Blood biomarkers of Alzheimer's disease in Australians habitually consuming various plant-based diets

Background: Evidence suggests that plant-based diets (PBDs) may be protective against neurodegenerative diseases such as Alzheimer's disease (AD). Objective: This study examined associations between blood-based AD biomarkers in individuals 30–75 years without current or diagnosed cardiovascular disease following different PBDs versus regular meat-eating diets (RMEs). Methods: This secondary analysis of the Plant-based Diets study measured Aβ_1–42/Aβ_1–40, p-tau181, NFL, and GFAP in 237 plasma samples using SIMOA from individuals following vegan, pesco-vegetarian (PVs), lacto-ovo vegetarian (LOVs), semi-vegetarian (SVs), or RME diets. Multivariable regression adjusted for age and sex. Results: Following adjustments for age and sex, plasma Aβ_1–42/Aβ_1–40ratio was significantly higher in PVs 0.011 (CI: 0.006, 0.016, p < 0.01), LOVs 0.011 (CI: 0.007, 0.016, p < 0.01) and SVs 0.015 (0.009–0.020, p < 0.01) groups compared to RMEs. Plasma p-tau181 was significantly higher in PVs 3.4 (CI: 0.4–6.4, p < 0.05) and LOVs 7.1 (CI: 2.5, 11.8, p < 0.01), NFL higher in PVs 5.2 (CI: 1.6, 8.7, p < 0.01) and LOVs 4.0 (CI: 1.6, 6.5, p = 0.01), and GFAP higher in PVs 26 (CI: 6, 47, p < 0.05) and LOVs 21 (5, 367, p = 0.01), all compared to RMEs. Conclusions: This analysis suggests that PBDs may be associated with blood-based AD biomarkers. Higher Aβ_1–42/Aβ_1–40levels in PV, LOV and SV dietary patterns compared to RMEs could indicate lesser amyloid burden, but elevated levels of other AD biomarkers in some PBDs warrant further investigation into nutrient-specific roles in AD pathology.