Levels of evidence for the association between different food groups/items consumption and the risk of various cancer sites: an umbrella review

This study aimed to determine the level of evidence on the association between food groups/items consumption and the risk of different cancer sites from the meta-analyses/pooled analyses of observational studies. A systematic search was executed in Scopus, PubMed/MEDLINE, and Web of Science. The criteria from the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) Expert Report were adopted for evidence grading. In summary, there was convincing evidence for the association between fibre intake and decreased risk of colon and breast cancer. Also, consumption of dairy products, milk, fruits, and fibre was associated with a probable decreased risk of breast cancer. Consumption of whole grains, dairy products, milk, fruits, vegetables, and fibre had a probable inverse association with the incidence risk of gastrointestinal tract cancers. More qualified studies are needed to find reliable findings on the association between various food groups/items consumption and the risk of different cancer sites.