More than 100 years ago people with tuberculosis were treated in sanatoriums where they were supposed to receive plenty of sunlight. Physicians thought this would help control their infections. Back in the 19th century, of course, scientific understanding of the immune system and its functioning was quite limited.
Does Sunlight Boost Immunity?
There is new evidence, however, that the basic impulse was appropriate. Researchers report that exposure to sunlight appears to activate T cells so they move more rapidly throughout the body.
What Do T Cells Do?
T cells play a crucial role in natural immunity. These white blood cells are crucial for hunting down invading pathogens and attacking them. When they become more mobile they do a better job fighting infections and cancer.
Perhaps this discovery of a sunlight boost to T cell motility explains why people who are exposed to more sunshine are less likely to develop autoimmune diseases and cancer.
Not Just Vitamin D:
While human skin makes vitamin D upon exposure to ultraviolet light, this mechanism is independent of vitamin D. The T cells in skin are extremely sensitive to blue light. This is among the wave lengths contained in sunlight, and it is not the same as ultraviolet light. At low doses, blue light triggers T cells to make hydrogen peroxide. This is what allows them to scoot around more quickly to areas that might need immune system attention.
