Your mother may have told you that you’ll catch your death of cold, but it was only recently that scientists were able to prove that cold weather does indeed make people sick. Yale University scientists found that lower temperatures weaken the nose’s first line of immune defenses.
The researchers discovered that cooler temperatures result in a “sluggish immune response” and leave people more susceptible to infection. The immune cells’ response was weaker under cold conditions, which enabled the rhinovirus to invade and multiply.
Later research by the Yale team found that in colder temperatures, immune cells were less likely to commit intentional suicide, or apoptosis, to prevent the spread of the virus to other cells. Under warmer conditions, cells sacrifice themselves via apoptosis to protect the body; however, colder temperatures slow down the infected cell’s ability to commit suicide. As we breathe in cold air, the temperature inside our nose drops and leaves immune cells at a disadvantage in protecting us from invading viruses and other pathogens.
Cold Weather and Immune Health: Getting to the Bottom of an Old Wives’ Tale
The idea that cold weather can make you sick (or weaken your immune system) has long been considered an Old Wives’ Tale, yet for centuries it’s been obvious that there’s an increase in colds, viruses, and other illnesses during the winter months. In fact, “flu season” in the United States begins as early as October and can end as late as May, a time frame in perfect sync with cooler temperatures throughout most of the U.S. According to the Centers for Disease Control (CDC), flu season is the period when flu viruses circulate at higher levels (get expert flu prevention tips).
While it would be easy to link cold weather with illness and place blame squarely on winter for a nasty bout of the flu, it’s not actually cold air that makes you sick. Germs are what make you sick; it just so happens that “cold air may contribute to conditions that lead to illness,” Healthline explains. There are a few things going on behind the scenes that contribute to this phenomenon.
Lack of Vitamin D Suppresses the Immune System During Cold Weather
During cold weather, people tend to stay inside more often. This means that people are not being exposed to as much sunlight, and a lack of vitamin D leads to a weakened immune system. Scientists know that vitamin D is critical to immune defense activation. When we get sufficient levels of vitamin D, our immune system’s killer cells, or T-cells, can react to invaders and protect us from serious infections.
In fact, T-cells first seek out vitamin D in order to activate; when a T-cell activates, it becomes a ruthless immune cell that seeks out and destroys every trace of a foreign pathogen. Researchers at the University of Copenhagen discovered that if T-cells cannot find enough vitamin D, they fail to activate and leave us vulnerable to infections and diseases.
Facts about the Nose and the Immune System
The effects of cold temperatures on your nose also play a role in the increased incidence of colds and illnesses during the winter months. You may not have considered your nose as part of your immune system, but it plays a very important role in protecting you from illness. Your nose is one of the first lines of defense against sickness because it is lined with ciliar, or tiny hairs. The mucus (snot) inside the nose keeps it from drying out, but it also works with cilia to collect dust, bacteria, and other potential invaders.
Nasal mucus is made of water, proteins, antibodies, and salt and becomes yellow or green when the body fights an infection. Our noses run when the body produces more mucus to flush invaders out; the immune system turns your nose to a faucet in order to keep you healthy. But, the immune response of your nose is suppressed by cold weather.
How to Boost the Immune System During Cold Weather
One of the best things people can do to keep their immune systems strong in cold weather is to wrap a scarf around their noses and moths. Keeping a higher temperature inside the nose enables the immune cells inside the nose to carry out apoptosis and protect the body from viruses. It’s also a good idea to eat well during the winter and include plenty of fruits, vegetables, whole grains, and lean proteins in your diet. Make it a point to get fresh produce from the market even when you can’t grow your own garden because of the cold temperatures.
You also can boost your immune system in winter by taking probiotics. The good bacteria found in probiotics strengthens the immune system and helps defend against infection. In fact, a study found that people who took probiotics had approximately 40% fewer colds and gastrointestinal infections. Products containing Lactobacillus gasseri, Bifidobacterium bifidum, and Bifidobacterium longum are most effective at boosting the immune system and protecting against colds and infections.