The Association between Total Protein, Animal Protein, and Animal Protein Sources with Risk of Inflammatory Bowel Diseases: A Systematic Review and Meta-Analysis of Cohort Studies.

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• According to the researchers, the effect of the high consumption of meat in increasing the risk of IBD is not related to the type of protein contained in it but could be due to cooking meat at high temperatures
• Other studies have reported that the consumption of animal proteins, especially processed and red meat, increases the risk of IBD
• Other studies related to dairy intake have been contradictory. There is also evidence reported of a positive effect from dairy exclusion in IBD patients.
• Further research is required to corroborate the findings of this systematic review.

Introduction

The authors conducted a dose-dependent meta-analysis of prospective cohort studies which examined the relation between total protein, animal protein, and animal protein sources with inflammatory bowel disease (IBD) in adults because the prevalence and incidence of IBD have exceeded globally.

Methods

Cochrane methodology was undertaken for the systematic review. Data from 11 prospective cohort studies with 8067 cases and 4,302,554 participants was extracted by 2 independent investigators. Evaluation of the quality and possible biases of included studies was performed. Risk ratios (RR) with 95% confidence intervals were chosen as the effect estimate. Various subgroup analyses were undertaken as well as metaregression analyses.

Results

• Seven cohort studies (7232 cases, 1,097,040 participants) were included in the analysis of dairy intake. Higher intakes of dairy was associated with a lower risk of IBD (RR: 0.81; 95% CI: 0.72, 0.90; n = 7)
• Consumption of protein from dairy products was found to be protective against IBD risk (RR = 0.77; 95% CI: 0.68, 0.88)
• Three prospective cohort studies with 1214 cases of IBD among a total of 535,738 subjects were included in the total meat analyses. Higher dietary total meat intake was not associated with the risk of IBD (RR: 1.24; 95% CI: 0.90, 1.70; n = 4)
• A positive linear association was found between total meat intake and risk of IBD. 100 g/d increment in dietary total meat consumption was associated with a 38% greater risk of IBD (RR: 1.38, 95% CI: 1.13, 1.68)
• Three prospective cohorts, among 492,497 participants and 4025 cases were included in the analysis of egg consumption. No association was found between egg consumption and IBD risk (RR: 0.92; 95% CI: 0.81, 1.04; n = 4).

Conclusion

The findings indicated no notable correlation between the intake of the majority of dietary protein sources and the incidence of IBD. IBD risk only escalated with higher total meat consumption, while the intake of protein from dairy products emerged as a protective factor against the risk of IBD.

• Dairy product consumption may be protective against IBD. However the studies included with statistically significant results did not control for alcohol intake and other confounding factors. The type of dairy product consumed, as well as a personalised approach, should be considered
• This study did not find any association between red or processed meat consumption and risk of IBD. However the subgroup analysis did find a significant association between red meat intake and IBD risk. This difference in results may be caused by differences in cooking methods, genetic factors, amount of meat consumption, confounding factors, and other environmental factors
• Total meat intake, as well as type of meat intake, and how meat is cooked, should be reviewed in clients with IBD, Crohn's Disease and Ulcerative Colitis.

• Intervention studies would need to be conducted to corroborate the findings of this systematic review
• Future research should fully consider cofounding factors, such as alcohol intake and body mass index (BMI)
• Future studies should further consider types of protein as well as dose and cooking implications.