Appendix D: gaps in the evidence
The Programme Development Group (PDG) identified a number of gaps in the evidence related to the programme under examination, based on an assessment of the evidence. These gaps are set out below.
1. There is a lack of evidence on the effectiveness of interventions targeting specific socio‑economic, ethnic, low‑income or vulnerable groups. More evidence is also needed on the differential effectiveness of interventions among these groups – and the effectiveness of different components within each intervention.
2. There is a lack of evidence about the effectiveness and cost effectiveness of interventions to improve the nutrition of mothers and children aged under 5, particularly those from disadvantaged, low‑income and minority ethnic groups.
3. There is a lack of good quality economic studies on public health interventions to improve nutrition in the UK.
4. There is a lack of well‑designed intervention studies on how to:
improve the nutritional status of women before and during pregnancy
enable pregnant women who are obese to reduce the associated health risks for both themselves and their babies
help postpartum women with their nutritional needs and weight
help improve iron intake and reduce salt intake among infants and young children
balance the benefits of improving vitamin D status and the associated risks of increased exposure to the sun.
5. There is a lack of studies that have adequately measured and validated nutrition levels before and after an intervention. Studies too often rely on self‑reported information alone. In addition, few studies include measured dietary change as an outcome measure (many rely on surrogate measures such as the baby's birth weight, which can be affected by confounding.)
6. There is a lack of intervention studies and evaluations providing process and qualitative data. This is needed so that the effective components of an intervention can be assessed and replicated on a wider scale.
7. There is a lack of well‑designed studies that have evaluated the use of food vouchers to encourage healthy eating.
The Group made 5 recommendations for research.