title: Effect of Nutrients, Dietary Supplements and Vitamins on Cognition: a Systematic Review and Meta-Analysis of Randomized Controlled Trials.
abstract: BACKGROUND
  Observational studies have suggested that various nutrients, dietary supplements, and vitamins may delay the onset of age-associated cognitive decline and dementia. We systematically reviewed recent randomized controlled trials investigating the effect of nutritional interventions on cognitive performance in older non-demented adults.
  
  
  METHODS
  We searched MEDLINE, CINAHL, Embase, and the Cochrane Library for articles published between 2003 and 2013. We included randomized trials of ≥ 3 months' duration that examined the cognitive effects of a nutritional intervention in non-demented adults > 40 years of age. Meta-analyses were done when sufficient trials were available.
  
  
  RESULTS
  Twenty-four trials met inclusion criteria (six omega-3 fatty acids, seven B vitamins, three vitamin E, eight other interventions). In the meta-analyses, omega-3 fatty acids showed no significant effect on Mini-Mental State Examination (MMSE) scores (four trials, mean difference 0.06, 95% CI -0.08 - 0.19) or digit span forward (three trials, mean difference -0.02, 95% CI -0.30 - 0.25), while B vitamins showed no significant effect on MMSE scores (three trials, mean difference 0.02, 95% CI -0.22 - 0.25). None of the vitamin E studies reported significant effects on cognitive outcomes. Among the other nutritional interventions, statistically significant differences between the intervention and control groups on at least one cognitive domain were found in single studies of green tea extract, Concord grape juice, chromium picolinate, beta-carotene, two different combinations of multiple vitamins, and a dietary approach developed for the control of hypertension.
  
  
  CONCLUSIONS
  Omega-3 fatty acids, B vitamins, and vitamin E supplementation did not affect cognition in non-demented middle-aged and older adults. Other nutritional interventions require further evaluation before their use can be advocated for the prevention of age-associated cognitive decline and dementia.
authors.affiliation: Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary, Calgary, AB;
authors.forename: Scott C
authors.initials: SC
authors.lastname: Forbes
authors.affiliation: Departments of Medicine, Clinical Neurosciences and Community Health Sciences, Faculty of Medicine, University of Calgary, Calgary, AB;; Alberta Seniors Health Strategic Clinical Network, Alberta Health Services, Calgary, AB.
authors.forename: Jayna M
authors.initials: JM
authors.lastname: Holroyd-Leduc
authors.affiliation: Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary, Calgary, AB;; Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, AB;
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Poulin
authors.affiliation: Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, AB;; Brenda Stafford Foundation Chair in Geriatric Medicine, Faculty of Medicine, University of Calgary, Calgary, AB;; Departments of Medicine, Clinical Neurosciences and Community Health Sciences, Faculty of Medicine, University of Calgary, Calgary, AB;; Alberta Seniors Health Strategic Clinical Network, Alberta Health Services, Calgary, AB.
authors.forename: David B
authors.initials: DB
authors.lastname: Hogan
keywords: dementia; macro-nutrients; micro-nutrients; nutrition