Why did terminal cancer patients hospitalized on the south side have a better quality of life and longer survival than those on the north side in the hospital?
One of my collaborators, a physician scientist, told me his clinical observation and the potential impact of sun exposure on our health condition. This medical doctor’s question is quite important for basic scientists to consider answers with scientific point of view. Indeed, there are many beneficial effects of sun exposure on human health. Hippocrates of Kos (460-377 BCE), the father of modern medicine, has mentioned this concept . Florence Nightingale (1820-1910), the founder of modern nursing, also mentioned a similar concept that light is one of essential points in securing the health of houses .
Vitamin D3 is recognized as the “sunshine vitamin.” Most humans depend on sun exposure to satisfy their requirements for vitamin D3; otherwise it can be obtained from fortified food, oily fish and vitamin D supplements . However, due to the destruction of the ozone layer in the past few decades , we are exposed to large amount of UVA and UVB, which cause skin aging, damage and cancer progression . Therefore, recommendations to avoid UV radiation exposure have been proposed, which may cause significant harm to public health due to vitamin D3 insufficiency . There are many diseases associated with vitamin D3 insufficiency . Therefore, maintaining a good balance between beneficial and adverse health effects from sunlight is an important issue for healthy aging.
Phototherapy is an alternative approach to receive beneficial effects from sunlight. Niels Ryberg Finsen (1860-1904), the founder of phototherapy in dermatology, developed the carbon arc lamp for skin therapy and he was awarded the Nobel Prize in Physiology or Medicine in 1903 . In our previous study, we have demonstrated the reduced expression of vitamin D3 in non-alcoholic steatohepatitis (NASH), and phototherapy with the artificial sunlight (full spectrum, color temperature 5500 K, color rendition index (CRI)>90Ra; Chang Gung Biotechnology, Taipei, Taiwan) and vitamin D3 supplementation ameliorated NASH progression in rats . In our recent study published in npj Biofilms and Microbiomes (https://doi.org/10.1038/s41522-021-00213-8), we applied phototherapy in food allergies (FAs) because of the increasing prevalence of FAs in westernized countries . There is currently no cure for FAs, and the traditional treatment is the avoidance of allergenic foods. Otherwise patients must carry a self-injectable form of epinephrine for emergency treatment of anaphylaxis. Here, we proposed applying phototherapy as an alternative approach for the prevention and treatment of FA-like allergic diarrhea.
Although the mode of action of phototherapy was not fully clarified in this study, one of the potential mechanisms underlining the beneficial impact of phototherapy could be the improvement in FA-associated vitamin D3 insufficiency. Another potential mechanism of phototherapy in the prevention of FA could be the modulation of gut microbiota. We performed fecal microbiota transplantation (FMT) to demonstrate the impact of microbiota composition in FA (Figure). Briefly, FA-associated dysbiosis could directly transfer FA symptoms in naïve BALB/c mice. On the other hand, the replacement of FA-associated bacteria with healthy microbiota may be a promising strategy for FA therapeutics. We identified the genus Lachnospiraceae_NK4A136_group (phylum Firmicutes) as an FA-associated microbacteria. In addition, one of the beneficial bacterial species, Parabacteroides goldsteinii (phylum Bacteroidetes), was enriched in phototherapy-treated mice. Although further studies are necessary, these unique microbes may play some roles in FA development and prevention.
Full text is available at the following link: https://www.nature.com/articles/s41522-021-00213-8.pdf
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