Associations between dietary inflammatory index and incidence of breast and prostate cancer: a systematic review and meta-analysis.

OBJECTIVES: Dietary inflammatory index (DII) scores have been inconsistently linked to cancer risks. Therefore, a systematic review and meta-analysis was performed to examine the associations between the DII and the risks of breast and prostate cancer among men and women.

METHODS: Relevant studies were identified by searching PubMed and EMBASE databases up to March 2018. Data were available from 13 studies; of these, four studies used a prospective cohort design and nine studies were case-control studies. A total of 231 947 individuals from nine countries were included in these studies for the meta-analysis. The results were pooled using a random-effects model.

RESULTS: A pooled, adjusted odds ratio (OR) analysis indicated that there was a direct relationship between the highest versus lowest DII scores and prostate cancer risk in men (OR: 1.31; 95% CI: 1.04-1.57) but not the breast cancer risk (BCR) in women (OR: 1.65; 95% CI: 0.96-2.33). In the subgroup analyses, a more significant association between DII score and increased BCR was noted in premenopausal (OR: 2.03; 95% CI: 1.06-3.00) than in postmenopausal women (OR: 1.52; 95% CI: 0.89-2.16). When the results were stratified by body mass index, a positive association was observed between DII score and increased BCR in women (OR: 1.83; 95% CI: 1.48-2.18). Furthermore, there was no significant association between the highest versus lowest DII score and BCR among women who received hormone therapy (OR: 1.29; 95% CI: 0.93-1.64).

CONCLUSIONS: Men and premenopausal women who exhibit higher DII scores have increased prostate and breast cancer incidence risks, respectively. Moreover, body mass index had positive associations with the relationship between DII score and BCR in women. Further prospective cohort studies with longer follow-up periods are needed to support this possible association between DII score and cancer incidence.