Dietary patterns tied to foot ulcer odds in type 2 diabetes case-control study

Adults with type 2 diabetes whose diets center on fish, olives and olive oil, vegetables, and fruits show markedly lower odds of diabetes-related foot ulceration, while those favoring sweets, snack foods, sugar-sweetened beverages, and refined grains show sharply higher odds, according to a hospital-based case–control study conducted in Tehran, Iran. The research, published in BMC Nutrition, is among the first to examine the link using empirically derived dietary patterns rather than single foods or predefined diet scores.

Researchers recruited 115 patients treated for a first-ever diabetic foot ulcer and 115 controls with type 2 diabetes but no current or previous foot ulcer. All participants completed a 147-item food-frequency questionnaire at enrollment. Because the design was retrospective, cases reported their habitual intake during the 12 months before their ulcer diagnosis, while controls reported intake during the 12 months before their interview. The team then applied principal component analysis to 26 food groups to identify dietary patterns that naturally cluster in the study population, and used multivariable logistic regression to estimate odds ratios for case status.

Two dietary patterns emerged from the analysis, and together they explained 22.67% of the variance in the food-group data. The first pattern was characterized primarily by fish, olives and olive oil, vegetables, and fruits. Participants in the upper half of scores on this pattern, compared with those in the lower half, had adjusted odds of foot ulceration of 0.05, with a 95% confidence interval of 0.02 to 0.14. In other words, higher adherence to this plant- and fish-forward pattern was associated with roughly a 95% reduction in the odds of being a case, after adjustment for the covariates included in the model.

The second pattern loaded on sweets, snack foods, sugar-sweetened beverages, and refined grains. Here the association ran in the opposite direction: participants scoring above the median had adjusted odds of foot ulceration of 5.74, with a 95% confidence interval of 2.33 to 14.12, compared with those below the median. The confidence intervals in both analyses lie well away from the null value of 1.0, indicating associations that were statistically robust within this sample, although the wide interval for the second pattern also reflects the moderate sample size.

The authors caution that these figures describe associations, not causal effects. In a case–control design, exposure and outcome are measured at a single point in time, and the temporal ordering between diet and ulcer cannot be established with certainty. The retrospective food-frequency reporting introduces the possibility of differential recall, meaning that patients who have experienced a foot ulcer may remember or report their past diets differently from controls who have not. Reverse causation also cannot be excluded: the onset of ulceration or worsening diabetes complications may itself alter eating habits before diagnosis, so that diet changes follow the disease process rather than precede it.

The hospital-based recruitment carries further limitations for interpretation. Cases and controls were drawn from clinical settings in Tehran, which may limit how far the findings generalize to community-dwelling populations or to other regions. The dietary patterns were derived from this specific sample, so the exact food-group composition of the two patterns may differ if the same analysis were repeated elsewhere. The modest share of variance explained by the two patterns, 22.67%, indicates that many aspects of food intake and lifestyle beyond these two dimensions were not captured by the retained components.

Diabetic foot ulceration is a serious complication of type 2 diabetes, arising from the interplay of peripheral neuropathy, peripheral arterial disease, and impaired wound healing, and it is a leading cause of lower-limb amputation worldwide. Nutritional research in this field has traditionally focused on glycemic control, micronutrients, or individual foods. By using principal component analysis, the study instead captured whole-diet behavior, reflecting the reality that people eat combinations of foods rather than nutrients in isolation. This empirically derived approach avoids some of the assumptions built into predefined diet-quality indices, though it depends on the food groups and population from which the patterns are extracted.

The biological plausibility of the observed associations can be framed in terms of established mechanisms. Diets rich in vegetables, fruits, olives, olive oil, and fish supply fiber, unsaturated fats, and micronutrients associated with better glycemic profiles and vascular health, pathways relevant to ulcer risk in diabetes. Conversely, patterns dominated by refined grains, added sugars, and snack foods are associated with higher glycemic load, which in the context of type 2 diabetes may worsen the metabolic environment in which neuropathy and impaired healing develop. The study did not test these mechanisms directly, and the authors present the associations as hypothesis-generating rather than as proof of any protective or harmful dietary effect.

The authors conclude that the findings suggest an association between empirically derived dietary patterns and the odds of diabetic foot ulceration in adults with type 2 diabetes, while emphasizing that retrospective dietary reporting and the hospital-based case–control design limit causal interpretation. They call for prospective studies to clarify temporality and causality. Until such studies are available, the results add to the evidence that whole-diet patterns, and not only individual nutrients, may be relevant to one of the most disabling complications of diabetes, while leaving open the question of whether changing diet after diagnosis would alter ulcer risk.

Subject of Research: Associations between empirically derived dietary patterns and diabetes-related foot ulceration in adults with type 2 diabetes

Article Title: Empirically derived dietary patterns and diabetes-related foot ulceration among adults with type 2 diabetes: a hospital-based case–control study

Article References: Javaheri-Tafti, F., Boroujeni, L. Z. B., Nikparast, A., Nikpayam, O., Rahmanian, R., Norouzi, M., Rashidkhani, B., Sohrab, G., & Hasani, M. (2026). Empirically derived dietary patterns and diabetes-related foot ulceration among adults with type 2 diabetes: a hospital-based case–control study. BMC Nutrition. https://doi.org/10.1186/s40795-026-01538-3

Image Credits: AI Generated

DOI: 10.1186/s40795-026-01538-3

Keywords: type 2 diabetes, diabetic foot ulcer, dietary patterns, case-control study, principal component analysis, food-frequency questionnaire, odds ratio, BMC Nutrition, nutrition epidemiology, refined grains, olive oil, retrospective dietary reporting