The association between global and prime diet quality scores and the risk of breast cancer: a case control study

Backgrounds: Despite established links between diet and breast cancer, the association of comprehensive diet quality indices specifically Global Diet Quality Score (GDQS) and Prime Diet Quality Score (PDQS) with BC risk remains underexplored. This case-control study evaluated the association between global and prime diet quality scores and the risk of breast cancer. Methods: Dietary intake of 125 newly diagnosed, histopathologically confirmed breast cancer cases and 250 age-frequency-matched controls (women ≥30 years) at Shaqra General Hospital was assessed using a validated semi-quantitative FFQ, and diet quality was evaluated by GDQS and PDQS indices, with multivariable logistic regression models (SPSS v26) adjusted for age, BMI, total energy intake, physical activity, family history of breast cancer, and smoking status, including trend analyses across tertiles of diet quality scores. Results: < 0.001) than controls. In multivariable models, higher total GDQS and positive GDQS scores were strongly associated with lower odds of breast cancer (e.g., total GDQS highest tertile aOR = 0.397; 95% CI: 0.279-0.653; Ptrend < 0.001), and higher total PDQS scores were similarly protective (aOR = 0.455; 95% CI: 0.309-0.761; Ptrend = 0.003). Negative GDQS and unhealthy PDQS scores were not significantly associated with breast cancer risk. Conclusion: A high diet quality, as indicated by high total GDQS and total PDQS scores, was associated with a decreased risk of breast cancer. These findings highlight a potential role of overall diet quality in breast cancer etiology but should be interpreted as observational associations rather than evidence of causal or therapeutic effects.