['Progressive microvascular dysfunction in type 2 diabetes mellitus (T2DM) may impair the ability of cerebral vessels to supply blood to brain regions during local metabolic demand, thereby increasing risks of dementia. Having previously demonstrated that resveratrol can enhance vasodilator function in the systemic circulation, we hypothesised that resveratrol could similarly benefit the cerebral circulation. We aimed to determine the most efficacious dose of resveratrol to improve cerebral vasodilator responsiveness (CVR) in T2DM.', 'In a double-blind, placebo-controlled, balanced crossover intervention, 36 dementia-free, non-insulin dependent T2DM older adults (49-78 years old) consumed single doses of synthetic trans-resveratrol (0, 75, 150, and 300\xa0mg) at weekly intervals. Transcranial Doppler ultrasound was used to assess CVR to a hypercapnic stimulus, both before and 45\xa0min after treatment. CVR, measured bilaterally in the middle cerebral arteries (MCA) and posterior cerebral arteries (PCA), was expressed as the percentage change in mean blood flow velocity from baseline to the peak velocity attained during hypercapnia. Resveratrol consumption increased CVR in the MCA; mean within-individual changes for each dose from placebo were 13.8\xa0±\xa03.5% for 75\xa0mg (P\xa0=\xa00.001), 8.9\xa0±\xa03.5% for 150\xa0mg (P\xa0=\xa00.016), and 13.7\xa0±\xa03.3% for 300\xa0mg (P\xa0<\xa00.001); only the 75\xa0mg dose was efficacious in the PCA (13.2\xa0±\xa04.5%, P\xa0=\xa00.016).'] Does low dose resveratrol improve cerebrovascular function in type 2 diabetes mellitus?