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Deep Dive: Subtle smarts from polyphenols for middle-aged adults

A recent meta-analysis suggests that polyphenols may impact some aspects of cognition in the short term. But that conclusion paints a picture with a really broad brush.

Study under review: Effects of Polyphenol-Rich Interventions on Cognition and Brain Health in Healthy Young and Middle-Aged Adults: Systematic Review and Meta-Analysis

Introduction

Nutrition has become a staple of preventive medicine, so researchers are delving deeper into components of foods or supplements that might optimize different aspects of health[1]. These so-called ‘bioactives’ are garnering more interest as life expectancy[2] and the associated burden of age-related global disease increases[3] alongside a lack of effective pharmacological treatments[4].

Various plant bioactives, such as carotenoids, alkaloids, and polyphenols, appear to improve health markers[1] or reduce risk of disease. Polyphenol compounds span a broad range of bioactives, such as flavonoids, phenolic acids, and other compounds that can be found in fruits, vegetables, spices, coffee, and wine. These compounds exhibit a broad range of benefits[5], from accelerated exercise recovery[6] to anticancer effects[7].

Recently, the neuroprotective effects[8] of polyphenols have been the focus of researchers attempting to prevent or even treat age-related neurodegenerative disease. A systematic review and meta-analysis[9] covered in NERD #67 reported that polyphenol-rich supplementation may improve some cognitive and brain functions in older (older than 55 years) adults. However, as a report from the World Health Organization suggests, the later in life the intervention begins, “the more costly and less effective the solutions are likely to be.”

Luckily, some studies have shown potential benefits[10][11] of polyphenol-rich supplementation on cognition and brain-related health measures in healthy young and middle-aged adults. However, as is generally the case, some results have been conflicting[12][13]. The various study designs, polyphenols used, doses, and durations of intervention, make the existing literature hard to analyze and interpret. Research is also further complicated by the lack of any diseases associated with polyphenol deficiency. Vitamin C is necessary to prevent scurvy, but it’s possible to live without resveratrol.

The authors of the study under review conducted a systematic review and meta-analysis to try and resolve the uncertainty behind polyphenol intake and its influence on cognitive and brain-related health measures.

Polyphenols are prominent plant bioactives that appear to have various health benefits, such as neuroprotection, but studies demonstrate mixed results and use different polyphenols, doses and durations of intervention. In addition, relatively few studies focus on people who would benefit most from their putative effects: young and middle-aged adults. This led researchers to conduct a systematic review and meta-analysis in an attempt to investigate the relationship between polyphenol intake and cognitive function in this age group.

What was studied?

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What were the findings?

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The bigger picture

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Frequently asked questions

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Other Articles in Issue #70 (August 2020)