The evidence is mostly based on observational studies, with heterogeneity, and potential residual confounding by tobacco and alcohol; several syntheses note small-study and publication-bias concerns. Findings are drawn largely from adult populations in Europe, Asia and the Americas; exposures are commonly self-reported with variable dose categories, limiting dose–response precision.
| Reference | Study type | Population | Intervention and comparison | Outcomes | Risk of bias «Additional comments for included studies...»2 |
|---|---|---|---|---|---|
| «Pavia M, Pileggi C, Nobile CG, ym. Association bet...»1 | MA | European, USA, East Asia | Observational studies | The contribution of fruit and vegetable intakes to the occurrence of oral cancer |
Moderate |
| «He T, Guo X, Li X, ym. Association between coffee ...»2 | MA | China, USA, Japan, Europe, Brazil, India Patients with oral cavity cancer | Case-control and cohort studies | Association between high versus low coffee intake and the risk of oral cavity cancer | Low |
| «Heller MA, Nyirjesy SC, Balsiger R, ym. Modifiable...»3 | SR, MA | China Non-smokers |
Case-control and cohort studies | Association between tea consumption and oral cavity cancer risk | Moderate |
| «Zhou H, Wu W, Wang F, ym. Tea consumption is assoc...»4 | MA | Asia, America, Europe, Africa | Case-control studies | The association between tea intake and the risk of oral cancer | Moderate |
| «Hu S, Yu J, Wang Y, ym. Fish consumption could red...»5 | MA |
European, USA, Asia | Case-control and cohort studies | Association between fish consumption and oral cancer risk | Moderate |
SR=systematic review; MA=meta-analysis
| Reference | Comments |
|---|---|
| «Pavia M, Pileggi C, Nobile CG, ym. Association bet...»1 | The assessment methods for fruit and vegetable consumption may vary between the studies. The possibility of selection bias, misclassification bias related to exposure, and failure to consider potential confounders cannot be ruled out. |
| «Heller MA, Nyirjesy SC, Balsiger R, ym. Modifiable...»3 | Mostly observational studies, small non-smoker subgroup, possible residual confounding, heterogeneity |
| «Zhou H, Wu W, Wang F, ym. Tea consumption is assoc...»4 | Studies were case-control studies, about half of the studies had a lower NOS score, heterogeneity was moderate and the exposure measure and dose conversions varied. |
| «Hu S, Yu J, Wang Y, ym. Fish consumption could red...»5 | Selection/memory bias, variation in exposure definitions and adjustments. |
NOS=Newcastle–Ottawa Quality Assessment Scale
| Reference | Number of studies and number of patients (I/C) | Absolute number of events (%) I | Absolute number of events (%) C | Relative effect (95% CI) |
|---|---|---|---|---|
| Level of evidence: low The quality of evidence is downgraded due to study limitations. |
||||
| «Pavia M, Pileggi C, Nobile CG, ym. Association bet...»1 Per additional portion of fruit consumed per day |
16 4918/65802 |
N/A | N/A | OR 0.51 (0.40-0.65) |
| «Pavia M, Pileggi C, Nobile CG, ym. Association bet...»1 Per additional portion of vegetables consumed per day |
15 4826/57993 |
N/A | N/A | OR 0.50 (0.38-0.65) |
| «He T, Guo X, Li X, ym. Association between coffee ...»2 Coffee (high intake vs. low intake) |
19 6456 /1969484 |
N/A | N/A | OR 0.68 (0.56-0.82) |
| «He T, Guo X, Li X, ym. Association between coffee ...»2 Coffee (moderate intake vs. low intake) |
18 6295/1969084 |
N/A | N/A | OR 0.85 (0.77−0.94) |
| «Heller MA, Nyirjesy SC, Balsiger R, ym. Modifiable...»3 Tea (yes versus no) |
2 740/2329 |
N/A | N/A | OR 0.53 (0.29-0.96) |
| «Zhou H, Wu W, Wang F, ym. Tea consumption is assoc...»4 Tea (higher intake versus lower intake) |
14 5920/10553 |
N/A | N/A | OR 0.70 (0.61–0.81) |
| «Hu S, Yu J, Wang Y, ym. Fish consumption could red...»5 Fish (highest category compared with lowest category consumption) |
15 5211/64794 |
N/A | N/A | OR 0.74 (0.64–0.85) |
I=intervention; C=comparison; CI=confidence interval; N/A=no value is available; OR=odds ratio