In this colonoscopy-based cohort, fruit and vegetables consumption was significantly associated with a lower prevalence of diverticulosis even after adjusting for common risk factors. Conversely, no associations were observed between red and processed meat intake and the risk of prevalent diverticulosis. Furthermore, we did not observe any effect modification by age, BMI, smoking, or red meat intake on the association between fruit and vegetables intake and prevalent diverticulosis.
Our finding of a lower risk of prevalent diverticulosis among participants with a higher fruit and vegetables intake is supported by several prior studies. In a large cohort nested within the Health Professionals Follow-up Study, Aldoori and colleagues15 found high-fiber diet to be protective against symptomatic diverticular disease. In a case-control study in Greece, Manousos et al6 observed a significant inverse association between vegetables intake and prevalence of symptomatic diverticular disease. Similarly, a study of diet and diverticulosis restricted to asymptomatic patients found that vegetarians had a lower prevalence of diverticulosis compared to non-vegetarians16. However, these studies either focused on symptomatic diverticulosis6,15 or failed to fully account for other lifestyle and confounding factors16. Therefore, our study, which carefully adjusts for known and putative risk factors for diverticulosis, significantly extends these findings.
In contrast to our findings, two studies conducted in South Korea and Taiwan found no significant associations between the consumption of fruit and vegetables and risk of diverticulosis10,11. However, the prevalence of diverticulosis in East Asian countries varies from 8 to 25%, an estimate that is significantly lower than those reported by us and others in Western populations8 − 11,16−18. In addition, diverticulosis predominately affects the right colon in Asia compared to the left in the West, likely due to distinct risk factors and mechanisms of development10. In the U.S., a cross-sectional, colonoscopy-based study observed no associations between the intake of fiber from fruit and vegetables and risk of diverticulosis, while total fiber intake was found to be associated with a higher prevalence of diverticulosis8. Similarly, a more recent study by the same research group found no associations between the consumption of fruit and vegetables fiber and total fiber and the prevalence of diverticulosis9. However, dietary information was collected up to three to four months after colonoscopy in both studies and participants may have been aware of their diagnoses at the time of diet collection, increasing the likelihood of recall bias8,9. Thus, misclassification of exposures may account for the lack of association between intake of fiber from fruit and vegetables and risk of prevalent diverticulosis.
The mechanism by which fruit and vegetables consumption influences the development of diverticulosis is currently unknown. Nearly fifty years ago, Painter postulated that low-fiber diets produce increased colonic pressures. Along with segmentation of the colon, these higher pressures cause the mucosa to herniate through weak areas in the muscle wall and form diverticula5. However, this hypothesis was based on ecological observations comparing the prevalence of diverticulosis in the West to that of native Africans, which failed to account for confounding variables and did not confirm the presence of diverticula in participants. The interaction between diet and the gut microbiota may mediate this process. In a recent study, Barbara et al.19 observed a depletion of Clostridium cluster IV in the gut microbiota of asymptomatic diverticulosis cases compared to controls without diverticula. Clostridium cluster IV includes many anti-inflammatory bacterial species that primarily function through the release of butyrate, the preferred energy source for colonocytes and a key contributor to the integrity of the colonic epithelial barrier20. In turn, increased intake of fruit and vegetables has been shown to significantly increase the abundance of Clostridium cluster IV in the gut microbiome21. Thus, fruit and vegetables consumption through its effect on Clostridium cluster IV could decrease the risk of diverticula formation. Nevertheless, further studies are needed to better examine this complex relationship between diet, gut microbiota, and diverticulosis.
Our study has several strengths. First, all cases of diverticulosis were confirmed through complete colonoscopy. Second, our study population was drawn from a longitudinal cohort in which dietary and lifestyle data were collected prior to colonoscopy, averting the potential for recall bias. Third, we accounted for multiple risk factors that could impact our observed associations, including age, BMI, smoking history, bowel movement frequency, dietary pattern, regular NSAID use, and physical activity.
The present study has several potential weaknesses that are worth highlighting. First, the participants were from a single center and predominately white, which may reduce the generalizability of our observations. Specifically, out of 549 participants enrolled in the cohort, 511 (93.1%) identified as Caucasian, 19 identified as Asian (3.5%), 13 identified as African-American (2.4%), 3 (0.5%) identified as Pacific Islander or Native Hawaiian, and 3 (0.5%) identified as Native American. Second, we based our dietary questionnaire on the SFFQ; however, our validation showed a moderate to good correlation between the two measures. In addition, adjusting for measurement errors would likely strengthen our observed association. Third, our dietary questionnaire did not distinguish between different types of fruit and vegetables. Therefore, we were unable to evaluate the relationship between individual foods in these groups and the prevalence of diverticulosis. Lastly, although dietary data was collected prior to the colonoscopy, diverticula were likely present for many years, preventing us from demonstrating a clear temporal association between fruit and vegetables consumption and risk of diverticulosis. However, medium-term studies on patterns of dietary intake over time have demonstrated remarkable stability22. Additionally, some participants may have known about their diagnosis of diverticulosis from prior colonoscopies (~ 40% had 2 or more colonoscopies prior to enrollment).
In conclusion, we found that frequent consumption of fruit and vegetables is associated with a decreased prevalence of colonic diverticulosis. Although our study does not address specific foods within these food groups, our results call to attention the potential role of diet as a whole in the prevention of colonic diverticula. Due to an aging population in the U.S., the prevalence and cost of diverticulosis are expected to continue to rise, highlighting the critical importance of identifying modifiable risk factors. Future studies should focus on the potential mechanisms underlying these associations, particularly with regards to the composition of the gut microbiome.