Prevalence and determinants of vitamin D deficiency and insufficiency among three immigrant groups in Finland: evidence from a population-based study using standardised 25-hydroxyvitamin D data

Abstract

Objective: We investigated the determinants of serum 25-hydroxyvitamin D [S-25(OH)D] and dietary vitamin D sources among three immigrant groups in Finland and compared their S-25(OH)D to the general Finnish population.

Design: Cross-sectional population-based Migrant Health and Wellbeing Study and the nationally representative Finnish Health 2011 Survey. S-25(OH)D was standardised according to the Vitamin D Standardisation Program. Vitamin D sources were assessed by interview.

Setting: Six different municipalities in Finland (60°-63°N).

Participants: Immigrants aged 18-64 years (446 Russians, 346 Somalis, 500 Kurds), 798 Finns aged 30-64 years.

Results: The mean of S-25(OH)D was 64 (95 % CI 62, 66), 44 (95 % CI 41, 46), 35 (95 % CI 34, 37) and 64 (95 % CI 62, 66) nmol/l for Russians, Somalis, Kurds and Finns, respectively. S-25(OH)D among Somalis and Kurds was lower compared with Finns (P < 0·001). The prevalence of vitamin D deficiency (S-25(OH)D <30 nmol/l) and insufficiency (S-25(OH)D <50 nmol/l) was higher among immigrants than Finns (P < 0·001). Vitamin D-rich foods differed between the groups; vitamin D-fortified fat spread consumption was higher among Somalis (91 %) than among Russians (73 %) and Kurds (60 %); fish was less consumed among Kurds (17 %) than among Russians (43 %) and Somalis (38 %); and 57 % Russians, 56 % Kurds and 36 % Somalis consumed vitamin D-fortified dairy daily (P < 0·001 for all). Daily smoking, alcohol consumption and winter blood sampling were determinants of vitamin D insufficiency (P ≤ 0·03). Older age, physical activity, fish and vitamin D-fortified dairy consumption were associated with lower odds of insufficiency (P ≤ 0·04).

Conclusions: Vitamin D status differed among immigrant groups and the determinants are, to some degree, associated with learned or existing cultural behaviours.

Keywords: 25-hydroxyvitamin D; Determinants; Finland; Immigrants; Vitamin D status.

Fig. 1

Flowchart of the study population. Maamu, Migrant Health and Wellbeing Study; Health 2011, Health 2011 Survey; S-25(OH)D, serum 25-hydroxyvitamin D

Fig. 2

Weighted mean and 95 % CI of standardised S-25(OH)D concentrations, adjusted for age and month of blood sampling. *P-values from t-tests (<0·001) for mean standardised S-25(OH)D differences between immigrant groups and the general Finnish population. S-25(OH)D, serum 25-hydroxyvitamin D

Fig. 3

Weighted prevalence of vitamin D status (S-25(OH)D) <30 and <50 nmol/l for immigrant groups and the general Finnish population, adjusted for age and month of blood sampling. *P-values from t-tests (<0·001) for differences between immigrant groups and the general Finnish population

Fig. 4

(a–c) Weighted prevalence and 95 % CI of consumption of vitamin D-rich foods among persons of Russian, Somali and Kurdish backgrounds. *P-values from t-tests (<0·001) for differences among immigrant groups