Light lessons: How to brighten up your health

Light is essential for health, but most of us aren’t getting enough of it, says functional medicine practitioner Dr Damien Downing. Here’s what you need to know about light and how to put the right light back into your life

In this century, there has been an explosion in research into light therapy, or what we now call “photobiomodulation” (PBM)—the use of light (photo) to modulate life processes (bio). In 2001, there were 52 scientific papers published on the topic, while in 2021 there were 667. That’s 12 times as many, and the research is still growing. The reason is that we keep discovering more and more benefits of light therapy.

One of the first sectors to start using PBM has been the aesthetics industry. There are now any number of mask-like devices that shine red and/or infrared light on the face to improve the skin and fight the signs of aging. In health and medicine in general, we keep being amazed by how many diseases, symptoms and dysfunctions light can benefit.

So why does it work? The simple answer is because we were built that way, from the bottom up. Like every other living thing, we need the energy from the sun. And not just some of it; we need all of it.

Here’s a look at different types of light, why they’re vital for health and how to get your daily dose.

HEV light

Throughout evolution, the bright bluish light in the morning has helped us to wake up. The high-energy visible (HEV) blue component of daylight at around 480 nanometers (nm) is most important for this.¹ It’s just to the blue side of turquoise.

That wavelength is picked up by nonvisual photoreceptors in the eye, cells that respond to light but have nothing to do with seeing. They signal a part of the brain called the suprachiasmatic nucleus (SCN), which is the chief pacemaker or clock in the brain.²

Suprachiasmatic means it sits atop the optic chiasm, where the optic nerves from the two eyes meet and cross, in a perfect position to collect light information. That sends a signal to the pineal gland to switch off production of the neurotransmitter and hormone melatonin, which starts the day in your brain. Without that signal, we may experience a breakdown of our normal circadian rhythm, known as chronodisruption.

As well as the obvious consequences—insomnia, fatigue—this can have a lasting impact on health, aging and diseases such as diabetes and even some cancers.

How to get more HEV light

Get outside. For a healthy body clock, get outside as soon as you can after waking, with no glasses on or contact lenses in, and look up at the sky. The best time to get out is early in the morning, when you have the best chance of catching both HEV and UVA light (see below).

Obviously, don’t look directly at the sun—you don’t need to. Just look up at the sky to get daylight hitting the nonvisual photoreceptors in your eyes and sending the wake-up message to the brain. Do it for a few minutes if it’s sunny, and longer if it’s darker.

Look out of a window. If you can’t get outside, at least stick your head out of a window and look up for five minutes on a bright, clear day, or longer if the weather is bad. Architects will tell you that most natural light shines downward, from the sky, so you get more light through a high window than through one on your eye level.

But avoid HEV at night. The other side of the coin is that this is the same blue light that is bad for you at night and that you get from all your screens. It’s bad because it still activates the SCN and suppresses or impairs sleep. But it’s only bad because it’s detached from the other two elements of daylight—ultraviolet (UV) and infrared (NIR).

UV light

Most of us are aware that exposure to UV light activates the production of vitamin D—vital for immunity, healing and much more. But it also sparks the production of an important hormone precursor called POMC (pro-opiomelanocortin). And while vitamin D is activated only by UVB rays of wavelength about 297 nm, POMC is triggered by all UV light.

UV light hitting the eyes triggers the release of POMC from the pituitary gland, the super-regulator of hormones in the body. This quickly leads to increases in all its multiple molecular products in the bloodstream, making POMC a major part of that whole-body regulation process.

POMC is also produced in the skin in response to UV light.³ This happens in the epithelial cells lining the microvessels of the skin.⁴ Released locally, POMC is split up by enzymes into three categories of hormone-type molecules, and these “offspring” have a local effect on the skin, most obviously in things like tanning (protection against overdose of the same UV light) but also in damping down inflammation and promoting repair.

All wavelengths of UV light have this effect. The strongest effect comes from the highest-energy UVC, to which we are never exposed unless we go into space. The next strongest comes from UVB, which also produces vitamin D in the skin.

The weakest one is UVA, which is 95 percent of the UV light that does reach us on the earth’s surface. It is orders of magnitude weaker in effect than UVB, but there is more of it around, certainly in the middle of a sunny day.

POMC and its offspring molecules are then carried in the bloodstream to the central system of hormonal regulation, the hypothalamic–pituitary–adrenal axis, where they contribute to the effect on the whole body. And because there is a lot of skin surface, there can be a lot of hormones released and a lot of impact on general functioning.

This has led us to reframe skin as an important neuroendocrine organ in its own right. And the most important component derived from POMC is alpha-melanocyte-stimulating hormone, or alpha-MSH.

Alpha-MSH has the following impressive properties, but bear in mind that we need a reasonable dose of UV light to produce it:

• Suppresses appetite by making us feel full, but also increases energy production⁵
• Damps down allergic and infective inflammatory reactions, but also has direct antimicrobial effects⁶
• Reduces damage to nerves and blood vessels from trauma, ischemia or infection
• Boosts tanning (melanin production), protecting tissues from damage by excessive UV (this is where its name comes from)
• Enhances sexual arousal and function (at least in laboratory animals)

So what happens when we systematically deprive ourselves of sunlight and therefore of alpha-MSH? Probably these effects in the general population:

• Increases in overweight, metabolic syndrome and type 2 diabetes, leading to prescriptions for weight loss drugs such as Ozempic
• Increases in chronic inflammatory disorders leading to prescriptions for anti-inflammatories and analgesics
• Exaggerated but ineffective inflammatory responses to infections, leading to prescriptions for antibiotics
• Increases in erectile and other sexual dysfunction, leading to prescriptions for medications such as Viagra

How to get more UV light

Get some midday sun. UVB light is generally available only around the middle of a sunny day, although this depends on the season and where you live. Eat your lunch outdoors or take a walk in the park if you can.

Half an hour outdoors in the middle of the day will get you enough light energy to boost your alertness, energy and mood. If you can expose some skin, too, there may be enough to boost your vitamin D and alpha-MSH a bit.

Take a vacation. If you have a bolt-hole in the Caribbean or a superyacht moored off the Costa Smeralda, make the most of it. Failing that, you might want to act like the hoteliers do and take a beach holiday in January or February, when you need the sun the most.

Years ago, I used to see a lot of couples in my practice who were struggling to conceive. If the woman had a problem of menstrual irregularity, I would recommend a beach holiday with daily sun exposure as the first treatment. Often, they would return with a better menstrual cycle and succeed in getting pregnant soon after.

Get out early for UVA. UVA kicks in about an hour after sunrise and gets gradually stronger as the sun gets higher in the sky (and so is reaching you through less and less atmosphere) until solar noon, when the sun is at its highest. It triggers the release of alpha-MSH from the brain and skin.

If you’re on vacation, go to the beach or pool early in the day to get a dose of UVA before the UVB kicks in. You might even get a better sun lounger.

Be sun-sensible. We’ve been programmed into thinking sunlight is dangerous, but it only is if you’re not sensible about handling it. Little and often is the rule—stay out in the sun too long and you’ll get burnt, which serves no purpose at all.

How long is enough and too much depends on your skin tone, and you can get a personal UV meter to tell you when you should get out of the sun. Good nutrition is also important to help your body to respond well to the sun, as are supplements like omega-3s and antioxidants like vitamins C and E.

NIR light

My apartment in London has a balcony facing west. On a sunny day, even in winter, it gets direct sunlight from about 11 a.m. onward. Step outside then and, even though the air may be chilly, you can feel the heat of the sun.

That’s due to the infrared photons, which make up about half the energy we get from the sun. It’s outside the visible range of light—you can’t see it, but you can certainly feel it as warmth. It penetrates farther into the body than visible light, so it can reach important organs and benefit them.

NIR just seems to make all cells work better, but most of us are deficient in it. Before electric lights, there was a natural rhythm to our lives; you couldn’t do much indoors by night, or even by day, because you couldn’t see what you were doing.

Most work happened outside in the daytime and stopped at dusk. Then there might well be a log fire or a campfire to enjoy for a while, then sleep. Then bright blue light in the morning and we’d start again.

That’s the 24-hour cycle that we evolved in for millions of years, and that we’re adapted to, designed for. We needed and still need both the light and the dark.

From sunlight, you get a big dose of infrared energy along with the visible light. You would also get infrared from sitting round a campfire at night. You can get a certain amount of infrared from traditional incandescent light bulbs, which have largely been phased out in favor of more energy-efficient LED bulbs.

The big drawback of incandescent bulbs is that only about 5 percent of the power they use becomes visible light—the rest becomes heat. That’s why you can now get an LED bulb that says it uses 5 W (watts) of electricity but produces the equivalent of an old 60 W incandescent bulb. This is great for energy saving but has removed another source of infrared, especially NIR, light from our lives.

Indoors, we’re screened from sunlight, and most of our lighting comes from electric lights or even from screens. Our eyes adapt so well that we don’t notice that bright sunlight is about 100 times brighter than the light above our desks. So we are all deficient in sunlight. Even worse, there’s none of that crucial part of sunlight that you can’t see, the NIR.

The best way of getting NIR is from the sun. The same real sunlight that gives you UVA and UVB also contains NIR, and even light clothing doesn’t screen it out. Getting two weeks of good exposure to sunlight, on a beach holiday for example, is a good way to get everything working distinctly better in your body and mind.

But there are other ways, including the red/NIR light boxes, masks and other devices that are now on the market. They shine light onto your skin, where it’s picked up by blood in the capillaries and carried around the body.

NIR in the body

Initially, it was thought that no light could penetrate farther than a few millimeters into the body. But this was wrong for two reasons.

First, think about the tissues that the light is going into; they are a mix of skin, fat, collagen and fluid. The light detectors we use to measure penetration tend to operate in straight lines; you shine a beam of light onto a slice of tissue, and at the other side is a tubular detector pointing straight at the light source.

This works fine if the tissue is transparent because the light goes straight through without being deflected. But it fails if the tissues are translucent (meaning you can see light through them, but you can’t see objects) because the light is scattered, so much less reaches the detector even though it may reach the tissues in all directions.⁷

The human eye is a good illustration of this; most light reaching the inside of the eye is infrared, coming in through the translucent eyelids and everywhere else. The visible light directed through the transparent lens onto the retina is just a small fraction.

The second reason we got it wrong about light penetration relates to fluid, and that’s important in two places: the brain and the womb. The brain is surrounded by clear amber-colored cerebrospinal fluid, which transmits NIR rather well, including down the folds of the brain surface to deeper parts.

Researchers took a 1-inch-thick slice of fresh human brain, shone NIR on one side of it and put an infrared camera on the other side. They could see the light clearly coming through the brain tissue, particularly in the folds, where there would be cerebrospinal fluid to conduct it even better.⁷

You can do a similar experiment for yourself; shine a light through the tissue of your hand, and you’ll see red light coming out the other side. Red penetrates well, but you won’t see the green and blue elements, which are absorbed more. This is what red light treatments use.

“Red light” is not a precise description because it’s mostly a combination of visible red LEDs at around 650 nm wavelength and invisible infrared LEDs at about 810 nm. The visible ones do penetrate the skin, but infrared penetrates much deeper.

The amniotic fluid surrounding babies in the womb has the same transmission quality as cerebrospinal fluid, meaning they can benefit from sunlight. In later pregnancy, the skin and tissues covering the “baby bump” stretch thin so they transmit more light, which the amniotic fluid conducts and scatters everywhere in the womb.

The flipside of this is that the more solid tissue the light has to get through, such as fat, the less it will reach its real target, such as muscles or the gut microbiome.

There’s a lot of discussion about whether light can influence the microbiome,8 and the answer is probably. So far the research has only really shown this in mice, and it took about two weeks to have an effect. But I wouldn’t bet on it being irrelevant for humans, and if there is a direct effect, then a big layer of fat will block it.

How to get more NIR

Get outdoors. Spend as much time in sunlight as you can without burning.

Go for green spaces. NIR is highly reflected by the environment, especially by green things. This means exposure to green spaces, forest bathing for example, doesn’t just make us feel good. It really is physically good for us.

In a green environment, close your eyes. There’s about five times as much NIR getting into your eyes as there is visible light. You can’t see it and you don’t feel it, certainly not as heat, but it does make you feel good. You want it on your skin as well as your eyes if possible.

Try artificial red/infrared light. Use light boxes, mats and other devices. They work, although the real thing is even better.⁷

Watch your weight. The more weight you put on, the more fat cells the NIR has to get through to reach other cells.

Light and melatonin

Light is crucial for the production of the hormone melatonin, which is not just produced by the pineal gland when it’s dark to help you sleep. Melatonin is also produced by every cell in the body, mostly in the mitochondria, during the day when you’re active—and it’s one of the most potent antioxidants there is.

Near infrared (NIR) light from sunlight boosts mitochondrial function in general and melatonin production in particular. So when you step outside in the morning, you switch on the adrenaline- or activity-driven local production of melatonin, and you switch off the nighttime or sleep production.

Vigorous exercise also rapidly triggers production of large quantities of mitochondrial melatonin, and if you do it in sunlight, the NIR will boost it even further.¹

The benefits of full-spectrum light

Full-spectrum light (FSL) is light that contains all the wavelengths you get from natural sunlight. It’s reasonable to assume this is our natural daytime environment, or as close to it as we can get without living in a tent.

Electrical FSL was invented by John Ott. He found out that pumpkins, apples and all sorts of plants needed FSL to develop properly. So do most animals, from fish to mammals.

Years ago I owned a share of a business making full-spectrum lighting. I installed it in my clinic and office and tried using it for sick people. It never became a successful business, but one thing we found was a very low sickness rate among the staff—nobody seemed to go off with colds and coughs.

We had a treatment unit with a couch completely surrounded by full-spectrum lights, about 25 fluorescent tubes with high-frequency “ballasts” to drive them. We treated one man with bad intermittent claudication. This condition involves furring up of the arteries that supply blood to the muscles, particularly in the legs, and causes pain through lack of oxygen sufficient to force the person to stop after a short distance. After 30 minutes under the FSL, he got up and walked briskly round the block.

There’s still a company called OttLite after John Ott, producing full-spectrum lights for wellness and to reduce eyestrain and improve clarity of vision. A quick search will show lots more businesses in the market, and lots of disputes about who has the best lights. I’m not in a position to judge that, but as someone with 30 years of experience using FSL, I can tell you that choosing a good one is worth the effort.

An organization called Science of Light (SOL; scienceoflight.org) recently started producing lights with both UV and NIR added in, designed for use whenever you’re looking at a device with a screen. It addresses all three known components of the mal-illumination problem: the lack of UV, the lack of NIR and the unhealthy radiation from the screen.

So FSL products nowadays are a much better proposition because infrared has been added in as well as ultraviolet. I’m sitting under one as I write this.

Six people who work from home regularly installed and used one of these, and they all reported benefits. These are some examples of what they told me:

• “I don’t feel drained, and my eyes don’t feel as tired as they did.”
• “I feel more energetic and physically active.”
• “I believe it helped improve my sleep cycle.”
• “My mood was better, especially before my monthly cycle.”

See Healthy Shopping: Light Up Your Life for some of the full-spectrum lights on the market.

Benefits without burning

You can and should avoid sunburn by practicing frequent brief exposure to UV light and longer exposure to near infrared (NIR). That’s what is in the daily outdoor environment, after all.

NIR is present from sunrise to sunset, even on cloudy days, and will stimulate you to make the antioxidant melatonin. Moderate exercise will also assist with that.

Regular NIR exposure will also help you to build up a solar callus—the slightly thickened top layer of skin that protects you and usually gives a smoother, healthier skin appearance.

Full-spectrum health

We need the whole of sunlight:

• Bright, high-energy visible (HEV) light in the eyes in the morning to activate daytime mode
• Ultraviolet (UVA and UVB) light on the skin to trigger the release of multifunctional alpha-MSH
• UVB light on the skin to trigger the production of vitamin D
• Infrared light (NIR) just about anywhere to boost both energy and melatonin
• Dark night to enable sleep and complete the circadian cycle

Adapted from Coherent Health: The Power of Light and Water by Damien Downing (Hammersmith Health Books, 2026)

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