How sunshine influences gut health
The latest research shows that Circadian Rhythm is so much more than the sleep and wake cycle, or even when to eat. It governs every cell in the body to optimise tasks at different times of the day. The microbiome, too, works differently depending on the time of day, and a number of aspects of digestion are timed. So, how does the body tell the time? How does circadian signalling impact digestion and the microbiome? And, how can you improve your gut health with getting your light exposure right? This post explains why circadian signalling is important for the whole body, in particular the gastrointestinal tract and all of the organs of digestion, and how to optimise your digestive health by improving your circadian rhythm. This is a new area that not many people are talking about, and it’s every bit as important as the microbiome discoveries of the past 20 years!
Come and join me down the Quantum Biology rabbit-hole, again - it’s fun!
Dromana beach at sunrise - photo by Julie Forrester 2024
Circadian rhythm, sunshine and gut health
This article covers -
What is circadian rhythm?
How does the body tell the time?
How can circadian rhythm affect digestion?
Why is sunshine important to gut microbes?
What is the impact of ‘dirty light’ sources?
Improving digestion with circadian signalling techniques
What is circadian rhythm?
We all know that circadian rhythm governs our sleep-wake cycle, but it’s also responsible for digestion and different organ functions at different times in a 24 hour cycle.
For thousands of years we’ve lived with a consistent light-dark cycle of the sun, with the length of daylight changing between seasons. It’s one of three things we can guarantee (the others being death and taxes!). Because of this, all organisms including humans, have evolved to be as efficient as possible, by conserving energy and resources . Meaning every cell has different functions at different times of the day.
You wouldn’t want to be digesting food, pooping, or producing hormones that keep you awake - in the middle of the night - would you?
We have processes for cleaning and maintaining cells like the glymphatic system in the brain which removes debris via the lymphatic system during specific times of the sleep cycle.
The entire lining of the gastrointestinal system can be repaired at night, while there’s no digestion occurring.
There are functions that restore and repair damage such as muscles after exercise, or consolidate memories.
Bowel movements are urine secretion are reduced during sleep,
Testosterone and cortisol are suppressed until waking in the morning.
Specific times of the day when we have more, or less energy
Specific times of the day/night when body temperature is highest or lowest
Specific times when blood pressure and heart rate are at their highest and lowest
These are only a few examples of the myriad of processes that are time-dependent.
In fact, every organ of the body is regulated by circadian rhythm.
Just the tip of the iceberg - in fact, every process in every cell is impacted in some way by circadian signalling.
How does the body tell the time?
Have you ever wondered what sets circadian rhythm? How does it know when to secrete melatonin for example, for sleep?
Light receptors in the back of the eye (melanopsin receptors)receive the frequency range 430-500 nm from the sun, which makes up the blue light spectrum. The retinohypothalamic tract (RHT) communicates this frequency to the suprachiasmatic nucleus (SCN) in the hypothalamus of the brain. The SCN translates this frequency to time by oscillating (vibrating at a particular speed). The proportion of blue light in sunlight changes throughout the day and so the frequency changes. The greatest proportion of blue light is when the sun is around 30 degrees above the horizon, peaking when the sun is at the highest point. In the afternoon the amount of blue light diminishes until there is almost none, leaving the red spectrum as the dominant signalling colour. Therefore, the ratio of blue light frequencies to red light frequencies is what tells our cells what time of day it is. We also receive these time signals via our skin, also communicating with the SCN via blue light.
Incidentally, almost 50% of sunlight in the red spectrum is received via skin chromophores (melanin and oxyhaemoglobin). These frequencies help maintain healthy mitochondria by producing natural antioxidants, regulating inflammation, producing master steroid hormones and structured water, crucial for the function of every cell.
Of course, too much sunlight can cause burning which is dangerous to the skin and health, so always take caution not to get burned!
Your mitochondria are important for every aspect of health, and the number and health of them can determine how well you are, not just how much energy you have.
The little bean-shaped ‘organelles’ (parts of cells) called the mitochondria are filled with a special form of water called structured, or exclusion zone (EZ) water. They have two layers of cell walls, with the internal layer containing a series of proteins that form the Electron Transport Chain, crucial for making ATP (the energy currency of our bodies) and a variety of other really important functions (this is the part everyone knows as ‘the body’s powerhouse’).
Mitochondria receive and transmit information from cell to cell, it is thought, via vibration of the EZ water inside the mitochondria itself and in other locations of the body. .
Stay tuned for a post all about the water in our body - it’s amazing, ground-breaking stuff!
How can circadian rhythm affect digestion?
When there is strong circadian signalling, all functions of digestion are optimised and timed appropriately.
Salivary glands secrete appropriate amounts of saliva, to lubricate the food, start breaking down carbohydrates with ⍺-amylase enzyme.
Optimal oesophageal function, mucosal lining, muscular contraction
Appropriate gastric acid secretion for breakdown of proteins, killing of pathogens ingested, and pH balance of the upper digestive tract
Appropriate motility (muscle contraction) in the stomach, small and large intestines
Regular stimulation of the MMC (migrating motor complex) - a stronger and coordinated contraction of the digestive tract, considered a cleaning function.
Appropriate release of ghrelin, signalling hunger
Optimal glucose, lipid and bile metabolism in the liver and gallbladder
Appropriate release of insulin, glucagon and other digestive enzyme secretion from the pancreas
Optimal barrier function (protective of intestinal hyperpermeability), release of GIP (enzyme for fat metabolism),digestion and absorption of nutrients in small intestines
Appropriate release of GLP1, PYY enzymes, optimal barrier function, and diversity and function of gut microbiota
Meaning that conditions such as IBS, visceral hypersensitivity, intestinal hyperpermeability (leaky gut), and problems of motility such as constipation and diarrhoea, can be improved by improving circadian signalling. As can symptoms of organic digestive conditions such as crohn's disease or ulcerative colitis can be improved.
Why is sunshine important to gut microbes?
It has been demonstrated in studies (2) that in addition to full-spectrum sunlight on the abdomen (or, near infrared, or infrared light therapy) can rapidly and positively increase the diversity and abundance of gut microbe species, and that seasonal variation of microbiome composition may be influenced by sun exposure.
Some of this benefit is thought to be via the increase of the body's natural production of Vitamin D. However, it is thought that the combination of benefits derived from appropriate timing and amount of enzyme secretion including (and importantly) stomach acid, appropriate strength and timing of peristalsis and the function of the MMC (migrating motor complex). It’s worth noting that poor/lack of function of the MMC has been associated with the development of SIBO (small intestinal bacterial overgrowth), SIFO (small intestinal fungal overgrowth), and SIMO (small intestinal methanogen overgrowth).
What is the impact of ‘dirty light’ sources?
Dirty light sources are considered to be any artificial light source that contains unnatural ratios of colour spectrums of light. Predominantly, (depending on the individual light) they have significantly unnatural amounts of blue light with abnormally low red light frequencies. Given the ratio of blue:red varies from hour to hour, season to season in natural sunlight, it would be near impossible to replicate this in artificial lighting. In addition, this ratio is static unlike natural sunlight that is changing constantly which communicates to the brain that it is mid-morning-midday all day and functions such as melatonin production are inhibited.
This includes most current lights - LEDs, compact fluorescent, fluorescent, halogen (usually found in older-style downlights). The old style incandescent lights of a ‘warm’ colour are a better choice, however, have been phased-out in most countries as energy inefficient. The newer lights have been designed with lighting and function in mind, without understanding the disruption to our circadian signalling.
For those people who work indoors all day, circadian signalling can be significantly impacted unless strategies such as regular ‘sunlight breaks’ and blue blocking glasses are used.
At home in the evenings, reducing the amount of bright light or swapping light bulbs or lamps for those with increased red light frequencies and wearing (quality) blue blocker glasses and long clothes to reduce skin exposure can help improve melatonin production and sleep.
Improving digestion with healthy circadian signalling
There are a number of really simple hacks to improve digestion, before you start spending money on supplements, testing or appointments. Firstly, check out my free guide 6 Healthy Habits to Reduce Digestive Discomfort.
To improve digestion (as well as sleep, mood, energy, hormone balance and more) try following circadian signalling strategies
Practice eating in an ‘early fueling window by having breakfast within an hour of waking or sunrise, and consuming your last food ideally before sunset (or 6-10 hours).
Wear orange/red blocking glasses, on waking before sunrise and after sunset to prevent blue light from artificial lighting sending the wrong time signals to your body.
Spend time outdoors, getting as much morning light as possible in the eyes and on the skin. Ideally, 20 mins - no sunglasses, no sunscreen, creams or moisturisers. Don’t get burned!
Try to see the sunrise and sunset every day, at least 5 mins of each.
Try to get 20 mins of full spectrum sunshine (ie. when the sun is between 30-45 degrees above the horizon on bare skin, 2 days per week (depending on your solar tolerance - i.e. don’t get burned).
If you can’t get sunshine, then 20 mins of full spectrum sunlight, use an infrared or near infrared lighting panel on the abdomen, 2 days per week is a good substitute.
If you are still having digestive issues, or you’d like help getting to the root cause of your digestive symptoms you can book a free 15-minute discovery call with me to chat about how I might be able to help. Absolutely obligation free.
Frequently asked questions -
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Yes and no! Sadly, there are a lot of blue blocking glasses available that claim to block blue light, but don’t do this effectively (or, in some cases at all!). This happens in so many areas of health, where a ground-breaking piece of information leads to a quick-money scheme to take advantage.
High quality blue blocking glasses are available from reputable suppliers and in Australia I highly recommend www.blockbluelight.com.au - use the code BLUEBLOCKJULIE for 10% off your purchases. They also carry a range of lamps, and red light panels. -
Just by improving your circadian rhythm, which is SO much more than just regulating sleep, you can improve your digestive function. At night many repair functions are signalled, including the repair and replacement of the cells that line the digestive tract, so a good 8 hours per night ensures this process gets all the time it needs. Especially important in intestinal hyperpermeability (leaky gut). Getting 20 mins of sunshine, or infrared or red light therapy directly on the abdomen, twice per week helps the diversity and abundance of microbial species in the gut. Diversity and abundance is the only thing that science is 100% sure of as beneficial to digestive health.
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Light is now known as a time signal for every cell in the body, including those cells that aren’t exactly ours (yes, all of our little microbe friends, in and on our bodies). The proportion of blue to red light tells the cells what time of the day it is and therefore what jobs it should be performing.
In the gut, this means the difference between optimal digestion and cleaning and repair functions. Think about the last time you drove on the freeway, and imagine if the road crew were trying to clean and repair during peak hour - it’s not going to be successful for their work, or for travel.
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Regulating sleep is really just the start. Circadian rhythm regulates every single cell in the body to optimise its resources by having different functions at different times of the day, for example:
We have processes for cleaning and maintaining cells like the glymphatic system in the brain which removes debris via the lymphatic system during specific times of the sleep cycle.
The entire lining of the gastrointestinal system can be repaired at night, while there’s no digestion occurring.
There are functions that restore and repair damage such as muscles after exercise, or consolidate memories.
Bowel movements are urine secretion are reduced during sleep,
Testosterone and cortisol are suppressed until waking in the morning.
Specific times of the day when we have more, or less energy
Specific times of the day/night when body temperature is highest or lowest
Specific times when blood pressure and heart rate are at their highest and lowest
And, this is just the tip of the iceberg!
