Ultraviolet B (UVB) intensity depends on a number of natural factors, including latitude, altitude, weather conditions, time of day and season, with human behavior and lifestyle playing an indirect role also. A recent study on women living in Vancouver, Canada, who were artificially exposed to UVB suggests that UVB increases diversity and richness of the gut microbiota, contributing to good health.
Gut microbiota influenced by the sun
Researchers replicated the study on Brazilian populations whose lifestyle and living conditions were very different from those of the Canadian women. They compared the gut microbiota of the Canadian city dwellers to that of various hunter-gatherer populations, including the Yanomami, an ethnic group living near the Equator, in a region of the Amazon which receives a high amount of sunlight. For the Yanomami, UVB rays are not blocked by pollution, clothing or sunscreen. Like that of the Canadian women, the gut microbiota of the Yanomami seemed to be modulated by exposure to UVB. It showed common characteristics (greater diversity, an increase in bacteria belonging to the Firmicutes phylum, a reduction in bacteria belonging to the Bacteroidetes phylum) that differentiates them from city dwellers. It was also particularly rich in proteobacteria, a peculiarity not fully understood by the researchers, who suggest that high exposure to UVB, due to the Yanomami’s lifestyle and the unique environmental conditions in which they live, may be responsible.
UVB, a factor to be explored
The authors believe that UVB, whether natural or artificial, merits consideration as a factor capable of influencing the composition of the human intestinal microbiota. They conclude that a more in-depth study that takes latitude, and therefore sun exposure, into account could shed new light on the relationship between the host, host’s health, gut microbiota and environment.
