Study under review: The Effect of (Poly)phenol-Rich Interventions on Cognitive Functions and Neuroprotective Measures in Healthy Aging Adults: A Systematic Review and Meta-Analysis
As the human body ages, its natural metabolic processes tend to create more oxidative stress while simultaneously losing the ability to dampen it. This imbalance can lead to chronic inflammation and tissue damage and is associated with chronic disease such as cancer, cardiovascular diseases, and neurodegenerative diseases.
While the cause of neurodegeneration is complex and likely involves many factors, multiple studies have suggested oxidative stress as a prominent factor and nutrition (specifically plant-based foods) as a preventive measure for age-related cognitive decline. Age-related cognitive decline manifests itself as a dwindling in memory, attention capacity, processing speed, and executive function (cognitive control of behavior)—all of which can be indicators of neurodegeneration.
Polyphenols, shown in Figure 1, are compounds that are generally not directly involved in the growth, development, or reproduction of plants, but confer protection against ultraviolet radiation, pathogens, and oxidation. They are commonly found in fruits and vegetables and their byproducts (e.g., red wine, dark chocolate, tea, etc.). Polyphenols have demonstrated potent antioxidant and anti-inflammatory activity and their intake is associated with a decreased risk of chronic diseases.
Recent studies have reported improvements in various measures of cognitive function, as well as biomarkers of neuroplasticity and neuroinflammation, from various sources of polyphenols. However, there are few studies on many different sources, doses, and durations of polyphenol supplementation and some studies have demonstrated somewhat conflicting results and relatively small sample sizes. This led the researchers of the study under review to conduct a systematic review and meta-analysis in an attempt to resolve the uncertainties regarding the impact of polyphenol intake on cognitive function in older people.
Greater oxidative stress is a prominent factor involved in age-related cognitive decline. Polyphenols are plant compounds with antioxidant and anti-inflammatory properties that may reduce the impact of aging on cognitive function. A high variety of polyphenol sources and cognitive tests, small sample sizes, and somewhat conflicting results in the existing literature led researchers to conduct a systematic review and meta-analysis in an attempt to resolve uncertainty regarding the impact of polyphenol intake on cognitive function.
Other Articles in Issue #67 (May 2020)
Herbs for hypogonadism: Exploring the effects of fenugreek on testosterone
Fenugreek boosts testosterone a tad according to this meta-analysis, but there are many reasons not to take these results at face value.
NERD Nulls: January-February 2020
Here's a quick rundown of some studies from earlier this year that didn't find clear effects!
Not just for making cakes: baking soda may improve exercise performance
Bicarb seems to boost muscular endurance a bit but may not affect strength.
Do different dieting strategies lead to loss of control after losing weight?
According to this recent trial, continuous energy restriction may have a very slight edge over intermittent energy restriction.
Digging into Paleo: Ancestral diets for glucose control
The early evidence isn't conclusive but looks promising. More evidence, especially from studies that strictly control for caloric intake, would be useful.
Deep Dive: Evaluating the health benefits of the Mediterranean diet as a ‘holiday diet’ requiring no calorie restriction or exercise
How much of a benefit does switching sedentary people eating a typical Western diet to an equicaloric Mediterranean diet provide? This trial aimed to find out.
Safety Spotlight: The Dark Side of Broccoli
A recent meta-analysis highlights some concerns around how certain drugs can interact with cruciferous veggies.