In this second article on the Gut Health series, we will look at scientific evidence of how deeply sleeps affects gut health.

Poor sleep and constipation are closely linked. Sleep habits that are not refreshing can make the transit time of food in the gut become out of sync. If we had to summarize the most important takeaways on the sleep/gut relationship it would be this:

1 - When sleep is in sufficient quality and quantity (6.5 - 8.5hrs/night) food transit in the gut provides absorption of nutrients into the cells.

2- Timing of meals is as important as light and dark cycles to strengthen our internal clock. This clock in turn will also regulate food transit and nutrient absorption.

A disruption in sleep quality, quantity or meal timing, will promptly also disrupt how food moves and is eliminated and nutrient absorption. In many cases, this disruptions can initiate an inflammatory process.

Sleep the only way for the brain to process and assimilate life experiences, being them good or bad, therefore detoxing us from stress and taking away excessive inflammation. 

In June of 2015, a study was published by the University and Hospital of Arhus, Denmark, which showed how Parkinson’s disease may begin in the gut. Dr. Elisabeth Svensson in an interview stated:

“Patients with Parkinson’s disease are often constipated many years before they receive the diagnosis, which may be an early marker of the link between neurologic and gastroenterologic pathology related to the vagus nerve” (1). 

We saw how the vagus nerve is central for understanding the gut as our second brain on the Fundamentals article of the Gut Health Series.

During sleep our food moves forward in the gut towards elimination. How in sync the transit time of food is with the light and dark cycles of a day affects all aspects of our health, like our metabolism, levels of energy and our immune system, which is about 75% located inside our gut.

In this article of the Gut Health series we will look at practical ways to improve sleep quality and quantity for better gut health. 

Before electricity our ancestors' stress levels were much lower, and they regulated their sleep in synchrony with the sunlight. When we are out of sync with nature’s light and dark cycles, we create stress in the gut. This stress, as we saw in Gut Health Fundamentals article , has a repercussion in the brain, and the response from the brain returns to the gut creating an inflammatory cycle. In this study, the microbiota becomes disorganized in mice as a result of not following nature’s light and dark cycles, along with having a poor diet. As we will explain more below, when we sleep poorly, or not enough, our tendency is to overeat and make poor diet choices, such as sugary foods.


There are three main factors that help to increase sleep quality:

- Decreasing blue light in the evenings.

- Wind down time before sleep.

- Darkness in the sleep environment.

Blue light is present in sunlight, but also in smart phones, computers, TVs and most ceiling lights. When the brain absorbs blue light at night, it breaks up our circadian rhythm, because the brain cannot differentiate between blue light coming from an electronic device and sunlight. In general terms, the pineal gland in the brain will take in the blue light from a screen as daylight. This decreases the production of melatonin, the essential hormone needed for us to fall and stay asleep. When melatonin is produced in adequate amounts, it will help us to stay asleep all night.

Note that 90% of our serotonin, the precursor for melatonin is produced in the gut. The gut and the brain respond to each other and are in constant connection via the vagus nerve, as we saw in Gut Health Fundamentals. 

Melatonin is also produced in the intestinal mucosa, and despite it not being fully understood, it plays a role in the internal biological clock as well, related to food intake, hunger and satiety, as it is suggested in this review article about the "Gut Clock" (2).

Exposure to blue light during the day is essential for the regulation of our light/dark cycles. So, having plenty of sunlight in the mornings, strengthens the internal clock. 

Decreasing Blue Light In The Evenings

- You can use orange light bulbs on table lights around the house, and turn off ceiling lights. Orange/amber color blocks blue.

- Use candles.

- Download f.lux for your computer for free. It will regulate blue light in your screen according to your sunrise and sunset times.

- Use blue light blocking sunglasses.

Optimizing Wind-Down Time

In general, 90 minutes of relaxation in the evenings, is optimal for good quality sleep. It decreases the amount of “unprocessed stress” that we take into our sleep, and it creates a better environment in the intestines for absorption, transit of food, and elimination. The following are some wind-down tips:

- Avoid looking at bright lights/screens without the blue light blockage for two to three hours before sleep.

- Plan activities that require low light.

- Take a bath with salts and candle lights.

- Listen to relaxing low volume music.

- Read something uplifting and calming.

- Connect to a partner, friends or a pet.

- Have a calming warm tea.

- Turn your communication devices off, or to airplane mode.

- Meditate. When done regularly at the end of the day, meditation will “take some load off” our minds, in turn lightening the load to be processed during sleep. I invite you to see meditation as a needed housekeeping in the mind and brain, so that we go to bed with a lighter mental baggage, thus having better chances to have refreshing sleep.

Darkness In The Sleep Environment

Even small amounts of light going through closed eyelids creates a stimulus in the brain. Complete darkness at night maximizes all metabolic processes and strengthens our internal clock. During the dark cycle of our circadian rhythm, nutrients are absorbed, toxins are separated and sent into the eliminating channels, our immune health is modulated; feelings, emotions and stress levels are processed and “cleaned out” of the brain, gut and our entire system.

These studies: (3, 4, 5, 6, 7, 8), illustrate the impact that evening blue light has on sleep duration and quality. It also shows how sleep and psychological disorders can be healed with light and darkness therapies. As we look at the whole picture, and look back at Gut Health Fundamentals, psychological disorders will have a direct inflammatory consequence in the gut lining, and they may even originate in the gut! 

Tips To Implement Darkness Inside The Bedroom

- Eliminate night-lights from the bedroom.

- Unplug any electronic device that has a stand-by light.

- Use blackout blinds combined with blackout curtains. Chris Masterjohn has a great tutorial - link below.

- Take the simple bedroom darkness test, see below!


In a nutshell:

- Eight hours is average optimal time for adults.

- More than 10 hours for children and teenagers.

- If you have sleep debt, let your body sleep for at least 2 to 5 days as much as it likes - some people will sleep 11 hours for a few nights to pay off sleep debt. After that, schedule 8 to 9 hours in bed each night and start waking up at the same time including weekends. Like this your bed time will self-regulate.

When someone has less than seven hours of sleep, it results in impaired reflex response and poor decision-making, In that state, it is difficult for the individuals themselves to discern if their reflex response is delayed, if they are acting impulsively, or if they are eating too much. These studies illustrate how shorter sleep duration decreases production of the hunger regulating hormone leptin (9), therefore increasing hunger and sugar cravings. Shorter sleep also contributes to less sensitivity to insulin (10), therefore increasing risk for metabolic disease like diabetes.

Sleeping 7.5 to 9 hours is a good tip to follow to support general health and the transit of food in the gut.

How To Have Enough Sleep:

- If you tend to wake up to go to the bathroom in the middle of the night, create a system to have most of your liquid intake in the mornings, and stop by 6 or 7 pm.

- Shut down and turn off all electronic devices inside you bedroom.

- Unplug all devices from the wall if you can, this will decrease EMF radiation, which can disturb sleep.

- Stick with the same wake up time everyday, unless you are sick. If you notice that you sleep more during the weekends, look into increasing sleep duration and quality during the week.

- Have as much sun exposure in the morning as possible. Morning exercise outdoors is a great way to improve sleep and sharpen the internal clock.

- If you need to take a nap during the day, keep it short, ensuring that it doesn’t cause you to go to bed later in the evenings.

- Avoid caffeine after lunch.

- Keep a sleep log for about two weeks to increase your awareness and to better understand how sleep affects your physical and mental state.


     1- Turn off all lights at night and wait two minutes.

     2- Put your hand in front of your face.

     3- If you can see your hand, block light sources that are coming to your room.

     4- If you cannot see your hand, you are ready. Sweet Dreams!


Last but not least: when your meal times are solid and constant, the body creates homeostasis, or balance around it and your rhythms of rest and alertness will be clearer, or, the body will receive a clear message of when to fall and stay asleep and when to be awake.

Look at a common scenario: Due to a larger workload, or other factors, you begin having lunch around 4pm. Then you are really tired and end up not being hungry for dinner or at bed time. It is not surprise that your body would become awake all fo a sudden in the middle of the night. This will have consequences in the absorption of nutrients, your hormones and yoru food elimination schedule.

At the end of the day, as the article “Gut Clock” illustrates, meal timing helps the body to have a strong circadian rhythm, therefore one is more likely to have a strong hormonal profile and detox capacity. Light, darkness and meal timing. Think about how can you manipulate them to feel your best.

Check out the Reference tools links below that we have mentioned in this article.

Did this reading pointed out anything new to you? How have you noticed that sleep affects your gut health? We would love to hear from you!


Laura Leite is a Certified Functional Diagnostic Nutrition Practitioner and a KRESSER INSTITUTE Provider, Personal Trainer and Pilates instructor. She and her partner live in Berkeley, California. Instagram

~ This article contains general information regarding nutrition and stress management only. It is not to be used as a prescription, or to replace medical advice or recommendations, in the prevention or treatment of any diagnosed condition, or any health issue.~


Links and References:

Lights Out: Sleep, Sugar and Survival

Parkinson's May Begin in The Gut


Blue Light Blocking Glasses

How To Make Your Room Pitch Black by Chris Masterjohn

Gut Clock: Implication of Circadian Rhythms in The Gastrointestinal Tract 

Circadian Disorganization Alters Intestinal Microbiota

Amber lenses to block blue light and improve sleep: a randomized trial.

Dark Therapy for Bipolar Disorder with Amber Lenses 

Light Through Eyelids Suppresses Melatonin

Dark Therapy for Mania

Increased Sleep Darkness Therapy for Bipolar Disorder

Blue Blocker Glasses Case Report Therapy for Mania

Decreased Production of the Hunger Regulating Hormone Leptin

Sleep and Insulin Sensitivity