I have previously written about the vast research showing that irradiation by red light or near-infrared appears to have health benefits. Thousands of research articles showing these benefits have been published.
In the scientific literature, this treatment with red light or near-infrared is called either photobiomodulation (PBM) or low-level laser (light) therapy (LLLT). I will be using the term photobiomodulation.
In photobiomodulation, the affected tissue is irradiated by light, usually from a laser or LED source. This irradiation appears to improve the function of the malfunctioning tissue.
2. Mechanisms of photobiomodulation
Most wavelengths of light (ultraviolet, blue, green, infrared) do not penetrate the skin at all. Instead, they are absorbed in the outer layers of skin.
On the other hand, red light and near-infrared belong to the so-called optical window. These wavelengths are able to significantly penetrate through the skin:
 |
| The mobile phone flashlight emits blue, green and red light. Only the red light penetrates through the finger. |
Red light and near-infrared are able to induce significant physiological changes inside the tissue. According to modern knowledge, the red light inside the cells activates the mitochondrial enzyme cytochrome c oxidase, improving the mitochondrial respiration and oxygen consumption (de Freitas&Hamblin 2016, Wang et al. 2017).
This shift in cellular metabolism leads to other changes in cell function, eg. gene expression and growth factor production (Prindeze et al. 2012).
In the scientific literature, there are numerous examples of the significant cellular effects of red light and near-infrared. Some of these discoveries were briefly presented in this dissertation from the University of Gothenburg.
Photobiomodulation results (animal studies)
| ||
Indication
|
Animal
|
Findings
|
Mouse
|
↑ATP, ↑cytochrome oxidase expression
| |
Rat
|
↑IFN-γ, ↓IgE, ↓IL-4, ↓Th1/Th2 ratio
| |
Rat
|
↑ATP, ↑mitochondrial membrane potential, ↑cytochrome oxidase, ↑memory function, ↓reactive gliosis, ↓inflammation, ↓tau hyperphosphorylation
| |
Rat
|
↑ATP, ↑cytochrome oxidase, ↑G6PD, ↑NADPH, ↑pAMPKα, ↓NADP, ↓LDH
| |
Mouse
|
↑ATP, ↑exercise performance, ↑cytochrome oxidase
| |
Rat
|
↓TNF-α, ↓IL-1β, ↓macrophage and CD8 lymphocyte infiltration
| |
Fruit fly
|
↑ATP, ↑lifespan, ↑mobility, ↓complement C3
| |
Rat
|
↓AST, ↓ALT, ↓LDH, ↓cirrhotic areas, ↓collagen deposition
| |
Mouse
|
↑IL-10, ↑IL-4, ↓TNF-α, ↓IFN-γ, ↓disease symptoms
| |
Rat
|
↓CK, ↓O2−, ↓SOD, ↓TBARS
| |
Dog, rat
|
↑ATP, ↓mortality, ↓infarct size, ↓troponin T
| |
Rat
|
↓IL-1β, ↓CX3CL1, ↓dorsal gliosis, ↓hyperalgesia
| |
Rat
|
↓TNF-α, ↓IL-1β, ↓IL-6, ↓neutrophils, ↓macrophages
| |
Rat
|
↑bone formation, ↑granulation tissue, ↑collagen fibers
| |
Rabbit
|
↑lumen area, ↓myointimal hyperplasia, ↓intima:media ratio
| |
Rat
|
↓TNF-α, ↓IL-1β, ↓hyperalgesia
| |
Mouse
|
↑ATP, ↓ROS, ↓injured area
| |
3. Human research on photobiomodulation
In humans, photobiomodulation has been studied for a few dozen different ailments. The list below shows some of these possible indications. New clinical trials are also constantly in progress.
In humans, photobiomodulation has been studied for a few dozen different ailments. The list below shows some of these possible indications. New clinical trials are also constantly in progress.
Regarding some of these indications, systematic reviews have also been published. The table below presents some of those, featuring over 6500 patients from over 140 randomized and controlled trials (RCTs).
Photobiomodulation: systematic reviews
| |||||||
Indication
|
Author
|
Review
|
Year
|
N
|
n
|
Quality
|
Results
|
Ren
|
M
|
2017
|
7
|
180
|
C
|
➕/➖ Photobiomodulation decreased pocket depth only in short term (1-2 months).
| |
Tchanque...
|
S
|
2016
|
4
|
131
|
C
|
➕ Photobiomodulation hastened the healing of foot ulcers.
| |
Zarei
|
S
|
2016
|
5
|
394
|
B / C
|
➕ Photobiomodulation was beneficial for androgenetic alopecia in men and women.
| |
Ribeiro
|
S
|
2016
|
11
|
555
|
C
|
➕ Photobiomodulation decreased pain.
| |
Delayed-onset muscle soreness
(DOMS)
|
Nampo
|
M
|
2016
|
15
|
317
|
C
|
➖ Photobiomodulation wasn’t associated with significant benefits. The meta-analysis was critisized for it’s methodological shortcomings, which might partially explain the negative result (Baroni&Leal-Junior 2016).
|
Huang
|
M
|
2015
|
7
|
211
|
B / C
|
➕/➖Photobiomodulation decreased pain, but didn’t improve function.
| |
Chen
|
M
|
2015
|
14
|
454
|
C
|
➕/➖ Photobiomodulation didn’t decrease pain, but brought functional improvements.
| |
Leal-Junior
|
M
|
2015
|
13
|
134+
|
C
|
➕ Photobiomodulation improved exercise performance and postexercise recovery.
| |
Huang
|
M
|
2015
|
9
|
518
|
B
|
➖ Photobiomodulation didn’t ameliorate pain. However, another research group re-analyzed the same material, and got a positive result (Stausholm et al. 2016).
| |
Orthodontic tooth movement
|
Ge
|
M
|
2015
|
9
|
211
|
C
|
➕ Photobiomodulation increased orthodontic tooth movement.
|
Smoot
|
M
|
2015
|
7
|
262
|
C
|
➕ Photobiomodulation decreased pain and upper limb volume.
| |
SBU
|
S
|
2014
|
18
|
1007
|
C
|
➕ Photobiomodulation decreased pain after the intervention and in the follow-up.
| |
Oberoi
|
M
|
2014
|
18
|
1144
|
B
|
➕ Photobiomodulation decreased pain and the risk of severe mucositis.
| |
Borsa
|
S
|
2013
|
10
|
147
|
B
|
➕ Photobiomodulation improved exercise performance and postexercise recovery.
| |
Gross
|
M
|
2013
|
2
|
109
|
C
|
➕ Photobiomodulation improved the markers (pain/disability/QoL/GPE).
| |
Brignard...
|
S
|
2012
|
9
|
599
|
C
|
➖ Photobiomodulation didn’t decrease pain of edema significantly.
| |
Tumilty
|
M
|
2010
|
25
|
963
|
B
|
➕/➖ Photobiomodulation was effective in 12 studies, and ineffective in 13 studies. The conflicting results might be related to treatment parameters.
| |
Chow
|
M
|
2009
|
16
|
820
|
B
|
➕ Photobiomodulation decreased pain acutely and in the long-term.
| |
Bjordal
|
M
|
2008
|
13
|
730
|
B / C
|
➕ Photobiomodulation decreased pain.
| |
Bjordal
|
S
|
2006
|
9
|
609
|
B / C
|
➕ Photobiomodulation decreased pain.
| |
Chow
|
S
|
2005
|
5
|
273
|
C
|
➕ Photobiomodulation decreased pain.
| |
Bjordal
|
S
|
2003
|
11
|
565
|
C
|
➕ Photobiomodulation decreased pain.
| |
M = meta-analysis; S = systematic review; N = amount of controlled studies; n = amount of subjects
| |||||||
The table includes my estimation of the quality of the evidence. B stands for “moderate evidence” and C for “weak evidence”. My estimates are not based on as strict criteria as GRADE scoring used by Cochrane Library.
It can be seen that many of these systematic reviews were published between 2014 and 2016. Photobiomodulation research is currently accumulating with a very fast pace, approximately 400 research articles per year. There will probably be dozens of new systematic reviews before the year 2020.
My overall conclusion of these systematic reviews is that photobiomodulation appears to be beneficial for a large variety of different indications. The evidence is mainly of moderate/weak quality, which implicates a need for additional randomized trials of high methodological quality.
My overall conclusion of these systematic reviews is that photobiomodulation appears to be beneficial for a large variety of different indications. The evidence is mainly of moderate/weak quality, which implicates a need for additional randomized trials of high methodological quality.
4. Animal research on photobiomodulation
Photobiomodulation has not been studied solely in humans. If you look at the literature, you can find studies conducted also in rats, mice, rabbits, dogs, pigs, minipigs, monkeys, sheep, horses, bovines, cats, sand rats, hamsters, gerbils, guinea pigs, frogs, toads, bumblebees, fruit flies, sea urchin larvae, snails, roundworms, earthworms and flat worms.
In animal studies, photobiomodulation has been studied with good results for nearly a hundred different indications. Impressive results have been reported for autoimmune diseases, brain diseases, osteoporosis, joint inflammation and dozens of other diseases:
As the list shows, there is a vast literature on photobiomodulation. The total amount of these animal studies indexed in PubMed is more than 1100.
5. The comprehensive research database
In order to learn as much as possible about red light and near-infrared, I have spent a plenty of time compiling photobiomodulation research into a spreadsheet. My spreadsheet includes currently more than 3800 scientific articles on the subject:
Here are some statistics that I've made based on the data. The PBM literature includes...
6. Photobiomodulation research examples: Eyes
6.1. Human studies
In 2008, two German physicians published a retrospective report of 203 patients with the age-related macular degeneration. According to the paper, treatment with near-infrared light (780 nm) improved visual acuity in 95 percent of the patients, and the treatment was also associated with reduced edema, bleeding, metamorphopsia, scotopia and dyschromatopsia.
The beneficial results lasted for 3-36 months after the treatment. The report was generally very promising. However, these kinds of retrospective reports are considered to have a high risk of bias, and should be confirmed by high-quality controlled studies (Ivandic&Ivandic 2008).
In 2016, Canadian researchers published very similar results from an observational study, where they used mainly a red LED light (660 nm). The therapy was associated with improved visual acuity and contrast sensitivty, and reduced drusen (Merry et al. 2016). This research group is currently working on a randomized trial (LIGHTSITE1) in order to repeat these findings with a proper methodology.
6.2. Animal studies
Photobiomodulation indications (animal studies)
| |
As the list shows, there is a vast literature on photobiomodulation. The total amount of these animal studies indexed in PubMed is more than 1100.
5. The comprehensive research database
In order to learn as much as possible about red light and near-infrared, I have spent a plenty of time compiling photobiomodulation research into a spreadsheet. My spreadsheet includes currently more than 3800 scientific articles on the subject:
Here are some statistics that I've made based on the data. The PBM literature includes...
- 500 randomized studies (incl. 220 double-blind and 80 single-blind studies)
- 1170 animal studies (800 rat studies, 220 mouse studies, 90 rabbit studies)
- 620 in vitro studies
- 340 narrative reviews & editorials
- 130 systematic reviews (incl. 54 meta-analyses)
6. Photobiomodulation research examples: Eyes
6.1. Human studies
In 2008, two German physicians published a retrospective report of 203 patients with the age-related macular degeneration. According to the paper, treatment with near-infrared light (780 nm) improved visual acuity in 95 percent of the patients, and the treatment was also associated with reduced edema, bleeding, metamorphopsia, scotopia and dyschromatopsia.
The beneficial results lasted for 3-36 months after the treatment. The report was generally very promising. However, these kinds of retrospective reports are considered to have a high risk of bias, and should be confirmed by high-quality controlled studies (Ivandic&Ivandic 2008).
In 2016, Canadian researchers published very similar results from an observational study, where they used mainly a red LED light (660 nm). The therapy was associated with improved visual acuity and contrast sensitivty, and reduced drusen (Merry et al. 2016). This research group is currently working on a randomized trial (LIGHTSITE1) in order to repeat these findings with a proper methodology.
6.2. Animal studies
Research groups from a wide range of countries (UK, Australia, Spain, Iran, Italy, India, USA) have studied the effects of photobiomodulation on retinal diseases.
According to the study results, red light appears protective against various sources of retinal degeneration, eg. age-related macular degeneration, diabetic retinopathy, light-induced retinal damage, oxygen-induced retinopathy and methanol toxicity (Eells et al. 2016, Geneva 2016).
Photobiomodulation: effects on eyes
| ||||||
Reference
|
Country
|
Animal
|
Model
|
💡
|
λ (nm)
|
Results
|
Iran
|
Rat
|
Methanol toxicity (retinal injury)
|
LED
|
670
|
↓RGC death, ↓injury of visual cortex
| |
Canada
|
Human
|
Age-related macular degeneration
|
LED
|
670
|
↑visual acuity, ↑contrast sensitivity, ↓drusen
| |
UK
|
Rat
|
Age-related macular degeneration
|
LED
|
670
|
↑oxidation of cytochrome oxidase
| |
Iran
|
Rabbit
|
Corneal alkali burn
|
Laser
|
810
|
↓injury area, ↓inflammation
| |
Australia
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↓photoreceptor cell death, ↑ONL thickness
| |
Spain
|
Rat
|
Retinal ischemia
|
LED
|
630
|
↓RGC death, ↓GFAP
| |
USA (OH)
|
Mouse
|
Diabetic retinopathy
|
LED
|
670
|
↓retinal O2−, ↓leukostasis, ↓ICAM-1 expression,
↓iNOS expression, ↓Ca2+ channel dysfunction
| |
UK
|
Mouse
|
Age-related macular degen. CFH(-/-)
|
LED
|
670
|
↑ATP
| |
UK
|
Mouse
|
Age-related macular degeneration
|
LED
|
670
|
↑ATP, ↑cytochrome oxidase expression
| |
Australia
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↓photoreceptor cell death, ↓8OHDG
| |
Italy
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↑b-wave amplitude, ↓photoreceptor cell death, ↓GFAP
| |
India
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↑ONL cells, ↑ONL thickness
| |
Italy
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↓photoreceptor cell death, ↓GFAP
| |
USA (OH)
|
Rat
|
Diabetic retinopathy
|
LED
|
670
|
↓RGC death, ↓retinal O2−, ↓leukostasis, ↓ICAM-1 expression
| |
Australia
|
M&R
|
Oxygen-induced retinopathy
|
LED
|
670
|
↓photoreceptor cell death, ↓retinal neovascularisation
| |
UK
|
Mouse
|
Age-related macular degen. CFH(-/-)
|
LED
|
670
|
↓TNF-α expression, ↓TLR2/4 expression, ↓macrophage activation, ↓MIF and calcitonin expression
| |
UK
|
Mouse
|
Age-related macular degeneration
|
LED
|
670
|
↑mitochondrial membrane potential, ↓TNF-α, ↓C3d, ↓macrophages
| |
UK
|
Mouse
|
Age-related macular degen. CFH(-/-)
|
LED
|
670
|
↑cytochrome oxidase, ↓C3, ↓GFAP,
| |
Australia
|
Mouse
|
Oxygen-induced retinopathy
|
LED
|
670
|
↓oxidative stress, ↓C3
| |
Australia
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↓C1s, ↓C2, ↓C3, ↓C4b, ↓C3aR1, ↓C5r1
| |
Australia
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↓photoreceptor cell death,↓LIF-, Edn2 and TNF-α gene expression, ↓Müller cell proliferation, etc.
| |
Australia
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↑b-wave amplitude, ↓photoreceptor cell death
| |
Australia
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↑a-wave amplitude, ↑b-wave amplitude, ↓photoreceptor cell death, ↓macrophages, ↓microglial activation
| |
China
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↑b-wave amplitude, ↓ONL damage
| |
Australia
|
Rat
|
Light-induced retinal damage
|
LED
|
670
|
↓expression of genes/ncRNA related to light-induced retinal damage
| |
USA (TX)
|
Rat
|
Mitochondrial optic neuropathy
|
LED
|
633
|
↑retinal structure, ↑cytochrome oxidase expression
| |
USA (WI)
|
Rat
|
Methanol toxicity (retinal injury)
|
LED
|
670
|
↑rod and cone function (ERG amplitude), ↓retinal histopathology
| |
7. Photobiomodulation research examples: Bone
7.1. Human studies
In a randomized trial of 50 patients with hand/wrist fractures, photobiomodulation with near-infrared laser (830 nm) reduced the pain and greatly improved functional parameters compared to the placebo group. Each subject had ten treatment sessions, each of which lasted 10 minutes per each fractured site (Chang et al. 2014).
7.2. Animal studies
Nearly one hundred scientific articles reporting the effects of photobiomodulation on bone repair have been published. The results have been mostly positive, and numerous research groups have reported similar changes, e.g. improved bone formation (Pinheiro et al. 2015).
Nearly one hundred scientific articles reporting the effects of photobiomodulation on bone repair have been published. The results have been mostly positive, and numerous research groups have reported similar changes, e.g. improved bone formation (Pinheiro et al. 2015).
Photobiomodulation effects on bone tissue (animal studies)
| ||||||
Reference
|
Country
|
Animal
|
Indication/model
|
💡
|
λ (nm)
|
Results
|
Brazil
|
Rat
|
Osteoporosis (ovx)
|
Laser
|
780
|
↑trabecular bone formation, ↑collagen fiber area
| |
Turkey
|
Rat
|
Midpalatal suture expansion
|
Laser
|
820
|
↑bone formation
| |
Brazil
|
Rat
|
Bone defect
|
Laser
|
670
|
↑bone stiffness, ↑serum ALP
| |
Turkey
|
Rat
|
Suture expansion
|
LED
|
618
|
↑bone formation, ↑osteoblasts, ↑osteoclasts
| |
Egypt
|
Rat
|
Gamma radiation of mandible
|
Laser
|
904
|
↑trabecular area
| |
Japan
|
Rat
|
Orthodontic mini-implant (tibia)
|
Laser
|
830
|
↑bone formation, ↑BMP-2 expression
| |
Brazil
|
Rat
|
Osteoporosis (ovx)
|
Laser
|
830
|
↑bone and collagen formation, ↔biomechanical properties
| |
Brazil
|
Rat
|
Osteoporosis (ovx)
|
Laser
|
904
|
↑bone formation
| |
Brazil
|
Rabbit
|
Orthodontic implant (tibia)
|
Laser
|
830
|
↑bone formation (CHA concentration)
| |
Israel
|
Rat
|
Mandibular trauma
|
Laser
|
633
|
↑bone mineralization
| |
Israel
|
Rat
|
Tibial injury
|
Laser
|
333
|
↑bone formation, ↑ALP activity
| |
8. Photobiomodulation research examples: Hypothyroidism
In a Brazilian randomized trial with 43 hypothyroid patients, ten sessions of photobiomodulation with a near-infrared laser (830 nm) resulted in a decreased levothyroxine requirement in the patients at the 9-month follow up.
Remarkably, forty-eight percent of the patients were able to keep their thyroid hormone levels within the reference ranges completely without a medication (Höfling et al. 2013, Höfling et al. 2010).
Similar positive results have also been reported in several Russian and Ukrainian studies that I’ve covered in another blog article.
9. Photobiomodulation research examples: Parkinson’s disease
In 2008, researchers from Wisconsin found that photobiomodulation was beneficial for an in vitro model of Parkinson’s disease (Liang et al. 2008). After that, researchers from Australia, France and Switzerland have published a large amount of research showing that photobiomodulation protects the brain and reduces the motor symptoms in various animal models of Parkinson’s disease, including MPTP- or 6OHDA-injected and α-synuclein overexpressing animals (Johnstone et al. 2016).
In 2016, a paper titled Near-infrared light is neuroprotective in a monkey model of Parkinson disease was published in the high-impact journal Annals of Neurology. In this study, red light was administered into MPTP-poisoned macaque monkey brain via an optical fiber. This treatment reversed most of the clinical symptoms in the majority of the monkeys (Darlot et al. 2016).
Most of the studies have used red light (670 nm), but in some of the papers, near-infrared (810 nm) has also been used. Usually the light has been administered transcranially or straight to the head via an optic fiber, but in one study, body irradiation also had remote neuroprotective effects on the brain, suggesting that photobiomodulation might have systemic effects (Johnstone et al. 2014, Kim et al. 2017).
 |
| (Johnstone et al. 2016) |
10. Photobiomodulation research examples: Heart and circulation
Research groups from Israel, USA, China and Brazil have investigated the effects of photobiomodulation on the recovery from myocardial infarct. Data from numerous trials conducted in mice, rats, dogs and pigs indicate that illuminating the heart with red light after an infarct could significantly decrease the injured area and therefore improve the heart function (Carlos et al. 2016, Blatt et al. 2016).
As an example, in this experimental study with dogs, photobiomodulation with near-infrared light appeared to decrease the injured area by approximately 50%. The treatment also reduced mortality in the dogs (Oron et al. 2001):
Brazilian researchers have also noted that photobiomodulation could alleviate pain, bleeding and other complications related to sternotomy (Fernandes et al. 2016, Lima et al. 2016a, Lima et al. 2016b, de Oliveira et al. 2014).
In the end of 1990s, researchers from the USA studied the effects of red light on restenosis and neointimal hyperplasia after balloon angioplasty in rabbits. The highly promising results were published in high-impact journals JACC and Circulation. Some additional studies have also been conducted in pigs and humans (Kipshidze et al. 1998, Kipshidze et al. 2001, Derkacz et al. 2010, De Scheerder et al. 1998, De Scheerder 2000, De Scheerder 2001a, De Scheerder et al. 2001b).
In 2012, a group of Austrian researchers discovered that red light induces the vasodilation of coronary arteries. The researchers concluded: “As LED sources are of small size, simple, and inexpensive build-up, they may be used during routine coronary artery bypass surgery to ease suturing of anastomosis by target vessel vasodilation” (Plass et al. 2012)
Korean researchers have also shown that illuminating rabbits with polarized light from a regular tungsten lamp could protect the animals from experimental atherosclerosis (Park et al. 2012).
11. Photobiomodulation research examples: Other indications
Alzheimer’s disease:
- Photobiomodulation has been studied for various animal models of Alzheimer’s disease, with good results (Lu et al. 2017, Farfara et al. 2015, Purushothuman et al. 2014, Grillo et al. 2013).
Exercise performance:
- Photobiomodulation has shown some efficacy for exercise performance, muscle growth, sarcopenia, myopathies and muscle injuries in animal and human studies (Ferraresi et al. 2016, Baroni et al. 2014, Leal-Junior et al. 2014, Corazza et al. 2013).
Hearing loss:
- Photobiomodulation appears to protect rodents from noise-induced hearing loss (Tamura et al. 2015, Lee et al. 2016, Tamura et al. 2016).
Oral mucositis:
- One of the most common complications of cancer treatments is the painful inflammation of oral mucosa. Photobiomodulation has been studied for this indication in approximately twenty randomized trials, very often with great results (Oberoi et al. 2014, Silva et al. 2015, Soto et al. 2015, Ferreira et al. 2016).
Thrombocytopenia:
- Quite recently a research group from Harvard Medical School published two papers, in which they demonstrated that photobiomodulation with visible red light can protect mice from multiple different models of this dangerous bleeding disorder. The first article was published in the high-impact journal Science Translational Medicine (Zhang et al. 2016, Yang et al. 2016).
Wound healing:
- Photobiomodulation has been studied in the treatment wounds and burns. More than a hundred animal studies have been published, but the human research is somewhat scarce (Gupta et al. 2015, Keshri et al. 2016, Ojea et al. 2016, Tchanque-Fossuo et al. 2016).
12. Photobiomodulation treatment 101
12.1. Introduction
In photobiomodulation, the body is locally irradiated by visible red light or invisible near-infrared.
 |
| It might look like this, though the beam size (1mm2 - 32cm2) and other parameters (wavelength, intensity, energy, number of sessions) vary a lot. (Image source: SpinalStenosis) |
The light is usually produced by a laser or LED device. Unlike common lamp light, in photobiomodulation light is monochromatic, consisting of one wavelength. Some of the most common wavelengths are presented below.
Common wavelengths in photobiomodulation
| |
Visible red
|
630, 633, 655, 660, 670 nm
|
Near-infrared (NIR)
|
780, 808, 810, 830, 850, 890, 904, 940, 1064, 1072 nm
|
Usually a wavelength ranging from 600 to 1100 nanometers is used. Within this range, some wavelengths have a stronger cellular effect than others, and some wavelengths (eg. 730 nm) might be utterly ineffective. These differences appear to be explained by absorption spectra of cytochrome c oxidase (Karu 1999, Karu 2010, Wong-Riley et al. 2005, Gupta et al. 2014, Wu et al. 2012).
It has also been shown that wavelengths 750 and 950 nm can inhibit mitochondrial function at the electron transport chain (ETC) level. While this might sound like a paradoxical and undesired effect, there is some evidence suggesting that it could actually be used after ischemia to effectively reduce the ischemia-reperfusion (IR) injury, for example in stroke (Sanderson et al. 2018).
It has also been shown that wavelengths 750 and 950 nm can inhibit mitochondrial function at the electron transport chain (ETC) level. While this might sound like a paradoxical and undesired effect, there is some evidence suggesting that it could actually be used after ischemia to effectively reduce the ischemia-reperfusion (IR) injury, for example in stroke (Sanderson et al. 2018).
There is also some evidence suggesting that longer wavelengths (eg. 980 or 10600 nm) might have an unique mechanism of action that isn't based on absorption by cytochrome c oxidase. Some hypotheses have been published, describing intracellular water as the primary photoacceptor mediating the photomodulatory effects observed with longer wavelengths (Wang et al. 2017, Hamblin 2017).
Near-infrared penetrates the tissue better than red light, so it’s more commonly used for treating body parts that are under the skin (brain, glands, joints, muscles). Visible red light is more commonly used in the treatment of wounds or skin diseases.
12.2. Treatment parameters
The following table provides the basic information about the most relevant treatment parameters (Hadis et al. 2016, Jenkins&Carroll 2011).
Photobiomodulation parameters
| ||||
Parameter
|
Alternative terms
|
Symbol
|
Unit
|
Usual range
|
Wavelength
|
-
|
λ
|
nm
|
630 - 1072 nm
|
Power (output)
|
Radiant flux
|
Φ
|
mW
|
50 - 1000 mW
|
Irradiance
|
Intensity, power density
|
E
|
W/cm2, mW/cm2
|
3 mW/cm2 - 70 W/cm2
|
Radiant energy
|
Energy, dose
|
Q
|
J
|
0.1 - 3000 J
|
Radiant exposure
|
Energy density, fluence, dose
|
H
|
J/cm2
|
1 - 400 J/cm2
|
Beam area
|
Spot size
|
A
|
cm2, mm2
|
1 mm2 - 32cm2
|
Here are some examples from various human trials. It can be noted that there are huge differences between the experiments (note: the energy density isn't reported - I will add it later).
Photobiomodulation parameters: examples
| |||||||
Indication
|
Wavelength
|
Power
|
Spot size
|
Energy
|
Irradiance
|
Treatment duration
|
Sessions
|
690 nm
|
80 mW
|
1 cm2
|
48 J
|
80 mW/cm2
|
10 minutes
|
10 sessions in 14d
| |
670 nm
|
40 mW
|
0.79 cm2
|
1.6 J
|
51 mW/cm2
|
40 seconds
|
1 session
| |
830 nm
|
50 mW
|
0.28 mm2
|
40 J
|
17 680 mW/cm2
|
13,3 minutes
|
10 sessions in 8wk
| |
850 nm
|
100 mW
|
0.79 mm2
|
48 J
|
13 000 mW/cm2
|
8 minutes
|
8 sessions in 4wk
| |
830 nm
|
800 mW
|
25 cm2
|
1250 J
|
32 mW/cm2
|
32 minutes
|
12 sessions in 6wk
| |
780 nm
|
7.5 mW
|
0.071 cm2
|
0.3 J
|
106 mW/cm2
|
40 seconds
|
4 sessions in 2wk
| |
12.3. Dose response
The therapeutic window of photobiomodulation is somewhat narrow and looks like this:
Underdosing has been suggested to explain many of the negative results in clinical photobiomodulation trials (Tunér&Hode 1998). The ineffectiveness of overdosing has also been demonstrated, especially in dozens of experimental studies (Huang et al. 2011). Thus, biphasic dose-response appears to be a very significant issue in photobiomodulation.
Low-to-moderate doses of light are often described as stimulating and high doses as inhibitory, because some markers that can be increased by low doses of light, have been shown to decrease with excessive light doses.
The exact mechanism of biphasic dose-response is not known, but it might be related to excessive formation of reactive oxygen species (ROS): “The Janus nature of reactive oxygen species (ROS) that may act as a beneficial signaling molecule at low concentrations and a harmful cytotoxic agent at high concentrations, may partly explain the observed responses in vivo” (Huang et al. 2011)
In some reviews articles, photobiomodulation is said to have a hormesis-like effect: “The hormetic response of both LLLT and MB consists of an increase in the effect at a low dose, followed by a decrease in the same effect with an intermediate dose, until the effect is equal to a control-type effect. With doses increasing beyond the hormetic zone, the effect decreases even further, until it is below the control effect.” (Rojas&Gonzalez-Lima 2013)
12.4. Treatment devices
In the past, the photobiomodulation light sources were mostly laser-based, expensive and only available to clinicians. Nowadays, the situation has improved and many companies are selling much cheaper LED devices directly to patients.
In the table below, I list some of the photobiomodulation devices that I’m aware of. (A note: As of 2019, this table is not really up-to-date anymore.)
Photobiomodulation devices (for consumers)
| |||||||
Device
|
💡
|
λ
nm
|
Φ
mW
|
E
mW/cm2
|
A
cm2
|
Comments
|
Price
|
B-Cure
|
Laser
|
808
|
67.5
|
15
|
4.5
|
+ Decent parameters
+ Device is small and battery-powered
|
~$700
|
LightWorks LW2
|
LED
|
660
850
|
718
455
|
25
16
|
29
|
+ Decent parameters
+ Large spot size
± Device emits both red light and NIR simultaneously
|
~$400
|
Handy Cure
|
LED
|
635
875
905
|
60-90
|
15-23
|
4
|
+ Decent parameters
+ Device is small and battery-powered
± Device emits both red light and NIR simultaneously
|
~$400
|
LED
|
830
|
?
|
200 (10cm)
20 (70cm)
|
?
|
+ Decent parameters
|
~$400
| |
LED
|
670
|
?
|
200 (0cm)
20 (60cm)
|
?
|
+ Decent parameters
|
~$90
| |
LED
|
850
|
?
|
200 (0cm)
10 (6cm)
|
?
|
+ Cheap and small (see my YouTube video)
- Very small spot size
|
~$20
| |
Halogen lamps
|
-
|
Broad
spectrum
|
?
|
?
|
?
|
+ Halogen and incandescent lamps emit red light and NIR, so they could theoretically be suitable for photobiomodulation
- Broad spectrum light hasn’t been studied significantly. Research has been done with monochromatic light (eg. 670 or 830 nanometers).
- It might be very difficult to find the right dose
|
$5
|
Sunlight
|
-
|
Broad
spectrum
|
?
|
?
|
?
|
+ In some studies, sunlight has been associated with better health outcomes, which could be related to the red light/NIR exposure.
- Broad spectrum light hasn’t been studied significantly. Research has been done with monochromatic light (eg. 670 or 830 nanometers).
|
Free
|
There are some arguments about the efficacy of laser vs. LED lights in photobiomodulation. In the past, photobiomodulation was called low-level laser therapy (LLLT) and basically all of the research was conducted with low-level lasers.
Nowadays there is an overwhelming evidence showing that photobiomodulation doesn’t require coherent light and light-emitting diodes (LEDs) are suitable for photobiomodulation, though laser light might have a better penetration depth into the tissue, because it produces so-called laser speckles.
“Most of the early work in this field was carried out with various kinds of lasers, and it was thought that laser light had some special characteristics not possessed by light from other light sources such as sunlight, fluorescent or incandescent lamps and now LEDs. However all the studies that have been done comparing lasers to equivalent light sources with similar wavelength and power density of their emission, have found essentially no difference between them.” (Hamblin 2017)
Since the light intensity decreases when the device is used from longer distance, it might sometimes be useful to have a measurement device to examine the light intensity from various distances. I’m using Tenmars TM-206 device, which costed approximately $50 in eBay. However, it should noted that the device might overestimate the irradiance of near-infrared wavelengths up to 2-fold.
 |
| Tenmars TM-206 |
12.5. Sunlight
“Wherever primitive races abandon nakedness for clothing, at once the tendency to disease, mortality, and degeneracy notably increases, though it must be remembered that the use of clothing is commonly accompanied by the introduction of other bad habits.” - Havelock Ellis (1909)
In many epidemiological studies, sunlight exposure and low latitude have been correlated with improved health, eg. decreased mortality, lower cholesterol levels and lower cancer incidence. The effects of sunlight have usually been attributed to increased synthesis of Vitamin D, but since sunlight also contains high amounts of red and near-infrared light, the beneficial effects could also be due to photobiomodulation (Lindqvist et al. 2014, Lindqvist et al. 2010, Grant&Mohr 2009, Grimes et al. 1996, Wong 2008).
In a way, photobiomodulation could possibly be described as a way to substitute for the lack of daylight. If modern humans would start spending their days mostly in outdoors without shirts, our direct exposure to light would probably increase up to 100,000-fold and would be comparable to the doses used in photobiomodulation therapies (Barolet et al. 2016, Karu 2010).
Light intensity in different contexts
| |
Place or context
|
Irradiance (mW/cm2)
|
Bedroom
|
0.01
|
Sunlight
|
5 - 20
|
Photobiomodulation
|
20 - 5000
|
12.6. Incandescent/halogen/heat lamps
In the beginning of 20th century, some physicians used incandescent lamps in the treatment of various ailments such as diabetes, obesity, chronic fatigue, insomnia, baldness and cachexia (Kellogg 1910, Cleaves 1904). Since incandescent lamps produce large amounts of red and near-infrared light, spectrum being comparable to sunlight, it is likely that their possible beneficial effects could be due to photobiomodulation.
However, since the amount of therapeutic wavelengths is difficult to measure with broad-spectrum lamps, it might be very difficult to find the optimal dosage. Therefore, I would not recommend incandescent, halogen or heat lamps for photobiomodulation purposes until there will be more scientific research about their usage.
 |
| Margaret Cleaves' 1904 book Light energy, its physics, physiological action and therapeutic applications has some interesting chapters about incandescent lamp therapy. |
13. Photobiomodulation science: 7 facts
Fact 1: The amount of photobiomodulation research has been growing exponentially. At the moment, approximately 400 new scientific articles are being published annually.
Fact 2: Photobiomodulation has dozens of different names. In the past, there was no consensus of the name of this treatment, so many different ones were used:
660nm LED light source
|
Laser light irradiation
|
Low-level light
|
Photobioactivation
|
670nm light
|
Laser phototherapy
|
Low-level light therapy
|
Photobiomodulation
|
λ780 nm laser light
|
Laser therapy
|
Low-power laser therapy
|
Photobiostimulation (PBM therapy)
|
830nm laser
|
Laser treatment
|
Low-power laser irradiation (LPLI)
|
Photo-enhancement
|
810-nm diode laser
|
LED-based red light photo-stimulation
|
Low-power laser stimulation
|
Photoradiation
|
CLASS IV laser therapy
|
LED-light
|
Low-power laser treatment
|
Photostimulation
|
Cold laser
|
LED phototherapy
|
Low power red laser light (LPRLL)
|
Physiotherapy laser
|
Far-red light
|
Light-emitting diode irradiation
|
Low-level phototherapy
|
Singlet oxygen energy (SOE light)
|
Far red/near infrared light
|
Light-Emitting Diode Phototherapy
|
Low reactive-level laser therapy
|
Short pulsed nonablative infrared laser irradiation
|
Helium-neon laser
|
Low dose laser irradiation
|
MID-laser therapy
|
Soft laser
|
He-Ne laser
|
Low-energy Helium-Neon laser irradiation
|
Monochromatic phototherapy
|
Therapeutic photobiomodulation
|
High fluence low-power laser irradiation
|
Low-energy laser irradiation
|
Nanoparticle-emitted light
|
Transcranial infrared laser therapy
|
Intravascular red laser therapy
|
Low energy light irradiation
|
Narrow-band light
|
Transcranial Laser Stimulation
|
Intravascular Low-Power Laser Illumination
|
Low-intensity laser irradiation (LILI)
|
Narrow-band red light phototherapy
|
Transcranial laser therapy
|
Intravascular low-power red laser light
|
Low-intensity laser therapy
|
Near infra-red
|
Transcranial low level laser (light) therapy
|
Irradiation
|
Low-level laser
|
Near-infrared light
|
Visible light
|
Laser 904 nm
|
Low-level laser energy
|
Near-infrared light treatment
|
Water-filtered infrared-A
|
Laser acupuncture
|
Low-level laser therapy
|
Polarized light therapy
|
Fact 3: Over 120 decent scientific journals (impact factor at least 3.0), and approximately 700 journals in total, have published at least one paper on photobiomodulation!
Some top journals are included, eg. The Lancet, PNAS, Circulation, Blood, Annals of Neurology and Science Translational Medicine. Click here for a detailed list about the articles published in the high-impact journals.
Some top journals are included, eg. The Lancet, PNAS, Circulation, Blood, Annals of Neurology and Science Translational Medicine. Click here for a detailed list about the articles published in the high-impact journals.
Fact 4: Photobiomodulation has also been mentioned in news feature articles published in the top journals Nature and Science.
“Eells and her colleagues found that NIR phototherapy counters methanol poisoning, which injures the retina and optic nerve, often causing blindness. The toxic metabolite is formic acid, which inhibits cytochrome oxidase. ‘In a rat model, NIR phototherapy is able to restore virtually normal retinal function, at least as judged by the electroretinogram,’ says Eells.
And neurobiologist Margaret Wong-Riley and her colleagues at the Medical College of Wisconsin in Milwaukee have shown that NIR phototherapy can also oppose the effects of cyanide on cell cultures. Cyanide poisons by binding to cytochrome oxidase. Wong-Riley’s team showed that phototherapy could halve the rate of apoptosis in cultured neurones, even when given before cyanide treatment.
But can NIR phototherapy relieve not just acute toxicity, but more chronic inflammatory conditions? The signs augur well. Eells and her colleagues have shown that NIR phototherapy could cut the rate of apoptosis by 50% in a rat model of retinitis pigmentosa, in which photoreceptors die by apoptosis during postnatal development causing retinal degeneration and blindness” (Nature 2006)
“Previous studies have shown that exposing cells to a particular wavelength of light, 670 nanometers, toward the red end of the visible spectrum, causes their energy-producing mitochondria to boost production of adenosine triphosphate, which powers the cells.” (Science 2017)
Fact 5: There are five scientific journals that have published a very large amount of photobiomodulation research. These journals are also feature many other light-related subjects in addition to photobiomodulation.
Photobiomodulation: important scientific journals
| ||
Publisher
|
Journal Title
|
Impact Factor
|
Wiley
|
Journal of Biophotonics
|
3.8
|
Elsevier
|
Journal of Photochemistry and Photobiology B: Biology
|
3.0
|
Springer
|
Lasers in Medical Science
|
2.5
|
Wiley
|
Lasers in Surgery and Medicine
|
2.1
|
Mary Ann Liebert
|
Photomedicine and Laser Surgery
|
1.6
|
Fact 6: Photobiomodulation research has been published in 71 different countries.
Photobiomodulation research countries
| |
Amount of articles
|
Country
|
1000+
|
Brazil
|
400+
|
United States (in 33 different states)
|
100+
|
China, Iran, Israel, Italy, Japan, Korea, Russia, Turkey
|
50-99
|
Australia, Canada, Germany, India, Spain, Taiwan, UK
|
10-49
|
Argentina, Austria, Belgium, Czech Republic, Denmark, Egypt, France, Greece, Hungary, Netherlands, New Zealand, Norway, Poland, Romania, Saudi Arabia, Serbia, Slovakia, South Africa, Sweden, Switzerland
|
Less than 10
|
Bosnia-Herzegovina, Bulgaria, Chile, Colombia, Costa Rica, Croatia, Cuba, Cyprus, Finland, Indonesia, Iraq, Ireland, Jordan, Kazakhstan, Kuwait, Macedonia, Malaysia, Mexico, Monaco, Nepal, Pakistan, Portugal, Puerto Rico, Qatar, Singapore, Slovenia, Sudan, Syria, Thailand, Ukraine, United Arab Emirates, Venezuela, Yemen, Yugoslavia
|
Fact 7: Hall of Fame of the photobiomodulation research is presented below:
Photobiomodulation: notable researchers
| ||||
Name
|
Position
|
University
|
Speciality
|
Research focus
|
Professor
|
University of Wisconsin-Milwaukee
|
Biosciences
|
Photobiomodulation and retinal degeneration.
| |
Assistant professor
|
University at Buffalo
|
Oral biology
|
TGFß1 in photobiomodulation mechanisms.
| |
Assistant professor
|
Harvard Medical School
|
Dermatology
|
Photobiomodulation and the brain. Has written dozens of articles and edited photobiomodulation-related books.
| |
Professor
|
Russian Academy of Sciences
|
Biophysics
|
Photobiomodulation and cell function.
| |
Professor
|
The University of Sydney
|
Neurobiology
|
Photobiomodulation and Parkinson’s disease.
| |
Professor
|
The University of Sydney
|
Anatomy
|
Photobiomodulation and Parkinson’s disease.
| |
Assistant professor
|
Australian National University
|
Anatomy
|
Photobiomodulation and retinal degeneration.
| |
Professor
|
University of Johannesburg
|
Photobiology
|
Photobiomodulation and stem cells.
| |
Professor
|
University College London (UCL)
|
Neurosciences
|
Photobiomodulation, mitochondria and retina.
| |
Professor
|
University of Bergen
|
Physiatry
|
Photobiomodulation, muscle and exercise.
| |
Professor
|
The University of Texas
|
Neurosciences
|
Photobiomodulation, brain and cognition.
| |
Professor
|
University of Birmingham
|
Oral biology
|
Photobiomodulation and oral physiology.
| |
Professor
|
Tel Aviv University
|
Photobiomodulation and heart.
| ||
Professor
|
Photobiomodulation, nerves and pain.
| |||
Dean
|
University of Otago
|
Physiotherapy
|
Photobiomodulation, wound healing and Achilles tendon.
| |
Provost
|
San Diego State University
|
Photobiomodulation, wounds and injuries.
| ||
Professor
|
Federal University of Bahia
|
Photobiomodulation and bone tissue.
| ||
Research professor
|
Boston University
|
Neurology
|
Photobiomodulation and traumatic brain injury.
| |
Professor
|
Medical College of Wisconsin
|
Neurology
|
Photobiomodulation and wound healing.
| |
Professor
|
Medical College of Wisconsin
|
Oral biology
|
Photobiomodulation and nerves.
| |
Dentist
|
-
|
Dentistry
|
Photobiomodulation treatment parameters. Has written many reviews and books on the subject.
| |
14. The ongoing clinical trials
I checked the ClinicalTrials.gov database to see whether there are any ongoing clinical trials examining the health effects of photobiomodulation. The amount of active trials was not high, but there were dozens of studies that are still recruiting participants:
Ongoing PBM/LLLT clinical trials
| ||||
Treatment indication
|
Country
|
Responsible party
|
Status
|
Identifier
|
Canada
|
LumiThera, Inc.
|
Active
|
NCT02725762
| |
USA
|
Theradome, Inc.
|
Active
|
NCT02528552
| |
Brazil
|
Federal University of Health Science of Porto Alegre
|
Recruiting
|
NCT02688426
| |
USA
|
University of Minnesota
|
Active
|
NCT02000908
| |
USA
|
University of Texas at Austin
|
Recruiting
|
NCT02851173
| |
USA
|
University of Florida
|
Recruiting
|
NCT02582593
| |
Norway
|
University of Bergen
|
Recruiting
|
NCT02749929
| |
Norway
|
University of Bergen
|
Recruiting
|
NCT03014024
| |
USA
|
University of California
|
Recruiting
|
NCT03160027
| |
Iran
|
Shahid Beheshti University
|
Recruiting
|
NCT03023761
| |
Brazil
|
University of Nove de Julho
|
Active
|
NCT02529657
| |
USA
|
University of Texas Southwestern Medical Center
|
Recruiting
|
NCT02948634
| |
Brazil
|
Uni. Estadual Paulista Júlio de Mesquita Filho
|
Recruiting
|
NCT02995070
| |
USA
|
VA Office of Research and Development
|
Recruiting
|
NCT01782378
| |
USA
|
University of North Carolina
|
Recruiting
|
NCT03044106
| |
Brazil
|
University of Nove de Julho
|
Active
|
NCT02636764
| |
Brazil
|
Federal University of Uberlandia
|
Recruiting
|
NCT03072004
| |
Brazil
|
University of Nove de Julho
|
Recruiting
|
NCT02529670
| |
USA
|
University of Texas at Austin
|
Recruiting
|
NCT02898233
| |
USA
|
Massachusetts General Hospital
|
Recruiting
|
NCT02959307
| |
Migraine
|
USA
|
The San Francisco Clinical Research Center
|
Recruiting
|
NCT02969642
|
USA
|
Erchonia Corporation
|
Recruiting
|
NCT03163810
| |
USA
|
Erchonia Corporation
|
Recruiting
|
NCT03066336
| |
USA
|
University of Pittsburgh
|
Recruiting
|
NCT02682992
| |
USA
|
Barbara Ann Karmanos Cancer Institute
|
Recruiting
|
NCT02723604
| |
France
|
Institut de Cancérologie de la Loire
|
Recruiting
|
NCT02696408
| |
France
|
Institut Cancerologie de l'Ouest
|
Recruiting
|
NCT01772706
| |
France
|
Nantes University Hospital
|
Recruiting
|
NCT02181439
| |
USA
|
Biolux Research Ltd.
|
Recruiting
|
NCT03202355
| |
USA
|
Biolux Research Ltd.
|
Recruiting
|
NCT02954133
| |
Brazil
|
Universidade Cidade de Sao Paulo
|
Recruiting
|
NCT02898025
| |
Brazil
|
Uni. Estadual Paulista Júlio de Mesquita Filho
|
Recruiting
|
NCT03000426
| |
Sweden
|
Uppsala University
|
Recruiting
|
NCT02789735
| |
Hong Kong
|
The University of Hong Kong
|
Recruiting
|
NCT02352038
| |
USA
|
University of Texas at Austin
|
Recruiting
|
NCT02926352
| |
Germany
|
Landstuhl Regional Medical Center
|
Recruiting
|
NCT03015116
| |
Brazil
|
Hospital de Clinicas de Porto Alegre
|
Recruiting
|
NCT02296697
| |
Belgium
|
Hasselt University
|
Recruiting
|
NCT02738268
| |
USA
|
University of Pittsburgh
|
Recruiting
|
NCT02384434
| |
USA
|
Cutera Inc.
|
Recruiting
|
NCT02910492
| |
Brazil
|
University of Nove de Julho
|
Recruiting
|
NCT03031223
| |
Spain
|
University of Castilla-La Mancha
|
Active
|
NCT02971215
| |
Brazil
|
University of Nove de Julho
|
Recruiting
|
NCT02839967
| |
Brazil
|
University of Nove de Julho
|
Recruiting
|
NCT03257748
| |
Brazil
|
University of Nove de Julho
|
Recruiting
|
NCT02928809
| |
Brazil
|
University of Sao Paulo
|
Recruiting
|
NCT02602431
| |
USA
|
Massachusetts General Hospital
|
Recruiting
|
NCT02233413
| |
USA
|
VA Office of Research and Development
|
Recruiting
|
NCT02356861
| |
Brazil
|
Hospital de Clinicas de Porto Alegre
|
Recruiting
|
NCT03229330
| |
Brazil
|
University of Nove de Julho
|
Active
|
NCT02416531
| |
USA
|
Mayo Clinic
|
Recruiting
|
NCT02877004
| |
This seems like a decent amount of effort from the scientific community, to investigate the effects of photobiomodulation in humans.
15. Criticisms and obstacles of photobiomodulation
In their article Low level laser (light) therapy and photobiomodulation: The path forward, a group of important photobiomodulation researchers summarized some reasons hampering the application of photobiomodulation in the medical community:
"The reasons for this skepticism and disbelief are many and various and differ depending on who you are talking to. Biomedical scientists often refer to a lack of mechanism, and the absence of agreement on dosimetry and parameters. Physicians often claim there is a lack of large clinical trials and not enough systematic reviews. Hospital and insurance administrators cannot agree on coverage and reimbursement. Finally (and regrettably) there has been marketing hype, over-promising and frank misinformation from some of the companies making devices (lasers, LED arrays, mixed clusters) that are used in the LLLT industry."
Many skeptic websites and blogs also have claimed that photobiomodulation (LLLT) is mostly a form of quackery. These sites include Science-Based Medicine, Skeptic North, SkeptVet, Device Watch and also the Wikipedia page on LLLT. These criticisms present some of the weaknesses of the photobiomodulation (PBM) research fairly, but since most of the PBM research has been published since the 2010, most of these criticisms are outdated and I would trust recent systematic reviews more than these articles that are mostly based on some quick internet searches.
Some skeptics claim that the effects of photobiomodulation might be based on thermal effects of red or near-infrared radiation. This is a question that has also been examined by the scientific community. Thermal effects of low-level light therapy are usually negligible and some experimental temperature-controlled studies also confirm the existence of athermal effects. Therefore, nowadays the biological effects of PBM are considered to be mostly of athermal nature (Lanzafame et al. 2004, Joensen et al. 2011, Jung&Grune 2012, Grandinétti Vdos et al. 2015).
The quality of randomized, blinded and placebo-controlled photobiomodulation studies is currently somewhat poorer than it could be. Especially these aspects could be improved:
A major obstacle in the application of PBM in the medical treatments has been the high price of PBM treatment devices. However, since the LED-based devices for in-home usage are becoming more popular, this aspect is probably going to improve a lot in the near future.
15. Criticisms and obstacles of photobiomodulation
In their article Low level laser (light) therapy and photobiomodulation: The path forward, a group of important photobiomodulation researchers summarized some reasons hampering the application of photobiomodulation in the medical community:
"The reasons for this skepticism and disbelief are many and various and differ depending on who you are talking to. Biomedical scientists often refer to a lack of mechanism, and the absence of agreement on dosimetry and parameters. Physicians often claim there is a lack of large clinical trials and not enough systematic reviews. Hospital and insurance administrators cannot agree on coverage and reimbursement. Finally (and regrettably) there has been marketing hype, over-promising and frank misinformation from some of the companies making devices (lasers, LED arrays, mixed clusters) that are used in the LLLT industry."
Many skeptic websites and blogs also have claimed that photobiomodulation (LLLT) is mostly a form of quackery. These sites include Science-Based Medicine, Skeptic North, SkeptVet, Device Watch and also the Wikipedia page on LLLT. These criticisms present some of the weaknesses of the photobiomodulation (PBM) research fairly, but since most of the PBM research has been published since the 2010, most of these criticisms are outdated and I would trust recent systematic reviews more than these articles that are mostly based on some quick internet searches.
Some skeptics claim that the effects of photobiomodulation might be based on thermal effects of red or near-infrared radiation. This is a question that has also been examined by the scientific community. Thermal effects of low-level light therapy are usually negligible and some experimental temperature-controlled studies also confirm the existence of athermal effects. Therefore, nowadays the biological effects of PBM are considered to be mostly of athermal nature (Lanzafame et al. 2004, Joensen et al. 2011, Jung&Grune 2012, Grandinétti Vdos et al. 2015).
The quality of randomized, blinded and placebo-controlled photobiomodulation studies is currently somewhat poorer than it could be. Especially these aspects could be improved:
- While the application of placebo is common the PBM literature, some minor methodological deficiencies have been revealed (Relf et al. 2008).
- Treatment parameter reporting also fails somewhat often (Tunér&Jenkins 2016).
- Regarding the randomisation, most trials apparently fail in the allocation concealment, which is quite an important methodological aspect in the assessment of study quality (risk of bias). These aspects should be improved in the future trials.
A major obstacle in the application of PBM in the medical treatments has been the high price of PBM treatment devices. However, since the LED-based devices for in-home usage are becoming more popular, this aspect is probably going to improve a lot in the near future.
16. Summary
- Red light and near-infrared irradiation produce measurable changes locally in cells/tissues/organs. This form of light therapy is called photobiomodulation (PBM).
- Animal studies show that photobiomodulation therapy could be beneficial for over 100 different diseases. Evidence from human studies is also emerging in a fast pace.
- Over 3800 photobiomodulation papers have been published in PubMed-indexed journals, over 120 of which have a good impact factor (> 3.0). Research has been conducted in at least 71 different countries.
Thanks for reading. If this article got you interested in photobiomodulation, please consider joining our discussion group in Facebook.
Best,
Vladimir Heiskanen
Dental student (University of Helsinki)
Finland
Appendix 1: Recommended reading
Book recommendations
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Author/Editor
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Book title
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Riegel and Godbold
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Hamblin, de Sousa and Agrawal
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Hode and Tunér
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Hamblin and Huang
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Scientific review articles
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Journal
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Article title
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AIMS Biophysics
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Mechanisms and applications of the anti-inflammatory effects of photobiomodulation
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Frontiers in Neuroscience
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BBA Clinical
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Biochemical Pharmacology
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Annals of Biomedical Engineering
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News features
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Source
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Article title
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The Australian
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Let There Be Light (2017)
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Massachusetts General Hospital
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Wisconsin Academy
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University of Sydney
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ScienceDaily
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Nature
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Scientific American
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Appendix 2: Photobiomodulation on social media
Photobiomodulation on social media
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Site
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Category
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Title
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Facebook
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Group
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Facebook
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Page
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Facebook
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Page
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Facebook
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Page
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Facebook
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Page
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