The human brain is a remarkable organ that governs our thoughts, emotions, and actions. For centuries, scientists have studied its complexities, uncovering various systems and mechanisms that contribute to its overall function. One such system that has gained significant attention in recent years is the glymphatic system. Often referred to as the brain's waste clearance system, it has emerged that the glymphatic system plays a vital role in long-term brain health and cognitive wellbeing.
Understanding the Glymphatic System
Our glymphatic system is made up of a micro-network of vessels within the central nervous system. It would still be considered a relatively ‘new’ discovery, having only been uncovered by researchers at the University of Rochester Medical Center in 2012. Prior to this discover it had been thought that lymphatic function only existed outside the central nervous system. The term "glymphatic" combines the words "glial" (a type of brain immune cell) and "lymphatic" (relating to the lymphatic system).
Unlike our traditional lymphatic system found throughout the rest of our body, the glymphatic system does not have lymph nodes or vessels that depend on our movement for proper circulation. Instead, it relies on a unique mechanism to facilitate waste clearance and the exchange of essential molecules within the brain. The system utilises the flow of cerebrospinal fluid (CSF) to flush out waste products and distribute nutrients to brain cells. What’s more, the glymphatic system activates during sleep, highlighting the critical role sleep plays in regulating optimal brain function.
Key Functions of the Glymphatic System
Waste Clearance: One of the primary functions of the glymphatic system is to remove waste products from the brain. As we go about our daily activities, our brain cells produce metabolic waste, such as excess proteins and toxic substances. The glymphatic system uses the time while we are sleeping to eliminate these waste materials, preventing the build-up of harmful substances that could impair brain function and contribute to neurodegenerative diseases.
Nutrient Delivery: In addition to waste clearance, the glymphatic system also plays a crucial role in supplying essential nutrients to brain cells. As cerebrospinal fluid flows through the glymphatic system, it transports glucose, lipids, amino acids, and other vital molecules that brain cells require for energy and proper functioning.
Implications for Brain and Cognitive Well-being
Neurodegenerative Diseases: Dysfunction or impairment of the glymphatic system has been implicated in various neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. In these conditions, there is an accumulation of toxic proteins, such as beta-amyloid and alpha-synuclein, respectively. A healthy glymphatic system ensures the efficient removal of these proteins, potentially reducing the risk or slowing the progression of neurodegenerative diseases.
Cognitive Function: The glymphatic system's role in waste clearance and nutrient delivery has important implications for cognitive function. By effectively eliminating waste products and providing essential nutrients, the glymphatic system supports optimal brain health, which is closely associated with our cognitive abilities such as memory, attention, and learning. Maintaining a healthy glymphatic system may help promote cognitive wellbeing and reduce the risk of age-related cognitive decline.
Brain Health Maintenance: The glymphatic system’s functions are not limited to waste clearance and nutrient delivery alone. It also contributes to maintaining a stable brain environment by regulating ion and water balance, controlling inflammation, and removing potentially harmful substances. A well-functioning glymphatic system ensures the overall homeostasis (cellular harmony) of our brain, which is essential for its long-term health and wellbeing.
Stroke and Brain Injury Recovery: Studies suggest that the glymphatic system may play a role in stroke and brain injury recovery. After an injury, the glymphatic system ramps up its activity to remove damaged cells, debris, and byproducts, facilitating the healing process. Enhancing glymphatic function through therapies or interventions may aid in the recovery and rehabilitation of individuals affected by stroke or brain injury.
Brain Ageing: Like many aspects of cellular machinery, glymphatic function declines as we age. As the system slows down, the accumulation of waste products and impaired nutrient delivery can contribute to age-related cognitive decline and raise our risk for neurodegenerative disease. By understanding and supporting glymphatic system health, it may be possible to slow down the cognitive decline often associated with ageing and improve long-term brain resilience.
Promoting a Healthy Glymphatic System
While the glymphatic system's study is relatively new, researchers have identified several factors that can influence its function and health:
Sleep: It goes without saying, that adequate sleep is crucial for the optimisation of the glymphatic system. If our sleep is broken or we experience sleep loss or insomnia, we will inevitably disrupt optimal glymphatic function and waste clearance. Getting on top of healthy sleep habits and ensuring we focus on the depth and quality of the sleep we get, will help the glymphatic system to maintain our brain health.
Hydration: As little as a 2% loss of hydration can impair brain function. Proper hydration is essential for maintaining optimal brain health and facilitating the flow of cerebrospinal fluid within the glymphatic system. Keeping ourselves well hydrated and topping up on essential nutrients that support our electrolyte balance can help to keep glymphatic function working at its best.
Physical Activity: We know that regular exercise has been shown to have positive effects on brain health. Research is now exploring whether exercise can enhance glymphatic system activity by improving cerebral blood flow and overall brain circulation. Exercise benefits brain health in many ways, including supporting BDNF, circulation and oxygenation. Many people who exercise typically report positive improvements in sleep, which will also benefit glymphatic function.
Diet: Consuming a balanced diet that includes brain-healthy nutrients, such as omega-3 fatty acids, antioxidants, vitamins and mineral, may support glymphatic function. Diets rich in fruits, vegetables, whole grains, lean protein, and quality oils and fats are generally beneficial for overall brain health.
Avoiding Risk Factors: Certain lifestyle choices and conditions can impair glymphatic system function. These include chronic stress, smoking, excessive alcohol consumption, and obesity. Minimising exposure to these risk factors can help maintain a healthy glymphatic system.
The discovery of the glymphatic system has provided valuable insights into the mechanisms underlying brain health and cognitive wellbeing. This unique waste clearance and nutrient delivery system plays a crucial role in maintaining brain function and preventing neurodegenerative disease. By understanding how the glymphatic system works and implementing lifestyle practices that promote its health, we can take proactive steps to support our brain health and potentially mitigate the risks associated with cognitive decline and neurological disorders.
REFERENCES
Jessen NA, et al. The Glymphatic System: A Beginner's Guide. Neurochem Res. 2015 Dec;40(12):2583-99.
He XF, et al. Voluntary Exercise Promotes Glymphatic Clearance of Amyloid Beta and Reduces the Activation of Astrocytes and Microglia in Aged Mice. Front Mol Neurosci. 2017 May 19;10:144.
Dolezal BA, et al. Interrelationship between Sleep and Exercise: A Systematic Review. Adv Prev Med. 2017;2017:1364387.