How Lifestyle Choices Affect Your Immune System

Our immune system operates continuously to keep us healthy, and the choices we make every day affect how well it functions. Alongside nutrition, factors like stress, sleep, exercise, sunlight, and cold temperature all impact immune resilience. Understanding how each of these elements contributes to immunity can help us build habits for a stronger, healthier body.

Link Between Stress and Immunity

Stress is an unavoidable, natural human response. However, feeling pressured and overwhelmed for an extended period of time (chronic stress) can have severe consequences for the immune system. When the body is under prolonged stress, it produces higher levels of cortisol [1], a hormone that suppresses immune function. Over time, this suppression weakens the body’s ability to fight infections and increases inflammation.

Long-term stress also slows wound healing and raises the risk of viral infections. The immune system depends on regulated signaling pathways, and constant stress disrupts these processes by altering the number and effectiveness of white blood cells (leukocytes). White blood cells are the body’s principal defense system against foreign invaders [2], including microbes such as bacteria, viruses, fungi, and parasites.

To counteract the negative effects of stress, adopt practices like:

• Meditation and deep breathing exercises
• Regular physical activity like walking or yoga
• Maintaining social connections
• Spending time in nature
• Journaling or creative expression [3]

Additional guide: 7 Super Duper Foods to Reduce Stress

Sleep & Immunity

Quality sleep is one of the most important yet often overlooked factors in immune health. During sleep, the body repairs itself, produces infection-fighting antibodies, and regulates inflammation. Studies show that sleep-deprived adults and children are more likely to catch illnesses like the common cold or flu.

Quality sleep—not just any sleep—supports the production of cytokines [4], which are proteins that help manage immune responses. Sleep deprivation reduces cytokine production, impairing the body’s response to infections.

The American Academy of Sleep Medicine says different age groups need different amounts of sleep:

• 4 to 12 months old: About 12 to 16 hours, naps included
• 1 to 2 years old: Approximately 11 to 14 hours, naps included
• 3 to 5: 10 to 13 hours, naps included
• 6 to 12: 9 to 12 hours
• 13 to 18: 8 to 10 hours
• Young and older adults: 7 to 9 hours

Tips for improving sleep naturally include:

• Sticking to a consistent sleep schedule
• Limiting screen time in the evening to reduce blue light exposure
• Creating a cool, dark, quiet sleep environment
• Avoiding caffeine, green tea, and other stimulants in the late afternoon and evening
• Establishing a relaxing pre-sleep routine, such as reading or taking a warm bath

Role of Exercise in Immune Health

Regular physical activity helps optimize immune system performance and lowers vulnerability to illness. Specifically, moderate physical activity, or movements that increase heart rate, improve circulation, support lymphatic flow, and promote immune cell movement throughout the body. It also reduces inflammation and stress hormone levels.

According to the World Health Organization, physically active individuals have lower incidences of noncommunicable diseases like hypertension, stroke, cardiovascular disease, diabetes, and several cancers. Exercise also improves the function of macrophages involved in detecting and destroying harmful organisms, including those associated with the common cold and flu.

Among the best exercises to boost immunity include:

• Moderate cardio, such as swimming, cycling, or brisk walking
• Strength training, around 2 to 3 times per week
• Mind-body exercises like yoga, tai chi, or qigong
• Outdoor activities, which may also provide sunlight exposure and stress relief

However, overtraining with inadequate recovery can lead to fatigue and heightened vulnerability to illness. Most medical professionals recommend resting two days a week to allow the body to recover from structured training. For more intense training programs, taking a full week off every three to four months helps reduce the risk of overtraining-related injuries. Light activity, such as walking for 30 minutes a day, is generally safe and beneficial.

Cold Therapy & Immunity

Cold therapy, including cold showers and ice baths, enhances immune function. A 2024 study available in the Journal of Thermal Biology concluded that regular cold showers boosted humoral and cell-mediated immunity by regulating antibodies, interleukin-2, and interleukin-4 [5].

Introduce and acclimate to cold therapy by:

• Ending a warm or room-temperature shower with 30 seconds of cold water
• Practicing cold water immersion in a controlled environment, such as a plunge pool or cryotherapy facility
• Spending short periods outside without heavy layers

As with any new wellness practice, monitor physical responses closely and consult a medical professional when underlying conditions exist.

Sunlight & Vitamin D

Vitamin D influences how the immune system detects and responds to threats [6]. One of the best ways to get it is through sunlight exposure. Exposure to the sun’s ultraviolet B (UVB) rays trigger the production of vitamin D, which helps modulate the immune response.

It also supports the function of T cells [7] and reduces the risk of respiratory infections. Being vitamin D deficient increases susceptibility to colds, flu, and autoimmune diseases.

For healthy, responsible sun exposure:

• Aim for 5 to 15 minutes of midday sun exposure on bare skin, about 2 to 3x a week.
• Consider supplementing with vitamin D during the winter or if you live somewhere with limited sunlight.

The Bottom Line on Lifestyle and Immunity

Each of these lifestyle factors—stress, sleep, exercise, cold exposure, and sunlight—interacts with and supports the immune system. None of them work alone to “fix” or improve health, but together, they help protect against diseases by strengthening the immune system.

Start with manageable habits today: a 30-minute walk daily, a consistent bedtime schedule, cold showers, and a few minutes outdoors. These changes build momentum and improve how the body feels and functions over time.

Tuning into the body’s needs and adopting resilience-building habits give the immune system the best chance to thrive. And, when the immune system is strong, everything else—from mood to energy levels, benefits too.

If you’re interested in more ways to support immune health naturally, read this Ultimate Guide to Strengthening the Immune System and the Best Foods for Your Health.

Additional References

[1] Harvard Health: Understanding the Stress Response

[2] Better Health Channel: Immune System Explained

[3] ScienceDirect.com, Journal of Creativity: Creative Expression and Mental Health

[4] National Library of Medicine: Sleep and Immune Function

[5] ScienceDirect.com, Journal of Thermal Biology: Regular Cold Shower Exposure Modulates Humoral and Cell-Mediated Immunity in Healthy Individuals

[6] National Library of Medicine: Vitamin D and the Immune System

[7] Journal of Clinical Endocrinology & Metabolism: Vitamin D Supplementation Modulates T Cell–Mediated Immunity in Humans