Thesis (M. Phil.)--University of Hong Kong, 1987.

Despite the medical advances in recent decades, cardiovascular disease (CVD) remains one of the leading causes of mortality in most developing countries. Ongoing efforts have been focused on evaluating new strategies targeting on novel risk factors. Vitamin D deficiency, a previously neglected condition, has recently attracted much attention from the scientific community with its potential extra-skeletal effects. There is accumulating evidence from epidemiological studies that a suboptimal 25-hydroxyvitamin D [25(OH)D] level is associated with all-cause and cardiovascular mortality, increased risk of coronary heart disease, stroke and peripheral vascular disease, and various traditional CVD risk factors including hypertension, diabetes mellitus (DM) and metabolic syndrome. Several theories have been proposed to explain these relationships but none receive universal recognition. There is recent laboratory evidence that vitamin D may exert specific effects in patients with DM. However, relationships between vitamin D deficiency and supplementation on vascular function in this group of patients are unclear. In this dissertation, I sought to explore the effects of vitamin D deficiency on vascular function in patients with type II DM in a cross-sectional study. In the later part, the results of a randomized controlled trial investigating the effects of daily vitamin D supplementation in type II DM patients are presented and discussed. The cross-sectional study (Chapter 3) investigated the association of vitamin D status with endothelial function as measured by brachial flow-mediated dilation (FMD) and circulating endothelial progenitor cell (EPC) numbers in 280 patients with type II DM. The results showed that suboptimal vitamin D status was more common among patients with DM. Furthermore, patients with vitamin D deficiency had significantly lower brachial FMD (mean difference = -1.43%, 95% CI: -2.31 to -0.55, P = 0.001) and CD133/KDR+ EPC counts (mean difference = -0.12%, 95% CI: -0.21 to -0.02, P = 0.022) than those with sufficient vitamin D after adjustment for age, sex and cardiovascular risk factors, including HbA1c levels. Based on these positive results, the objectives of the randomized controlled trial (Chapter 4) were to study and confirm the effects of daily oral vitamin D supplementation on the vascular function in this group of patients. Over a 12-week period, 100 DM patients with suboptimal vitamin D status were randomized to receive 5,000 IU/day vitamin D or placebo. There were no reported adverse events including hypercalcemia, although a slight increase in serum ionized calcium (treatment effect 0.037 mmol/L, P = 0.018) was recorded in the vitamin D group. Despite a significant improvement in serum 25(OH)D in the treatment group, supplementation of vitamin D did not result in any significant improvement in vascular function as determined by FMD, circulating EPC count or arterial stiffness (all P > 0.05). Furthermore, the serum level of high-sensitivity C-reactive protein, oxidative stress markers, low- and high-density lipoprotein and glycated haemoglobin were also similar between two groups (all P > 0.05). The results of this study did not support a therapeutic role of supplementation with vitamin D for cardiovascular benefits. In conclusion, the results of these studies demonstrated that deficiency of vitamin D was associated with worse vascular function in patients with type II DM. However, vitamin D supplementation did not result in any significant benefits on vascular function or improvement in traditional CVD risk factors in DM patients. Further large clinical trials on vitamin D supplementation in patients with DM using clinical outcomes rather than surrogate CVD markers are necessary to confirm its benefits. / published_or_final_version / Medicine / Master / Master of Research in Medicine

Background Vitamin D deficiency is prevalent in many places across the world. Breastfeeding has been suggested to be a significant predictor of vitamin D deficiency during infancy, which is preventable through proper supplementation. However, whether Hong Kong should adopt the international recommendation for supplementation of exclusive breastfed infants is still not yet answered. Objective: To review the available evidence regarding the association between breastfeeding and vitamin D deficiency during infancy, as well as the effectiveness of vitamin D supplementation of breastfed infants as an intervention measure. Methods A total of 5112 potentially relevant articles were searched and identified from MEDLINE (OVID, Pubmed), Science Citation Index Expanded (ISI Web of Science), Cochrane Central Register of Controlled Trials, EMBASE, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) and Chinese database (CNKI) without restriction from inception to July-06-2012. 5065 articles were excluded after the initial scanning of title and abstracts. 36 were subsequently excluded due to methodological issues. A total of 11 studies were included and reviewed by two independent reviewers. Results This review pooled together a total of 1126 exclusively breast-fed infants for less than one year old from 11 studies. The pooled average prevalence of vitamin D deficiency was 54.2%. The association between breastfeeding and vitamin D deficiency during infancy has been reported consistently, and it was found to be one of the strongest predictors of vitamin D deficiency for infants less than one year old. Sunlight exposure, season, and skin pigmentation were also found to be important affecting factors. Supplementation to breastfed infants with the dosages as recommended by American Academy of Pediatrics (AAP) seem to be effective in lifting up the vitamin D levels. Conclusions The Hong Kong Government and relevant health sectors should conduct local epidemiological study to investigate the problem of concern among our breast-fed infants, and seriously consider or evaluate the AAP recommendation of supplementation. / published_or_final_version / Public Health / Master / Master of Public Health

published_or_final_version / Biochemistry / Master / Master of Philosophy

The objectives of the present study in rural Nepali pregnant women living in the terai were: 1) to identify the risk factors of severe anemia and investigate whether risk factors for anemia without iron deficiency, iron deficiency without anemia and iron deficiency anemia (IDA) were different; 2) to examine the effect of vitamin A supplementation, alone or combined with iron, on hemoglobin (Hb) and soluble transferrin receptor (sTfR); and 3) to identify the risk factors of low birth weight (LBW) and preterm delivery, focusing on maternal Hb concentrations. The prevalence of severe anemia (Hb < 8.0 g/dl) in this population (n = 3531) was 4.2% and that of iron deficiency was 31%. Logistic regression analyses indicated that risk factors of severe anemia included hookworm infestation, impaired dark adaptation, lack of iron supplement intake, a diet low in heme iron and malnutrition manifested by thinness and short stature. These same factors differed among non-iron-deficient anemic, iron deficient non-anemic, and iron-deficient anemic pregnant women. We found a significant positive correlation between Hb and retinol concentrations (Pearson r = 0.212, P < 0.0001) and one fourth of our anemic subjects were also vitamin A deficient. There was no evidence that vitamin A alone significantly increased Hb and decreased the prevalence of anemia (n = 498). However, vitamin A, when given together with iron, had an added beneficial effect on Hb but not sTfR. In addition, women with initially compromised iron status benefited more from iron and vitamin A supplementation. The prevalence of LBW and preterm delivery was 22% and 20%, respectively (n = 915). There was an increased risk of LBW associated with short stature, thinness and impaired dark adaptation. The association between Hb measured during the second trimester and risk of LBW had a U-shaped distribution, with risk increasing significantly with Hb < 8.0 g/dl. Based on our findings, we recommend that Hb is evaluated during the second trimester as an indicator of increased LBW risk. While vitamin A supplementation to all pregnant women is recommended, routine supplementation of iron and deworming during pregnancy are essential.

Objective: This thesis aims to construct a framework for studying vitamin D deficiency in young Canadian children. Methods: A practice based research network was created to collect vitamin D data from children 1-5 years of age in Toronto, Canada (TARGet Kids!). A cross-sectional pilot study was completed and a larger study proposed to determine the prevalence and predictors of low vitamin D. Results: The prevalence of low vitamin D (<50nmol/L) in the pilot study was 32% (29/92, 95% CI: 22-42%). Using multivariable linear regression, lower vitamin D level was associated with lower milk volume, higher BMI and watching TV during snacks. A larger study involving 2400 children 1-5 years of age has been proposed. Interpretation: Pilot data has suggested that 30-80% of toddlers in this setting have low vitamin D. A study to clarify these findings and form the basis of a large longitudinal vitamin D cohort has been proposed.

Objective: This thesis aims to construct a framework for studying vitamin D deficiency in young Canadian children. Methods: A practice based research network was created to collect vitamin D data from children 1-5 years of age in Toronto, Canada (TARGet Kids!). A cross-sectional pilot study was completed and a larger study proposed to determine the prevalence and predictors of low vitamin D. Results: The prevalence of low vitamin D (<50nmol/L) in the pilot study was 32% (29/92, 95% CI: 22-42%). Using multivariable linear regression, lower vitamin D level was associated with lower milk volume, higher BMI and watching TV during snacks. A larger study involving 2400 children 1-5 years of age has been proposed. Interpretation: Pilot data has suggested that 30-80% of toddlers in this setting have low vitamin D. A study to clarify these findings and form the basis of a large longitudinal vitamin D cohort has been proposed.

Thesis (PhD)--University of South Australia, 1999

Thesis (M.S.)--University of Delaware, 2008. / Principal faculty advisor: Cheng-Shun (Richard) Fang, Dept. of Health, Nutrition, & Exercise Sciences. Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1976.