Long-time readers will know that I’m all about brain health. Improving the strength, function, and longevity of my brain is the reason why I exercise nearly every day, the reason I avoid sugar, the reason why I meditate, and the reason why I make sleep a priority. But I don’t know everything there is to know about brain health, so when I learn something new that seems important, I adjust my routines accordingly. Today, I want to tell you about an important new idea I learned recently and what I’m doing to implement it.
Several years ago, I read A Mind For Numbers by Dr. Barbara Oakley, which revealed an important function of sleep I’d never heard of: While you’re asleep, your brain quite literally cleans house – flushing out the metabolic byproducts that build up during the day.1 So if you don’t get enough sleep, you won’t be as sharp the next day, and you won’t feel as good.1 I chalked that up to just one more reason to get a good night’s sleep. This summer, however, I finally learned more about how this process works, and what I learned led me to change my routine in a pretty big way.
In The Longevity Paradox, Dr. Steven Gundry, MD, describes how the “glymphatic system” works: Cerebrospinal fluid flows “through the brain, cleaning out the spaces in between cells. … To make room for the fluid to wash out your brain, your cells actually shrink in size when you are in deep sleep. … This allows the full ‘brain wash’ process to go twenty times as fast when you are in deep sleep as when you are awake and helps explain why a good night’s sleep is so restorative.”2 Oh, and he also says that this is very important for preventing Alzheimer’s and other forms of age-related brain decline.2
Furthermore, Gundry explains how to optimize this process: “The glymphatic system is most active during the specific stage of deep sleep that happens very early in the sleep cycle. And the glymphatic system, just like your digestive system, requires a great deal of blood flow. This means that if you eat too soon before going to bed, your blood will all flow to your gut to aid in digestion and will not be able to reach your brain to complete the all-important brain wash.”2 Specifically, he advises that we try to leave at least four hours between our last meal and bedtime.2
Four hours! I thought. Impossible! You see, because of my work schedule, I’ve been eating dinner late at night for the past five years. (I’m a tutor.) I usually get home from work after 9pm, and my routine has been to eat a large meal, go for a walk, do my stretches, and go to bed. I can eat at work, but my typical dinner is a huge salad, with a bowl of tempeh, and a plate of carrots with a jar of peanut butter for dipping. This feast does not easily lend itself to being stored in the employee fridge or eaten while working with students.
Despite this, I’m happy to report that over the last month, I have succeeded in changing my routine in order to eat my last meal several hours before bedtime. And it works! I’m sleeping better and feeling more well-rested during the day; my mind seems both sharper and happier all day long. There’s no way to be sure that optimizing my glymphatic system is the reason, and I’m just a case study of one, but I’m very pleased with the results of this change.
Changing my eating routine took some mental flexibility. I’ve switched my salad to lunchtime because it’s easier to eat before working with students, and I’ve shifted my dinner to a smaller meal that’s easier to eat on the fly (usually a bowl of homemade curry). To have enough time between meals, I’ve had to start eating breakfast earlier, which often means eating before exercise, daily wisdom, meditation, and writing. I’ve had my morning routine for so long that making this change felt pretty unnatural, but it’s proving to be for the best.
Also, my effort to make this change didn’t go very well at first. It took some trial and error, and there were a few false starts that resulted from poor planning. And I have no intention of being overly rigid about this. If I’m out late with friends and there’s delicious food to be had, I’ll probably indulge. I’m going to strive to not eat before bed most of the time, but I’m also going to give myself permission to be human. The most important thing for me is that I now know that this practice is one of the many little choices I can make that will add up to a big difference in the long run.
And for you, dear reader, the important thing to take away from this article probably isn’t the particulars of the glymphatic system but the notion that you should be open to changing your ways in light of new information.
1 Oakley, Barbara. A Mind for Numbers: How to Excel at Math and Science (Even If You Flunked Algebra). Penguin, 2014.
2 Gundry, Steven R., MD. The Longevity Paradox: How to Die Young at a Ripe Old Age. Harper Wave 2019.