It may be something that you’ve not thought about before. If light impacts sleep and sleep impacts the balance in the gut, as research is finding, it’s a fairly simple leap and may go some way to explaining the propensity towards weight gain, obesity and even diabetes amongst those who suffer with insomnia or work night shifts. Here’s how, why and what you can do to address it.
Circadian rhythm is affected by excess blue light from various sources (such as lights, phones, televisions- anything with an LED inside!) Our circadian rhythm is the 24 hour internal body clock that follows the day/night pattern and manages essential internal functions, for example sleeping and digesting (you can read in more detail in our blog “what’s so bad about blue?”). Today’s modern lifestyle of long work hours, differing shift patterns, over exposure to artificial light sources, early mornings, late finishes and possible late night eating can all negatively impact our circadian rhythm. This is due to our internal clocks struggling to keep up with the contrasting information of the light/dark cycle in comparison to our behaviour. The impact on these natural rhythms increases the risk of gaining weight or developing metabolic syndrome (which has been linked to diabetes and obesity).
Figure 1. “Circadian rhythm, gut microbiota, and metabolism. The light/dark cycle is the zeitgeber for the central clock in the brain, while signals from the brain entrain peripheral clocks, e.g. in the intestine.”
Well, given that circadian rhythm is known to be skewed by exposure to blue light, let’s consider how this disruption impacts the activity in the gut. One 2014 study on mice on the impact of circadian rhythm on our gut microbiome found that “the gut microbiota was affected in mice who experienced changes to their night/day rhythms, indicating a central role for clock-controlled mechanisms in regulating gut micro bacteria”.
Image: Cartoon visual of circadian rhythm effects on the mind
Artificial light with excess blue content (which describes almost all LED light) impacts our bodies natural rhythms counterintuitively to sunlight. This, in turn, disrupts sleep patterns and many other functions within our bodies. The lack of sleep has been found to have a profound impact on the balance of gut microbiota. Another study with 9 male (human) volunteers found that “just two nights of sleeping for only four hours significantly decreased insulin sensitivity compared to normal sleep”. Later in the research the scientists state that there were “also significant changes to microbial populations… associated with a disturbed metabolism and even obesity”.
“Disruptions in sleep, diet and eating patterns influence the daily dynamics of gut microbiome structure and activity”
Many features of the modern lifestyle may contribute to the current epidemic of metabolic health problems; including high fat/sugar convenience foods and poor sleep. These lifestyle factors disturb both our circadian timing system, but also the make-up of our gut microbiome. Good sleep and a healthy diet at appropriate times throughout the day may in fact be necessary for maintaining metabolic homeostasis. Equally, manipulating the microbiome with what we eat may ease a negatively affected circadian rhythm- plant based foods are a rich source of fiber, the undigested components of which can maintain colic health as well as synchronize circadian rhythms.
Image: Aerial view of a group of people eating together
So what’s the answer? Let’s take away three key practical elements that will help to reinstate balance:
- Begin winding down for sleep by 9pm with less blue light exposure (reduced screen time or more gentle light bulbs) and sleep by 10.30pm.
- Avoid eating late! Our intestines manage the “transport of proteins required to uptake and absorb the energy that gives us nutrients, glucose, amino acids and triglycerides” and therefore the timing of our meals and snacks are equally as important as a healthy diet in managing the rhythm of our microbiomes.
- Change the bulbs in the bedroom/space that you like to wind down in during the evenings, for lighting with a managed balance of blue content to avoid overproduction of cortisol.