Vitamin D status, dietary intake and supplement use in mothers and their infants, aged 0-12 months

Vitamin D is essential for the regulation of calcium and phosphorus metabolism and is essential for musculoskeletal health. The main source of Vitamin D for the UK population is the action of ultraviolet B radiation (UVB) on skin, but diet and supplementation also provide vitamin D and are particularly important when exposure to sunlight is limited (SACN, 2016). Vitamin D status is currently assessed by measuring circulating total 25-hydroxyvitamin D (25(OH)D). The Institute of Medicine currently indicates a threshold of <30nmol/L for deficiency and >50 nmol/l for sufficiency (Ross et al. 2011).

In the UK, SACN set a reference nutrient intake (RNI) of 10ug (400IU) per day for individuals aged 4 and over (SACN, 2016). This is the average amount needed to maintain total 25(OH)D above 25nmol/l for 97.5% of the UK population when UVB exposure from the sun is minimal (SACN, 2016).. Minority ethnic groups with dark skin, such as those of African, African Caribbean or South Asian origin, should also consider taking a vitamin D supplement all year round as they are at increased risk of deficiency (Darling et al, 2018; Darling et al, 2021).  Additionally, it is also recommended that pregnant and breastfeeding women take a vitamin D supplement to ensure optimal health. The vitamin D concentration of breastmilk varied between women, however, and may be dependent on vitamin D status. Infants under 1 year of age, who are breast-fed or receiving less than 500mL/day of formula milk, are also, therefore, recommended to receive a daily supplement of 8–10 μg of vitamin D throughout the year.

Despite these recommendations, the most recent National Diet and Nutrition Survey (NDNS) in the UK, found 16% of adults aged 19-64 years had a 25-hydroxyvitamin D (25-(OH)D) concentration less than 25 nmol/L (the level below which there is increased risk of poor musculoskeletal health at a population level). Other studies have found lower 25-(OH)D in pregnant women compared the non-pregnant population and that babies born to mothers with low 25-(OH)D are much more likely to be deficient (VioStreym et al., 2013). Previous studies in mothers and babies aged under 1 year, have found that both maternal and infant adherence to vitamin D supplementation may be low, further increasing the risk of vitamin D deficiency in these already at-risk populations. In the UK, one study found only 34.6% of breastfeeding mums, 43.5% of breastfed babies and 12.5% of formula/mixed‐fed babies receiving less than 500 mL of formula took or received a supplement on the day of measurement (Pearce & Langley-Evans, 2021). A similar study in Ireland also found only 30% of families gave a supplement to their infants every day throughout a longitudinal study (Hemmingway et al., 2020). In both studies, some parents reported usually or sometimes giving supplements, but compliance with recommendations was poor. These studies were on largely Caucasian populations and did not rigorously explore vitamin D status using blood analysis.

This PhD aims to explore dietary intake, adherence to supplementation, exposure to sunlight and vitamin D status in mother-infant pairs, where infants are aged 0-12 months. Sheffield has a diverse population, and it is hoped the project will engage pregnant women from diverse backgrounds, who are at increased risk of vitamin D deficiency. This PhD represents Sheffield Hallam University’s commitment to the Sheffield City Region, contributing to the region’s health, culture and environment. 

To apply for a self-funded PhD, you will need to meet our entry requirements and provide:

1. fully completed Sheffield Hallam University application form

2. research proposal (4-6 sides of A4 in length).

3. transcript of marks from your highest qualification (we require a dissertation mark of 60+).

4. copy of your award certificates

5. two references, one ideally from an academic source. References must be supplied as recent letters on headed notepaper or on the reference section on the University's application form.

6. Where English is not your first language, we require evidence of your English language ability to the following minimum level of proficiency. A current IELTS score of 7.0 overall (with all component marks of 7.0 or higher and preferably Academic IELTS); or a current TOEFL test with an overall score of 100 internet based (with a minimum component score of 23 in listening and reading, 26 in writing and 22 in speaking) or recognised equivalent testing system. Your test score must be within the last two years.

Information on entry requirements, tuition fees and other costs can be found here https://www.shu.ac.uk/courses/business-and-management/phd-sheffield-business-school-management-finance-service-sector/full-time

How to apply

Please submit your application to [Email Address Removed]