All life on earth absorbs sunlight for energy…including humans
In a Nutshell
For me, sunlight has become as essential as exercise or diet
Sunlight is used by the human body and supports overall health
Studies show that adequate sun exposure reduces the chance of disease and early death
About three or four years ago, I began noticing that I was tanning more easily in the summer. I connected this to reducing my dietary seed oils intake and my skin ridding itself of its unhealthy load of industrially processed, damaging oil. This left me wondering whether I was better adapted to sunlight - and whether I might benefit more from it. That led to my first article about sunlight around this time last year.
This past summer, I deliberately (and safely) maximized my sunlight exposure. The result was surprising: I experienced noticeably greater stamina in exercise, particularly mountain biking. In this article, I explain why that might be, and I review evidence for sunlight’s broad health benefits. I’ll cover:
A reminder of the nature of sunlight and how it enters the human body
How all life uses sunlight
The beneficial impact of sunlight on human health
The nature of sunlight and how it enters the human body
Figure 1 shows that the sun radiates a wide spectrum of energy, including the parts that reach us on earth, namely ultraviolet (UV), visible, and infrared (IR). I’ll refer to them collectively as sunlight.
Figure 1: The spectrum of energy emitted by the sun highlighting the proportion reaching the human body and the small range we perceive as visible light
The UV, visible, and IR that reaches us on earth makes its way into the human body to varying degrees (Figure 2).
Figure 2: Sunlight enters the human body to varying degrees. UV is very shallow and penetrates only the surface of skin. IR gets deep into human tissues and their mitochondria
The more I have read, the more convinced I have become that the IR, and specifically what is called near-IR, plays a major role in health - likely explaining my own improvements in stamina and energy
All Life Uses Sunlight
I did touch upon this in my original article. Here I’ll expand and link to a podcast below that you might find interesting. My selected summary of that podcast is:
The sun constantly gives off energy as light (photons)
UV, visible and IR energy reaches us on earth
All life that has evolved on earth over billions of years has been exposed to and has used UV, visible, and IR light energy
Near-IR (a type of IR) constitutes more than 50% of the light energy that reaches us
Near IR penetrates the human body and reaches organs, bones, and unborn babies
The energy level needed to drive human metabolism is the same as the energy of the near-IR light that reaches us on earth. This is taken as evidence that humans likely evolved to use the sun’s near-IR light energy
Plants and animals have evolved to use sunlight in different ways
Plants convert visible light energy into chemical energy (sugars) through photosynthesis
Animals use sunlight in several ways
Near-IR energy to make our metabolism faster and more efficient
UVB creates vitamin D and has other beneficial effects
Every part of sunlight reaching us is thought to influence our metabolism (see the work of Chris Patrick below). However, I’m going to limit my discussion of the health effects of sunlight to the benefits UV hitting our skin and the benefit of near-IR reaching deep into our bodies.
UV hitting our skin
Most of the published literature on sunlight is specific to UV. Perhaps this is because we have known for years that sunlight creates vitamin D in our skin (from cholesterol), and adequate vitamin D prevents rickets. Perhaps also we’ve been told that sunlight is dangerous and should be avoided. Whatever the reason, there is much literature on the effects of UV on human health, and much of it is eye-opening, at least to me.
UV, specifically UVB, is the high energy part of sunlight responsible for most of what we know about sunlight’s health benefits. You can find more about vitamin D and sunlight from previous articles.
“…we’ve known for a long time that exposure to sunlight should be viewed through the lens of risk versus benefit”
We’ve known about the production of vitamin D and the potential for harm caused by too much UV exposure for many years. To put this another way, we’ve known for a long time that exposure to sunlight should be viewed through the lens of risk versus benefit. Let’s take a look at the many known benefits.
As early as eleven years ago, we knew that avoiding the sun likely increased the risk of death (from any cause) [1]. Scientists in Sweden followed almost 30,000 Swedish women over a 20-year period to assess the effects of sun avoidance on their wellbeing. In 2014 the scientists published their findings and concluded:
“The results of this study provide observational evidence that avoiding sun exposure is a risk factor for all-cause mortality. Following sun exposure advice that is very restrictive in countries with low solar intensity might in fact be harmful to women’s health”
In other words, women who chose to avoid the sun, were more likely to die earlier.
Digging into the academic literature, I discovered that UV exposure has been credited with reducing heart disease, cancer, auto-immunity, dementia, type-1 diabetes, and benefitting pregnancy.
Heart disease
In the human population, there is growing evidence that more sunlight is associated with lower rates of heart disease and lower blood pressure [2]. In mice it has been shown that that skin exposure to UVB prevented heart disease (atherosclerosis) by increasing the role of that part of the immune system that protects arteries and reducing the role of the part that damages them [3].
Cancer
A number of human studies show evidence that exposure UVB can result in lower rates of cancer [2,4] The evidence for 15 types of cancer, including bladder, breast, cervical, colon, endometrial, esophageal, gastric, lung, ovarian, pancreatic, rectal, renal, and vulvar, is strong [4].
Immunity, autoimmunity, fertility, pregnancy and dementia
Vitamin D is credited with having a beneficial effect on immunity, autoimmunity, fertility, pregnancy, and dementia [5 reference 24]
Psoriasis, atopic dermatitis
UV-based therapy treats immunoinflammatory cutaneous disorders such as Psoriasis and atopic dermatitis [3 in the discussion].
Type 1 diabetes
The incidence of type 1 diabetes around the world varies with exposure to sunlight. Incidence rates approached zero in regions with high levels of UVB, and increased as UVB exposure decreased [6].
The accumulation of information on the benefits of UVB has resulted in a multi-national call to action to reassess public health advice [2]:
“…current public health advice on sun exposure ought to be reconsidered to communicate a better balance of the benefits and harms of sunlight, particularly at higher latitudes where ambient levels of [UV radiation] are comparatively low even in summer”
Near IR reaching deep into our bodies
Figure 2 shows that near-IR light reaches deep into the human body and touches our blood, connective tissue, organs, bones, and our unborn babies. With the exception of red blood cells, which don’t contain them, the energy from near-IR will reach and affect things called mitochondria in our cells.
What is a mitochondrion?
A mitochondrion (singular) is a very small component of the cells of most plants, animals and fungi. It has traditionally been described as the "powerhouse of the cell" because it generates energy. It is now recognized that mitochondria (plural) also play roles in cell division, differentiation and death, hormone production, and influence metabolic flexibility. The more we understand mitochondria, the more we may be tempted to conclude that those tiny bodies may play a bigger role in determining human health than DNA.
In my review of Chris Palmer’s excellent book on mental health, I wrote the following:
“Dr. Palmer emphasizes that there may be more than one route to metabolic dysfunction in the brain, including insulin resistance, hormonal imbalance, vitamin deficiency, stress, and gut microbiome alteration. However, he concludes that, irrespective of the starting point, brain cell mitochondrial dysfunction is the common root cause of mental illnesses including depression, anxiety, bipolar disorder, schizophrenia, and neurodegenerative diseases such as Parkinson’s and Alzheimer’s.”
The central role of mitochondria in human metabolism, healthy and unhealthy, is also recognized in a wide range of so-called chronic diseases caused by poor diets. Chris Palmer’s take:
“Mitochondrial function affects every cell in the human body through their involvement in all aspects of cell function, neurotransmitters, hormones, inflammation, immune system function, regulation of gene expression, development, and the maintenance and health of cells.”
Effects of sunlight on mitochondria
Longer wavelengths of light, including red and near-IR, have been shown to affect mitochondrial function in ways that improve mobility, vision, cognition, and general performance, especially as we get older [discussions in 7 and 8]. Additionally, when our bodies are exposed to those wavelengths, we see effects in those parts of the body that are exposed plus other parts of the body not exposed directly. It is not clear how this happens, but it is clear that the effects of light are transmitted around the body [7,8].
Before finishing, I want to come back to my improved exercise energy. I’m pretty sure I haven’t gained muscle this year (I’ve probably lost some), I’m not eating anything differently, and in the summer of 2025 I didn’t ride as much as I did in 2024. Nevertheless, I had more energy for the longer rides and steeper ascents. I put this down to being more deliberate about getting more sunlight, and in particular, more near-IR. The more near-IR, the more efficient the mitochondria I have [7]:
“Mitochondria regulate metabolism, but solar light influences its rate”
Sensible sun exposure
Reduce dietary seed oils as much as possible. This will reduce the damage they cause in our skin, and reduces the chance of sunburn
Develop a solar callus – increase exposure gradually like exercise training
See the sun within 30 minutes of waking up and before looking at screens
Tailor UV exposure to previous exposure, skin type, and latitude (Apps like DMinder and MyCircadian may help)
Avoid sunglasses in the morning
Use hats, clothing, and shade instead of heavy sunscreen when possible
Get outside as much as possible, safely
Summary
For me, sunlight has become as essential as exercise or diet - a natural resource I actively seek out. Like water or food, too much can be harmful, but the right dose is life-enhancing.
The evidence is clear: sunlight provides a net health benefit.
Near-IR – enhances mitochondrial efficiency, improving metabolism and performance with no downsides I can find
UVB – supports immunity, reduces disease risk, and extends lifespan when exposure is managed safely
If you want to find out more, I’ve listed my go-to people for information on this subject after the References section
References
1. Lindqvist PG, Epstein E, Landin-Olsson M, Ingvar C, Nielsen K, Stenbeck M, Olsson H. Avoidance of sun exposure is a risk factor for all-cause mortality: results from the Melanoma in Southern Sweden cohort. J Intern Med. 2014 Jul;276(1):77-86. doi: 10.1111/joim.12251. Epub 2014 Apr 23. PMID: 24697969.
2. Alfredsson L, Armstrong BK, Butterfield DA, Chowdhury R, de Gruijl FR, Feelisch M, Garland CF, Hart PH, Hoel DG, Jacobsen R, Lindqvist PG, Llewellyn DJ, Tiemeier H, Weller RB, Young AR. Insufficient Sun Exposure Has Become a Real Public Health Problem. Int J Environ Res Public Health. 2020 Jul 13;17(14):5014. doi: 10.3390/ijerph17145014. PMID: 32668607; PMCID: PMC7400257.
3. Sasaki N, Yamashita T, Kasahara K, Fukunaga A, Yamaguchi T, Emoto T, Yodoi K, Matsumoto T, Nakajima K, Kita T, Takeda M, Mizoguchi T, Hayashi T, Sasaki Y, Hatakeyama M, Taguchi K, Washio K, Sakaguchi S, Malissen B, Nishigori C, Hirata KI. UVB Exposure Prevents Atherosclerosis by Regulating Immunoinflammatory Responses. Arterioscler Thromb Vasc Biol. 2017 Jan;37(1):66-74. doi: 10.1161/ATVBAHA.116.308063. Epub 2016 Oct 20. PMID: 27765767.
4. Grant WB. Ecological studies of the UVB-vitamin D-cancer hypothesis. Anticancer Res. 2012 Jan;32(1):223-36. PMID: 22213311.
5. Greenhalgh I, Butler AR. Sanatoria revisited: sunlight and health. J R Coll Physicians Edinb. 2017 Sep;47(3):276-280. doi: 10.4997/JRCPE.2017.314. PMID: 29465107. 4
6. Mohr SB, Garland CF, Gorham ED, Garland FC. The association between ultraviolet B irradiance, vitamin D status and incidence rates of type 1 diabetes in 51 regions worldwide. Diabetologia. 2008 Aug;51(8):1391-8. doi: 10.1007/s00125-008-1061-5. Epub 2008 Jun 12. PMID: 18548227.
7. Powner MB, Jeffery G. Light stimulation of mitochondria reduces blood glucose levels. J Biophotonics. 2024 May;17(5):e202300521. doi: 10.1002/jbio.202300521. Epub 2024 Feb 20. PMID: 38378043.
8. Jeffery G, Fosbury R, Barrett E, Hogg C, Carmona MR, Powner MB. Longer wavelengths in sunlight pass through the human body and have a systemic impact which improves vision. Sci Rep. 2025 Jul 8;15(1):24435. doi: 10.1038/s41598-025-09785-3. PMID: 40628952; PMCID: PMC12238558.
9. I. Kalampouka, R. R. Mould, S. W. Botchway, A. M. Mackenzie, A. V. Nunn, E. L. Thomas, J. D. Bell, J. Biophotonics 2024, 17(8),e202400046. https://doi.org/10.1002/jbio.202400046
Useful Resources
If you’re interested in learning more yourself, I’ve listed below sources that you may find useful. I think of these as fitting into three categories, namely deeply technical, academic, and non-academic influencers.
Deeply technical
Jack Kruse – Kruse was the first person I stumbled across on the subject of sunlight and human health. I listened to a six-hour podcast he did with Andrew Huberman, and afterwards was convinced that I’d never be able to understand the sun’s effects. Kruse is a MD, a board-certified neurosurgeon, author, and health educator. He focuses on the roles of light, circadian rhythms, and environmental factors and how they drive mitochondrial health and quantum biology. He describes himself as a "mitochondriac". His views on health optimization are unconventional to put it mildly. His writing is dense and when I read anything from him, I feel like a like a parched man trying to quench my thirst from a fire hydrant, except I don’t understand what’s happening to me.
Academic
I encountered Fosbury and Zimmermanan in a podcast by Max Gulhane. I find them understandable, and they provide me with the basic principles I need to figure out and remember how sunlight benefits human health.
Bob Fosbury - Bob Fosbury is a British astrophysicist, emeritus astronomer at the European Southern Observatory (ESO), and honorary professor at the UCL Institute of Ophthalmology in London. His career has spanned over 50 years, bridging astronomy, optics, and interdisciplinary biology. Most recently he has contributed greatly to the study of how sunlight's spectrum interacts with human mitochondria to influencing health and vision. His views on how sunlight affects human biology resonate strongly with those of Jack Kruse but he articulates them in a way that is understandable to me.
Scott Zimmerman – Scott Zimmerman is an optical engineer and inventor, focused on the intersection of light and human biology. He argues that modern artificial lighting, such as LEDs, lacks essential near-IR from sunlight, leading to widespread health issues like mitochondrial dysfunction, hormonal imbalances, and so-called chronic diseases. His research suggests that near-IR penetrates the body deeply, stimulating antioxidants and repair mechanisms. His ideas align closely with quantum biology and the views of Jack Kruse and Bob Fosbury.
Non-academic influencers
Borg, Gulhane, and Hussey take the works of Kruse, Fosbury, and Zimmerman and make them more understandable to a lay person like me. If you are interested in this subject, you may wish to start with these guys.
Cameron Borg - Cameron Borg is an Australian nutritionist and podcaster who writes on Substack and hosts the Ricci Flow podcast. He has a background in pulmonary science, and emphasises the importance of light exposure, electromagnetic fields (EMFs), hydration, sleep, breathing, and nutrition on mitochondrial function and overall health. He is critical of modern lifestyles and technologies, including artificial lighting, and believes they have contributed to so-called chronic diseases. He advocates instead for nature-aligned practices such as morning sunlight exposure. He is aligned with the likes of Scott Zimmerman and Bob Fosbury in promoting sunlight as a primary health regulator.
Max Gulhane - Max Gulhane, MD is an Australian physician and podcaster specialising in regenerative medicine, hosts the Regenerative Health podcast, and runs various retreats. He promotes the importance of sunlight and ancestral nutrition to reverse metabolic disorders. He is critical of sun avoidance and processed foods, arguing that they disrupt mitochondrial function and, by extension, human health. Gulhane’s philosophy aligns with Jack Kruse, Bob Fosbury and Scott Zimmerman.
Stephen Hussey - Dr. Stephen Hussey, MS, DC is a chiropractor, functional medicine practitioner, and author. He believes that modern lifestyles disrupt natural physiological processes and result in heart disease, chronic pain, type 1 diabetes, and autoimmune disorders. He challenges traditional views of cholesterol, the heart's function, and pain management. He believes that health is about adapting to stress through understanding human evolution, quantum biology, and mitochondrial health. Hussey's ideas parallel those of the individuals above by linking light, and structured water to cellular energy and disease prevention.
For those that really want to get in the weeds, take a look at the graphic and extensive supporting references on Chris Patrick’s article entitled Humans are Solar Powered. I agree with this quote from him about life’s challenges:
“99 problems but the sun ain’t one.”