How Your Gut and Circadian Rhythm Affect Your Brain

Bacteria in your gut may affect cognitive development early in life


People have over 1,000 different species of bacteria in the gut, and everybody has a unique combination of between 250 and 500. How exactly they interact with the brain is still a mystery, although there is a growing number of studies that show a correlation, not causation.

The first human gut microbiome study found that 1-year-old infants with higher levels of specific gut bacterial colonies had better cognitive scores compared to infants with other gut microbiome colonies. The infants had better gross motor skills, perceptual abilities, and language development by age 2.

There is a bidirectional signaling between the brain and the gut microbiome, involving multiple mechanisms. While psychological and physical stressors can affect the composition and metabolic activity of the gut microbiota, experimental changes to the gut microbiome can affect emotional behavior and related brain systems, according to research. Interactions among the microbiota composition, brain biochemistry, and behavior may be particularly important at critical neurodevelopmental stages.

The connection between the gut and brain is a complex one and it involves melatonin, also known as the “sleep hormone.”

 “When considering the mood and cognitive changing impact of the microbiome, before we run off buying even more probiotics, emerging science is suggesting that our connection to the circadian, light dark cycles play an important role of who governs the microbiome,” Dr. John Douillard, author of Eat Wheat says.

Gut bacteria are sensitive to melatonin and express endogenous circadian rhythmicity, according to a study. Melatonin is the oldest hormone on the planet, over 3 billion years old, he adds. It is produced by the pineal gland and regulates sleep and wakefulness. “We evolved around melatonin to keep us in sync with the circadian cycle,” Dr. Douillard says. “Many hormones act in rhythm with melatonin, and when the circadian rhythm is disturbed, it affects everything.”

Melatonin levels flow throughout the day to keep people in check, according to Dr. Douillard. The hormone is the “most powerful antioxidant in the body as it triggers the release of other antioxidants, or cleaning agents” to rid the body of bad things such as microbes, which are more active at night, he adds. “Think of it as the genitor who cleans the body while you sleep.”

Every hour you’re not sleeping, when you should be, is an hour if melatonin production you didn’t get. “When the sun sets at 6 p.m. and we regularly turn the lights off at 11 p.m., there is 5-hour delay in melatonin production,” Dr. Douillard says. This has a negative effect in the long-term. “The result is an alteration of the melatonin and cortisol rhythm, both of which impact the microbiome.”

To avoid problems, you want to fix the host of the problem, not treat the symptoms, according to Dr. Douillard. Get off processed foods and start eating organic foods that are in season, Dr. Douillard says. “These are the real probiotics.” Microbes in the soil change from season to season; there is more diversity of “bugs” in your food and, consequently, better immunity. 

Also, you should do yourself a favor and fall asleep two hours after the sundown, eat healthy foods that contain melatonin, and get enough sunlight during the day because this will help produce more melatonin at night.

Related stories:

What Do Probiotics Really Do and Do You Need Them?

Are Vitamins and Supplements Worth Taking?

The Most Dangerous Legal Drugs