How Stress Affects the Immune System and What You Can Do About It

You may have heard it said that stress is bad for your health. Let’s get into how and why that’s true, with extra emphasis on how it affects your immune health through its impact on cortisol levels. Getting supportive nutrition daily can help.

How stress influences immune function

Scientists and medical researchers have long studied the correlation between stress and the immune system. Medical discoveries nearly a century ago began to show that stress can affect normal immune function.¹ Since then, more research has revealed that ongoing stress may influence immune system activity and affect how the body responds to everyday challenges.²

How does stress affect the immune system? The short answer: Cortisol

Stress is medically defined as “the state of homeostasis being challenged.”³ Homeostasis is the maintenance of stable internal physiological conditions in an organism. In humans, it pertains to the body’s ability to keep conditions such as body temperature, blood sugar, fluid balance, and pH within a stable, healthy range, despite changes or challenges in the external environment. Simply put, stress throws your body off balance. It causes biological and psychological responses that impact this stable environment, influencing your body’s overall well-being and, with it, your immune function.⁴

One of the responses is the production of cortisol. Cortisol is a hormone produced by your body’s adrenal glands that plays a key role in supporting the body’s stress response, metabolism, and normal immune function, and energy use in the body. Its levels rise when the body experiences physical or psychological stress. (For which reason, it’s sometimes called the stress hormone.⁵)

The Role of Cortisol in Immune Response

How does cortisol affect the immune system? On the one hand, cortisol is required for the normal function of nearly every system in the body. It plays a critical role in helping the body adapt to its environment, particularly through its effects on glucose production and the breakdown of proteins and fats.⁶

On the other hand, cortisol levels that are too high or too low can contribute to physical changes that may affect normal immune function. When cortisol secretion is severely reduced or absent, the body struggles to respond to stress. Elevated cortisol levels over time, meanwhile, can also affect metabolism, sleep patterns, mood, and cardiovascular health, all of which play a role in your overall wellbeing, thereby supporting your body’s normal immune function.

Supporting your immune health during stressful times

Life is stressful. So what next?

A balanced approach to stress management (and with it: balanced cortisol levels) includes simple, daily, healthy habits—basic things you already know to do, like prioritizing proper nutrition, sleep, and exercise. All of these healthy actions also support normal immune function.

A healthy diet supports a healthy body. When you’re properly nourished with the right balance of vitamins and essential nutrients, your body is better supported to manage daily stress, build resilience, and respond to modern mental and physical stressors.

Let’s talk about nutrients. Foundational nutrition is a key part of the equation to support your body’s resilience to everyday stressors. Eat whole, nutritious foods so your body gets the fuel it needs to support its daily functions. And if you want to really support your micronutrient needs, AG1 is a daily Foundational Nutrition supplement option that supports whole-body health—not just by a daily dose of necessary nutrients, but also with adaptogens to support stress resilience.

Beyond nutrients: get sleep and get activity. A balanced body benefits from a balance of exercise and rest.

Lastly, pursue a calm, positive mindset. Stress may feel like it’s only mental, but has very real physical effects, and the state of your body can either buffer or amplify that impact. A state of calm and a pursuit of positivity keep your heart rate down and your mood up, which helps let your body know it’s okay to relax and just do its job to the best of its ability.

Tips to manage stress

By now, we understand that stress is bad for the body. So what can we do about it? Some common methods for managing stress include:

• Keeping a consistent sleep schedule
• Exercising consistently (including strength training and moderate cardio)
• When things get busy or overwhelming, try some deep breathing or meditation
• Spend time outdoors
• Limit caffeine when particularly stressed
• Consume prebiotics and probiotics for gut and immune support
• Eat a balanced diet to provide your body with the nutrients it needs.

Tip from our team: You can further support your body’s stress response with adaptogens. Ingredients like ashwagandha, eleuthero, licorice root, and rhodiola—found in AG1—can help your body adapt to physical and mental stress while promoting overall energy, resilience, and a balanced mood.

A stressed mind may lead to a stressed body (and vice versa). A stressed body may cause changes in the overall normal function of your immune system. That’s why supporting yourself with foundational nutrition and other daily health practices is essential. The compounded effects of healthy living and an adequate supply of nutrients will support your body, even when the stress of life wants to take over both your mental and physical well-being.

References:

1. Segerstrom SC, Miller GE. Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry. Psychol Bull. 2004;130(4):601-630. doi:10.1037/0033-2909.130.4.601
2. Herbert TB, Cohen S. Stress and immunity in humans: a meta-analytic review. Psychosom Med. 1993;55(4):364-379. doi:10.1097/00006842-199307000-00004
3. Lu S, Wei F, Li G. The evolution of the concept of stress and the framework of the stress system. Cell Stress. 2021;5(6):76-85. doi:10.15698/cst2021.06.250
4. Alotiby A. Immunology of Stress: A Review Article. J Clin Med. 2024;13(21):6394. doi:10.3390/jcm13216394
5. Kaur J, Gandhi J, Sharma S. Physiology, Cortisol. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538239/
6. Magomedova L, Cummins CL. Glucocorticoids and Metabolic Control. Handb Exp Pharmacol. 2016;233:73-93. doi:10.1007/164_2015_1