Is cold weather bad for our immunity?

We are well into winter, but contrary to what many have been told about the dangers of cold exposure, there is little scientific support that the cold directly depresses immune function and makes us sick. What may be occurring during the cold winter months is a vitamin D decrease due to fewer daylight hours and less time spent outside. People with low vitamin D levels tend to have increased rates of infections. 

Colder weather also makes people less active, which decreases their blood circulation. Increased circulation, such as seen during exercise, may mobilize specialized cells within our immune system. These cells are used for fighting infection, but when we have little physical movement they are not delivered to all parts of the body. 

Furthermore, movement may also increase body temperature, which could slow virus replication as viruses are known to replicate faster in cold conditions.  

Viral strains

Most people are familiar with the common cold caused by the virus class known as rhinoviruses. There are at least over 150 variations of the rhinovirus, and these variations are known as strains. Strains are essentially the same virus, but with some slight changes to the virus makeup.  

There are over 200 different viruses that can be spread person to person and many cause cold and flu symptoms. Influenza, the cause of seasonal flu typically seen from October through April here in North America, is an example. Another is the Sars-Cov-2 virus that causes COVID and its related symptoms. Both kinds of viruses can transform into new strains, which sadly can make us quite sick.

Cold dry air

The cold dry air during winter allows viruses to spread more easily, since our mucous membranes dry out and are not as effective in blocking the viruses from entering our bodies.   Unfortunately, the decreases in temperature and humidity seen during winter may also allow viruses to replicate faster. 

People in warm weather climates without dramatic temperature or humidity decreases may have more cases of flu during the rainy season. This is likely due to more time being spent indoors around others.

Close contacts

Greater time around others, particularly indoors, increases the risk of virus exposures. This is due to increased person-to-person contact, which exposes one to more virus-containing respiratory droplets in the air and on surfaces. 

Cold exposure therapy 

While cold weather may introduce physiologic stressors and a triggered immune response, cold exposure can also trigger a beneficial cascade of immune cells and beneficial neurotransmitter effects. The overall result can have a positive impact on the body over time.  

The benefits of cold exposure include:

1. Reduced inflammation: Short exposure to the cold can reduce the inflammatory responses that trigger damaging blood enzymes and neurotransmitters. Exercise creates an inflammatory response by breaking down muscle fibers that rebuild over time and cause eventual muscle growth. 

If you use cold therapy a day or two after exercise, the immune response from the cold may reduce the muscle discomfort. Also, the increased respiratory rate and larger breaths from exercise may flush out viruses and bacteria from our lungs and noses. 

The benefits of cold exposure can be obtained from super cold dry air at -200F to 260F, cold showers, or any cold water exposure done over a few minutes.

2. Better brain function: Brain function and mood may be boosted by the release of norepinephrine, the neurotransmitter involved in focusing attention and mood. Low levels of norepinephrine can lead to depression or ADHD.

3. Fat loss: Fat loss, from an increase in burned calories, occurs when brown fat activation is triggered by cold exposure. Triggering is done to generate heat, which allows for better body functions. 

Brown fat is found around our organs, and its presence is increased by exercise. White fat, typically found under the skin, is an insulator to trap heat, but large amounts of white fat increase the risks of heart disease and stroke. The beneficial caloric increase of brown fat activation burns calories, which decreases the overall amount of white fat. 

What can one do to stay healthy?

• Humidify the air taken in during dryer days.
• Generate internal heat by exercising regularly.
• Wash hands with alcohol based products to kill viruses.
• Consider masking when around others if an outbreak is known.
• Eat nutritious foods whenever able.
• Get adequate sleep to lower stress hormones.
• Lastly, do get vaccinated against the viruses. We have vaccines that aid one’s immune response.