Dietary B vitamins and glioma: A case–control study based on Chinese population

**Background:** B vitamins are water-soluble micronutrients essential for energy metabolism, DNA synthesis, and cellular function. While vitamins A, C, and E have been studied for glioma prevention, the role of B vitamins in glioma risk is largely unknown. This study aimed to evaluate the association between dietary intake of five B vitamins (thiamine, riboflavin, nicotinic acid, folate, and biotin) and glioma in a Chinese population.

**Methods:** A population-based case-control study was conducted at Beijing Tiantan Hospital from 2021 to 2022. A total of 506 glioma cases (diagnosed per 2021 neuro-oncology criteria) and 506 age- and sex-matched healthy controls were enrolled. Dietary intake over the past 12 months was assessed using a validated 111-item food frequency questionnaire. Daily intakes of thiamine, riboflavin, nicotinic acid, folate, and biotin were calculated using the China Food Composition Tables. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between B vitamin tertiles and glioma, adjusting for age, BMI, occupation, education, household income, high-risk residential area, smoking, allergies, head trauma, family cancer history, physical activity, and energy intake. Restricted cubic spline models evaluated dose-response relationships.

**Key Results:** Compared with the lowest tertile, the highest tertile of each B vitamin was associated with a significantly reduced risk of glioma: thiamine (OR=0.09, 95%CI: 0.05–0.20), riboflavin (OR=0.12, 95%CI: 0.06–0.25), nicotinic acid (OR=0.24, 95%CI: 0.12–0.47), folate (OR=0.07, 95%CI: 0.03–0.15), and biotin (OR=0.14, 95%CI: 0.07–0.30). Continuous analyses showed that each 0.1 mg/day increase in thiamine reduced risk by 9% (OR=0.91, 95%CI: 0.86–0.96), each 0.1 mg/day increase in riboflavin by 30% (OR=0.70, 95%CI: 0.64–0.78), each 5 mg/day increase in nicotinic acid by 38% (OR=0.62, 95%CI: 0.50–0.77), each 100 μg/day increase in folate by 69% (OR=0.31, 95%CI: 0.23–0.42), and each 10 μg/day increase in biotin by 24% (OR=0.76, 95%CI: 0.66–0.88). Subgroup analyses by pathological type and grade revealed differences: thiamine was protective only for glioblastoma (OR=0.89, 95%CI: 0.79–0.99) and high-grade gliomas (OR=0.88, 95%CI: 0.82–0.96), while biotin was protective for astrocytoma (OR=0.55, 95%CI: 0.36–0.84) and high-grade gliomas (OR=0.79, 95%CI: 0.65–0.96) but not for glioblastoma or low-grade gliomas. Riboflavin, nicotinic acid, and folate showed consistent protective effects across subtypes and grades. Dose-response analyses showed nonlinear relationships for thiamine, nicotinic acid, and biotin, and linear relationships for riboflavin and folate. For example, the risk of glioma stabilized after thiamine intake exceeded 0.91 mg/day (P-nonlinearity <0.0001) and after folate intake exceeded 404.93 μg/day (P-nonlinearity=0.2168). Sensitivity analyses excluding participants by age, sex, BMI, education, income, smoking, allergies, or family cancer history confirmed the robustness of findings for thiamine, riboflavin, nicotinic acid, and folate, but biotin results were not significant in low-BMI subgroups.

**Clinical Implications:** This study provides the first comprehensive epidemiological evidence that higher dietary intake of thiamine, riboflavin, nicotinic acid, and folate is associated with a substantially lower risk of glioma in Chinese adults. The dose-response data suggest potential thresholds beyond which additional intake may not confer further benefit. These findings support the hypothesis that B vitamins may play a role in glioma prevention, possibly through antioxidant, DNA repair, and epigenetic mechanisms. However, the inconsistent results for biotin and the case-control design limit causal inference. Prospective cohort studies and trials are needed to confirm these associations and to explore optimal intake levels for glioma prevention.