New research continues to emerge daily demonstrating the important effects that gut bacteria have on the health of the human body. In addition to promoting a healthy digestive tract and a strong immune system, research indicates that gut flora also help regulate our circadian rhythms. Read on to learn about how gut bacteria affect circadian rhythms, and how taking care of your microbiome and circadian rhythms simultaneously can benefit your overall health!
What are circadian rhythms?
Circadian rhythms are the physiological changes that take place in your body over the course of a 24-hour cycle; they are regulated by collections of genes and proteins referred to as “body clocks.” The “master” body clock resides in a portion of the brain called the suprachiasmatic nucleus (SCN). The clock in the SCN is perhaps the most well-understood body clock; it is affected primarily by light/dark cues, and it plays a starring role in regulating your sleep/wake cycles. The SCN is the first body clock to get thrown off by things such as jet lag and shift work.
In addition to the master clock in the SCN, "peripheral clocks" exist in other body organs and tissues. The other body clocks are not as well-understood as the SCN, but a growing body of research indicates that they are no less important. The body clock in the liver governs detoxification, and the clock in the pancreas regulates insulin production. All of the body clocks work in synchrony to create circadian rhythms that regulate hormone release, metabolism, digestion, and immunity.
It has recently been discovered that the body also possesses an intestinal body clock. The rhythms of the intestinal body clock affect metabolism, absorption of nutrients, and immunity. The intestinal body clock also communicates with the SCN in the brain, the pancreas, and the liver. Microbes living in the gut have a profound influence on the intestinal body clock, which then affects all of the other clocks. Maintaining a healthy microbiome is therefore crucial for regulating circadian rhythms. In addition, external cues that affect the other body clocks, such as light exposure and sleep habits, provide feedback to the microbiome in a complex feedback loop. These systems therefore must be considered from a holistic perspective, rather than in isolation.
Gut microbes demonstrate circadian rhythms
In a study published in the scientific journal Cell, researchers analyzed fluctuations in the adherence, quantity, and metabolic activity of gut microbes in the intestines of mice every six hours for a total of forty-eight hours. They found that gut microbes have daily “routines” in which they travel to different locations throughout the intestine. (1) These circadian oscillations in gut microbe activity cause the tissues of the intestine to be exposed to different microbes and their metabolites over the course of a day. The metabolites produced as a result of gut microbe circadian rhythms influence genes associated with the intestinal, pancreatic, and liver body clocks. A healthy microbiome is therefore essential for regulating the circadian activities of all three of these organs.
The circadian rhythms of gut microbes affect insulin homeostasis, body weight, and detoxification
Circadian rhythms in the intestine, pancreas, and liver are crucial for regulating metabolism, insulin release, body weight, and detoxification. Gut microbes play an important role in controlling these circadian rhythms, as I described above. A disrupted microbiome may therefore throw off metabolism, cause insulin resistance, weight loss resistance, and impaired detoxification. In addition, disrupted gut circadian rhythms may contribute to gastrointestinal disorders (see “Disrupted circadian rhythms may cause GI disorders” below).
Erratic eating habits disrupt gut microbe circadian rhythms
It has been found that erratic eating patterns, such as eating non-stop all day or eating late at night, disrupts the circadian rhythms of gut microbes. Their travels throughout the gut become disorganized, leading to disruption of the intestinal body clock and an overall uncoupling of circadian rhythms of the host in which they live (i.e. you!). (2) Disrupted gut circadian rhythms have been associated with insulin resistance, high cholesterol, and obesity. (3) Fortunately, a practice called time-restricted feeding can normalize gut circadian rhythms, and may prevent these complications. Time-restricted feeding is a dietary practice in which eating is only allowed during a certain window of time each day, such as an eight-hour period from 8 am to 3 pm. Research has found that this eating practice optimizes metabolism, and can correct problems associated with gut circadian disruption, such as insulin resistance. (4)
The Standard American Diet (SAD) disrupts gut circadian rhythms
Interestingly, a diet high in processed carbohydrates and polyunsaturated fats (which are staples of the SAD diet) disrupts gut microbe routines and intestinal circadian rhythms. However, a diet that is low in processed sugars and polyunsaturated fats, and rich in EPA, DHA, and antioxidants, has been shown to normalize intestinal circadian rhythms. Eating a whole-foods, nutrient-dense, unprocessed diet is therefore key for keeping your gut microbes happy, and your intestinal body clocks “ticking” on schedule! (5)(6)(7)
Antibiotic use disrupts circadian rhythms
Antibiotic use disrupts intestinal circadian rhythms by wiping out populations of beneficial gut microbes, which are needed to regulate the intestinal body clock. (8) This means that antibiotic use could play a role in the development of disorders associated with circadian disruption, such as insulin resistance, sleep disruption, and obesity. Fortunately, restoration of beneficial gut microbes with prebiotics and probiotics may help rehabilitate normal circadian rhythms.
Sleep disruption and blue light impair gut microbe rhythms
Poor sleep habits, including chronic sleep disruption and shift work, detrimentally alter the activities of gut microbes. This ultimately affects the intestinal body clock and the pancreatic body clock, which governs insulin production. Not surprisingly, chronic sleep disruption has therefore been linked to insulin resistance (due to impaired activity of the pancreas) and obesity. (9) Blue light and artificial light exposure at night also disrupts circadian rhythms by sending signals to the master body clock in the brain that it is daytime (blue light promotes wakefulness, and is part of the spectrum of daylight). This prevents melatonin release, which is required for regulating the activities of gut bacteria. (10) Avoiding these types of light exposure several hours before bed will allow normal melatonin production to take place, thus keeping gut microbe and intestinal circadian rhythms functioning optimally.
Disrupted circadian rhythms may cause GI disorders
Disrupted circadian rhythms may predispose people to gastrointestinal disorders. Circadian rhythm disruption caused by abnormal sleep habits and a SAD diet has been linked to the development of Inflammatory Bowel Disease (IBD); it alters microbial production of metabolites that normally keep the gut healthy, such as short-chain fatty acids. (11) Circadian rhythm disruption also increases intestinal permeability, commonly referred to as leaky gut. (12) Leaky gut allows inflammatory toxins produced by bacteria to leak into the systemic circulation; this phenomenon has been linked to chronic diseases such as cardiovascular and neurodegenerative disease. Finally, disrupted circadian rhythms may increase the risk of gastrointestinal infections by decreasing immune function, which normally defends the gut against pathogens. (13)
If you want to heal your gut, you must fix your circadian rhythms
Gut health is an extremely popular topic in the natural health world, yet it is rarely brought up in the context of circadian rhythms. However, in light of the research I have presented here, it appears that circadian rhythm optimization is crucial for promoting gut health. All the gut-healing supplements in the world won’t matter if you are disrupting your circadian rhythms by eating late at night, exposing yourself to blue light in the evening, and not getting optimal sleep. To really help your gut heal, try the following tips:
- Get plenty of sunlight exposure during the day
- Wear blue light-blocking glasses at night
- Practice time-restricted feeding
- Don't eat late at night (this goes along with time-restricted feeding)
- Aim for eight hours of sleep a night
I recommend these blue light-blocking glasses for use at night. I start wearing mine about two hours before I go to bed.
If you combine these tips with prebiotic and probiotic supplementation and a whole foods-based, nutrient-dense diet, you will have a strong foundation for healing your gut, whether you struggle with IBD, leaky gut, or chronic infections.
For more information about ways to optimize your circadian rhythms, check out my free ebook "Feed your Body Clocks: Nutrition tips to Optimize your Circadian Rhythms." You can get the ebook by signing up to be on my email list!