Why June 20th (Summer Solstice) is the healthiest day of the year, according to Circadian Light Research Center

PR Newswire
Wednesday, June 19, 2024 at 4:20pm UTC

Why June 20th (Summer Solstice) is the healthiest day of the year, according to Circadian Light Research Center

PR Newswire

BOSTON, June 19, 2024 /PRNewswire/ -- The summer solstice offers the greatest opportunity to obtain the healing properties of sunlight because it is the longest day of the year. It also has the fewest hours of darkness illuminated by electric light before we retire to bed. This minimizes our exposure to the circadian clock-disrupting effects of evening blue-rich LED and fluorescent lights.

As former Harvard professor, Dr. Martin Moore-Ede, explains in his Amazon best-selling book THE LIGHT DOCTOR: Using Light to Boost Health, Improve Sleep, and Live Longer, the healing power of natural daylight is substantial. Large-scale prospective studies show that people who are exposed to the most outdoor natural daylight are the healthiest and live the longest. Their rates of cardiovascular disease and diabetes are significantly less than those who spend most of their time indoors.

Equally, the adverse impact of blue-rich electric lights in the nocturnal hours after sunset is considerable. Those exposed to the most blue-rich light after sunset are the sickest and have the shortest life expectancy. The use of lights at night, after the sun has set, that emit sky-blue wavelengths (including most LED lights in the market today) disrupts our circadian rhythms and increases the risks of obesity, diabetes, heart disease, and endocrine-sensitive cancers like breast and prostate cancer.

The seasonal differences in Northern US states, and cities like Boston, Chicago, and Seattle, can be substantial. When the sun sets at 9 pm after 16 hours of daylight only one hour of electric light is required if you retire to bed at 10 pm. In contrast at the winter solstice on December 21st, when darkness sets in at 4 pm, a full six hours of evening electric light exposure is required, and there are only eight hours when you can go outside and benefit from the healing power of daylight.

It takes very little electric light at night to have an adverse effect. A recent large-scale study of 85,000 people with 13 million hours of light sensor data and 670,000 person-years of follow-up, showed that even dim bedroom light (1-6 lux) increased the risk of a diabetes diagnosis by 35% and the risk increased by 73% with brighter bedroom lights.

Of course, on any given day there are other health factors to consider besides day length and night length. Too much hot sunlight can be harmful. However, obtaining the daylight benefits for circadian clocks does not require the brightest and hottest sunlight. One or two hours of natural outdoor daylight in the morning, before the sun reaches its peak, is the most effective at synchronizing and strengthening the circadian system. And you don't need to be under full sunlight – sitting, or walking in shaded areas outdoors delivers enough of the blue-rich daylight signal needed to maintain healthy circadian clocks.

About Martin Moore-Ede M.D., Ph.D.

For over 40 years, Dr. Moore-Ede has been a leading world expert on circadian clocks and the health problems caused by electric light at night. As a professor at Harvard Medical School (1975 – 1998), he led the team that located the suprachiasmatic nucleus, the biological clock in the human brain and showed how human circadian clocks are synchronized by light. As Director of the Circadian Light Research Center he identified the sky-blue wavelengths in white light that synchronize circadian clocks, but disrupt them at night, and developed the first healthy circadian-friendly lights to protect human health.

*Amazon best seller interior lighting design

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SOURCE Circadian Light Research Center