Letter: Inflammatory Potential of the Diet and Risk of Crohn's Disease and Ulcerative Colitis. Authors' Reply

Abstract

We thank Drs. Zhou, Sun Liu for their interest in our study [1, 2]. We suggest that a high inflammatory score of the diet (ISD) is associated with a higher risk of developing Crohn's disease (CD) but not ulcerative colitis (UC).

First, Zhou et al. suggested that results might be biased as the number of food items included In the Food Frequency Questionnaires ranged from 98 to 2059 across centres. However, this potential bias was taken into account by stratifying the analyses by centre as stated in the statistical analysis section of the manuscript.

Second, Zhou et al. stated that no false discovery rate was performed for multiple comparisons. However, in our study, there was only one exposure (inflammatory score of the diet) for two outcomes (CD and UC). Correcting for false discovery rate does not modify our results (P_trend = 0.009 for CD and 0.208 for UC) [3]. Additional analyses according to sex or to items of the inflammatory score of the diet are only exploratory and do not require adjustment for multiple testing [4].

Third, Zhou et al. suggested that our analyses were underpowered to study an interaction between the ISD and sex for this risk of CD/UC, and that we should include a larger sample size, particularly men. However, the EPIC cohort is one of the largest cohorts worldwide as 394,255 participants from eight European countries, including 268,599 women and 125,656 men were included in the analyses. Even if a population as large as possible is desirable, this objective seems difficult to achieve. As the interaction tests for ISD between women and men and the risk of developing CD were not significant (p = 0.44 for quartile 2, 0.99 for quartile 3, and 0.66 for quartile 4), a differential effect of ISD between women and men is unlikely.

Finally, Zhou et al. mentioned that the analyses were not adjusted for some confounders such as antibiotic use, breastfeeding history, and prior gut infections. Indeed, these potential confounding factors were not available in our database. Therefore, as in all non-randomised epidemiology studies, residual confounding cannot be excluded.

In conclusion, our results suggest that a high inflammatory score of the diet is associated with a higher risk of developing CD but not UC. These results are in agreement with those reported in another study that used similar methodology with another inflammatory score (empirical dietary inflammatory pattern) [5].

Antoine Meyer: conceptualization, validation, writing – original draft. Aurélien Amiot: validation, conceptualization, writing – review and editing.

This article is linked to Meyer and Zhou et al. papers. To view these articles, visit https://doi.org/10.1111/apt.18497 and https://doi.org/10.1111/apt.70124.