Defining solutions for the improvement of food and nutrition security in the UK: parsnips as a case study for improving folate status through dietary intervention

Abstract

Achieving food and nutrient security remains a pressing challenge in the UK, with inadequate dietary quality and widespread micronutrient deficiencies contributing to poor health outcomes. In response, this thesis investigates the potential of parsnips (Pastinaca sativa L.) as a case study crop for addressing these challenges. Parsnips were selected as a domestically produced, underutilised, yet micronutrient-dense root vegetable with scope to support
healthier and more sustainable diets. Within this context, folate (vitamin B9) was identified as a nutrient of particular interest: it is naturally present in parsnips and simultaneously represents a major public health concern, with consistently low intakes and high deficiency rates across the UK population, especially among adolescents. While forthcoming legislation to mandate folic acid fortification of flour will help alleviate deficiency, fortification alone cannot provide a long term or holistic solution. This research therefore examines the extent to which parsnips could serve as a complementary dietary source of folate, exploring their nutritional potential from field to fork and their integration into everyday diets through school meal provision as a practical intervention model.

A mixed methods approach combined analysis of nationally representative intake and biomarker data, laboratory studies of parsnip folate content, and modelling of school meal provision. National survey data highlighted that 74.4% of adolescent females had folate intakes below the RNI threshold. Laboratory analyses revealed statistically significant 14.3% difference in total folate content across parsnip varieties and identified 5-methyltetrahydrofolate and tetrahydrofolate as the predominant folate vitamers. Storage trials showed parsnip folate content was maintained over four weeks, while cooking experiments demonstrated that roasting and microwaving increased folate concentration by 67.2% and 96.4%, respectively, whereas boiling caused losses of 18.5%. Nutritional analysis revealed substantial variation in folate provision across school meals in Southampton, UK. A reformulation case study showed
that substituting boiled parsnip for boiled potato in Bangers and Mash could increase folate provision by 134.8% for a cost increase of 15.8% per portion.

The findings demonstrate that parsnips are a robust dietary source of folate, retaining nutrient value through storage and cooking methods, and that their integration into institutional food systems could meaningfully improve folate intake. More broadly, this work highlights the potential for UK-grown, nutrient-dense crops to strengthen domestic food systems. By linking crop science, nutrition, and public health, the thesis provides novel evidence of how diet-based interventions can enhance micronutrient security. Future work should expand beyond folate to consider other micronutrients and crops, but the case of parsnips demonstrates the feasibility and value of leveraging traditional, locally appropriate foods in sustainable nutrition strategies.

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Identifiers

ORCID for Annabelle Fisher: orcid.org/0000-0003-2230-7954

ORCID for Philip Calder: orcid.org/0000-0002-6038-710X

ORCID for Jenny Baverstock: orcid.org/0000-0003-1777-2894

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