Pregnant women are a high risk group for vitamin D deficiency¹. In Europe, this is especially true for pregnant women from ethnic minorities. Vitamin D deficiency is reported to be prevalent among pregnant minority women in the Netherlands², UK³, Sweden⁴˒⁵ and Norway⁶.
Factors that contribute to the vulnerability of pregnant minority women to vitamin D deficiency include¹:
- Having a darker skin pigmentation
- The cultural and religious practices for e.g. substantial body covering
- Spending a limited time outdoors
- Vegetarianism and a lack of fortified foods in the diet
- Possible complications of low vitamin D status during pregnancy include preeclampsia, preterm delivery and gestational diabetes. Infants born with low vitamin D status have been shown to have an increased risk for low birth weight, rickets, infection, asthma and autism.
Vitamin D deficiency is an issue in the UK⁷. Figures show up to a quarter of the UK population have low levels of vitamin D in their blood and the majority of pregnant women do not take vitamin D supplements¹. Studies have found that vitamin D deficiency is reported to be prevalent (over 50%) among pregnant minority women and in particular, women from South Asian & Middle Eastern descent⁸˒⁹. This has been identified as a public health issue, and the National Institute for Health and Clinical Excellence (NICE) recommends that vitamin D supplementation may be given to women at greatest risk for deficiency including women of South Asian, African, Caribbean or Middle Eastern origin⁹. In addition, attempts to improve awareness among health professionals have been made. For instance, the UK Chief Medical Officers have made efforts to communicate with health professionals the importance of vitamin D supplementation in at-risk groups¹. This is a step in the right direction, and communication between health professionals and health organizations should be encouraged.
When individuals are unable to receive adequate vitamin D production from the sun, the only dietary sources of importance in a typical Norwegian diet are fatty fish, vitamin D enriched margarine and fortified milk. Individuals commonly supplement with a multivitamin or cod liver oil to improve their vitamin D status.¹⁰. A systematic review concluded that existing data suggests that vitamin D status is sufficient in the general population¹⁰. The classification of sufficient vitamin D status used in the review was a vitamin D level >20 ng/ml. However, ethnic minorities, especially Pakistani’s, are at a high risk of vitamin D deficiency. Factors responsible for this are greater skin pigmentation, avoidance of direct sun exposure combined with religious or cultural clothing habits. Also, a diet poor in vitamin D and lack of supplementation contribute to the prevalence of vitamin D deficiency¹¹. In regards to dietary intake, Pakistani women do not consume many foods containing vitamin D and rely heavily on fortified margarine, which is their main source of dietary vitamin D, contributing to almost 75% of estimated intake of vitamin D¹⁰. This may partly explain the high prevalence of vitamin D deficiency in pregnant Pakistani women, as a survey conducted in Norway showed that 83% of pregnant Pakistani women were vitamin D deficient¹².
A population-based, multi-ethnic cohort study¹³ compared the prevalence of vitamin D deficiency among ethnic minority women and non-ethnic minority women. Ethnic origin was defined by the participant’s mother’s country of birth. They concluded that only 20% of non-ethnic minority women had low vitamin D levels; whereas, vitamin D deficiency was found to be more prevalent among ethnic minorities (South Asian (84%), Middle Eastern (79%), Sub-Saharan African (75%) and East Asian women (43%) women in early pregnancy)¹³.
Reports conclude that the Netherlands has a high prevalence of vitamin D deficiency⁷. A study published by the American Society of Clinical Nutrition reported a high prevalence of vitamin D deficiency in pregnant non-Western women in the Netherlands and concluded that screening should be recommended¹⁴. In all non-Western groups, the majority of the subjects (Turkish, 84%; Moroccan, 81%; other non-Western women, 59%) were vitamin D deficient¹⁴. A serum 25(OH)D concentration level below 10 ng/ml was used as a threshold to determine vitamin D deficiency.¹⁴.
To tackle this public health issue, the country has added vitamin D to the food supply. Now, margarine, as well as other spreads have been fortified with vitamin D ¹⁵.
Vitamin D deficiency has found to be common in pregnant ethnic minority women in Sweden⁴ ˒¹6 ˒¹7. For example, one study found that 77.9% of pregnant ethnic minority women were severely vitamin D deficient (<10 ng/ml; <25 nmol/l) compared with 3.9% of pregnant Swedish controls⁴. In particular, studies have found a high prevalence of severe vitamin D deficiency among Somali women¹6 ˒¹7. A study found that immigrant women had lower intakes of vitamin D from dietary sources and supplements than Swedish women (3.1 vs. 5.1 mg/day respectively) ¹7. Interestingly, fatty fish, a main contributor of vitamin D in food, was consumed in equal amounts in immigrant and Swedish women¹7. However, immigrant women consumed less vitamin D fortified foods (milk and margarine) and consumed more meat than Swedish women¹7. This is presumably because these foods are not common to their traditional food habits,¹7 and this needs to be taken into consideration when implementing food fortification interventions to reach this high risk group.
Tackling the issue
Vitamin D deficiency in pregnant women from ethnic minorities is clearly a public health problem in Europe that warrants further action.
- It is crucial that health professionals become more aware of the high prevalence of vitamin D deficiency. All individuals should test their vitamin D levels twice a year (once in the early Spring for your lowest level and once in August for your highest levels) in order to ensure that they are maintaining a healthy vitamin D status.
- More research needs to be conducted in this area to accurately measure the full extent of the problem. Additionally, qualitative research into the knowledge base that pregnant women from ethnic minorities have regarding vitamin D deficiency and the importance of vitamin D should be investigated. Also, gaining knowledge of the barriers that these women face when attempting to maintain a healthy vitamin D status would also be useful.
The Vitamin D Council recommends individuals supplement with 5,000 IU vitamin D3 daily when they are unable to receive safe, sensible sun exposure. For more information on how to receive the vitamin D your body needs, please click here.