Effects of Curcumin on Cognitive Function—A Systematic Review of Randomized Controlled Trials

Abstract

Curcumin is a polyphenol present in turmeric and is credited with anti-inflammatory, antioxidant, and chemoprotective properties. Questions remain surrounding curcumin’s bioavailability and the mechanism by which it may exert neuroprotective effects. Following PRISMA 2009 guidelines, a systematic review was conducted to identify randomized, placebo-controlled trials investigating the effects of curcumin supplementation on cognitive function in older adults (>50 years). Five databases were searched (CINAHL, Cochrane Library, PubMed, SCOPUS, Web of Science) with five studies identified, each using different forms of curcumin and validated cognitive screening measures, meeting inclusion criteria. Curcumin doses ranged from between 90 and 4,000 mg/day, with significant improvements found in three of the five studies. Firstly, the most recent study found improvements with 90 mg of curcumin twice daily in tests of selective reminding (p = 0.002), visual memory (p = 0.01), and attention (p < 0.0001) over 18 months in non-demented individuals. The second study found improvement in Montreal Cognitive Assessment tool with 1,500 mg/day curcumin over 52 weeks (p = 0.02). Another study found improvement in serial three subtraction task responses after 4 weeks compared with the placebo group (p = 0.044). Of the adverse events reported (n = 58), gastrointestinal symptoms were most common (n = 34). Before curcumin can be recommended to treat or reduce rates of cognitive decline, well-designed trials with standardization in dose, method of assessing cognition, and duration, are required to determine the most bioavailable form of curcumin with minimal adverse effects.