If you are someone who works out a lot, you can be especially susceptible to viruses owing to the fact that physical exertion can upset the regulation of cortisol. More commonly, increased cortisol production is linked to stress. Whether the stress is physical, psychological, chemical, biochemical, environmental, or even imaginary, the adrenal glands are hardwired to intensify their production of cortisol.
So what the heck is cortisol? Cortisol destroys the body’s natural killer cells, which are key to the immune system’s defense against invading illnesses. Because massage reduces the amount of cortisol in the body—as demonstrated by several studies that measured cortisol in subjects' saliva before and after massage sessions—“your immune cells get a boost,” according to Tiffany Field, director of the Touch Research Institute at the University of Miami School of Medicine. Even in people with severely compromised immune systems, such as those with breast cancer, massage has been shown to suppress cortisol and give the immune system a lift.
Cortisol levels that are chronically elevated, incidentally, can also lead to an accumulation of abdominal fat. This is because glycogen stored in the liver and in muscle tissue is mobilized to raise blood sugar level and because digestion is inhibited as a response to the perceived threat. Such blood sugar imbalances can also interfere with the ability of cells to be nourished by the glucose in one’s diet and can increase the permeability in the intestinal wall, both of which can leave you nutritionally deprived, further weakening one’s immunity.
It is not advisable to get a massage if you are in the throes of a cold or the flu because of the way massage can spread viruses through the body more quickly than would happen naturally. If you aren’t sick, though, but have been exercising vigorously or have been experiencing any other kind of stress, regular massage can help bolster your immune system.