Whether you stub your toe or suffer from persistent low back pain, the likely culprit of your symptoms is inflammation. Inflammation is a term we hear quite frequently in the media. Let us break the concept down a bit further to understand how inflammation can have detrimental impacts on the brain and its relation to chronic neurodegenerative diseases.
Inflammation is a vital part of the body’s defence mechanism to danger. When tissue damage occurs, like stubbing your toe, the inflammatory response begins rapidly – this includes an increase in the size of blood vessels (vasodilation), an increase in blood flow and an increase in the permeability of the walls of the surrounding vessels, which allow white blood cells (the body’s ‘first responders’) to enter the scene and repair the damage. All of these explain why that same stubbed toe is red, painful, and swollen.
Chronic inflammation is marked by the continued infiltration of white blood cells for months to years. Whether there was an initial insult (i.e.. a car accident or sports-related accident) to trigger the injury or an individual is suffering from an auto-immune condition, this chronic process typically results in more damage than benefit. Chronic inflammation results in several destructive processes – including fibrosis (or scarring) of the nearby tissue and the release of substances called reactive oxidative species (ROS) that damage critical cellular structures.
In the brain, we have two main populations of cells that respond to inflammation: microglia, which are the ‘garbage disposal trucks’ of the brain and consume debris like dead or infected cells; and astrocytes which make up the blood-brain barrier, protecting our brains from infection and disease.
Advances in research have allowed us to understand how dysregulated inflammation in the brain is linked to neurodegenerative diseases like Alzheimer’s and Parkinson’s Dementia. The brain’s defence mechanisms cannot modulate the inflammatory response and thereby control fibrosis and ROS, which is key to the onset and progression of such diseases. Risk factors such as age, obesity, smoking, and sleep disorders are associated with chronic inflammatory states. However, specific dietary changes are emerging as protective factors to stave off ongoing neuroinflammation.
In a 2021 article published by Dr. Kristi Crowe-White and colleagues from the University of Alabama’s Department of Nutrition in the Journal of Nutrition in Gerontology and Geriatrics, watermelon emerged as a potential candidate to improve cognitive function by decreasing neuroinflammation. Second only to tomatoes, watermelon is one of the richest sources of lycopene.
Lycopene is an organic carotene-based compound that gives watermelons and tomatoes their bright red colour. Owing to its rich antioxidant and anti-inflammatory properties, lycopene has been previously studied amongst animals and humans as a potential intervention to slow or prevent chronic disease. For instance, a 2019 article by Zwilling et al. published in NueroImage found that older adults with higher baseline levels of lycopene in their blood had better cognitive functioning than their peers. Lycopene has similarly been shown in animals to reduce oxidative stress and dysregulated inflammation precipitating neurodegenerative disease.
Thus, Dr. Crowe-White selected lycopene-rich watermelon juice as the intervention in this study. Twenty-four otherwise healthy, post-menopausal women were randomized to receive either two daily servings of pasteurized 100% watermelon juice or a placebo beverage. Participants were followed over four weeks and, at the end of the study, received a battery of tests, including measures of cognitive function and blood levels of inflammatory markers.
Women who consumed watermelon juice throughout the study had an 81% average increase in their
lycopene levels compared to those in the placebo group. However, this study did not demonstrate any change in blood markers of inflammation nor tests of cognitive function. Therefore, they could not conclude that watermelon juice directly impacted brain function among the women in this study. However, it is essential to note that the small size of this study may not have been able to generate the robust data needed to demonstrate a change.
While the research may still be a few steps away from directly linking watermelon to improved cognition, this superfood can potentially elevate lycopene levels linked to several health benefits by reducing overall inflammation.