Gut health: Circadian Biology and Light Cycles
This information might surprise you as it’s the opposite of what most gut health experts say or do NOT say.
Everyone’s microbiome is influenced and adaptive to our environments, such as light exposure and the absence and circadian rhythm in which you entrain your biology to the environment. Your microbiome is adaptive to these signals, and it shows that:
Think about how intermittent fasting and the timing of your meals relate with your microbiome and circadian biology. These have key roles in our metabolism and genes working like clockwork. PER2 and NAD activity.
Why is the microbiota essential?
The microbiome is a defense element that helps protect our outside environment by guarding our barrier to potential threats of other potentially pathogenic organisms that can disrupt the harmony of our biology; the microbiome has a pivotal role in the way we detoxify both metabolic and environmental toxins, they help us with our metabolism by providing vitamins, supporting electrolyte absorption, produce energy substrate used for colonocytes, influence cell signaling and cell cycles with histone deacetylation effects influencing Sirtuns and NAD activity. It can also be a sink for producing molecular hydrogen for our metabolism, which is essential for optimal health.
The standard theory is that what we eat is the most critical factor shaping our microbiome. This may be true, but only partially.
The food we consume can be a significant factor but is less relevant than one may think.
Our internal biology and relationship with our environment is what controls our physiology and allows our gut to function with oxygen delivery, nitric oxide production, the enteric nervous system, hormonal influence such as ghrelin, leptin, estrogen/progesterone, and, as mentioned above, our circadian biology.
Our microbiome is developed in the womb but kicks into action in the post-natal period relating to the mother’s breast milk, a.k.a. liquid gold. Research proves that this critical period plays a role in our social interaction later in life by developing oxytocin neurons.
The gut microbiome, comprising many organisms from bacteria, viruses, yeasts, and parasites (all commensal), has a metabolism similar to ours and a circadian rhythm, affecting their abundance.
Studies show that chronic jetlag, constant darkness, and reversal of the light‐dark cycle could disrupt the daily oscillation of gut microbe (Thaiss et al., 2014; Voigt et al., 2014). At the same time, mice with their clock gene knockout (absent) have arrhythmic gut microbiota.
Take home: it is not just about the composition of what you eat, whether you are a vegan, omnivore, or carnivore, nor the quality of the items - organic, grass-fed, or wild, but also the timing of food intake (eating windows) and on top your circadian rhymes. This is entrained in our skin and eyes, which also play a crucial role in this process.
Why eating a circadian rhythm diet is important
Think of resetting a stopwatch every 24 hours or winding up an old-fashioned antique clock. Our biology requires the exact mechanism but does it by light and darkness. In the morning, we have a unique spectrum of light uniquely encoded in sunrise, which contains unique information and photons with specific wavelengths and temperatures (intensity) to turn on our system. It is like a car using a manual with first, second, and third gear. Each wavelength has a unique biological effect on exciting electrons in our biology. Einstein describes this as the photoelectric effect.
It so happens that our eyes are an extension of our brain - they act as a wire, like your electrical system at home. However, this time, they are excited by the kinetic effect of sunlight. We have photoreceptors that are sensitive to this light signal and link to our nervous system - the sympathetic part that is wired to our brain and gathers this information to make sense of what time it is and where we are in space and time domains.
Is your circadian biology affecting your microbiome and gut health?
Without the signal of going outside (downloading) or without the nutritional needs, essential fatty acids, dopamine, oxygen, hydrogen, EZ water, vitamin A, riboflavin, vitamin B2, cholesterol, hemoglobin, tryptophan, and melanin are not gained. Therefore, we lack the full effect. The partial effects can also be problematic if we cover our eyes with contacts, glasses, or sunglasses or receive light via a window.
Melanopsin in Health and Disease
The receptor that picks up this blue light is melanopsin.
“Melanopsin, a light receptor that measures the intensity of incoming light, is found in rare, specialized cells embedded in the retina.”
“It sends its signals directly to the human circadian clock, which sits just above the point where the optic nerves cross. Although only half the size of a pencil eraser, it synchronizes the body’s daily rhythms with the sun’s rising and setting, telling the body when it is time to go to sleep, when to be hungry, and when to wake up. But it does more than that. Just like a meter in a camera that allows the aperture to be adjusted, mRGCs also control pupil size.” (Salk Institute, 2010)
Blue light “turns on” your body
It is a blue light-sensing photoreceptor found in our eyes, brain (18 different sites), gut, subcutaneous adipose tissue, and blood vessels. Its gene is OPN4. Nine known opsins are in the human body. (Ondrusova et al., 2017)
The melanopsin found in blood vessels throughout our body can directly influence nitric oxide, blood pressure, and the flow of oxygen and nutrients loaded in cholesterol and hemoglobulin - the unique ferryboats of our biology.
“We report the presence and acute regulation of GPCR Opn4 receptors in blood vessels. We also provide a previously unidentified mechanistic insight into the signal mechanisms by which their stimulation produces photo relaxation, a phenomenon vascular biologists have described for over five decades.”
Blue light detection is found in the eyes, brain, gut, subcutaneous adipose tissue, and blood vessels.
“For example, humans possess nine different opsins. Three opsins are expressed in cone photoreceptor cells, which determine the three colors in our vision: red, green, and blue. A rhodopsin, which functions under dim light conditions, is expressed in rod photoreceptor cells. Melanopsin is the opsin that functions in the circadian regulatory system and pupil constriction of the eyes. In addition to these, we have encephalopsin, neuropsin, RGR opsin, and peropsin.” (Sikka et al., 2014)
Melanopsin has been found in humans and detected in the retinas of many non-mammalian vertebrates, including chicken, frog, turtle, and various fishes such as zebrafish, goldfish, and cod.
The whole point of sensing the light environment is to favor the probability of adaptation with survival and reproduction. When we feel the environment, it alters our physiology to adapt to the stimulus. It, therefore, influences processes such as leptin, insulin, the amount of serotonin or dopamine, and thyroid activity. The light spectrum and temperature through the eyes essentially control our metabolism and, therefore, can open the gateways for health or this ease. It is that simple.
The peripheral systems and organs such as the gut are responsive to what happens with the brain and eyes - in terms of evolutionary biology on all animals - light and dark cycles were the first and most predominant signal that dictates the actual end product of our food cycle, seasonal, and diurnal eating patterns. Nevertheless, there is scope for the microbiome also to have a bidirectional role in supporting our circadian biology from their metabolic by-products, such as serotonin and dopamine production in the small intestine.
“The gut microbiome itself synchronizes the host's circadian biological clock by releasing different natural signals.” (Lotti et al., 2023)
Not only are you running the risk of having a distorted microbiome population by lacking these things, but you are opening the doors to hormonal disruptions such as estrogen and testosterone activity, cardiovascular risk, cancer, and mental health with neurodegenerative diseases such as Parkinson’s disease.
If you need to optimize your circadian biology - the hope of probiotics + prebiotics + cleanses, detoxes, fasts, diet regimes, or fiber frenzy diets are counterproductive.
In the alternative health space, there is a theory of vitamin A toxicity or dangers of consuming foods such as the liver, which is high in vitamin A.
Vitamin A is a family with multiple forms. Light mediates a configurational change:
"Opn4 uses 11-cis-retinaldehyde as a chromophore. Light stimulation causes a conformational change that photo-isomerizes the protein to all-trans-retinal, resulting in a conformational change in the receptor and downstream G protein signaling". (Díaz, Luis Pedro Morera and Guido, 2015)
You will find that most dermatologists recommend topical vitamin A retinol. However, this product choice reduces how light works naturally with the actual retinol in one’s skin.
Without the stimulus of naturally occurring blue light, the conformational change does not happen, which is why many rely on exogenous factors like a cream.
How and why does Vitamin A improve skin health?
These truths are how one can genuinely improve skin health without retinol creams. Yes, it takes more time to see results, but they would be far-reaching and spectacular for overall health regarding hormones, thyroid activity, and gut health.
Consumption of vitamin A via diet is likely the number one anti-skin aging modality.
“Vitamin A and its derivatives are among the most effective substances slowing aging.” (Zasada and Budzisz, 2019)
Retinoids regulate cell apoptosis, differentiation, and proliferation. Anti-wrinkle properties of retinoids promote keratinocyte proliferation, strengthen the protective function of the epidermis, restrain transepidermal water loss, protect collagen against degradation, and inhibit metalloproteinase activity.
The type of light controls the microbiome just like the type of food.
The Gut and Microbiome Circadian Biology Connection Take Home
The importance of circadian biology - dictating downstream effects such as microbiome diversity or even human digestive function is relatively unexplored via prominent figures in the gut health space. They are typically tied to the functional medicine playbook of supplements, stool testing, and taking anti microbial not diving deeper into the understanding of redox chemistry, oxygen, and hypoxia factors influencing barrier integrity and projections to the lumen of the gut or blood flow or the enteric nervous system impacting the overall digestive system.
What happens when light enters the eyes and skin and is projected to the brain, becoming the conductor of our biological systems? How do they play and work together?
“Recent evidence showed that ipRGCs can modulate many additional physiological functions such as emotion, hair regeneration, and body temperature (Fan et al., 2018; Fernandez et al., 2018; Rupp et al., 2019). Since ipRGCs provide environmental luminance signals for many non‐image‐forming visual functions, they could also influence gut microbiota.”
“Our data demonstrates that light input from ipRGCs is a critical regulator of the gut microbiome. Gut microbe composition and oscillation are significantly altered without ipRGC signaling through a sympathetic circuit. Moreover, nighttime light exposure also alters gut microbe composition and diversity through ipRGCs and the non‐sympathetic circuit.” (Lee et al., 2022)
Artificial light at night opens the door for potential digestive disturbances such as SIBO, inflammation with intestinal permeability (leaky gut), and potential increases in bacterial species associated with metabolic syndrome.
“dLAN might be a risk factor for inflammation and metabolic disorders. Indeed, a recent study showed that arrhythmic gut microbiota is linked to patients with type 2 diabetes. Since we only house mice under dLAN for 2 weeks, further study could focus on the relationship between chronic dLAN and metabolic or inflammation‐related disease.” (Reitmeier et al., 2020)
Embrace downloading in the morning with natural sunlight to control your circadian rhythm. You need to have skin and eyes in the game - I feel that if you live in the northern hemisphere and complain of “no sun,” then you need to be outside longer and more often to have the same effect/stimulus. But the irony is that we spend less time outdoors in the winter and more indoors - without any changes to sleeping earlier and increase the artificial light in our lives, which is not the same as natural light outside with its wavelengths and lux. Humans require temperatures and wavelengths to optimize our biology.
I am a massive fan of artificial blue light-blocking glasses - for that reason. Not for the reasons like keeping lights on or staying indoors all day but instead to use when you have no control or in situations like at the airport, on a train, at a shopping mall, etc.
The overall point of using them is to minimize the effects in the short term or, more so, in the wintertime. They should not be an excuse to abuse blue light exposure.
References:
Díaz, N.M., Luis Pedro Morera and Guido, M.E. (2015). Melanopsin and the Non-visual Photochemistry in the Inner Retina of Vertebrates. Photochemistry and Photobiology, 92(1), pp.29–44. doi:https://doi.org/10.1111/php.12545.
Lee, C.-C., Liang, F., Lee, I., Lu, T.-H., Shan, Y.-Y., Jeng, C.-F., Zou, Y.-F., Yu, H. and Chen, S. (2022). External light‐dark cycle shapes gut microbiota through intrinsically photosensitive retinal ganglion cells. EMBO Reports, 23(6). doi:https://doi.org/10.15252/embr.202052316.
Lotti, S., Dinu, M., Colombini, B., Amedeo Amedei and Sofi, F. (2023). Circadian rhythms, gut microbiota, and diet: Possible implications for health. Nutrition Metabolism and Cardiovascular Diseases, 33(8), pp.1490–1500. doi:https://doi.org/10.1016/j.numecd.2023.05.009.
Ondrusova, K., Fatehi, M., Barr, A., Czarnecka, Z., Long, W., Suzuki, K., Campbell, S., Philippaert, K., Hubert, M., Tredget, E., Kwan, P., Touret, N., Wabitsch, M., Lee, K.Y. and Light, P.E. (2017). Subcutaneous white adipocytes express a light sensitive signaling pathway mediated via a melanopsin/TRPC channel axis. Scientific Reports, 7(1). doi:https://doi.org/10.1038/s41598-017-16689-4.
Reitmeier, S., Kiessling, S., Clavel, T., List, M., Almeida, E.L., Ghosh, T.S., Neuhaus, K., Grallert, H., Linseisen, J., Skurk, T., Brandl, B., Breuninger, T.A., Troll, M., Rathmann, W., Linkohr, B., Hauner, H., Laudes, M., Franke, A., Le Roy, C.I. and Bell, J.T. (2020). Arrhythmic Gut Microbiome Signatures Predict Risk of Type 2 Diabetes. Cell Host & Microbe, 28(2), pp.258-272.e6. doi:https://doi.org/10.1016/j.chom.2020.06.004.
Salk Institute (2010). Melanopsin looks on the bright side of life. [online] Salk Institute for Biological Studies. Available at: https://www.salk.edu/news-release/melanopsin-looks-on-the-bright-side-of-life/
Sikka, G., Hussmann, G.P., Pandey, D., Cao, S., Hori, D., Park, J.T., Steppan, J., Kim, J.H., Barodka, V., Myers, A.C., Santhanam, L., Nyhan, D., Halushka, M.K., Koehler, R.C., Snyder, S.H., Shimoda, L.A. and Berkowitz, D.E. (2014). Melanopsin mediates light-dependent relaxation in blood vessels. Proceedings of the National Academy of Sciences, 111(50), pp.17977–17982. doi:https://doi.org/10.1073/pnas.1420258111.
Thaiss, Christoph A., Zeevi, D., Levy, M., Zilberman-Schapira, G., Suez, J., Tengeler, Anouk C., Abramson, L., Katz, Meirav N., Korem, T., Zmora, N., Kuperman, Y., Biton, I., Gilad, S., Harmelin, A., Shapiro, H., Halpern, Z., Segal, E. and Elinav, E. (2014). Transkingdom Control of Microbiota Diurnal Oscillations Promotes Metabolic Homeostasis. Cell, 159(3), pp.514–529. doi:https://doi.org/10.1016/j.cell.2014.09.048.
Voigt, R.M., Forsyth, C.B., Green, S.J., Mutlu, E., Engen, P., Vitaterna, M.H., Turek, F.W. and Keshavarzian, A. (2014). Circadian Disorganization Alters Intestinal Microbiota. PLoS ONE, 9(5), p.e97500. doi:https://doi.org/10.1371/journal.pone.0097500.
Zasada, M. and Budzisz, E. (2019). Retinoids: active molecules influencing skin structure formation in cosmetic and dermatological treatments. Advances in Dermatology and Allergology, 36(4), pp.392–397. doi:https://doi.org/10.5114/ada.2019.87443.