There are three major mechanisms that allow cold viruses to infiltrate our immune systems in the winter:
1) Adapting To Colder Temperatures Affects The Immune System
The least important factor, although still significant in effectively battling and surviving cold is the body's ability to maintain its internal core temperature around 98.6F (37C) degrees.
The reason our parents have always insisted we stay warm to prevent colds is not an old wives tale at all. Our physiological systems which adapt to cold and wet environments causes the most heat to escape the body and makes it more difficult for the body to replace lost heat. This directly depresses our immune system in the process.
The body will inherently expend its resources differently in order to keep itself warm. During this process, the body will modify physiological mechanisms and reallocate the amount of carbohydrates used. Accordingly, the body is more responsive to glucose in the winter and consumption of foods high in sucrose can further depress this delicate system.
Many of these physiological systems slow down as the body attempts to balance the internal body temperature to external stimuli. As temperatures get colder, the nervous system will slow down and the impulses that move our muscles and blood flow will also be affected.
Simultaneously, the body will use more carbohydrates to produce lactic acid. This lactic acid combined with the deceleration of the nervous system will also force the body to slow down, so that it can retain heat. As cold increases, blood vessels constrict and causes blood flow resistance to increase.
The more heat the body can conserve, the more successful the body is at keeping its core temperature in a healthy range.
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