Limited epidemiologic evidence links cancer risk to dietary acid load and methionine intake. Acid stress and metabolic acidosis are closely related to cancer development. Methionine is the main acidogenic amino acid and exerts epigenetic influences. We recently reported preliminary results on dietary acid load, methionine intake, and breast cancer risk. Therefore, both variables deserve further epidemiologic analysis. We revisited a Uruguay-based case-control study (572 cases/2,294 matched controls); women were recruited from 4 central hospitals, and all were interviewed using a specific questionnaire. Food-derived nutrients were calculated from available databases. Dietary acid load was estimated based on a validated formula: the potential renal acid load (PRAL) score. OR was estimated by logistic regression, adjusting for potential confounders. We found significant, direct associations between the breast cancer risk and PRAL (OR = 3.33) and methionine intake (OR = 5.87). Trends were significant (P < 0.001).PRAL and methionine displayed higher ORs among subsets with a positive family history of cancer compared to a negative one:OR = 6.16 vs. 2.80 (PRAL); OR = 11.8 vs. 4.86 (methionine). Both estimates were higher in pre- than postmenopausal women: OR = 5.91 vs. 2.96 (PRAL); OR = 8.76 vs. 5.39 (methionine). In conclusion, an acidogenic dietary style may increase a breast cancer risk. Furthermore, our findings suggest that methionine intake, showing comparable or even higher ORs than the dietary acid load scores themselves, might influence the risk associated with acid-base imbalance, ultimately leading to cancer. Additional research on methionine-induced epigenetic influences is warranted.

Objective: Adherence to vegetarian diets has been associated with physical health benefits, whereas vegetarian mental health is less well documented. We sought to investigate whether adherence to a vegetarian diet was associated with depression in a nationally-representative sample of US adults. Methods: We used population-based data from the US National Health and Nutrition Examination Surveys to examine said associations. Depression was assessed using the Patient Health Questionnaire (PHQ-9), vegetarian status was self-reported. Multivariate regression was used to measure the magnitude of associations, controlling for a range of covariables known to be associated with depressive symptoms. Results: Our analysis included 9,584 individuals, of which 910 individuals had PHQ-9 scores suggestive of depression. Vegetarian diet was associated with reduced odds of PHQ-9 defined depression (odds ratio [OR]: 0.49 [95% confidence interval {CI}: 0.24–0.98], p=0.047) in a model adjusting for sex, age, ethnicity, income, and marital status. When adjusting for additional factors (educational level, smoking status, serum C-reactive protein, and body mass index) in a second model, the previously observed association was no longer significant (OR: 0.66 [CI: 0.34–1.26], p=0.203). Conclusion Vegetarian diet was not associated with PHQ-9 defined depression in this nationally-representative sample of adults. Additional longitudinal examinations are warranted to evolve the understanding of the role of vegetarian diets in mental health.