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Diet and lifestyle factors associated with vitamin D status in healthy women living in the United Kingdom and the Kingdom of Saudi Arabia.

Bushnaq, Taqwa Abdulraheem (2016) Diet and lifestyle factors associated with vitamin D status in healthy women living in the United Kingdom and the Kingdom of Saudi Arabia. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Background: Vitamin D is integral to bone health and skeletal growth. There is now growing evidence that vitamin D deficiency is one of the most common diseases worldwide, not only in countries with limited sunshine, such as the United Kingdom (UK) but also in countries with substantial sunshine, such as the Kingdom of Saudi Arabia (KSA). Aims: The aim of the research was to study vitamin D intake and lifestyle factors that may affect vitamin D production in women adopting different clothing styles within two countries, Saudi women in the KSA, as well as the UK covered (UKc) and the UK uncovered (UKun) women. Methods: The study methods were designed to collect participants’ dietary vitamin D intake, sun exposure routine, other influential lifestyle factors, and vitamin D status. Participants were asked to complete, a vitamin D questionnaire (which included: demographic information, food frequency questionnaire (FFQ) and sun-exposure questionnaire), a 3-day food diary, and a blood sample was taken. A total of 192 participants were recruited and of these 145 completed the vitamin D questionnaire. The 3-day food diary were completed by 57 women, and 79 women gave a blood sample. Data were explained as mean±standard-deviations or percentage(frequency). Statistical test including ANOVA and Chi-square was used to determine differences between groups. Regression modelling was used to determine predictors of doctor-diagnosed vitamin D deficiency. Results: The FFQ estimation of dietary vitamin D intake was 3.6±3µg/day, 9.2±11µg/day, and 8.6±6.5µg/day, for the KSA, the UKc and the UKun group respectively (p˂0.01). The 3-day food diary estimation of dietary vitamin D intake was 1.4±1.3µg/day, 1.0±1.0µg/day, 3.3±3.2µg/day, for the KSA, the UKc and the UKun group respectively (p=0.03). Bland-Altman plot showed the two methods had low agreement, mean difference -3.93µg. The sun-exposure assessment at peak-time was 2.3±2.8hour/day, 3.0±2.4hour/day, 1.2±1.4 hour/day for the KSA, the UKc and the UKun group respectively (p˂0.01). Whereas, assessment of fractions of exposed body surface area (BSA) at peak-time was 0.11±0.04, 0.09±0.03, 0.14±0.09 for the KSA, the UKc and the UKun group respectively (p˂0.01). The reported data of vitamin D status showed that previous diagnoses of vitamin D deficiency reported by 28.3%(n=41) of the participants, KSA 8.3%(n=12), UKc 17.9%(n=26) and UKun 2.1%(n=3). The collected blood samples showed that 79%(n=15) of the KSA group had vitamin D deficiency, with average level 7.53±6.91ng/ml. However, vitamin D level of the UK groups could not be obtained. Logistic regression modelling identified that supplements use and reasons for supplementation, log of average BSA exposed at peak hours and residency were predictors of being diagnosed with vitamin D deficiency of the total population (n=192). Conclusion: Dietary vitamin D intake was very low for all the study groups regardless of residency. Sun-exposure habits varied between the group and this was most significant factor in previously diagnosed vitamin D deficiency. It may be difficult to change sun-exposure habits due to cultural or religious reasons and therefore dietary factors need to be studied to identify alternatives to sun-exposure in those who do not wish to expose their skin.

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