Duodenal ulcer and refined carbohydrate intake: a case-control study assessing dietary fibre and refined sugar intake An association between duodenal ulceration and a low fibre intake and a high refined carbohydrate diet has been reported. We therefore compared the current diet, smoking habits, social class, and possible other risk factors of 78 patients with duodenal ulcer and a community control group matched for age and sex. Logistic regression for matched sets was used to calculate the relative risks for successive quintiles of dietary fibre and sugar intake before and after adjustment for total calorie intake and for the possible confounding effect of other known risk factors. Relative risks did not differ materially or consistently for total dietary fibre or for the cereal moiety whether adjusted or not for calorie intake. By contrast, relative risks tended to be reduced with high vegetable fibre intake and with low refined sugar intake. After controlling for smoking and social class, both of which were associated with ulcer disease, and for relative weight (Quetelet's index), the relation between ulcer disease and low refined sugar intake persisted, while that with high vegetable fibre intake was reduced. The results of this study indicate that a lack of cereal or total fibre intake plays no part in duodenal ulcer development but that a low refined sugar intake may be a protective factor. 