The Solution

Why natural light?

We have evolved with light that constantly changes both in intensity and spectral composition, through cycles on several levels (like days, lunar months, or years). It always comes from a black-body radiator: some hot material which emits light according to its temperature. This also includes wood fire, which does not affect our sleep negatively.

In the past decade, much research has been done to discover how various frequencies of the spectrum have specific physiological effects. These effects often act in different directions but through overlapping mechanisms — therefore, they are also in interaction with each other. We still know little about the details and we are far from having a complete map of the spectrum regarding the effects of every frequency band.

On the one hand, this means that light can be used to evoke a desired biological reaction in therapeutic applications (e.g. photobiomodulation: using red and near-infrared light for tissue healing).

On the other hand, electric light with highly unnatural spectra can disturb the physiological balance that our body expects from our light environment. Therefore, the safest option to preserve health is as much natural light as possible.

The role of long-wavelength light in tissue recovery (photobiomodulation)

Near-infrared light has pervasive and important effects through local melatonin production:

Zimmerman & Reiter (2019) Melatonin and the optics of the human body. Melatonin Research, 2.

Deep red light improves declining eyesight through enhancing mitochondrial performance:

Shinhmar et al. (2020) Optically improved mitochondrial function redeems aged human visual decline. The Journals of Gerontology: Series A, 75.

Cytokine expression and improving aged mitochondrial function in the retina by long-wavelength light:

Shinhmar, Hogg, & Jeffery (2023) Exposure to long wavelength light that improves aged mitochondrial function shifts acute cytokine expression in serum and the retina. Plos One, 18(7).

Photobiomodulation can protect the retina from oxidative stress, with implications for macular degeneration:

Kim & Won (2022) Effect of Photobiomodulation in suppression of oxidative stress on retinal pigment epithelium. International Journal of Molecular Sciences, 23.

A summary on the many benefits of sunlight through photobiomodulation, including how red and near-infrared light slows down tissue aging:

Heiskanen, Pﬁﬀner, & Partonen (2020) Sunlight and health: Shifting the focus from vitamin D3 to photobiomodulation by red and near-infrared light. Ageing Research Reviews, 61.

A short summary on the importance of long-wavelength light in general lighting:

Veto (2020) Correspondence: Daylighting: Why infra-red should be explored. Lighting Research & Technology, 52.

Ongoing study at Pacific Northwest National Laboratory on the cognitive, mood, and cardiovascular effects of long-wavelength light:

Roddick (2022) Near Infrared Effects on Cognitive Performance, Mood, & Cardiovascular Physiology.

Short summary on NASA projects in photobiomodulation, including for eye health:

https://spinoff.nasa.gov/NASA-Research-Illuminates-Medical-Uses-of-Light

Some positive effects of near-infrared supplementation in the morning:

Giménez et al. (2022) Effects of Near-Infrared Light on Well-Being and Health in Human Subjects with Mild Sleep-Related Complaints: A Double-Blind, Randomized, Placebo-Controlled Study. Biology, 12.

Different frequency — different effect (in various applications)

Potential role of daylight in preventing short-sightedness:

Hobday (2016) Myopia and daylight in schools: a neglected aspect of public health? Perspectives in Public Health, 36.

Photons convey important information content to cells:

Moro et al. (2022) The code of light: do neurons generate light to communicate and repair? Neural Regeneration Research, 17.

Closely adjacent frequency bands can have opposing effects:

Sanderson et al. (2018) Inhibitory modulation of cytochrome c oxidase activity with specific near-infrared light wavelengths attenuates brain ischemia/reperfusion injury. Scientific Reports, 8.

Morse et al. (2022) Sometimes less is more: inhibitory infrared light during early reperfusion calms hyperactive mitochondria and suppresses reperfusion injury. Biochemical Society Transactions, 50.

Long wavelengths (red and near-infrared) can counteract photochemical harm from short wavelengths (blue & UV):

Albarracin, Eells & Valter (2011) Photobiomodulation protects the retina from light-induced photoreceptor degeneration. Investigative Ophthalmology & Visual Science, 52.

Heinig et al. (2020) Photobiomodulation mediates neuroprotection against blue light induced retinal photoreceptor degeneration. International Journal of Molecular Sciences, 21.

Menezes et al. (1998) Non-coherent near infrared radiation protects normal human dermal fibroblasts from solar ultraviolet toxicity. Journal of Investigative Dermatology, 111.

Red light can compensate for mitochondrial harm by blue light, with relevance to age-related macular degeneration:

Núñez‐Álvarez et al. (2019) Blue light negatively affects the survival of ARPE 19 cells through an action on their mitochondria and blunted by red light. Acta Ophthalmologica, 97.

Age-related macular degeneration protection index: nothing beats natural light (see Planckian radiators, Figure 4):

Schierz (2019) Is light with lack of red spectral components a risk factor for age-related macular degeneration (AMD). CIE Proceedings of the 29th CIE Session.

Retinal ganglion cells: oxidative stress from blue light reduced by red light:

Núñez-Álvarez & Osborne (2019) Blue light exacerbates and red light counteracts negative insults to retinal ganglion cells in situ and R28 cells in vitro. Neurochemistry International, 125.