Forbes et al. carried out a systematic study on 24 randomized controlled trials published in Can Geriatr J. (2015) that examined whether nutrients, dietary supplements, and vitamins could improve cognitive functioning in middle-aged and older adults without dementia. All our trials were required to last at least three months and evaluated the effects of omega-3 fatty acids, B vitamins, vitamin E, or other nutritional interventions.
Some other nutritional interventions, such as green tea extract, Concord grape juice, chromium picolinate, beta-carotene, and combinations of multivitamins, demonstrated some promising effects on cognition in isolated studies, and further research is needed.
This systematic review and meta-analysis of randomized controlled trials offer moderate to strong evidence in the hierarchy of evidence-based medicine.
The review included:
Since systematic review and meta-analysis of RCTs are counted amongst the highest levels of evidence, this study has great credibility. Nevertheless, findings suggested no effect of omega-3s, B vitamins, or vitamin E on cognitive functioning, which indicate that while there is strong evidence, the efficacy of these supplements remains unsupported.
Strength: Due to systematic review and pooled meta-analysis of randomized controlled trials
Limitation: No significant benefits found for most nutrients; other individual studies showed potential for various interventions, but need to be researched further
Future Research Needed: Longer-term trials investigating specific populations, lifestyle factors, and biomarker interactions
The review found that there was no solid evidence for improvement of cognitive function by omega-3, B vitamins, and vitamin E in healthy middle-aged and older adults. Some other dietary compounds showed their potentials, but more studies are needed before endorsing them to prevent cognitive decline or dementia. Presently, the well-balanced diet, regular physical ability, and good lifestyle is the best condition for cognitive health, leaving further research into the nutrient-lifestyle factor-genetics-biomarker interactions for understanding better the long-term effects on brain health.
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