Vitamin D deficiency is a major UK public health concern, affecting 4-23% of the population (1) . Natural dietary sources are limited, and without mandatory fortification, the vitamin D content of foods is variable by product and brand (2) . Dietary interventions could inform fortification policy, but no research has explored a whole-diet, household-level approach for vitamin D fortification (3) . This study aimed to test the feasibility of a vitamin D (bio)fortified shopping basket in influencing intake and to assess the practicality of methods for a future large-scale intervention. This one-week feasibility study recruited five diverse households using the Tesco Five Families segmentation model: (1) young adults (20–40y) without children, (2) older adults (40–60y) without children, (3) young families (all children 10y), and (5) pensioners (>60y, no children at home). Consenting households were randomly assigned to receive either a vitamin D (bio)fortified basket (n=3) containing 17 foods naturally rich in, or (bio)fortified with, vitamin D (e.g., ready-to-eat cereals, eggs, yogurt, milk, bread, salmon, sardines) or a matched control basket (n=2) with naturally lower sources of vitamin D (e.g. cod, ham) or unfortified equivalents. Participants were asked to replace their usual foods with the study foods. Baseline and endpoint measures included demographics, anthropometry and a validated vitamin D FFQ (4) . The views and acceptability of study foods were assessed quantitatively (rating: 1=extremely dislike>10=extremely like) and qualitatively (interviews). Views on the study methods, willingness to purchase vitamin D-fortified foods and interest in participating in a larger study were also obtained. Twelve participants (intervention n=7/control n=5; ages 4–70y) included one child, one adolescent, and ten adults with equal gender distribution. All were omnivores/pescatarians. Compliance to the study diet was good and most households integrated study foods into routines with ease. Vitamin D intake increased in those from the intervention group (3.2±1.5 to 18.1±8.1 µg/d; p<0.001) but not in controls (6.4±6.0 to 4.3±3.9 µg/d; p=0.095). Acceptability of study foods in the control basket were rated higher than those in the intervention basket (8.5 vs 6.7 out of 10, respectively), mainly driven by participants who didn’t like oily fish. Price was described as a consideration in the willingness to purchase fortified foods. All but one household were willing to join a larger study, with blood sampling cited as the reason for refusal. Overall, study methods were well received and demonstrated feasibility. Study foods were generally well accepted, with lower scores largely reflecting personal food preference. Replacing unpopular fish products, tailoring baskets for households with/without children, and addressing blood sampling concerns could be considered as refinements to the protocol. This pilot provides assurances in regards the proposed study approach and guidance for optimising a larger intervention to improve vitamin D intake.
Frazer et al. (Fri,) studied this question.