Your lifestyle is key when trying to restore gut health. Factors such as nutrition, physical activity, sleep, and stress all play big roles in building a strong, healthy gut.
Looking strictly at diet, there are a few things we can tweak to improve gut health. For the most part, many people focus on the content of their diet; things like fiber content, macronutrient ratios, calorie intake, and supplemental nutrients.
But other aspects of diet are equally important. Time-restricted eating is a practice where people only consume food during a certain period of the day and fast for the rest. For example, some people restrict their eating to between 12pm and 8pm while fasting the rest of the day.
There are many reasons to do this, but one in particular is to restore gut health. Nutrient sensing pathways in our cells such as mTOR and AMPK play a pivotal role in the gut by regulating circadian rhythms.
These pathways govern the ability of the gut to regenerate by regulating inflammation, maintaining a healthy number of stem cells, and controlling when cells in the gut are replaced.
A recent paper summarized how mTOR regulates gut health. Here we’ll break this paper down and discuss how time-restricted eating may optimize gut health by turning mTOR on and off.
What is mTOR and how does TRE affect it?
The mammalian target of rapamycin, or mTOR, is a nutrient sensing pathway in our cells. It functions as a switch between growth and breakdown; ultimately determining whether anabolic or catabolic processes predominate. Activation of mTOR stimulates anabolic processes while inhibition of mTOR stimulates catabolic processes.
Throughout the body, mTOR acts as a nutrient sensor, and is regulated by other nutrient sensing pathways such as AMPK. The presence of nutrients activates mTOR, while the absence of nutrients inhibits mTOR. Specifically, mTOR is primarily activated by amino acids and insulin(And vice versa).
It would be tempting to believe that we want greater activation of mTOR rather than less. This couldn’t be further from the truth: Unlimited growth leads to Cancer. But low mTOR activation can prevent healing in the gut.
We want an appropriate balance of mTOR activation, which optimizes regeneration in the gut. As you’ll see, proper timing is also essential. In fact, mTOR plays an integral role in regulating our circadian rhythms.
Unfortunately, as we grow older, mTOR signaling becomes dysregulated. Overall, there is an increase in mTOR activation with aging that may explain the increased risk of Cancer. Rapamycin, an inhibitor of mTOR, has been show to delay aging and prevent Cancer.
How does mTOR restore gut health?
Much like it does in other cells, mTOR regulates growth and breakdown in the gut. The effect of mTOR depends on the cell type, but there is a general consensus of how mTOR regulates gut health. Below is a depiction of the different cell types in the gut:
The cells in our gut start life as intestinal stem cells in areas known as crypts. These stem cells are interspersed between paneth cells that secrete antimicrobial peptides and function as nutrient sensors for the intestinal stem cells.
Fasting inhibits mTOR in paneth cells, but activates mTOR in intestinal stem cells. This causes stem cells to increase in number to enhance our regenerative ability, a process called proliferation. Eating activates mTOR in paneth cells, causing intestinal stem cells to move up the crypt in to the transit amplifying zone.
Eventually, stem cells become enterocytes through a process called differentiation. Enterocytes are the cells that make up the intestinal wall and pass nutrients from the gut into the blood and lymph. As they age, enterocytes travel up the villi towards the tips as they are replaced with new enterocytes. They are eventually sloughed off as they reach the tips of the villi, and passed in the stool.
Here we begin to see where the proper balance of mTOR takes shape. If we chronically activate mTOR, this leads to constant growth in the gut and depletion of stem cells. If we chronically inhibit mTOR, we can’t build the proper structure in the gut.
Furthermore, immune cells in the gut also affect, and are affected by, mTOR. This ebb and flow of mTOR activation in the gut helps promote a healthy gut.
Time-restricted eating to restore gut health
As you can probably tell, the regulation of gut health by feeding and fasting periods revolve around mTOR. We humans generally eat during the day and fast overnight.
Unfortunately, many people really don’t follow this pattern. Many eat breakfast between 7-8am, and still eat as they get close to bedtime around 10pm. That equates to an eating window of 14 hours and a fasting window of 10.
Additionally, it’s not simply about how long we consume food; how much we eat matters too. The more food you eat, the longer it’s going to take to digest as it sits in the gut.
Overall, it’s easy to think of your feeding window as when you cause damage in your gut and your fasting period as when you repair it. It’s a little more complicated than that, but it illustrates the same basic concept: Balancing use and repair is critical to gut health.
Time-restricted eating is a great way of scheduling your fasting period to give your gut a break. It balances use and repair through activation, and inhibition, of mTOR, respectively.
The health of our gut depends quite a bit on our behavior. The modern lifestyle, which essentially constitutes a 24/7 non-stop food orgy, is no good for gut health. It’s no surprise that functional gut problems are becoming more and more common.
Nutrient sensing pathways such as mTOR play a major role in regulating the state of the gut. In the gut, mTOR plays a role in regulating the amount of stem cells we have, the inflammatory state, and the regenerative capacity.
Through time-restricted eating, we can help improve the state of our gut by improving its regenerative capacity. Furthermore, the inflammatory state of the gut also has an effect on mTOR, and mTOR regulates immune function in the gut.
We’ve actually covered quite a bit of the legwork for taking advantage of mTOR in some of the emails we’ve sent out. This paper adds to that discussion, and we’ll be sending out a new email next week to compile that information in a single document. We’ll talk about other nutritional factors that regulate mTOR and why circadian rhythms are a critical piece of this puzzle.
If you haven’t yet, sign up for the email list in the right-hand margin to get access to that compilation email. We’ll cover what this means for gut inflammation, when to limit fiber intake, and the whole nine yards.