Abstract
This systematic review and meta-analyses aimed to assess whether malnutrition may increase the incidence of oral cancer. Following the PRISMA statement, the research was conducted on PubMed, Scopus, and MEDLINE via OVID without any time restrictions. The risk of bias was assessed, and the quality of evidence for each performed meta-analysis was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. Sixty-one articles met the inclusion criteria and seven studies underwent quantitative evaluation. For our meta-analysis on hypovitaminosis B, three studies with a total of 90,011 patients were included. An odds ratio of 2.22 was found. Our meta-analysis on the correlation between vitamin C and oral cancer included one study with a total of 866 patients and the derived odds ratio was 1.06. Our meta-analysis on the relationship between vitamin D deficiency and the incidence of oral cancer included three studies with a total of 12,087 patients and the odds ratio was -2.58. The GRADE system showed a moderate strength of evidence due to the presence of studies with a high risk of bias and high indirectness of the data given. The present findings suggest that an inadequate intake of vitamins, particularly vitamin D, poses a risk for the onset of oral cancer.