| Summary: | UK Biobank is an open access prospective cohort of 500,000 men and women. Information on the frequency of consumption of main foods was collected at recruitment with a touchscreen questionnaire; prior to examining the associations between diet and disease, it is essential to evaluate the performance of the dietary touchscreen questionnaire. The objectives of this paper are to: describe the repeatability of the touchscreen questionnaire in participants (n=20,348) who repeated the assessment centre visit approximately 4 years after recruitment, and compare the dietary touchscreen variables with mean intakes from participants (n=140,080) who completed at least one of the four web-based 24-hour dietary assessments emailed to participants post recruitment. For fish and meat items, 90% or more of participants reported the same or adjacent category of intake at the repeat assessment visit; for vegetables and fruit, and for a derived partial fibre score (in fifths), 70% or more of participants were classified into the same or adjacent category of intake (Kappa weighted > 0.50 for all). Participants were also categorised based on their responses to the dietary touchscreen questionnaire at recruitment, and within each category the mean group intake of the same food group or nutrient from participants who had completed at least one web-based 24-hour dietary assessment was calculated. The comparison showed that the dietary touchscreen variables, available on the full cohort, reliably rank participants according to intakes of main food groups.
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