Canada fortifies certain products with folic acid and has periconceptional supplementation guidelines – policies designed to improve folate status and reduce the incidence of poor birth outcomes. Though optimal folate concentrations have been linked to health benefits, concerns have been raised regarding potential associations with adverse health outcomes. Direct biochemical assessment of the folate status of Canadians based on a nationally representative sample has not been done in more than 40 years. The overall purpose of this research was to investigate the folate status of the Canadian population. All analyses used the nationally representative 2007–2009 Canadian Health Measures Survey (CHMS). Red blood cell (RBC) folate was measured by Immulite 2000 immunoassay. Key findings indicate that folate deficiency (<305 nmol/L) was virtually non-existent in the Canadian population (6–79 years old). Still, one-fifth of women of childbearing age (WCBA; 15–45 years old) had sub-optimal concentrations for the prevention of neural tube defects (<906 nmol/L). Folic acid supplement intake was a primary determinant of WCBA achieving a RBC folate concentration ≥906 nmol/L. A distinct shift towards elevated RBC folate concentrations emerged. Three hypothetical cut-offs (1450 nmol/L, 1800 nmol/L and 2150 nmol/L) were examined to create dialogue since a universal definition of high RBC folate concentration does not exist. Females, participants aged 60¬–79 years, and those who were overweight or obese had the greatest prevalence of having high RBC folate at each cut-off. We conducted the first national-level comparison of RBC folate concentrations between the United States and Canada. Two different folate assay methods – microbiologic assay (NHANES) and Immulite 2000 immunoassay (CHMS) – necessitated the application of a conversion equation. Median Canadian RBC folate concentrations (adjusted to microbiologic assay) were lower than those of Americans but unadjusted Canadian median RBC folate values were higher. Canadian WCBA were less likely than American WCBA to have RBC folate ≥906 nmol/L, though Canadian WCBA with unadjusted RBC folate values were more likely to achieve this cut-off. These results indicate a need for strategies targeting WCBA to improve compliance with folic acid supplement recommendations. The strength and necessity of supplements for the general population should be re-assessed. Further, harmonization of folate measurement procedures in future surveillance efforts would support comparisons and inform policy directions.

Background: The relationships between both obesity and diabetes and the exposure to insecticides, specifically organophosphates and pyrethroids, in the adult Canadian population are not well-understood. Methods: Urinary concentrations of 4 organophosphate metabolites (DEP, DEPT, DMP, and DMPT) and of 4 pyrethroid metabolites (cis-DBCA, cis-DCCA, 3-PBA, and trans-DCCA) were measured for 1,147 adult Canadians aged between 18-79 years old. The geometric means and medians of both creatinine-adjusted and unadjusted urinary insecticide metabolites were estimated. Multiple linear regression and logistic regression analyses were employed to examine the associations between the insecticide metabolite concentrations and obesity and diabetes measures. Results: Both insecticides had detectable levels in over 70% of CHMS respondents. Most metabolites demonstrated a negative significant relationship between their urinary concentrations and BMI as well as waist circumference. No significant relationship was found in regard to HbA1c levels or for diabetes. Conclusion: Organophosphate and pyrethroid metabolites were detected in more than 70% of Canadian adults. Our data showed no evidence that organophosphate and pyrethroid exposures increase the risks of obesity and diabetes in adults. These results should be interpreted with caution as diet may play a large confounding role in the relationships of study.

Objectives: This thesis examines the risks among Canadian children and adolescents for developing cardio-metabolic diseases, extending evidence that is well-established for adults to pediatric populations. As well, novel indicators and cut-offs for the measurements of disease risks are proposed and associations between physical activity, weight status, socio-economic status and cardio-metabolic health are examined. Methodology: Secondary data analysis was conducted using data from three cycles of the Canadian Health Measures Survey (CHMS), a nationally representative data set which includes measured anthropometric characteristics. A population health approach was applied throughout, underpinned by the World Health Organization’s Conceptual Framework for Action on the Social Determinants of Health. The thesis was designed such that a series of four manuscripts successively built on the key findings from each previous research paper: 1. Establishing the prevalence of Metabolic Syndrome and its risk factors for 10-18 year olds using the International Diabetes Federation child, adolescent and adult definitions. 2. Estimating pre-obesity epidemic waist circumference reference values for Canadian children 6-10 years using reference data from the 1981 Canada Fitness Survey, the Third National Health and Nutrition Examination Survey (1988-1994), and the CHMS through regression of linear, logarithmic and quadratic functions. This work facilitated an expanded age range for the subsequent projects as age- and sex-specific cut-offs based on a Canadian population prior to the obesity epidemic had not been available. 3. Cardio-metabolic risk by body mass index (BMI), waist circumference (WC), and a combined BMI-WC indicator quantified the associations between a dichotomous cardio-metabolic risk variable, and obesity, using three indicators of obesity including a novel indicator, for ages 6-18 years. 4. Association between cardio-metabolic risk and inflammation quantified the associations between inflammation, using high-sensitivity c-reactive protein (CRP) as a marker, and cardio-metabolic risk to determine if high CRP was a significant predictor of cardiometabolic risk among 6-18 year olds. Results: For Paper 1 (n=1228), only 2.1% were classified as having the Mets though 38% had at least 1 MetS risk factor. For Paper 2, logarithmic regression predicted WC cut-offs with the lowest degree of error. For Paper 3 (n=2678), 35% were classified as having cardio-metabolic risk with significantly higher levels among those classified as obese and/or having a low level of physical activity. All indicators of obesity had significant associations with cardio-metabolic risk. For Paper 4 (n=1831), 43.6% of children and 62.0% of adolescents with high CRP levels were classified as having cardio-metabolic risk, a significant relationship. Participants from households with moderate to high income and/or education had the lowest prevalence of MetS risk factors and abdominal obesity. Conclusions: High CRP is a useful indicator of cardio-metabolic risk for pediatric populations. With further research, novel combinations of BMI and WC may be shown to be more predictive for cardio-metabolic risk than these indicators individually. The substantial prevalence of multiple risk factors which predict premature onset of chronic disease foreshadows potential years of morbidity in adulthood for Canada’s youth population.

Background: Metabolic syndrome (MetS) is a clustering of traditional cardiovascular risk factors including central obesity, dyslipidemia, insulin resistance, and hypertension. The prevalence of MetS increases risk of cardiovascular disease and type 2 diabetes and increases with age. Purpose: To compare prevalence and correlates of MetS (and components) in Canadian and Korean older adults. Methods: This study consisted of secondary data analysis, using data from the Canadian Health Measures Survey (CHMS) (cycle 1) and the Korea National Health and Nutrition Examination Survey (cycle 4). The study sample included adults aged 60 to 79 years and who provided fasting blood samples. To compare prevalence of MetS between countries, the same diagnostic criteria (Harmonizing definition) were used. Similar measures of potential explanatory variables for MetS, such as physical activity, dietary patterns, comorbidity, gender, household income adequacy, education, marital status, alcohol consumption, smoking, psychological distress, and duration of sleep were also used where possible. Univariate and multiple logistic regression models were used to examine the cross-sectional relationship between these study variables and MetS. Principal component and cluster analyses were conducted to derive dietary patterns. Results: Included were 550 (weighted N=4,886,039) and 3,040 (weighted N=4,267,182) Canadians and Koreans aged 60 to 79 years, respectively. The prevalence of MetS was 42.0% and 52.2% in the Canadian and Korean sample, respectively (p<.0001). The prevalence of MetS in Korean women was 60.5% and explained the overall increased prevalence in the Korean sample. Results of the descriptive analysis, as well as the univariate and multiple logistic regression analyses indicated that the prevalence and pattern or joint distribution of explanatory variables differed across the two populations. In the Canadian sample, the final multivariate model comprised household income, marital status, alcohol consumption and psychological distress, with evidence of an interaction between adequacy of household income and marital status. In the Korean sample, the final multivariate model comprised comorbidity, gender, education, marital status, physical activity, and dietary pattern, with evidence of an interaction between comorbidity and marital status and between gender and education. Conclusions: Findings of this study provided insight into possible underlying mechanisms that might lead to between-country differences in prevalence of MetS and to inconsistent measures of association between MetS and an individual factor like physical activity or dietary intake across studies.

The increased number of international immigrants and associated global problems of health deterioration and vitamin D (vitD) deficiency/insufficiency may lead to significant burdens for host countries. This thesis investigated immigrants’ health deterioration and vitD status through a comprehensive analysis of Canadian national vitD data, systematic evaluation of the quality/content of clinical practice guidelines, and global systematic review of vitD status and determinants among first-generation immigrants. Immigrants had lower serum 25-hydroxyvitamin D (S-25(OH)D) and higher melanin levels than non-immigrants. S-25(OH)D levels improved over time, with ethnicity the main factor explaining variations. The longer immigrants lived in Canada, the higher the prevalence of chronic diseases (CDs), potentially reflecting health deterioration. Low levels of accumulated S-25(OH)D may impact CD-related biomarkers, partially explaining immigrants’ health deterioration over time. Local and international guidance regarding immigrants’ vitD deficiency/insufficiency was lacking. Improving immigrants’ vitD status requires prevention and intervention programs (e.g., vitD supplementation/screening), relevant national/international guidelines, and longitudinal research clarifying the complex bidirectional association between S-25(OH)D and CDs.