The healing powers of light

By Helen Albert, Community & Press Editor, Biochemical Society

Serotonin molecule

It’s that time of year again, short days, long nights, all feeling a bit of the ‘winter blues’ before we all head off to rest and recuperate over the Christmas break. We all know that sunlight can be therapeutic and indeed much of the literature suggests that exposure to sunlight triggers the release of the happiness hormone serotonin.


It seems that the healing powers of light are much broader than simply making us all feel good about ourselves. Earlier this month Li-Huei Tsai and her colleagues at the Massachusetts Institute of Technology in the US published a paper in Nature that showed that optogenetic techniques could improve symptoms of Alzheimer’s in a mouse model of the disease.

Neuron with amyloid plaques

As part of normal brain function, there is a continual process of neurons firing off signals to other neurons, commonly thought of as ‘brain waves’. One type of brain wave, gamma oscillations, is reduced before the onset of cognitive decline and the formation of hard accumulations of protein called amyloid plaques on the brain in Alzheimer’s patients. The researchers first exposed the neurons to light using optogenetics techniques, but subsequently tested the effects of flickering light alone. They found that this non-invasive strategy stimulated more gamma oscillations and appeared to reduce levels of amyloid protein in the brains of the mice.

The researchers are now hoping to test whether exposure to this type of light could have beneficial effects for people with Alzheimer’s disease.

Photodynamic therapy (credit: National Cancer Institute, USA)

Earlier this week, research published in The Lancet Oncology, showed the benefits of light therapy for men with early stage prostate cancer. The Phase III trial of vascular-targeted photodynamic therapy, which involves injecting patients with a light sensitive drug (padeliporfin) that is then activated using a laser to destroy the cancerous tissue, showed that 49% of patients who received the light therapy went into complete remission compared with only 13.5% of the control group.


“These results are excellent news for men with early localized prostate cancer, offering a treatment that can kill cancer without removing or destroying the prostate” commented Professor Mark Emberton, Dean of UCL Medical Sciences and Consultant Urologist at UCLH.

He added “This is truly a huge leap forward for prostate cancer treatment, which has previously lagged decades behind other solid cancers such as breast cancer.”

Also this week it emerged that in addition to boosting our levels of serotonin and raising our vitamin D levels, exposure to sunlight may have other benefits.

Bottle of Super-D oil capsules, London, UK, 1940–1945. Wellcome L0057855, CC BY 4.0.

Recent research has shown a link between vitamin D levels and the immune system. Gerard Ahern and his colleagues from Georgetown University in the US may have found an explanation for this link, as their research (published in Scientific Reports) showed that exposure to low levels of blue light, found in sunlight, makes T cells move faster.


When white blood cells in the blood sense an infection they release a chemical called hydrogen peroxide that kills the bacteria or other infectious organism and summons T-cells to come and help fight the infection.

“We found that sunlight makes hydrogen peroxide in T cells, which makes the cells move. And we know that an immune response also uses hydrogen peroxide to make T cells move to the damage” Ahern said. “This all fits together.”

front-cover_dec16_124x164The researchers recognize more work needs to be done to understand the details of their discovery, but believe it might lead to the development of light-based therapy to boost immunity if the beneficial nature of the light exposure is confirmed.

You can read about more light-related research in the December ‘Shine a light’ themed issue of The Biochemist, the Biochemical Society’s magazine. You can also follow the magazine on Twitter @The_Biochemist.

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