A meta-analysis of the effects of energy intake on risk of digestive cancers

Abstract

Aim: To quantitatively assess the relationship between energy intake and the incidence of digestive cancers in a meta-analysis of cohort studies.

Methods: We searched MEDLINE, EMBASE, Science Citation Index Expanded, and the bibliographies of retrieved articles. Studies were included if they reported relative risks (RRs) and corresponding 95% CIs of digestive cancers with respect to total energy intake. When RRs were not available in the published article, they were computed from the exposure distributions. Data were extracted independently by two investigators and discrepancies were resolved by discussion with a third investigator. We performed fixed-effects meta-analyses and meta-regressions to compute the summary RR for highest versus lowest category of energy intake and for per unit energy intake and digestive cancer incidence by giving each study-specific RR a weight that was proportional to its precision.

Results: Nineteen studies consisting of 13 independent cohorts met the inclusion criteria. The studies included 995,577 participants and 5620 incident cases of digestive cancer with an average follow-up of 11.1 years. A significant inverse association was observed between energy intake and the incidence of digestive cancers. The RR of digestive cancers for the highest compared to the lowest caloric intake category was 0.90 (95% CI 0.81-0.98, P < 0.05). The RR for an increment of 239 kcal/d energy intake was 0.97 (95% CI 0.95-0.99, P < 0.05) in the fixed model. In subgroup analyses, we noted that energy intake was associated with a reduced risk of colorectal cancer (RR 0.90, 95% CI 0.81-0.99, P < 0.05) and an increased risk of gastric cancer (RR 1.19, 95% CI 1.08-1.31, P < 0.01). There appeared to be no association with esophageal (RR 0.96, 95% CI 0.86-1.07, P > 0.05) or pancreatic (RR 0.79, 95% CI 0.49-1.09, P > 0.05) cancer. Associations were also similar in studies from North America and Europe. The RR was 1.02 (95% CI 0.79-1.25, P > 0.05) when considering the six studies conducted in North America and 0.87 (95% CI 0.77-0.98, P < 0.05) for the five studies from Europe.

Conclusion: Our findings suggest that high energy intake may reduce the total digestive cancer incidence and has a preventive effect on colorectal cancer.

Keywords: Cancer prevention; Diet; Digestive cancer; Energy intake.

Figure 1

Flow diagram of the search strategy and study selection.

Figure 2

Summary relative risks of digestive cancers. A: The highest vs lowest category of energy intake from included cohorts; B: An increment of 1 MJ/day energy intake from included cohorts. Squares represent study-specific relative risk (RR) estimates (size of the square reflects the study-specific statistical weight, that is, the inverse of the variance); horizontal lines represent 95%CIs; diamonds represent summary RR estimates with corresponding 95%CIs.

Figure 3

Publication bias in the studies. Begg’s funnel plot indicating no publication bias in the studies included in this meta-analysis. No indication of publication bias was noted from both visualization of the funnel plot and Egger’s test.