The Healing Power of Light

Story at-a-glance

  • Sunlight provides a number of important health benefits, over and beyond vitamin D synthesis, that you simply cannot get from food or a supplement
  • Heliotherapy, or sun therapy, is when you use sunlight directly without removing or altering any part of the light spectrum. Early examples include the use of sunlight to treat tuberculosis prior to the discovery of antibiotics
  • Humans are adapted to sunlight as a complex stimulus that, at a certain dosage, keeps your entire system running; when you remove that stimulus (sunlight), you end up with health problems


This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.

By Dr. Mercola

By now you're probably aware of the importance of vitamin D. Ideally, it's best to get it from the sun, because sunlight provides a number of other benefits as well, over and beyond vitamin D synthesis, that you simply cannot get from food or a supplement.

Alexander Wunsch is a German physician of holistic medicine and photobiology. He's also the CEO of Medical Light Consulting in Heidelberg, Germany. He believes, like I do, that the sun is a great healer.

He believes that it's the unity of biophysics and biochemistry that allows for life, and provides the human body with the essential ingredients for optimal health.

Earlier in his career, he invented a cranial electrotherapy stimulation (CES) device, which helps you to optimize your brain function and beneficially influence your nervous system and hormone system.

"It was called Brainman and was in the early '90s. [Then] I got interested in other frequency ranges; not only the brainwave frequencies but the frequencies we can capture with our ears and detect with our eyes," he says.

I got interested in the method called chromotherapy... which is the treatment of the body with colored light...

For example, green initiates a chain reaction in your system, which tends to balance your autonomous reactions. The blue light of the sky induces other specific reactions. I found out that I could use this quite successfully to alter biological functions."

The Importance of Heliotherapy for Optimal Health

After working with the visible part of the color spectrum, Alexander began investigating the effects of near-infrared, which is the frequency range coming after visible red, at the end of the rainbow color spectrum. Near-infrared is a very important radiation, and more than 40 percent of visible light is near-infrared.

"In nature, it's a very important spectral portion of the whole spectrum we are given by the sun," he says. "Finally, I got interested in the effects of ultraviolet light.

I knew from my medical studies that we have to be careful with ultraviolet light. I started to collect old textbooks on light therapy, light biology, or photobiology. What I learned from these books was quite amazing.

Most of them were written in the times before the era of antibiotics. The doctors, the physicians, had to be very diligent using sunlight and also using ultraviolet light sources for artificial application of ultraviolet radiation. Finally, I came to the conclusion that we are perfectly adapted to the radiation of our sun."

Heliotherapy, or sun therapy, is when you use sunlight directly without removing or altering any part of the light spectrum. Early examples of heliotherapy include the use of sunlight to treat tuberculosis prior to the discovery of antibiotics, and they did that quite successfully.

Sunlight was also used to treat rickets and other diseases associated with light deficiency (which we now know as vitamin D deficiency). According to Alexander humans are adapted to sunlight as a complex stimulus, and when you remove that stimulus (sunlight), you end up with problems.

"We need the stimulus at a certain dosage to keep our system running," he says. "Sunlight exposure is definitely much more than tanning. Tanning is just what you see, what is visible on your skin...

This is one very important part: if your skin is exposed to sunlight, you will experience some invisible changes in your circulatory system. The capillaries, for example, will be modified under the influence of sunlight.

The skin is closely linked to the autonomic nervous system (ANS). It's a kind of an external organ of the vegetative system in your body. For example, when you live under summer conditions, we need much more water in our system in order to produce enough sweat, in order to cool down our body.

This means that sunlight not only influences the skin, but it influences all the inner organs as well. It's a kind of concert, which is started by the stimulus of sunlight."

Vitamin D: A Chronobiological Stress Hormone

Wunsch views vitamin D as a kind of "seasonal stress hormone," explaining that chronobiological stress hormones such as adrenocorticotropic hormone (ACTH), and adrenaline-cortisol hormone blends are what enable you to get up in the morning, and help regulate the blood sugar concentration in your body, just to name a couple of their functions. 

"When you think about the different tasks between summer and winter, it's like reprogramming your heating system in your house, because in summer, the main focus is cooling down the system.

You have an intake of 1.5 kilowatts on the square meter, which means if you stay naked out in the sun, your body has to digest a lot of energy, which in the end, is transformed into thermal energy.

Cooling is the main task during the summertime and heating is the main task during winter time. This is linked to, for example, the circulatory system. It's linked to our digestive system and so on," he explains.

When we talk about sun exposure to optimize vitamin D production, we're really only looking at a small portion of the action spectrum of light, because ultraviolet B radiation is the only portion able to photosynthesize vitamin D in your skin.

"As a consequence, when you think vitamin D is the only benefit you can get from sunlight, you will automatically focus on the ultraviolet B radiation [while ignoring all other portions of the light spectrum]," he notes.

But the health effects and benefits of sunlight are not restricted to ultraviolet B. Swiss specialist Dr. Auguste Rollier, who has written text books on heliotherapy, emphasized that the composition of the different parts of the light spectrum are of crucial importance to achieve all of the benefits you can get from the sun.

"For example, when you look at the cellular effects of ultraviolet B and ultraviolet A, it really depends on the dose if the radiation is beneficial to your system, or if the radiation unfolds odd reactions or effects as well. What we can say is that ultraviolet radiation photosynthesizes vitamin D on one hand, but on the other hand, it's able to seriously damage cells. Ultraviolet B can alter the DNA structure. Ultraviolet A can produce and photosynthesize the reactive oxygen species in the tissue.

To cope with these side effects, your skin needs other parts in the spectrum. For example, the near-infrared and the red light, which we find in sunlight in a pretty large amount, provide metabolic power to the cells...I'm convinced that the full blend of specific wavelengths we have under the sun enables our body to react in the best way," Mr. Wunsch says.

The Drawbacks of Windows and Artificial Lighting

It's important to realize that when we're talking about sunlight exposure, the light spectrum you're exposed to when sitting by a window is not the same as the spectrum you're exposed to outdoors. Sunlight filtering through a window is actually more akin to poor quality artificial light, due to the fact that parts of the light spectrum are being filtered out. In order to be energy efficient, modern windows filter near-infrared light, and as mentioned, this range actually helps counteract some of the harmful effects of ultraviolet light.

"We face a common problem in the artificial light area and in the use of window glass. Both are factors which eliminate important parts of the spectrum," Wunsch says. "For that reason, we have to be careful with windows and artificial light. Let's say, you sit in your office and your eyes signal, "There is enough light around me." Your intrinsic hunger for light may be satisfied by the light you perceive through your eyes. But there is an expression called "biological darkness." This is what most of us might experience when we are indoors, sitting behind windows under artificial light sources."

One of the ways you can avoid that, when the weather cooperates, is to open up your windows to get unfiltered sunlight exposure. Alternatively, take a walk outside, wearing minimal clothing. Interestingly, and contrary to what most of us have been told elsewhere, Wunsch notes that the only artificial light source that provides natural full-spectrum light is the incandescent lamp, which is currently being phased out and replaced with energy-saving bulbs like LEDs.

"You have all the different wavelengths contained in the spectrum [in the incandescent bulb]. There is a cut in the emission by the glass tube in the short wavelength part, but in the visible part and in the near-infrared part, the incandescent lamp is pretty active. The incandescent lamp is the only artificial light source with a natural spectrum, with a natural spectral distribution," he says.

"I have a distinction regarding artificial light: 1) artificial light with natural spectrum represented by incandescent lamps and halogen lamps, and 2) artificial light with the synthetic spectrum, which produces a kind of light surrogate. It's a low-quality replacement of what your body expects from light. In nature, there is a natural alliance between luminance on one hand and warmth or heat on the other. All natural light sources represent this alliance of heat and luminosity. This is what your body expects and this is what your body needs...

All the spectra, which are produced in the way that you have light and heat in combination, lies between the color temperature of a candle with 2,000 kelvin and the color temperature of sunlight with 6,500 or 6,000 kelvin. In between we have the incandescent lamp with 2,700 kelvin, which gives you as well 100 percent or CRI 99 to 100 color rendition. This already demonstrates that our eye seems to be closely adapted to the natural way to produce light. This is thermal light...

Our eyes are very intelligent sensors, which make a kind of white balance automatically. When you measure or even when you look at colors under candlelight, and this is the only light source around, you will have a full-color rendering. You have the full-color rendering with incandescent lamp, halogen lamp, and you have it with sunlight as well. I measured it personally. I do not believe what I'm told. I always try to get direct proof. I measured it, and it's true. Our eye is able to adapt to the color temperature of the light as long as the light follows the natural laws, which are represented by the natural light sources – sunlight and fire."

Disregarding Biological Adaptations Tend to Promote Poor Health

Your body is adapted to very specific lighting conditions: bright unfiltered daylight during the day, and low level fire-light in the evening followed by darkness. This rhythm of light and dark is what drives your circadian clock. This is discussed in much greater depth in my interview with Dan Pardi. Modern life, however, has inverted these natural conditions, leading to light deficiency during the day, and light excess at night. To correct the situation, you need to make sure you receive a healthy dose of sunlight ideally around high noon, and at night, try to reduce the levels of light you're exposed to. I recommend getting an hour or more of sunlight during the middle of the day if you can, but 30 minutes may suffice.

To avoid skin damage from overexposure, start out with just a few minutes in early spring, and note how your skin reacts over the next two to four hours. If you notice your skin taking on a pinkish tint, stop the exposure and go inside. This is admittedly hard to do if you have darker skin, but you should still be able to notice a slight reddishness. Staying out beyond this phase is not going to provide you with any benefit, only potential skin damage, so do pay attention and avoid overexposure. That said, your body is intrinsically able to quickly adapt to sun exposure, Alexander says, provided you train it in a gradual manner.

"Start, for example, with five minutes. The next day you can expose yourself for 10 minutes. You just double the exposure time looking at your individual reaction in the afternoon or at night, because there is a delay in our skin reactions. There is a delay time of two to four hours... [Also, when] you go out into the sun, my recommendation would be to expose those parts of your body which normally are covered by clothes, and cover those parts of the body which normally are exposed. It means it's advisable to wear, for example, a hat with a large rim in order to protect your head and your face from overexposure."

On cloudy days, the benefit you will receive is clearly going to be reduced. However, Mr. Wunsch believes that being outside is a good idea regardless, because the heat or cold on your skin brings your skin into a reaction flow. He describes the skin is an organ that responds to environmental factors such as light and temperature, and these environmental factors allow your skin to cleanse and perform a number of adaptive functions. For example, your skin becomes thinner during the winter and thicker during the summer—provided you expose your skin in a diligent way to natural sunlight. So do go outside and expose yourself to whatever climate conditions you find yourself in.

I believe this is all sage advice worth applying. Because the more I study natural medicine, the simpler it becomes. The ultimate strategy is to replicate the practices of our ancient ancestors as closely as possible; by our lifestyle, our exposure to sun, our contact with the earth, the food that we eat and the water we drink. The further you veer off from your ancestral adaptations, exposing yourself to newer strategies and toxic chemicals, the more likely you are to contract disease, because your body is not adapted to those exposures.

Scientific Evidence of Biophotons

Dr. Fritz-Albert Popp was a pioneer of biophoton research, which is still widely disregarded in the US, despite the scientific evidence for their existence. As Mr. Wunsch notes, you can measure biophotons, and basic chemistry tells you that every chemical reaction goes along with an exchange of photonic energy. In the past, I suggested that elevated biophoton levels might be one of the benefits of eating raw food.  He agrees that biophotons are surrogate markers for the "liveliness" of food, adding:

"In each of single cell [of your body], in every second, you have around 100,000 chemical reactions going on in order to maintain the processes of life, the biological functions [of the cell]. There are some methods to measure if there is light coming from a living cell. In fact there is light coming from it. These biophotons, which are produced by biochemical reactions, you cannot say they do not exist because you can measure them.

But most scientists are unwilling to believe that these biophotons have anything to do with the regulation of the chemical processes. This is kind of strange because, as a scientist, you should not go into 'believe' or 'not believing' things. If you only look at biochemistry, you only look at 50 percent of the truth. The process of life is only understandable when you take biophysical and biochemical processes into account at a portion of 50 percent each. The biophysical part is fairly covered by the biophoton theory."

More Information

The majority of Alexander Wunsch's work is published in German, but his blog,, is bilingual, and does contain some English material. His website,, has both English and German language options, and provides basic information on how to use colored light in your home to improve your personal health. General awareness about the health benefits and importance of sunlight may still be lacking, but there are changes afoot. The United Nations Educational, Scientific, and Cultural Organization (UNESCO) has declared 2015 The International Year of Light,1 for the purpose of raising public awareness about the importance of light on human health.

"We all should be aware of the fact that when the sun were to stop shining, nothing would be alive in two or three days on this planet," Wunsch says. "When we are eating, we are eating transformed light. We can prove this scientifically, as you know. I think even if we are not able to estimate the influence light has on our biological system as a whole, it starts on the single cell [level] and it ends in our consciousness, in our mental functions. Light is a symbol in our culture, which will always be our companion."

+ Sources and References

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