Nutraceuticals: using food to enhance brain health by modulating postnatal neurogenesis in animal models and patient populations.

Adult hippocampal neurogenesis, while occurring throughout life, decreases with age and in some neurodegenerative diseases. As decreased hippocampal neurogenesis is correlated with cognitive decline, efforts have been made to increase levels of neurogenesis, either through natural compounds, environmental interventions or novel pharmacological compounds. Nutraceuticals are food products with medical benefits such as antioxidation, anti-inflammation or neuroprotection. There has been increasing interest in these "functional foods" and their active compounds in recent years, providing natural alternatives to de novo pharmaceuticals. This review highlights key nutraceuticals that promote neurogenesis and/or improve cognitive outcomes. By outlining the effects of these compounds in the animal models employed and in clinical populations, we also suggest further investigations. We examine common targets and pathways through which these nutraceuticals are believed to exert pro-neurogenic effects. Most nutraceutical preparations contain multiple components, any of which may exert effects on neurogenesis. Identifying key active compounds in nutraceuticals may enable researchers to better understand their effects and standardize doses across studies. The less stringent regulatory requirements for nutraceuticals can be a double-edged sword. While allowing easier access to the beneficial effects, higher doses of these compounds may have detrimental effects. Hence, research in this field should not only aim to identify the benefits of these compounds but also to identify efficacious and safe dosages for them. Our aims are to provide understanding of nutraceuticals, provide evidence for their benefits on neurogenesis and neurogenesis-related behaviors and finally to summarize potential mechanisms and help guide future work.