Turmeric improves post-prandial working memory in pre-diabetes independent of insulin

Background and objectives: Cognitive impairment develops with pre-diabetes and dementia is a complication of diabetes. Natural products like turmeric and cinnamon may ameliorate the underlying pathogenesis.Methods: People ≥ 60 years (n=48) with newly-recognised untreated pre-diabetes were randomised to a double-blind metabolic study of placebo, turmeric (1 g), cinnamon (2 g) or both (1 g & 2 g respectively), ingested at a white bread (119 g) breakfast. Observations were made over 6 hours for pre- and post-working memory (WM), glycaemic and insulin responses and biomarkers of Alzheimer's disease (AD)(0, 2, 4 and 6 hours): amyloid precursor protein (APP), γ-secretase subunits presenilin-1 (PS1), presenilin-2 (PS2), and glycogen synthase kinase (GSK-3β). Differences between natural product users and non-users were determined by Students t and chi square tests; and between pre-test and post-test WM by Wilcoxon signed rank tests. Interaction between turmeric and cinnamon was tested by 2-way ANOVA. Multivariable linear regression (MLR) took account of BMI, glycaemia, insulin and AD biomarkers in the WM responses to turmeric and cinnamon.Results: No interaction between turmeric and cinnamon was detected. WM increased from 2.6 to 2.9 out of 3.0 (p=0.05) with turmeric, but was unchanged with cinnamon. WM improvement was inversely associated with insulin resistance (r=-0.418, p<0.01), but not with AD biomarkers. With MLR, the WM responses to turmeric were best predicted with an R2 of 34.5%; and with significant turmeric, BMI and insulin/glucose AUC beta-coefficients.Conclusions: Co-ingestion of turmeric with white bread increases working memory independent of body fatness, glycaemia, insulin, or AD biomarkers.