Risk factors influencing vitamin D status of ethnic minority adults in northern England and the efficacy of calcifediol supplementation in 25-hydroxyvitamin D concentrations

Almujaydil, Mona Sulaiman (2018) Risk factors influencing vitamin D status of ethnic minority adults in northern England and the efficacy of calcifediol supplementation in 25-hydroxyvitamin D concentrations. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Background: Hypovitaminosis D is a major health concern in the UK. Reduced sunshine exposure and limited dietary sources of vitamin D, coupled with other factors lead to increased risk of hypovitaminosis D among the whole population especially amongst ethnic minorities (EMGs) due to their eating habits and high skin pigmentation. Vitamin D3 supplement is the most common form of vitamin D used today to correct deficiency, however, evidence shows that calcifediol may increase vitamin D levels more rapidly. Aims: To determine differences in the risk factors for hypovitaminosis D among different EMGs in the UK, and to investigate the efficacy of calcifediol supplementation, and its effect on improving vitamin D levels in deficient adults from EMGs. Methods: A self-reported questionnaire was completed by 253 participants to assess sun exposure behaviours and lifestyle factors. Food frequency questionnaire (FFQ) was used to estimate vitamin D intake. Overall, seventy-four ethnic minority participants had their vitamin D level measured. 42 of these participants had a vitamin D level ≤30 nmol/l and were subsequently supplemented with 140 μg/week of calcifediol for 5 weeks. Results: Dietary intake of vitamin D and supplement intake were low among all participants regardless of ethnicity (P>0.05). Ethnic differences were found in socioeconomic status, time spent outdoors and sun index (p<0.001). Other risk factors included being overweight or obese (64% Arab and 39% Afro/Caribbean); smoking and alcohol intake (13.3% Arab, 45.5% Afro/Caribbean); history of vitamin D deficiency (35% Arab and 24% South Asian). Vitamin D level was low across all of the population studied (29.9 nmol/l), dietary intake of vitamin D (1.26 μg) and total intake of vitamin D (2.83 μg). The median level of 25(OH)D (26.6 nmol/l) significantly increased rapidly to more than ≥75 nmol/l (151.4) in all groups, it declined over the next 5 weeks after supplement termination, while nevertheless remaining above the baseline value (55.9 nmol/l). Conclusion: Dietary habits and sun exposure behaviours varied between EMGs, but they all were at risk of developing vitamin D deficiency. The calcifediol supplement was found to improve vitamin D status in all the groups and resulted in improved levels even after the five week termination period.