Winter Might Make Us More Likely to Get Ill. But How and What We Can Do to Strengthen the Immune System During the Winter

13 December 2025

Winter is here, and we are seeing a rise in the cases of flu and colds. Also, some of us might feel a bit sicker or experience more severe symptoms of preexisting conditions. But is winter the real culprit, or is there something else?

As winter approaches, let’s break down the (complex) link between immune health and winter.

Besides, we will learn science-backed ways to strengthen our immune system.

Does Winter Really Make Us Sick?

The answer is far from simple.

Let’s first understand how winter days may make us more likely to get sick.

Colder, darker months may increase inflammation in the body, putting us at a higher risk of developing diseases of the blood vessels and heart, joint problems, and mental health problems.

Lower temperatures during winter may impair our immune system’s ability to trap microorganisms before they can infect us. (1) That might be one of the reasons we see a surge in cold and flu cases during the winter.

Note: It’s not that winter directly causes these diseases. It’s that winter-associated excess inflammation may make us more susceptible, especially if we already have other risk factors. Besides, winter may worsen the symptoms in those with preexisting health issues. (2)

How to Strengthen the Immune System in Winter?

The foundation of health remains the same, regardless of the season. It includes quality sleep, a healthy diet, sunlight, stress management, exercise, and mindful use of supplements. However, we may need certain tweaks and additional tips to maintain health during the winter.

Get enough sunlight

Sun exposure is crucial for maintaining the body’s sleep-wake cycle. The cycle, also known as the body’s internal clock, regulates our immune function and the body’s response to vaccines. It also affects how our immune system clears germs from the body. (3)

Next, our skin makes vitamin D when exposed to the sun’s UV rays. Also called the “sunshine vitamin”, it is essential for healthy immune function. Studies show that a lack of vitamin D may make us more likely to catch an infection. (4)

Unfortunately, sun exposure during autumn and winter months in the UK is not enough to produce vitamin D in the skin. (5) That’s why we rely on dietary sources, which again may fail to provide sufficient amounts of vitamin D. Thus, experts recommend taking over-the-counter vitamin D (10 micrograms or 400 IU for individuals older than age 4) during the winter.

The bottom line is that getting out in the sun is essential, even though winter sunlight will do little (if any) to the vitamin D levels. There are several other benefits to sun exposure during winter, such as improved mood, strong immune health, and better sleep.

Sleep well

During sleep, the levels of stress hormones drop, and our body and mind are relaxed. As we slip into the deeper stage of sleep, the bone marrow releases new immune cells into the bloodstream. In the meantime, energy-rich molecules, like glucose, move from the muscles to the immune system. (6)

All these processes stimulate and strengthen our immune system, making us more competent at fighting disease-causing microorganisms.

On the other hand, poor sleep (both short- and long-term) can weaken the immune system and make us sick.

According to the NHS, healthy adults should get 7 to 9 hours of sleep each night. To get sufficient quality sleep, we should follow a sleep schedule. Anyone having problems falling or staying asleep should consider avoiding:

  • Alcohol, tea, or coffee at least 6 hours before bedtime.
  • High-intensity exercise at least 4 hours before bedtime.
  • “Screens” at least an hour before bedtime.

Exercise regularly

Exercise, as simple as walking, is great for our immune system. Exercise, irrespective of the type, helps strengthen our immune system in several ways.

First, exercise helps clear bacteria and viruses out of the respiratory tract. This may make us less likely to catch a cold, flu, or other diseases. Second, exercise signals the body to make more white blood cells, the body’s major infection-fighting cells.

Lastly, physical activity lowers the levels of stress hormones, which can help protect against infections. Regular exercise improves sleep, increases blood flow, and strengthens bones and muscles, all contributing to a healthy immune system.

While any form of exercise is great for health and immunity, overdoing it can harm. Those who already meet the weekly recommendations should not exercise more just to support immunity.

Manage stress

Long-term stress can weaken our immune system, making us prone to both infectious diseases and chronic diseases. While short bursts of stress usually protect against illnesses, long-term stress can strain the immune system and increase inflammation.

Related: Chronic Inflammation Is Widespread In the UK. Here’s What You Can Do to Keep It At Bay

Several lifestyle changes can help manage chronic stress, such as:

  • Eating a healthy diet and staying hydrated.
  • Getting enough quality sleep.
  • Regular exercise.
  • Practising mindfulness or meditation to help the body and mind relax.
  • Maintaining healthy relationships and staying socially active.
  • Having some “me time” each day to identify stress triggers and how our mind responds to them.
  • Helping others and being grateful for what we have.

It’s also important not to look for our peace of mind in alcohol or caffeine. Those who choose to drink should stick to the recommended limits. As for caffeine, 400 mg per day, which is typically the amount present in 4 or 5 cups of coffee, appears safe for most people.

Eat a healthy diet

When we talk about diet, we are focusing on a healthy eating pattern rather than a specific ingredient. Our body is a complex machine, and no single ingredient is enough to balance hundreds of processes that run continuously 24 hours a day.

A healthy diet comprises “real” foods that feed the body. These include whole grains, fruits, vegetables, lean proteins, healthy fats, and complex carbs.

For example, home-made chicken broth is great for supporting immunity during winter. Apart from the savoury taste, it contains anti-inflammatory substances that may help alleviate symptoms of upper respiratory tract infections. (7)

We may occasionally enjoy ultra-processed foods, but they should never be part of our everyday diet. The same applies to alcoholic drinks. High in calories but lacking essential nutrients, ultra-processed foods can harm our health and immunity in two ways.

First, they make our immune system less effective at fighting against disease-causing infections. Second, they impair the immune system’s ability to eliminate harmful germs that are already in our body. (8)

The compound effect is that we tend to get sick more often, and it takes longer to heal once we get sick.

Further Reading: How food processing starves our bodies of nutrients, leaving us feeling run down and tired

Key Takeaways

  • Winter does not directly make us sick. However, increased inflammation during the winter might make us more likely to catch an infection.
  • Colder temperatures may worsen symptoms in those with preexisting medical conditions.
  • Quality sleep, a healthy diet, sunlight, stress management, exercise, and mindful use of supplements are the pillars of health during the winter (and also summer!).
  • Avoid or limit ultra-processed foods and alcohol.

Frequently Asked Questions

  1. How can I boost my immune system in the winter?

Tips to strengthen the immune system in the winter:

  • Eat a healthy diet, which includes lots of fruits and vegetables, whole grains, lean proteins, healthy fats.
  • Be sure to get enough vitamin C, zinc, selenium, and iron.
  • Get enough sunlight and sleep well.
  1. Why is my immune system so weak in winter?

We may feel that our immune system is less efficient at fighting colds during the winter. Several factors may be responsible for this. These include less sunlight (low Vitamin D levels), drier air irritating nasal passages, increased time indoors (increasing germ spread), and germs viruses thriving in cold conditions.

  1. Does cold weather affect your immune system?

Cold weather does not directly cause colds. However, some studies suggest that cold temperatures may make it harder for our immune system to clear viruses. Likewise, some viruses can grow better during the winter. The combined effect might be what makes colds more common during the winter.

Useful Link: Vitaliti liquid supplement supporting immune health

References:

  1. Huang, Di, et al. “Cold Exposure Impairs Extracellular Vesicle Swarm–mediated Nasal Antiviral Immunity.” Journal of Allergy and Clinical Immunology, vol. 151, no. 2, Dec. 2022, pp. 509-525.e8, doi:10.1016/j.jaci.2022.09.037.
  2. “Seasonal Immunity: Activity of Thousands of Genes Differs From Winter.” University of Cambridge, 12 May 2015, www.cam.ac.uk/research/news/seasonal-immunity-activity-of-thousands-of-genes-differs-from-winter-to-summer.
  3. Ding, Jun et al. “Circadian rhythm regulation in the immune system.” Immunology vol. 171,4 (2024): 525-533. doi:10.1111/imm.13747
  4. Aranow, Cynthia. “Vitamin D and the immune system.” Journal of investigative medicine : the official publication of the American Federation for Clinical Research vol. 59,6 (2011): 881-6. doi:10.2310/JIM.0b013e31821b8755
  5. “Vitamin D Deficiency: Migrant Health Guide.” GOV.UK, 3 Mar. 2021, www.gov.uk/guidance/vitamin-d-deficiency-migrant-health-guide#.
  6. Besedovsky, Luciana et al. “Sleep and immune function.” Pflugers Archiv : European journal of physiology vol. 463,1 (2012): 121-37. doi:10.1007/s00424-011-1044-0
  7. Rennard, B O et al. “Chicken soup inhibits neutrophil chemotaxis in vitro.” Chest vol. 118,4 (2000): 1150-7. doi:10.1378/chest.118.4.1150
  8. Munteanu, Camelia, and Betty Schwartz. “The relationship between nutrition and the immune system.” Frontiers in nutrition vol. 9 1082500. 8 Dec. 2022, doi:10.3389/fnut.2022.1082500