation (r = 0.66) between measures of faecal ATNC concentration and the percentages of positive cells on an individual basis.

Life expectancy is often determined by cardiovascular disease, cancer, stroke, and diabetes which become increasingly prevalent with age. Epidemiological studies have revealed links between birth weight and the subsequent development of those diseases. Animal studies have implicated poor fetal nutrition in causing adaptations to the development of disease. The work described in this thesis examined the effects of protein restriction during different periods of development on subsequent growth and longevity. It was established that it was not the duration of protein restriction but the timing of dietary manipulation which was essential for regulating growth. Protein restriction during lactation was found to programme appetite and gave rise to permanently slower growth rates but increased longevity. In contrast growth restriction caused by maternal protein deprivation during fetal life followed by rapid catch-up growth was associated with reduced survival. Telomeres are thought to play a role in cellular ageing and senescence. Therefore the possibility that the observed differences in longevity were related to changes in telomere length was investigated. Age-related shortening of telomeres was detected in the liver and kidney of control male rats. Brain telomere lengths remained relatively constant throughout life. Kidney telomere lengths were significantly shorter in 13 month old male rats who had been growth retarded during fetal life and then experienced rapid catch-up growth compared to rats who were growth retarded during lactation. No such differences were observed in the liver or brain. In summary this thesis demonstrates that protein restriction during fetal life, followed by catch-up growth resulted in decreased longevity associated with increased telomere shortening in the kidney. In contrast protein restriction during lactation permanently reduced the rate of growth and the rate of telomere shortening but prolonged longevity. This may provide a mechanistic basis for epidemiological studies linking early growth retardation to adult degenerative diseases.