In the past the explanation for the reason that colds become common in the winter was not adequately explained. One theory for example, suggested that the reason for the spread of the cold virus was that in the winter, people are more likely to huddle together to keep warm, and this act would facilitate the spread of a virus. However, no compelling evidence was presented to support this or any other theory. More recently a logical explanation as to why the common cold spreads during the winter has become apparent. During the winter, vitamin D levels drop because the sun’s light is less strong (assuming a northern latitude, in southern latitudes the opposite is true). Vitamin D is required by the immune system for the creation of antiviral proteins that protects the body from viruses including the common cold. Therefore without adequate sunlight, the immune system is reduced in its efficiency and this facilitates the spread of infections, particularly upper respiratory tract infections, like the common cold.
Eat Well, Stay Healthy, Protect Yourself