Lately, Alex talked to me about several very specialized red light therapy topics. The "systemic effects" of red light therapy was one of these topics.
And, because there's not an extreme number of studies available on this topic, it became easier for me to take a deep dive into all the science on this topic. As often, tons of these studies are animal studies but many human studies exist as well.
A second source of inspiration for doing more research on this topic were a series of two podcasts by Dr. Jack Kruse, Dr. Andrew Huberman, and Rick Rubin, part one and part two, which are beyond excellent and awe-inspiring. These podcast episodes last 6.5 hours taken together and go into many systemic effects of infrared, visible, and ultraviolet light.
For nerds, topics such as the collagen and water systems as semiconductors across the body are included and a systemically pervasive melanin system across the body. If you've got time, I highly recommend checking out that podcast.
But, in today's blog post, we'll talk about the systemic effects of red light therapy. You'll find a table of contents on my approach below:
Table Of Contents
- "Systemic Effects" Of Red Light Therapy Definition
- 18 Systemic Effects Of Red Light Therapy
- Conclusion: Bring On The Red Light Therapy Systemic Effects Revolution
"Systemic Effects" Of Red Light Therapy Definition
So what do I and the scientists in the red light therapy space mean when talking about the "systemic effects" of red light therapy?
A systemic effect is a non-localized effect. So let's say you're treating a sprained ankle. And, after a few days of several red light therapy sessions a day, you're noticing that your hip pain improves as well.
That's a systemic effect right there. Another example is when you're applying red light therapy to the brain. Perhaps you're using a Vielight product up your nose. In that case, the blood is so-called "irradiated". That blood moves not only through your brain but your entire body and will have effects in many different places. The blood will pass along many organs such as the heart, lungs, lymph system, and more, all affecting these tissues.
How to understand this principle?
Well, in my opinion, it isn't good to view the human body as a machine. A car is a simple example thereof. A car is mechanistic. And, if you have a flat tire because you drive through a nail on the road, only that tire is damaged. The rest of the system, all the car's mechanical parts, are unaffected.
The human body, on the contrary, is an organism. So in a way, everything affects everything else. If, like that car, you have a nail driving through your feet, it's not just your feet that are affected. Your lungs, heart, spine, circulatory system, brain, and especially the immune system are affected. Pain is generated in the spine and brain. The immune system creates inflammation around the affected area and probably throughout the body. Your breathing becomes heavier and your heart rate increases dramatically immediately. And, while you're recovering, your resting heart rate will stay higher for weeks, perhaps, until the wound has healed. Your nutritional demands shoot up as you're recovering. And, due to the higher stress hormones such as cortisol and adrenaline, digestion may be altered, your sleep may be impacted, and so forth.
Organisms, therefore, are highly complex, and you cannot stipulate a simple cause-and-effect relationship. The juxtaposition between mechanism and organism has a long philosophical tradition that I won't explore here (1; 2; 3). But hopefully, the examples above illustrate the differences sufficiently. In modern scientific terms, organisms are "complex systems". If you change one variable in a complex system, all the other variables may be and often are affected to one degree or another.
Financial markets and the climate are examples of such complex systems. The human body is too. And to re-iterate, in mechanical systems affecting one part won't affect another part. If I break a leg off the chair I'm sitting on the rest of the chair is unaffected. If a room of my house burns down and the fire doesn't spread (not taking smoke damage into account), the rest of my house is unaffected. So mechanisms usually pertain to inert objects.
Next up, let's look at some examples of systemic effects, specifically those within red light therapy:
18 Systemic Effects Of Red Light Therapy
I reviewed all available studies on the systemic effects of red light therapy. I used Vladimir Heiskanen's Photobiomodulation (PBM) research - a comprehensive database for this, as he categorized studies on red light therapy's systemic effects there. You can find these studies yourself by searching for "systemic effects."
I've also subdivided all the results by benefit/effect. In case there were studies investigating a systemic effect and nothing was found, I've mentioned that.
You can easily scan these benefits/effects below:
1. Bone Formation
- In a 2014 study, 24 rabbits were divided into two groups (4). One group received red light therapy at 830nm light. A 4 Joule dose was used every 48 hours. The light was applied to the right paw. The animals received a screw in their "tibia," the biggest bone in the lower leg.
The left tibia that didn't receive any red light therapy at all showed better bone repair in the animals that were treated with the 830nm light than the control group. So even though the researchers didn't treat bone formation/repair with light on that side of the body, that outcome still improved on a systemic level.
- Another study looked for systemic effects in rats (5). The systemic effects weren't found and only local effects were shown for bone repair.
The researchers were brilliant as they divided the animals into four groups in total. Group number one didn't receive treatment, group two received treatment but not to the local area where the bone formation ought to occur. Group three received treatment in both the local area and far away from it. And group four received light on the local area only. Only in the early stages of bone formation did groups three and four outperform groups one and two. In later stages, the outcomes were similar.
- Although overall there's some contradictory evidence I think some systemic effects for bone formation can be claimed to exist
2. Alzheimer's Disease
- A 2022 review explored the non-pharmacological options for treating Alzheimer's Disease (6).
Many other factors that influence brain health are affected as well. The researchers write:
"Pathway enrichment analysis revealed significant upregulation of genes including stem-cell-related CXCR4 signaling, adipocytokine signaling, oxidative stress response pathways, and those relating to cell proliferation and migration" (8).
Many different mechanisms by which local treatment outside the brain affects physiological risk factors for Alzheimer's disease exist.
For instance, by treating the bone marrow in a non-brain area of the body, eventually, the "beta-amyloid" plaques that are posited to cause Alzheimer's disease deposits are reduced in some brain areas. Learning and memory improved while beta-amyloid deposits went down with a whopping 68%.
- I could mention many other mechanisms here that are included in the review. But it's better if you want more information on this topic to read it yourself (6).
- Another review from 2016 confirms these effects (9; 10). By stimulating the mesenchymal stem cells in the bone marrow, outside the brain, health effects for Alzheimer's disease are nevertheless accomplished. Beta-amyloid was better broken down once more here. Learning and memory capacity improved as well.
- If you're interested, a 2019 review takes a deeper dive into this topic (50).
- A 2018 study used light on the back and on the legs for people who had both lower back pain and depression (11). The study used 660nm and 850nm light. 12 spots on the tights and lower and middle back were treated in total, with a high power output of 100 mW/cm2 but only a 30-second treatment time.
Overall, the depression score improved significantly in the group receiving the red light therapy.
So, shining light on the lower parts of the body seems to have a systemic effect in that the brain is likely indirectly affected. Hopefully, these effects can be tested in more higher-quality studies, as this study had some limitations.
4. Parkinson's Disease
- Once more, a similar outcome as what we had on Alzheimer's disease, this time concerning Parkinson's. In a very recent 2023 study, animals received red light therapy at the abdomen and legs and received brain-health benefits (12).
Specifically, the dopaminergic cells were affected again by shining light on the abdomen or legs. Not only was the effect strong, the researchers speculate that the effect of shining light on the legs and abdomen gives a more substantial effect than by using transcranial red light therapy (such as the Vielight).
Other similar studies confirm these results (14; 15; 17).
For instance, in one study cited animals were treated with red light therapy very distal from the brain, on the body (7). There was still a protective effect for the "substantial nigra", the main dopaminergic center in the brain.
Also, the key here is to understand that even if we used transcranial red light therapy, the light never reaches the dopaminergic centers of the brain directly. A 2021 review study confirms this (13). The researchers write:
"In relation to Parkinson's disease, given that the major zone of pathology lies deep in the brain and that light from an extracranial or external photobiomodulation device would not reach these vulnerable regions, stimulating the distressed neurons directly would require intracranial delivery of light using a device implanted close to the vulnerable regions. For indirect systemic stimulation, photobiomodulation could be applied to either the head and scalp, using a transcranial helmet, or to a more remote body part (e.g., abdomen, leg). In this review, we discuss the evidence for both the direct and indirect neuroprotective effects of photobiomodulation in Parkinson's disease and propose that both types of treatment modality, when working together using both intracranial and extracranial devices, provide the best therapeutic option." (13)
So, you'll need to place a red light therapy device directly inside the brain if you want lots of light to reach the regions affected by Parkinson's disease. All the effects we're getting are therefore dependent in a big part on the systemic effects of red light therapy.
Overall, in both Parkinson's disease and Alzheimer's the red light therapy is neuroprotective, so it prevents cell death that these diseases are both characterized by (15).
5. Atherosclerosis (Heart And Blood Vessel Disease)
- In a 2012 study rabbits were fed a high cholesterol-causing diet (18). One group of rabbits then received light treatment and another cholesterol medication. Result?
The light therapy worked just as well as the cholesterol-lowering medication in reducing plaque formations in the arteries and lowering overall cholesterol levels.
20 minutes of daily "polychromatic light therapy" - meaning that there's a full spectrum of light emitted, not just red - had superior effects to 5 minutes per day. Blood flow also improved due to light exposure.
Please keep in mind that here, once again, light affects tissues at a far deeper level than it penetrates. So there are probably many factors responsible for a kind of "domino effect" whereby the light has effects deep inside the body.
- In another 2013 study, blood flow was tested in human participants (19). Only one treatment session was used and red light therapy to the foot's arch didn't improve blood flow or oxygen saturation across the body.
- Another 2021 study did find improvements in systemic blood flow (20). 660nm and 850nm light were applied here. The LEDs were only applied to the right foot of the study participants. Both feet saw a physiological response to the light, however, indicating changes in the central nervous system. The researchers speculate that there's a mechanism in both the nervous system and circulatory system that responds to the light.
- One more 2002 study confirms this outcome (21). People who have diabetes either received a real or a sham red light therapy intervention. These people also had blood flow problems. By irradiating one of the two feet with red light therapy, both feet had an increase in temperature and blood flow. There was a 1.7 degrees Celsius in the foot that didn't receive any red light therapy treatment, if the other foot did receive a treatment.
- In a 2008 study, the back of the hand was irradiated by 385nm (UV) to 750nm (NIR) light (22). Blood flow in the irradiated hand increased by 32% after 2 minutes and 45% after 20 minutes. In the non-irradiated hand, blood flow increased 9% in 5 minutes and 39% in 20 minutes, almost equally as good as the irradiated hand!
- Far infrared light may affect blood coagulation despite research quality being low (23). Only in vitro studies are available now.
- Light treatment affects stem cells that are available in the blood, as well as parts of the immune system such as macrophages (24). As a result, many different health outcomes may be affected by this. The researchers write:
"These cells may consequently home in on the impaired target organs and improve their function, as has been previously shown in experimental animal models." (24).
- One more recent 2021 study had an extremely lovely setup (52). The study's outcomes were cholesterol levels, blood pressure, triglycerides, and glucose levels. All of these biomarkers are extremely important for preventing heart disease.
Participants were divided into six groups. One group received no red light therapy, three others at different spots of the radial artery in the arm, one group received light in the mouth under the tongue, and one group got the therapy both under the tongue and through the nose (for targeting the brain).
The full text of the study states the following about the results (53):
"The results of the present study indicate that ILIB can be safely used as an adjunct method to regulate blood pressure (systolic and diastolic), glucose, triglycerides and cholesterol (total, LDL and HDL). [...] In addition, treated patients have indicated significant improvements in physical performance, mental sharpness, cognitive levels, weight loss and quality of lives."So, that outcome is extremely promising. Spot treatment, such as light received on the arteries of the arm or up the nose, will thus have systemic effects for heart and blood vessel health. Even the most important parameters, such as blood pressure and blood glucose, are affected.
Well, you may know that Alex just did a terrific experiment lately with the Omnilux Mask for Men, with before and after pictures. In that video, Alex taped one part of the mask so that one part of his face wouldn't receive any treatment.
The problem in hindsight - I didn't know this either yet, so don't blame me! The problem is that there is somehow a systemic effect from skin treatment. In a study, participants with acne received treatment with 1,450nm light three times per month on average on one part of their faces (25).
So here's the super surprising outcome:
"Within participants, on average, the lesion count reduced by the same amount on both sides of the face [median 0, 95% confidence interval (CI) -4 to 2]. On average, acne grade reduced by the same amount on both sides (median 0, 95% CI -1 to 0). Twelve months after the last treatment (n = 23) the change in lesion count and grade between the treated and control sides of the face remained similar. Treatment was well tolerated." (25).
- A 2018 study confirms these effects, showing that systemic effects exist in skin treatment (26). Other studies also show a systemic effect, although the treated side receives more benefits than the untreated side (27). After six months, the treated site looks slightly less wrinkled than the untreated side.
7. Diabetes And Blood Glucose Management
Diabetes has many side effects such as retinopathy, where the blood vessels of the eyes are damaged. In a 2015 study, some diabetic rats were exposed to red light therapy while others were not, to manage symptoms (27). The heads of the rats were covered so they wouldn't receive any light exposure.
Although the language is quite complicated, here are the results and conclusion section of the study:
"Results: [Photobiomodulation] intervention improved diabetes-induced changes in superoxide generation, leukostasis, expression of ICAM-1, and visual performance. PBM acted in part remotely from the retina because the beneficial effects were achieved even with the head shielded from the light therapy, and because leukocyte-mediated cytotoxicity of retinal endothelial cells was less in diabetics treated with PBM. SnPP+PBM significantly reduced iNOS expression compared to PBM alone, but significantly exacerbated leukostasis. In study 2, PBM largely mitigated diabetes-induced retinal calcium channel dysfunction in all retinal layers.Conclusions: PBM induces retinal protection against abnormalities induced by diabetes in pigmented animals, and even as an intervention. Beneficial effects on the retina likely are mediated by both direct and indirect mechanisms. PBM is a novel non-pharmacologic treatment strategy to inhibit early changes of diabetic retinopathy." (27)
- In simple terms, rats' eye health improved, and retinopathy symptoms decreased. Mechanisms that explain this effect can be found in how the immune system is affected, systemic levels of nitric oxide, and others.
- One more study investigates the effects of light therapy on people with diabetic neuropathy (37).
Diabetic neuropathy is another common side effect of diabetes, which is mostly nerve degeneration in the hands, feet, and lower legs. The light was applied to the muscles of the feet. A blend of 810nm and 980nm light was used at a 20%-80% ratio. The light was also emitted at the lumbar region, the lower back.
Results? The functional capacity of the participants receiving the light treatment was far better than the performance of the controls. Inflammation also went down in the intervention group. Pain and quality of life also improved in the intervention group.
Also, one important thing to remember is that even if you'd project this light locally into the body where the nerves are located, such as the hands, feet, and lower legs, it still wouldn't reach the nerves, arguably. The light only penetrates several millimeters for the wavelengths that penetrate the deepest, such as 810nm light and 1,070nm light. Depending on the nerve - some of which are more superficial such as the radial nerve and some are located deeper like the ulnar nerve and many in the lower leg - most light won't reach these nerves. So red light therapy relies largely on a systemic effect there anyway.
8. Androgenetic Alopecia (A Common Form Of Hair Loss)
- In a human study, 100 patients with androgenetic alopecia were enrolled (27). One part of their head received a sham treatment (not real, for placebo correction), while the other received the real intervention.
Treatment was made up of three 30-minute sessions per week. As a result, both sides of the body saw improvement in hair quality and coverage, even thought the intervention side did better. The sham-controlled side still received benefits though, surprisingly.
Hair thickness, the number of hairs, the coverage of hair on the scalp, and the researchers' assessment all improved a bit more on the intervention side. The study protocol was applied for 24 weeks, so you'll probably have to wait a while to get the best results. Why? The results were better with treatment after 24 weeks than after 12 weeks - so you'll have to stick to the treatment for hair loss purposes for a while.
9. Heart (Myocardial Infarction)
- The systemic effects of red light therapy in case of a heart attack were studied (28). 808nm light was used.
It turned out that applying the light to the bone marrow reduced heart scarring after a heart attack. Circulating stem cells were also 2.5X higher in the light-treated group than the group that didn't receive light treatment. Moreover, the density of blood vessels was way better in the light-treated group.
- A 2011 rat study confirms these effects (29). Light was applied to the tibia bone, the biggest bone of the lower leg. The scarring process after a myocardial infarction was way better in the group receiving the light. And the infarct size was reduced significantly compared to the control group.
- For stem cell therapy with the aim of improving heart and brain health, irradiating the bone may be a very promising strategy for getting the most out of the therapy (51). When these stem cells are injected, they travel to the infarcted tissue in the heart. Red light therapy may optimize the entire environment for optimal stem cell acceptance in the heart as well as ensure these cells arrive there.
10. Systemic Inflammation
- Next up, there's a 2006 human study (30). 480nm - 3,400nm (NIR or MIR) light was applied to the sacral area, the lowest part of the lower back. Overall inflammation levels across the body, measured in the blood, fell dramatically after that session after half an hour already. Researchers state:
"Exposure of a small area of the human body to light leads to a fast decrease in the elevated pro-inflammatory cytokine plasma content and to an increase in the the anti-inflammatory factor concentration, which may be an important mechanism of the anti-inflammatory effect of phototherapy. These changes result from transcutaneous photomodification of a small volume of blood and a fast transfer of the light-induced changes to the entire pool of circulating blood." (30).
That result is incredible and I'd like to see more follow-up studies as so many diseases are affected by excessive inflammation. So, if you shine light on your lower back, your entire body will benefit.
Please keep in mind that full-spectrum white light was used here, with all the colors of the rainbow, so including blue, green, yellow, orange, red, and near-infrared, and potentially middle infrared (depending on how you define the cutoff points).
- The same topic was studied in another study, specifically with COVID-19 infections (31). Patients either received light treatment or a placebo. The red light therapy used 620-635nm light. The patients were mild to moderately sick from COVID-19. 8 LEDs treated the back of the patients where major arteries are located.
Once again, a massive effect on inflammation was found. Interleukin-6 levels were decreased with 82.5% for instance, Interleukin-8 with 54.4% and TNF-alpha with 82.4%. There was no change in the placebo group.
Treatment occurred twice daily for three days in total. So these effects are incredibly huge and occur pretty quickly. And it seems like the light can also help you deal with the infamous cytokine storm that COVID-19 is known for.
- Similar effects can be found in rheumatoid arthritis, a health condition also characterized by excessive chronic inflammation and immunological problems (32).
One human study is fascinating on this topic (33). Here, one hand affected by rheumatoid arthritis was treated with red light therapy while the other was not. Patients received twelve treatments over four weeks, an average of three per week.
72% of patients reported pain relief, but the results were equally good in both hands. During the treatment process, the patients didn't know which hand received the actual treatment or which didn't. All outcome measurements were equally suitable for both hands, actually, which is crazy.
- Another in vitro study confirms these outcomes (43).
11. Muscle Growth (Hypertrophy) And Muscle Strength
- An animal study shows that spot treatment, such as the vein on the tail of a mouse and the calf muscle had systemic effects (34). Muscle size was improved across the body with this treatment.
- Human studies confirm this outcome (35). There were so-called "erogenic effects" found.
12. Healing, Such As Recovery From Burns And Wound Healing
- Wound healing improves in animals in both the part of the body that is treated and the non-treated part (38). The same is true for recovery after burns and a nervous system injury.
- Another study with humans confirms this outcome (57). Areas not directly receiving light still gained wound-healing benefits.
- One animal study showed no effect for systemic wound healing (58). Others do show an effect, so most studies still posit a systemic effect (59; 60; 61; 62).
- In relation to cancer cells, light of 480nm to 3,400nm (all the way from blue light to middle infrared light) may inhibit cancer cell formation (39). If you have cancer though, I don't recommend using red light therapy before you've discussed that with your doctor.
13. Oral Health
- In animal studies, bone repair benefits for oral health exist (40). The side that didn't receive the light treatment also showed improvements in bone repair. This effect is confirmed in humans, although the quality of this study type is low (case-control) (41).
Animal studies, moreover, show increased osteoblasts with red light therapy irradiation (42).
- In animals, spot treatment causes animals to show less pain behavior than parts that aren't treated by the light (44). The researchers claim that red light therapy acupuncture could be used as a post-operative pain control therapy.
Other animal studies confirm these results (45; 46). For instance, 830nm light increases the circulating opioids for painkilling. Here, the blood was irradiated to achieve the painkilling effect.
- Not many human studies exist on this topic, but one does (47). Eighteen patients were divided into a placebo and treatment group. All of these patients received a new hip, a total replacement, because osteoarthritis or other reasons made it difficult to walk and get through daily life.
The light was applied along the incision, and a combination of 640nm, 875nm, and 905nm light was used with both LEDs and lasers. Overall pain intensity went down as well as inflammation, as a result of red light therapy. These inflammation levels are markers for systemic inflammation, not local.
15. Allergic Rhinitis (No Effect Found In Studies)
- No effects were found in an animal study for testing the systemic effects of red light therapy in allergic rhinitis (48). Hay fever is an example of allergic rhinitis, although the disease is more encompassing.
Local benefits were found. This again demonstrates why so many people with allergic rhinitis benefit significantly from this treatment. Use a Vielight, for instance, if you want fewer symptoms or hay fever or allergic rhinitis.
16. Airway Health
- This study divided human patients with pneumonia into two groups (49). Both groups receive conventional therapy, such as physical therapy. However, only one group receives red light therapy at 940nm light, with a 300 LED panel. That panel was projected at the chest and abdominal area. Treatment lasted daily for seven days.
Here are the impressive results of the study:
"Results: There was a statistically significant recovery difference after treatment in the LED group compared with the CON [Control] group for erythrocytes, hemoglobin, leukocytes, segmented and band neutrophils, lymphocytes, and monocytes (p < 0.05). The greatest differences between the LED and CON groups were lymphocyte count reduction (60% vs. 16%), erythrocyte increase (86% vs. 35%), and leukocyte reduction (28% vs. 15%)." (49).
So, on a systemic level, there are significant effects on the blood, such as the number of red blood cells, white blood cells, and different immune cells.
17. Thyroid (No Effect Found In Studies)
- Animals received either no light therapy or red light therapy up the brain (54). 830nm light was used for 13 days. The red light therapy treatment didn't result in any systemic effects, as levels of thyroid hormones didn't differ. Both T4 and T3 levels were measured in the blood.
Don't worry too much about this outcome, though - if you've got thyroid problems, I know from looking at the studies that the effects of red light therapy shone directly on the thyroid are pretty strong and potentially life-changing! In this case, you'll probably have to shine the affected area and not opt for systemic effects.
Another animal study confirms these results (55). No effects on the thyroid gland were found using 830nm light.
- Poor mice were injected with snake venom in this study (56). 633nm and 904nm light was tested and the latter had a better outcome. Besides better local recovery at the place where the snake venom was applied, systemic effects also happened. Biomarkers for recovery, such as creatine kinase, lactate dehydrogenase, alkaline phosphatase, and acid phosphatase, all returned to normal quicker than with the 633nm group or control group.
And that's it. The systemic effects of red light therapy. Quite a few effects and many to be discovered, arguably.
I'll conclude with that and give you my 30,000-foot view:
Conclusion: Bring On The Red Light Therapy Systemic Effects Revolution - And Light Therapy In General!
In the introduction, I talked about the epic Dr. Jack Kruse, Dr. Andrew Huberman, and Rick Rubin part one and part two interviews. It's quite likely that Dr. Kruse has found several underlying mechanisms by which light can have systemic effects.
These red light therapy studies I've quoted in this blog post support that idea. Of course, as always, these ideas will be further refined over time and how we view this thesis's details will be revamped.
But nevertheless, what's most important here is that there's overwhelming evidence that systemic effects of red light therapy exist. Whether it's for pain, muscle growth, systemic inflammation, brain diseases or bone formation, there's ample evidence that treating one area of the human body also affects others.
This doesn't mean that you should only use spot treatment, though. Full-body treatment probably has far superior effects than just treating one single area of the body. Here's an analogy to understand that principle. If you only train your grip strength in the gym, the strength of your whole body will increase. The reason is that your nervous system becomes more efficient in recruiting motor units, among others. But that outcome doesn't mean you get the best results overall by training your grip strength. All parts of the human body need to be trained if you want to become as athletic as possible (depending on the sport, of course).