Emerging Insights On Light In Human Health

Photo©Patrick Daxenbichler/123rf

Like water and food, natural light is a vital source of sustenance and healing. We need to receive natural light through our eyes in the early hours of the day, and again as the sun is going down. Our hormonal systems, nervous systems — in fact, our whole wonderfully orchestrated inner terrain — relies on the signals provided by the different qualities of light at those times. The diminishing light at dusk triggers processes of rest, digestion, cleansing, and regeneration. Dawn light awakens our active, productive, social processes.

Our circadian rhythm is tied in many, many ways to healthy function. When the natural cycles of night and day, dark and light, are disrupted, consequences spread throughout our physiology. For instance, scientists have learned that our microbiota, too, need that stable rhythm of natural light to sustain healthy digestion, metabolic processes, hormone balance, and to keep inflammation in check.

While we may have to make special efforts to remove artificial light from our environment at night, it’s well worth it to do so. Not only light, but also darkness informs our bodies, guiding our metabolic, nervous, and endocrine systems, and promoting restorative, regenerative processes. Lack of darkness during the night reduces our focus, memory, and learning ability during the day. Everything from mood to arthritis to cancer is impacted by the light cycle.

Our natural light generator — the sun — emits a broad range of light waves. On one end of the spectrum, we have short ultraviolet waves: we need these to generate the tremendously important hormone vitamin D in our bodies; however, we know that too much ultraviolet exposure results in burning. Balance and common sense are vital, since both vitamin D deficiency and sunburn are known risk factors for skin and other cancers. At the other end of the light spectrum, red and infrared wavelengths have emerged as strong drivers of physical and mental health and are already being used clinically for health and beauty. Red wavelengths are known to promote tissue healing, and therapeutic devices are available both in professional settings and for home use.

Reported on Nature.com, a professor of neuroscience in the UK led a research study aimed at better understanding the effects of infrared light on our cells and tissues.¹ The team found that frequencies in sunlight can penetrate and even pass all the way through the human body. Infrared light simulating a section of the sunlight spectrum was shone on the chests of participants and was measured emerging from their backs using a spectrometer or radiometer. As the light passes through cells, it improves mitochondrial function and ATP production, translating to improved physiological performance. This was especially true with respect to improved visual function when receiving sunlight through the eyes, perhaps because certain structures in the eye have the greatest density of mitochondria of all the tissues of the body.

One of the most important findings of the study, however, is the systemic effects of light: infrared light received even on a small area of the body causes healthy changes and better mitochondrial functioning throughout the body.

The Benefits Of Getting The Full Spectrum

While sunlight contains a spectrum of wavelengths, a red light therapy device emits only a small fraction of that spectrum, commonly just one wavelength and at one steady intensity. For the body, this is quite unlike natural sun exposure. As the study’s authors point out, the full spectrum of sunlight has always been present, impacting all life on Earth. Our bodies benefit in various ways from the whole range of natural light, as different wavelengths trigger different physiological changes, which actually balance each other and support resilience. Reducing the spectrum to a single wavelength could actually promote ageing of cells and tissues.

We know that eating a diverse selection of plants provides far greater nutrition than eating only one. Applying just one wavelength of light therapeutically is a little like reducing the wonderful variety of vegetables and fruits available to always eating broccoli. Broccoli is great, but we’re missing out on so many other phytochemicals and nutrients if we limit our diets so severely.

Many people are spending significant amounts of money and placing their hopes for healing in red light therapy, when simply being outdoors a little each day might provide greater benefit. Infrared light passes through most clothing, and plenty of sunlight reaches us even on cloudy days. Just fifteen minutes of sunlight exposure can start a cascade of healthy processes lasting twenty-four hours or more.

Perhaps most wonderful of all is the profound feeling of well-being, the lift of our spirits, which natural light gives us. We are all familiar with the everyday miracle of seeds germinating, plants growing and blooming in response to light. It turns out we’re not so different! Both the reverent depictions of the sun found in ancient cultures around the world and the emerging science tell us the same story: natural light is an integral part of our life and healing.

Susan Ratliff is a holistic health practitioner emphasizing the synergy of natural lifestyle restoration, nutritional therapy, unicist homeopathy, and personalized meridian/acupressure techniques for emotional health. She offers an online course on holistic and complementary cancer care and prevention, and is the author of Homeopathy Rising: A Deep Introduction to Earth’s Fastest Growing Medicine. Visit smratliff@pm.me.

Notes

1. Jeffery, G., Fosbury, R., Barrett, E. et al. “Longer wavelengths in sunlight pass through the human body and have a systemic impact which improves vision.” Sci Rep15, 24435 (2025). https://doi.org/10.1038/s41598-025-09785-3

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