The Glymphatic System: The Brain’s Waste Disposal System

By Ram Rao, Ph.D., Principal Research Scientist for Apollo Health

In 2012, a team of researchers demonstrated for the first time that the brain is equipped with a unique waste-carrying drainage system called the glymphatic system. The glymphatic system removes waste proteins from the brain in a similar way that fluids and waste are removed by the rest of the body’s lymphatic system. The brain gets rid of tissue waste, including dead neural cells, beta-amyloid plaques, and tau tangles associated with Alzheimer’s disease, by emptying the waste into the glymphatic system. Recent studies have shown that:

1. The waste-carrying glymphatic system is more active during sleep than it is during the day.

2. It is damaged by stroke and trauma.

3. Waste removal via the glymphatic system improves with exercise.

One of the reasons physical and mental exercises have a beneficial effect on brain structure and function is that exercise stimulates the waste-carrying glymphatic system. Mice that used a running wheel showed more than a two-fold increase in glymphatic flow than mice with no access to exercise. The increased glymphatic flow following exercise may be just what the brain needs to clear away cellular trash and function at its best.

Studies also indicate that the functional activity of the glymphatic system decreases with age. A recent comparison of the glymphatic system in old versus young mice showed a dramatic reduction in the waste removal activity in old mice compared to young mice. The major consequence of a decrease in glymphatic activity is a reduction in the clearance of cellular trash from the brain, which is a hallmark of neurodegenerative diseases, including Alzheimer’s disease.

Interestingly, recent studies have shown that low doses of alcohol improve waste clearance from the brain, perhaps suggesting that small amounts of alcohol not only suppress inflammation in the brain but also help to clear away the trash, including the toxic molecules associated with Alzheimer’s disease. Animals that were exposed to low levels of alcohol showed less inflammation in the brain, their glymphatic system was more efficient in draining out the brain waste, and they performed better in the cognitive and motor tests compared to control mice that were not exposed to alcohol. In contrast, the brains of animals exposed to high levels of alcohol displayed abnormal inflammation together with impairment of the animal’s cognitive abilities and motor skills. This generally supports the studies that have associated low levels of alcohol consumption with a lower risk of dementia and higher amounts with a greater risk. The activation of the waste-carrying glymphatic system may be one of the main mechanisms by which low doses of alcohol improve overall brain health, but we caution you not to directly translate information gleaned from mouse studies into clinical practice.

Thus, the waste clearance system is a unique method developed by the brain to remain functionally active and resilient and to make way for new thoughts and ideas. We now know why healthy lifestyle choices like a nourishing diet, adequate sleep, mental and physical exercise, and a low dose of alcohol intake may be a simple yet effective way to tweak the glymphatic waste disposal system and thereby strengthen the structure and function of the brain.

For more information about Alzheimer’s disease and lifestyle interventions to improve memory and cognition, please visit Apollo Health.