The hypothesis that milk consumption decreases short-term appetite and food intake and improves glycemic control compared with other caloric beverages in healthy young adults was explored in four experiments. The first two experiments compared isovolumetric amounts (500 ml) of milk (2% M.F.), chocolate milk (1% M.F.), a soy beverage, infant formula, orange juice and water on satiety and food intake and blood glucose before and after a meal provided at 30 min (Experiment 1) and 120 min (Experiment 2). Pre-meal ingestion of chocolate milk and infant formula (highest in calories) reduced food intake at 30 min, but not 2 h. Only milk reduced post-meal blood glucose in both experiments suggesting that its macronutrient composition is a factor in blood glucose control. Experiment 3 compared the effects of ad libitum consumption of milk (1% M.F.), regular cola, diet cola, orange juice and water at a pizza meal on fluid and ad libitum food intake and post-meal appetite and glycemia. Fluid volume consumed was similar, but all caloric beverages added to total meal-time energy intake. However, milk lowered post-meal blood glucose and appetite score. In Experiment 4, the effect of isovolumetric (500 ml) beverages of whole milk (3.25% M.F.) and each of its macronutrient components, protein (16 g), lactose (24 g), and fat (16 g) on glycemic control and gastrointestinal hormonal responses were examined. The reduction in post-prandial glycemia was mediated by interactions between its macronutrient components and associated with hormonal responses that slow stomach emptying and increase glucose disposal. Thus, the results of this research do not support the hypothesis that milk consumption decreases short-term appetite and food intake compared with other beverages; however, milk improves glycemic control by insulin-dependent and independent mechanisms.

Background: The value of soy, as an effective component of a cholesterol lowering diet, is currently questioned due to smaller lipid reductions than previously reported for the currently approved US FDA health claim for soy. Nevertheless, intrinsic and extrinsic factors may exist that influence the effectiveness of soy, but little research has been done in this area. Such factors include the soy isoflavone content, dietary components that alter colonic fermentation and the colon’s ability to biotransform isoflavones (i.e. equol status). Objective: To determine if specific factors, such as dose of soy isoflavones and those that alter colonic fermentation, influence the hypocholesterolemic effect of soy. Furthermore, whether cholesterol reductions differ depending on the interindividual variation in isoflavone biotransformation (i.e. equol status), when soy is consumed under different dietary conditions (i.e. with specific factors). Methods: 85 men and postmenopausal women (42M, 43F) with hyperlipidemia participated in one of three substudies where soy foods, containing 30-52g/d of soy protein, were provided over a one-month period under the following conditions: 1) high-normal (73mg/d) or low (10mg/d) soy isoflavones (N=41); 2) with or without a prebiotic (10g/d polyfructans) to increase colonic fermentation (N=22); or 3) with a reduced carbohydrate diet (26% of calories) to decrease colonic fermentation (N=22). Results: Unmodified soy foods significantly reduced LDL-C by 5.1%±2.0% (P=0.016). LDL-C reductions were not altered with increased soy isoflavone content nor were the effects dampened with reduced carbohydrate. However, coingestion of soy with a prebiotic improved the cholesterol lowering effect of soy. Equol producers (N=30) showed a relative increase of 5.3±2.5% in HDL-C (P=0.035) after soy compared to nonproducers (N=55), but no significant differences were observed for LDL-C or other lipids. Equol excretion was increased with increased soy isoflavone content, but not with the addition of a prebiotic. Conclusion: The effectiveness of soy, as a cholesterol lowering food, may be improved with the addition of prebiotics, but not with decreased carbohydrate or increased isoflavones. Equol status appears to alter the HDL-C, but not the LDL-C response. These data support the continued use of soy foods as part of the dietary approach to coronary heart disease risk reduction.

The objective of this work was to characterize the expression pattern of the main intestinal mucin and glycosyltransferases genes in the distal ileum, caecum, proximal and distal colon of 5, 10, 15, 21, 25 and 32 days old mouse pups by real-time PCR. We found that all genes considered, except for Muc13 followed a spatio-temporal expression pattern. As a potential modulator of mucin gene expression, gut microbiota composition was also analyzed in the same animals. We found that neither the total bacterial numbers nor the relative abundance of the main microbial phyla vary after 21 days of age. The characterization of the postnatal intestinal mucus layer gene expression may aid to understand disease-related deviations and help designing nutritional interventions to sustain the intestinal barrier.

The objective of this work was to characterize the expression pattern of the main intestinal mucin and glycosyltransferases genes in the distal ileum, caecum, proximal and distal colon of 5, 10, 15, 21, 25 and 32 days old mouse pups by real-time PCR. We found that all genes considered, except for Muc13 followed a spatio-temporal expression pattern. As a potential modulator of mucin gene expression, gut microbiota composition was also analyzed in the same animals. We found that neither the total bacterial numbers nor the relative abundance of the main microbial phyla vary after 21 days of age. The characterization of the postnatal intestinal mucus layer gene expression may aid to understand disease-related deviations and help designing nutritional interventions to sustain the intestinal barrier.

This thesis assessed whether advantages existed for animal (calcium caseinate) versus vegetable protein (barley protein-enriched flour) foods when fed at 30 g protein per day to 23 healthy hyperlipidemic subjects for 4 weeks in a randomized crossover study. Outcomes included serum lipids, serum markers of oxidative stress and the growth response of LNCaP prostate and MCF-7 breast cancer cells when incubated in vitro with individual subject’s study serum as an indication of whether the treatment promoted or inhibited cell growth. There was no treatment effect on blood lipids or biomarkers of oxidative stress nor was in vitro cell growth different between treatments. However, after pooling the two treatments, both MCF-7 and LNCaP cell growth was related positively to the change in oxidized LDL. MCF-7 growth was negatively related to the non-HDL-C: HDL-C ratio suggesting that raising intracellular cholesterol and reducing oxidative stress may have preventive and possibly therapeutic advantages.

Background: The value of soy, as an effective component of a cholesterol lowering diet, is currently questioned due to smaller lipid reductions than previously reported for the currently approved US FDA health claim for soy. Nevertheless, intrinsic and extrinsic factors may exist that influence the effectiveness of soy, but little research has been done in this area. Such factors include the soy isoflavone content, dietary components that alter colonic fermentation and the colon’s ability to biotransform isoflavones (i.e. equol status). Objective: To determine if specific factors, such as dose of soy isoflavones and those that alter colonic fermentation, influence the hypocholesterolemic effect of soy. Furthermore, whether cholesterol reductions differ depending on the interindividual variation in isoflavone biotransformation (i.e. equol status), when soy is consumed under different dietary conditions (i.e. with specific factors). Methods: 85 men and postmenopausal women (42M, 43F) with hyperlipidemia participated in one of three substudies where soy foods, containing 30-52g/d of soy protein, were provided over a one-month period under the following conditions: 1) high-normal (73mg/d) or low (10mg/d) soy isoflavones (N=41); 2) with or without a prebiotic (10g/d polyfructans) to increase colonic fermentation (N=22); or 3) with a reduced carbohydrate diet (26% of calories) to decrease colonic fermentation (N=22). Results: Unmodified soy foods significantly reduced LDL-C by 5.1%±2.0% (P=0.016). LDL-C reductions were not altered with increased soy isoflavone content nor were the effects dampened with reduced carbohydrate. However, coingestion of soy with a prebiotic improved the cholesterol lowering effect of soy. Equol producers (N=30) showed a relative increase of 5.3±2.5% in HDL-C (P=0.035) after soy compared to nonproducers (N=55), but no significant differences were observed for LDL-C or other lipids. Equol excretion was increased with increased soy isoflavone content, but not with the addition of a prebiotic. Conclusion: The effectiveness of soy, as a cholesterol lowering food, may be improved with the addition of prebiotics, but not with decreased carbohydrate or increased isoflavones. Equol status appears to alter the HDL-C, but not the LDL-C response. These data support the continued use of soy foods as part of the dietary approach to coronary heart disease risk reduction.

This thesis assessed whether advantages existed for animal (calcium caseinate) versus vegetable protein (barley protein-enriched flour) foods when fed at 30 g protein per day to 23 healthy hyperlipidemic subjects for 4 weeks in a randomized crossover study. Outcomes included serum lipids, serum markers of oxidative stress and the growth response of LNCaP prostate and MCF-7 breast cancer cells when incubated in vitro with individual subject’s study serum as an indication of whether the treatment promoted or inhibited cell growth. There was no treatment effect on blood lipids or biomarkers of oxidative stress nor was in vitro cell growth different between treatments. However, after pooling the two treatments, both MCF-7 and LNCaP cell growth was related positively to the change in oxidized LDL. MCF-7 growth was negatively related to the non-HDL-C: HDL-C ratio suggesting that raising intracellular cholesterol and reducing oxidative stress may have preventive and possibly therapeutic advantages.

Arginine synthesis is a complex, age-dependant process involving multiple precursors and enzymes, and the interorgan transfer of substrates. The objectives of this thesis were to elucidate arginine synthesis from enteral precursors in newborn infants and in healthy adults using stable isotope methodology. In the first, of four studies, I validated the use of a non-invasive methodology using urinary amino acids for stable isotope studies of arginine synthesis and demonstrated a known, but under-recognised, problem with D-amino acid contamination of tracers. Implementing chiral chromatography, this issue was further investigated using samples from previous studies in our laboratory with several different isotopes. I demonstrated the novel finding that the impact of D-amino acids is dependent on the tracer used, and also on the age of the subject. In the second study, I used a multi-tracer design to assess arginine synthesis from enteral proline or glutamate in healthy preterm infants. Labeled arginine (M+2), proline (M+1) and glutamate (M+3) were given enterally to fifteen stable, growing preterm infants (gestational age at birth 30-35 weeks) at 1-3 weeks’ postnatal age. I found only arginine synthesis from proline, with no synthesis from glutamate. I conclude that enteral proline is the major contributor to arginine synthesis in vivo in human preterm infants. In the third study, I measured arginine synthesis from enteral proline in adults. I have demonstrated that enteral proline contributes significantly, ~25%, to newly synthesised arginine. In the fourth study, I used two glutamine tracers, 1-13C and 2-15N, to determine if glutamine is a carbon or nitrogen donor for arginine. I showed that enteral glutamine contributes ~50% of the carbon skeleton for arginine and that the 2-15N tracer significantly overestimates arginine synthesis, with the labeled N being transferred through transamination from pyrroline-5-carboxylate (to ornithine, rather than directly from glutamate to pyrroline-5-carboxylate. In conclusion, proline is the sole precursor for arginine in human neonates and combines with glutamaine as the dietary precusor in adults. As a precussor for arginine, though, glutamine’s main role is in provision of nitrogen independent of the carbon skeleton.

H. pylori has been classified by World Health Organization as type I carcinogen for its association with gastric cancer. Among its suggested pathological pathways is oxidative stress, which may reduce the bioavailability of dietary antioxidants. The main objectives of this thesis were to estimate the prevalence of H. pylori infection in Ontario and to assess its effect on the bioavailability of two main dietary antioxidants, vitamins E and C. To estimate the prevalence of H. pylori infection, a volume of 10 ul of plasma was aliquoted from stored blood of 1306 adults from Ontario. The blood samples belonged to controls of a population-based study of colorectal cancer. The overall weighted seroprevalence of H. pylori was 23.1% (95% CI: 17.7-29.5) with males having higher infection rates than females. Seroprevalence of the infection increased with age and number of siblings. Being non-white, born outside Canada and immigrating at an age greater than 20 years increased risk for H. pylori infection. An inverse association with seroprevalence was found for education and alcohol consumption. In order to investigate whether H. pylori positive compared to H. pylori negative subjects have lower changes in plasma concentrations of ascorbic acid and alpha tocopherol when supplemented with these vitamins, H. pylori negative (n=32) and H. pylori positive (n=27) volunteers received vitamin C (500 mg) and alpha tocopherol (400 IU) supplementation daily for 28 days. H. pylori infection status was determined by 13C urea breath test. Post supplementation plasma ascorbic acid and alpha tocopherol were significantly higher than pre supplementation concentrations in both groups. The changes in plasma ascorbic acid and alpha tocopherol were not significantly different between H. pylori negative and positive groups (ascorbic acid: 13.97±16.86 vs. 20.87±27.66, p=0.76; alpha tocopherol: 15.52±9.4 vs. 14.47±15.77; p=0.39 for H. pylori negative and positive groups respectively). The weighted seroprevalence of H. pylori infection was 23.1%. Age, sex, ethnicity, place of birth, age at immigration, education and alcohol consumption were factors associated with the infection prevalence in the population studied. In addition, we found no effect of H. pylori infection on the bioavailability of vitamins E and C.

The effects of high maternal folate status on the offspring are unknown; however, early life exposure to environmental stimuli, including dietary factors, is thought to influence the risk of developing chronic disease. An animal study was performed to determine the effect of maternal folic acid supplementation during pregnancy and lactation on DNA methylation and global gene expression patterns in the offspring. Supplementation of the maternal diet with folic acid (5, 8, and 25 mg/kg diet) induced global DNA hypomethylation in the liver of juvenile and adult offspring, and altered the expression of the imprinted H19 gene and genes involved in lipid metabolism, coagulation, and iron transport and homeostasis. Our data suggest that intrauterine and early postnatal periods are susceptible to changes in DNA methylation and gene expression in response to high levels of folic acid, which may be associated with health status and disease later in life.