Circadian rhythm is an internal time clock or pattern that influences processes throughout the human body.
Along with the sleep-wake cycle, our circadian rhythm affects changes in blood pressure, basal body temperature, hormonal release and organ function.
Daylight and darkness greatly influence these rhythms and the 24-hour cycle it follows. And when our circadian rhythm is off, it can result in a world of hurt. Case in point…
Because natural light is crucial for maintaining circadian rhythm, some scientists believe that insufficient exposure leads to what they call “circadian misalignment.”
This has inspired researchers in Switzerland and Germany to investigate if this misalignment is a risk factor for one of the fastest-growing metabolic conditions — type 2 diabetes.
Could more daylight be the key to improving our glycemic profile?
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Metabolic health benefits from natural light
People with type 2 diabetes have an inefficient metabolism that can’t convert food into energy efficiently, resulting in blood sugar imbalances.
And according to Charna Dibner, an associate professor at the University of Geneva and the University Hospitals of Geneva (HUG), “It has been known for several years that the disruption of circadian rhythms plays a major role in the development of metabolic disorders that affect an increasing proportion of the Western population.”
So, he and fellow researchers recruited 13 volunteers aged 65 and over, all with type 2 diabetes, to see if exposure to natural light would impact any improvements.
The subjects spent 4.5 days in specially designed living spaces at Maastricht University, lit either with natural light through large windows or with artificial light. After a break of at least four weeks, they returned for a second session, this time in the other light environment.
Even during this short period of time, the researchers observed an overall improvement in the participants’ metabolic profiles. Being exposed to natural light kept blood glucose levels in the normal range for more hours per day, and their levels showed less variability.
“In addition, their melatonin level was a little higher in the evening, and fat oxidative metabolism was also improved,” according to Patrick Schrauwen from the German Diabetes Center.
Blood and muscle samples were also taken from the volunteers before, during, and after each light treatment to analyze the regulation of molecular clocks in those cells.
“Together, the results clearly show that the internal clock and metabolism are influenced by natural light. This could be the reason for the improved blood sugar regulation and the improved coordination between the central clock in the brain and the clocks in the organs,” explained Charna Dibner.
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What’s behind natural light’s impact on metabolic health
This study is the first evidence of the beneficial effect of natural daylight on metabolic health compared to artificial light. It was also a world-first controlled crossover study, eliminating concerns about variability among subjects in factors such as age and genetics.
Next, they plan a longer study carried out in “real-life” conditions.
Still, there is some speculation about why natural light, rather than artificial light, affects metabolic health. But, for starters, artificial light does not help the body produce vitamin D, as natural light does.
Dr. Richard Siegel, an endocrinologist and co-director of the Diabetes and Lipid Center at Tufts Medical Center, in an interview with Prevention magazine, cited research that suggests vitamin D supplementation can help reduce the risk that someone with prediabetes will develop full-blown diabetes. I wrote about similar findings here.
There may also be another indirect connection…
Though the light study didn’t mention vitamin D, they noted an increase in melatonin among the participants. Melatonin improves sleep, an important factor in blood sugar management. The body also needs adequate levels of vitamin D to produce serotonin, which converts to melatonin.
Regardless, this first-of-its-kind study supports the role of natural daylight in promoting a healthier metabolic profile.
To take advantage, we’ve got to break out of a bad habit: some estimates suggest most of us spend 90% of our time indoors. So, if the weather is cooperative, get outside and enjoy the daylight. If it’s not, sit by a window that lets the light in and soak it up.
Just remember to pull the curtains at night, leave screens out of your bedroom (smartphone, tablets, etc.) and ditch the nightlight. Research from 2018 says light at night can negatively impact your metabolic health.
Sources:
Natural daylight during office hours improves glucose control and whole-body substrate metabolism — Cell Metabolism
Exposure to natural light improves metabolic health — Eureka Alert
Intratrial Exposure to Vitamin D and New-Onset Diabetes Among Adults With Prediabetes: A Secondary Analysis From the Vitamin D and Type 2 Diabetes (D2d) Study — Diabetes Care
Scientists Find Simple Habit That May Improve Blood Sugar Management in Older Adults — Prevention
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