Explore the gut-brain connection in Parkinson’s disease and how light therapy may support neuroprotection and symptom relief.
Margaret Jarrett was diagnosed with Parkinson’s disease eight years ago. Although she was troubled by many symptoms common in Parkinson’s—resting tremor, unsteady gait, and vivid nightmares—the loss of her sense of smell upset her most. An avid gardener, she had always delighted in the scent of her roses, and missing that fragrance left her downhearted.
“You take something like your sense of smell for granted,” Jarrett, 72, said. “You don’t realize how precious it is until it’s gone.”
Parkinson’s disease combines movement problems such as resting tremor, muscle rigidity, poor balance, and slowed movement. It can also bring neurological symptoms like depression, insomnia, memory loss, and confusion.
The cause remains unknown, but the condition is linked to dopamine depletion and neuron loss in the brain’s basal ganglia.
Current treatment centers on physical therapy and medications that raise brain dopamine levels. One newer approach is exposure to infrared light.
Dr. Ann Liebert, coordinator of photomolecular research at the Australasian Research Institute, is exploring whether infrared light can modify the gut microbiome in humans.
The gut microbiome—trillions of bacteria, fungi, and protozoa from hundreds of species—has drawn growing scientific interest. Altered microbiomes have been associated with obesity, type 2 diabetes, cardiovascular disease, and depression. Several studies report marked changes in the gut flora of people with Parkinson’s, and fecal transplantation has shown protective effects in animal models of the disease.
The reason is unclear, but researchers note that Parkinson’s brains accumulate misfolded proteins called Lewy bodies; similar proteins appear in certain gut sensory cells. Animal data suggest these abnormal proteins might travel from gut to brain via the vagus nerve. Supporting this, people who have undergone vagotomy—surgical cutting of parts of the nerve—appear to have a lower lifetime risk of developing Parkinson’s.
“We know that infrared light may ease Parkinson’s symptoms and protect brain cells, so we wanted to test whether it could also modify the gut microbiome,” Liebert said.
Preliminary results from the first six Adelaide participants, including Margaret Jarrett, look encouraging.
“The six patients showed up to a 20 percent rise in beneficial microbes linked to lower obesity and greater short-chain fatty acid production. Bacteria associated with rheumatoid arthritis, Crohn’s disease, and insulin resistance decreased,” said Hosen Kiat, professor of cardiology at Macquarie University, who oversaw the trial.
“For the last three years I couldn’t smell flowers,” Jarrett said. “Several weeks into the trial I began to notice my roses, daphnes, and gardenias again—it was wonderful.”
Another participant, Barry Weldon, 70, had a similar experience. “My sense of smell improved markedly. One day I walked into the house and, for the first time in ages, could smell the soup my wife was cooking.”
PubMed search on Parkinson’s and microbiome
Ron Till, 68, noticed a striking change. “The trial let me sleep again,” he said. “It was remarkable.”
His neurologist had warned him not to expect much, but revised his view after seeing the results. “He called it voodoo medicine and said it probably wouldn’t work,” Till recalled. “Yet at my three-month check-up he told me, ‘You’re testing better than when you first saw me ten years ago.’”
Retired geologist Sean Kennedy, 76, also gained steadier balance and coordination. “My juggling has improved,” he noted.
In a review in Photobiomodulation, Photomedicine and Laser Surgery, Liebert and colleagues note that while the precise way light therapy alters the microbiome remains unclear, the approach shows promise.
“If PBM [light therapy] can influence the microbiome in humans, it may offer an extra therapeutic avenue for several diseases—including cardiovascular and Parkinson’s disease—that have so far lacked effective options,” the authors write.
Kiat is encouraged by the possibilities. “If we can safely nudge the microbiome toward a healthier state with an inexpensive, easy method, inflammatory and neurodegenerative diseases might also improve,” he said.
Gold Coast GP Mark Jeffery has used lasers in practice for over four years and believes current data support exploring light therapy for conditions such as Parkinson’s, Alzheimer’s, depression, and chronic pain.
“Low-level laser therapy appears to have minimal side effects and is among the safest interventions we can offer,” he says.
Liebert adds that the early findings will guide a larger, double-blind, randomized controlled trial planned for this year. “The technique could eventually span many medical fields,” she said.
Weldon’s neurologist, Chris Kneebone, remains cautiously optimistic. “We need to await the full trial data,” he said.
His advice to patients curious about infrared light for Parkinson’s? “If you’d like to try it, go ahead. I have no evidence to discourage it, but no clear proof it helps either.”
Jarrett, meanwhile, is convinced the therapy has benefited her. She is back tending her garden and feels more energetic than she has in years.
“I feel ready to take on the world again,” she said. “My garden has never looked better.”
