Light is perhaps one of the most underappreciated healing agents available. James Carroll, an expert in light as therapy, also known as photobiomodulation, has the ambitious goal of making photobiomodulation a first-line therapy for 100 diseases in 100 countries, by the time he's 100 years old — which is about 45 years from now.
Carroll has already spent the last 30 years of his life investigating the healing power of light — a passion that grew out of his involvement with the tissue repair research unit at Guy's Hospital in London in the 80s. At the time, he had a business raising government grant money, and Guy’s Hospital was one of his clients.
He was able to see some of the work they were doing on cells and small rodents using lasers. “I thought, this is amazing; this is going to be in every corner of every department of every hospital in the whole world within the next five years,” Carroll says. While the technology didn’t catch on as quickly as he’d imagined, his enthusiasm for it led to a change in careers as he went to work for the laser company supplying the technology for the research.
From Lasers to LEDs
In those earlier days, most light therapy made use of lasers, as light-emitting diodes (LEDs) were not readily available back then. Some of the first lasers Carroll used operated in the 15 milliwatts range. Over time, the lasers got increasingly stronger.
Today, 30-watts LED diodes are quite common. (An important point to be made is that the LEDs used for light therapy are not identical to LED lighting used in homes and offices. The LEDs used in photobiomodulation technologies typically have a very focused and narrow wavelength and cannot be used for lighting a room.)
That’s not to say that more power is better. On the contrary, there’s a Goldilock’s Zone in which most of the therapeutic effects are found. According to Carroll, cells respond optimally to a range between 5 and 50 milliwatts per centimeter squared (mW/cm2).
“If you want to have successful in vitro studies, that's where you need to be. Similar doses seem to work in superficial wound healing and inflammation, and unless you're going for deeper targets, that's usually enough.” As for timing, as little as one minute will typically render results. An average treatment is typically in the 10 to 20-minute range.
Most modern light therapy products are in the 600 to 1000 nanometer (nm) range, with a gap around the 700s. A number of studies have suggested the 700-nm range has no beneficial health effects, although the issue has not been definitively settled as of yet. There’s still a lot to learn, but great headway is being made.
According to Carroll, about 500 randomized controlled human clinical trials and some 4,000 laboratory studies have already been published on photobiomodulation, and each month approximately 30 new papers are added to this body of literature. Carroll has developed a database where he collects studies and so far, he has over 80,000 studies in this database on photobiomodulation.