Effect of long-term nutraceutical and dietary supplement use on cognition in the elderly: a 10-year systematic review of randomised controlled trials

Abstract

Nutraceuticals have generated interest as a way to mitigate the cognitive decline in older adults. The aim of this systematic review was to determine the evidence for these claims from the scientific literature in randomised, double-blinded, controlled trials (duration: ≥1 year; participants: n≥100; age(mean): ≥65 years). Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched four electronic databases (PubMed, Scopus, CINAHL and Web of Science) and identified twenty-five studies published between the 15·June·2006 and 14·June·2016. Interventions included B-vitamins, n-3 fatty acids, antioxidant vitamins and herbs. Of the B-vitamin studies, four found benefits to cognition with supplementation. The first of these B-vitamin studies, in individuals with mild cognitive impairment (n 266; duration=2 years), included benefit to executive function (P=0·015) and improvements in the Mini-Mental State Examination (MMSE) among participants with baseline homocysteine above 11·3 µmol/l (P<0·001). In the same sample, the second study found cognitive benefits of B-vitamins dependent on the higher baseline plasma n-3 fatty acid status. The third B-vitamin study (n 900; duration=2 years) reported improved performance in immediate (P=0·046) and delayed recall (P=0·013), whereas the fourth study (n 856; duration=2 years) reported slower rate of cognitive decline in the MMSE (P=0·05). One study investigating DHA treatment (n 402; duration=1·5 years) revealed the slower rate of cognitive change in apoE e4 non-carriers (P=0·03). As only five included studies revealed notable benefits, presently based on the specific compounds explored here, there is not compelling evidence to support the use nutraceuticals to improve cognition in the elderly. Future long-term trials of nutraceuticals should investigate interactions with lifestyle, blood biomarkers and genetic risk factors.

Efficacy of Vitamins on Cognitive Function of Non-Demented People: A Systematic Review and Meta-Analysis

“…However, the effects of vitamins on cognitive function of non-demented elderly have been inconsistent even in meta-analyses on randomized or quasi-randomized, placebo-controlled trials [6][7][8][9][10][11][12][13][14]. These conflicting results may be attributable to several limitations of previous meta-analyses.…”

“…These conflicting results may be attributable to several limitations of previous meta-analyses. Firstly, the proportion of the subjects with mild cognitive impairment (MCI) was not uniform across the studies, and the effect of vitamins on cognitive function may be different between subjects with normal cognition and those with MCI [6][7][8][9][10][11][12][13][14]. Secondly, the effect of different geographical locations or ethnicities was not considered in all previous meta-analyses, even though they are related to dietary habits and genetic backgrounds.…”

“…Secondly, the effect of different geographical locations or ethnicities was not considered in all previous meta-analyses, even though they are related to dietary habits and genetic backgrounds. Thirdly, most previous meta-analyses did not examine the isolated effects of vitamins by allowing the inclusion of minerals or other cofactors as intervention material [6][7][8]12,14].…”

Reversal of β-amyloid induced microglial toxicityin vitroby activation of Fpr2/3

“…Nevertheless, oAβ was clearly able to induce ROS production at levels capable of damaging bystander cells, which if replicated in vivo may be a driving factor in ongoing neuronal damage and secondary neuroinflammation seen in AD. Production of ROS is far from the sole damaging effect of oAβ in the brain, as is borne out by the, at best, equivocal results from clinical trials of antioxidants in AD [50,51]. Nevertheless, targeting a receptor with the potential to suppress ROS production, restore microglial metabolic homeostasis and promote resolution, as is the case for Fpr2/3, has significant potential for therapeutic development.…”

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

“…12 Therefore, non-pharmacological treatments, such as dietary supplements and nutraceuticals, have come into focus for the potential treatment of neurodegenerative conditions. 13 In particular, plant polyphenols are increasingly being investigated for their potential in the prevention or treatment neurodegenerative conditions, due to their pleotropic activities in the human body. 14 Polyphenolic compounds, such as curcumin, are being acknowledged for their associations with various beneficial health effects.…”