Personalized cognitive improvement by dietary supplements

Abstract

Several recent clinical studies have demonstrated a positive effect of turmeric/curcumin on a variety of medical conditions. Curcumin supplementation improved artery endothelial function and reduced oxidative stress, which is associated with cardiovascular disease, in healthy middle-aged and older adults. 5 Curcumin also demonstrated anti-inflammatory activity by significant reduction of serum atherosclerotic low-density lipoprotein levels in patients with mild chronic obstructive pulmonary disease (COPD). 6 Curcuminoids significantly prevented the development of diabetes in a prediabetic group, 7 and markedly increased anti-oxidant activity in the blood of patients with type II diabetes. 8 Curcumin significantly reduced neuropathic pain, 9 significantly decreased pain in aged patients with knee osteoarthritis, 10 and decreased pain and prevented muscle injury after running. 11,12 Supplementation of curcuminoids to standard antidepressants showed a significant reduction of anxiety and depression in patients with major depressive disorder. 13 Moreover, curcumin extracts significantly improved depressive symptoms and demonstrated anxiolytic effects in patients with atypical depression. 14 The positive effects on cognition was confirmed in several clinical trials. A randomized, placebo-controlled, double-blind study demonstrated that curcumin prevented cognitive decline in older adults. 15 Another study showed significant improvement of sustained attention, working memory tasks, and mood after curcumin treatment. 16 Moreover, recent studies with mouse models of Alzheimer disease found that curcumin ameliorates cognitive decline and improves synaptic functions. Ongoing studies of the effect of curcumin on Alzheimer disease patients are currently being assessed. 17 On the molecular level, curcumin inhibits the formation and promotes the disaggregation of amyloid-β plaques, attenuates the hyperphosphorylation of tau and enhances its clearance, binds copper, lowers cholesterol, modifies microglial activity, inhibits acetylcholinesterase, mediates the insulin signaling pathway, and has antioxidant and anti-inflammatory activity. 18 Green tea extract Several clinical studies found healthy effects of green tea in humans. Two independent double-blind, placebo-controlled clinical trials demonstrated that green tea extract (GTE) significantly reduced blood pressure in obese pre-hypertensive women, 19 and obese hypertensive patients. 20 GTE reduced pockets of inflammation in patients with chronic periodontitis, 21 and significantly reduced body weight and waist circumference in obese women. 22 Neuroimaging analysis (functional magnetic resonance imaging, fMRI) of healthy volunteers showed that GTE activated the dorsolateral prefrontal cortex (DLPFC), a key area that mediates working memory in the human brain. 23 A randomized, double-blind, placebo-controlled study using a combination of GTE and l-theanine demonstrated improved memory and attention in subjects with mild cognitive impairment. 24 A double-blind, placebo-controlled trial demonstrated that GTE significantly increased visual recognition memory in young adults with Down syndrome. 25 Mechanistically, GTE induction of neuronal plasticity resulted in cognitive improvement. 26 In addition to anti-oxidative and anti-inflammatory activities, GTE may improve cognitive function by the inhibition of arterial stiffness. 27 Although the above described clinical studies demonstrated significant improvement of cognition by characterized curcumin and green tea extract, there are several concerns that need to be addressed.