I lectured this past year for A4M (an ongoing board certification program for integrative physicians) at their Endocrinology 2 Symposium. They asked me to suggest some speakers, and I immediately thought of Dr. David Blask MD Ph.D.
Dr. Blask has his lab below our offices at Tulane’s Center for Bio-environmental Research. Where I was a distinguished hormone scholar, in years past.
Dr. Blask is the world’s foremost pioneer and researcher in melatonin. Dr. Blask has labs studying melatonin, at Tulane and also at Tufts University.
Dr. Blask tells us that while we sleep, melatonin is a major controller of many functions of our physiology. Including keeping blood sugar healthy.
Melatonin is secreted in darkness. It is more a “darkness hormone” than a sleep hormone.
But the Western Hemisphere is more and more lit up. More and more artificial light at night (LAN).
Exposure to artificial LAN at night is a ubiquitous environmental risk factor in all modern societies.
The intensity of urban light pollution has increased to the point that it not only affects residents of large cities, but also those in distant areas. Like suburbs and even forest parks that may be hundreds of miles away from the light source.
The circadian cycle is part of health and healthy melatonin
Earth's 24-hour day-night cycle creates in most healthy organisms, including mammals, a built-in circadian (roughly 24-hour) timing system. This innate circadian rhythm is adapted to the natural holy grail of light and dark periods of life.
A healthy planet has clear-cut light and dark. This keeps us healthier.
But. light pollution is altering circadian rhythms. In us all.
Light pollution has been linked to premature death in insects, birds, and other animals.
Artificial LAN has especially been connected to increasing the risk of metabolic dysregulation. Through altering the timing of food intake (when we eat) and various blood markers, like blood sugar and blood insulin.
Rats exposed to artificial LAN developed altered food intake. This then causes glucose intolerance, elevated blood sugar, and higher levels of insulin.
Insulin (when elevated), and blood sugar (when elevated), are pro-aging issues in our tissues.
Mice exposed to nocturnal dim white light of minimal brightness for 4 weeks had increased body mass and reduced glucose tolerance compared to animals whose environment was completely dark at night, despite having roughly equivalent energy consumption and expenditure. Often, living shorter lives.
A study of night-shift workers found that those exposed to brighter LAN were more likely to have “disrupted circadian rhythms”. Linked to greater risks of heart disease.
Other research found that higher LAN exposure was associated with a 13% and 22% increase in the likelihood of being overweight and obese.
Exposure to LAN in the bedroom is reported to be positively associated with the development of diabetes in humans, especially as we age.
Diabetes is an epidemic. Around the world.
Modern humans living in cities are prone to being shifted away from a natural 24-hour day-night cycle, to one of round-the-clock working and leisure time. Often staying out late. Continually exposed to artificial LAN. With more risk of developing type 2 Diabetes.
The China Noncommunicable Disease Surveillance Study took a look at all this in 98,658 adults.
Participants at each study site were assigned an average artificial outdoor LAN exposure level. This was figured out using night-time low-light image data of the Earth's surface from the US Defense Meteorological Satellite Program (DMSP).
The study found that the highest quintile of LAN exposure was associated with a 28% increase in the prevalence of diabetes. Compared to those within the lowest quintile areas.
Chronic exposure to residential outdoor LAN was positively linked with higher blood glucose levels, increased insulin resistance, and more cases of diabetes.
The more light exposure, the poorer the health of the beta islet cells (which control blood sugar).
The researchers estimated that more than 9 million cases of diabetes in Chinese adults aged 18 years- are due to outdoor LAN exposure.
This means that brighter skies cause less secretion of melatonin. Less healthy beta cells. More type 2 Diabetes.
Moral of this story:
Keep your rooms darker at night. Consider melatonin replacement.
However… Dr. Blask reminds us that “biology is not linear”.
Dr. Blask’s own doctor uses melatonin to help with sleep but needs to go up to 40 mg of melatonin replacement, to accomplish this.
In comparison, Dr. Blask takes melatonin to help him sleep. But he takes less than one mg. Or else he wakes up groggy.
Knowledge is power. Stay strong.
Dr. B.
Reference:
Outdoor light at night in relation to glucose homeostasis and diabetes in Chinese adults: a national and cross-sectional study of 98,658 participants from 162 study sites. Diabetologia, 2022; DOI: 10.1007/s00125-022-05819-x