A recent population-based study investigated the association between meat intake and the presence of colorectal polyps, and further explored this association according to histologic subtypes of colorectal adenoma and their location in the colorectum. The results suggest that there is no significant association between red or processed meat consumption and prevalence of adenomas.
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Over the past decade several studies have evaluated the association of meat intake and the risk of developing colorectal adenoma. Some studies provided evidence that intake of red and processed meat is a risk factor for colorectal cancer (CRC). However, other studies did not support this association. Few studies have investigated the association of meat intake and colorectal polyps according to the histologic subtypes and subsites.
The American Journal of Clinical Nutrition recently published a cross-sectional, population-based study in Germany that investigated the association of meat intake in relation to colorectal polyps and further examined the association according to the type of adenoma or the location in the colorectum. The study included 15,950 participants aged >55 years who underwent a screening colonoscopy. Prevalence ratios (PRs) and confidence intervals (CIs) were calculated for associations between meat intake and the most-advanced findings from a colonoscopy.
Patients were asked to fill out a questionnaire about family history, sociodemographic and lifestyle factors. The results of colonoscopy were recorded independently by two investigators. In addition, participants also completed a 6-item food frequency questionnaire (FFQ) that included their consumption of red meat, processed meat, and poultry in the previous 12 months. Participants were classified based on their colonoscopy findings: CRC; advanced adenoma (adenoma with either more than 1 cm diameter, tubulovillous or villous components, or high-grade dysplasia); other adenoma; hyperplastic polyp (HPP); or unspecified polyp. Participants with a normal colonoscopy were used as control group for comparison.
The results of the basic model, adjusted for age and sex, showed that higher intake of processed meat (multiple times per day) and red meat (more than once a day) increased the prevalence of advanced adenomas. After adjustment for potential confounders, there was no significant association between red or processed meat intake and prevalence of any adenomas or advanced adenoma. Furthermore, there was no association observed with other findings such as HPP, non-advanced adenoma, advanced neoplasm and CRC. There was no association observed between poultry intake and any adenoma or advanced adenoma.
Site-specific analysis revealed that processed meat intake (more than once a day) was associated with prevalence of advanced adenomas in the rectum but not the proximal colon. In addition, there was a nonsignificant positive association noticed for processed meat intake and the prevalence of any adenomas in the rectum. Interestingly, there was no association found between red meat or poultry intake and the prevalence of advanced adenomas or any adenomas with regard to their location in the colorectum.
The subgroup analysis showed a positive association between red meat intake (more than once a day) and the prevalence of advanced adenomas in participants aged 65 and up. Â High intake of processed meat (more than once a day) was not associated with the prevalence of any adenoma and advanced adenoma. Furthermore, there was no difference in PRs of small or large adenomas and no difference was observed when adenomas were investigated based on their morphology or shape.
As reported by the authors, Prudence R Carr and colleagues, this is the first study to evaluate associations by adenoma shape and the largest to report results by morphology. The large number of participants in this study allowed stratified analysis of specific adenoma features that have previously not been reported. In addition, polyp status for all the participants was known as they all underwent a complete colonoscopy. However, there were a few limitations of the study. A considerable proportion of participants completed the questionnaire after the colonoscopy whereas most of the participants completed it before the colonoscopy. Furthermore, the FFQ that was used did not determine portion size and had a limited number of food items.
Results obtained from this large colonoscopy-based screening study show that there are no significant associations between the consumption of red or processed meat and the prevalence of any adenomas or advanced adenomas. However, there was a positive association observed between processed meat intake and the prevalence of advanced adenomas in the rectum only. In addition, poultry intake was not found to be associated with colorectal polyps.
Not all studies conducted in the past have shown consistent results and mechanisms to explain these associations remain unclear. Although this was a large population-based cohort study, further research should be undertaken to confirm these findings.
Written By:Â Preeti Paul, MS Biochemistry
