Middle Eastern Women's Health Study-Phase II : the effect of monthly 50,000 IU or 100,000 IU vitamin D supplements on Vitamin D status in pre-menopausal Middle Eastern women living in Auckland : a research report presented in partial fulfilment of the requirements for the degree of Master of Sciences in Human Nutrition at Massey University, Albany, New Zealand

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Background: Middle Eastern women are at increased risk of vitamin D deficiency/insufficiency due to a number of specific lifestyle risk factors. Vitamin D supplements (50,000 IU/month) are prescribed by General Practitioners to correct vitamin D deficiency in this population in New Zealand. However, no research has investigated whether this dose of vitamin D supplement is useful for vitamin D deficiency treatment in Middle Eastern women or if larger doses are needed. Objectives: The primary objective of this study was to conduct a double-blind, randomised, placebo-controlled trial with vitamin D supplementation for 6 months. We aimed to assess the adequacy of supplementation with monthly 50,000 IU and 100,000 IU in optimising serum 25(OH)D concentrations (= 50 nmol/L and = 75 nmol/L) in a group of Middle Eastern premenopausal women living in Auckland. The secondary objective was to identify those factors affecting serum 25(OH)D response to the given doses of vitamin D supplements. Results from this study will help medical practitioners to provide the best options for treating vitamin D deficiency in Middle Eastern women living in New Zealand. Method: Women of Middle Eastern origin, = 20 years old and in premenopausal stage, having no major illness, living in Auckland (n=62) were recruited for the study in winter 2013. All were required to take study tablets (50,000, 100,000 IU or placebo/month) for 6 months and were required to visit the Human Nutrition Research Unit at Massey University on 3 occasions (baseline, 3-months, and 6-months). Blood samples were collected to measure serum 25(OH)D concentrations and calcium levels. Participants were required to complete questionnaires about their demographics, medical history, skin colour, lifestyle change and physical activity level. Height, weight, body fat percentage (BFP) and blood pressure were measured. Participants were also required to complete four day food dairies. The primary outcomes were the changes in serum 25(OH)D concentration and serum calcium level. Results: Mean baseline serum 25(OH)D was 46.0±15.0 nmol/L. Supplementation with 50,000 IU/month and 100,000 IU raised the mean serum 25(OH)D concentrations from a baseline of 44.0±16.0 and 48.0±11.0 nmol/L to 70.0±15.0 and 82.0±17.0 nmol/L at 6 months, respectively (P<0.001 for both treatment groups). The mean serum 25(OH)D concentration of women assigned to placebo group increased from 45.0±18.0 nmol/L at baseline to 54.0±18.0 nmol/L at 6 months (P<0.01). The mean serum 25(OH)D concentrations reached a Hajar Mazahery MEWH Study-Phase II Abstract plateau after 3 months of supplementation. Of 62 women, 59.7% had serum 25(OH)D concentrations <50 nmol/L and only 3.3% had serum 25(OH)D = 75 nmol/L. At 6 months, the proportion of subjects achieving serum 25(OH)D concentration of 75 nmol/L or more was 31.6% and 66.7% in women receiving monthly 50,000 IU and 100,000 IU, respectively (P=0.002). There were no reports of hypervitaminosis D (serum 25(OH)D >225 nmol/L) or hypercalcemia (serum calcium = 2.7 mmol/L). Response to vitamin D supplementation varied widely (increasing 1.0 to 80.0 nmol/L). In a regression analysis, dose (P<0.001), baseline serum 25(OH)D concentration (P<0.001) and baseline BFP (P=0.01) were the only variables to reach statistical significance as predictors of the change in serum 25(OH)D over 6 months. Conclusion: The prevalence of vitamin D deficiency/insufficiency was high in this study population highlighting the significance of the situation. Monthly intake of 100,000 IU vitamin D for 6 months was more effective than 50,000 IU in achieving serum 25(OH)D concentrations of 75 nmol/L, though it did not ensure a serum 25(OH)D concentration of 75 nmol/L or more in all people. Factors affecting serum 25(OH)D response to supplementation should be taken into account when an optimal dose for individuals is determined. The unexpectedly large variance in serum 25(OH)D response to a fixed dose of vitamin D highlights the importance of follow up and measurements of serum 25(OH)D when supplementation is used in clinical practice.
Middle Easterners, Women, Arab women, Health and hygiene, Nutrition, Vitamin D status, Vitamin D supplementation, Vitamin D in human nutrition, Research Subject Categories::INTERDISCIPLINARY RESEARCH AREAS::Domestic science and nutrition