5 Things That Can Weaken Your Immune System

5 Things That Can Weaken Your Immune System

Your immune system is your stalwart protector against unwanted invaders, and it takes its job seriously. A well-functioning immune system has both brawn and brains: it’s smart enough to correctly identify a threat and balance the response, and strong enough to successfully defend you from it. No one’s immune defenses are bulletproof, but the better your defenses are working, the more resilient you are against common bugs.

Of course, if you want your immune system to stay at the top of its game, you have to treat it right. That means taking good care of yourself so that your body has the resources it needs for self-defense. Unhealthy lifestyle choices and lack of self-care can chip away at your resilience and weaken your immune defenses. You may not even notice it until you catch a bug and find it harder than you expected to bounce back.

You can keep your immune system in good shape by making smart, healthy lifestyle choices like keeping your nutrition balanced and getting enough sleep. In the meantime, keep an eye out for these not-so-healthy habits that can take a toll on your immune health. Here are 5 common things that can weaken your immune system:

1. Too Much Stress

We tend to think of stress as psychological, but it’s physical, too. Stress triggers a cascade of chemical and physical reactions that put the body into immediate survival mode. But what helps us survive in the short-term isn’t very good for us in the long-term. Persistent stress takes a toll on our health, including our immune health.1 

The stress hormone cortisol plays an important role in regulating our inflammatory and immune responses. But if we have excess cortisol from too much stress, we eventually become less responsive to it. Our immune cells may also become less sensitive to cortisol, which can impact their ability to regulate healthy inflammation and lead to a weaker immune response.2 Stress can also decreases certain immune cells such as lymphocytes, which help defend against unwanted invaders.3

Managing your stress better may require some lifestyle changes. Make sure you’re giving yourself regular time to unwind by doing something soothing or fun, whether that’s yoga or a walk in nature, dancing or singing, journaling or crafting, or just talking with your friends. There are also supplements that can help with stress management, such as ashwagandha, an herb that's been shown to help reduce excess cortisol.4  

2. Lacking Nutrients

Your immune system needs a consistent, healthy supply of vitamins, minerals, and protein to function at its best. Fresh, whole foods like fruits and veggies, nuts and seeds are full of important nutrients like vitamins A, C, E, and zinc that work together to support the immune system. However, research shows that most Americans don’t eat enough of these healthy foods, and that insufficient vitamin and mineral intake is surprisingly common in the U.S.5 Lack of one or more of these nutrients can impact your body’s production of immune cells and antibodies, or weaken their immune activity.6 

Even when you’re trying to eat healthy, your diet may be lacking in variety. To get the full range of vitamins and minerals you need, make a habit of eating a variety of whole foods, including vegetables, fruits, nuts, legumes, and whole grains. If you avoid meat or dairy, make sure you’re getting enough protein from other sources, since lack of protein can also lower your immune response.7 A daily multivitamin can also help cover any vitamin or mineral gaps in your diet.

3. Not Enough Sleep

In our hyper-productive culture, lack of sleep has become all too common. But sleep is one of your body’s built-in mechanisms for keeping you healthy, and it should not be taken for granted. Not only is healthy sleep essential for your body’s repair and recovery, it also helps strengthen your immune system. 

During your sleep, your body produces protective proteins which support a healthy immune system and stress response. Lack of sleep can decrease these proteins, as well as reduce the production of immune cells and antibodies. Studies confirm that those who don’t get good sleep are more likely to catch what’s going around and take longer to recover.8

That’s not good news, considering that nearly a third of us don’t get enough sleep.9 If you frequently have trouble sleeping, try some of these tips for getting a good night’s sleep, or learn more about the most likely reasons you aren’t sleeping. Sleep aid supplements may also offer support as you reset your sleep patterns.

4. An Unhealthy Gut

Gut health issues aren’t just uncomfortable, they can affect your health in multiple ways. Immune health is a good example: about 75% of your immune system lives in your gut, which is considered your body’s largest immune organ. Your friendly gut bacteria play a key role in your defense, helping to keep unfriendly microbes in check, regulate immune responses, and maintain a healthy gut barrier, which helps keep harmful substances out of the bloodstream. But if your gut is unhealthy and overrun by unfriendly bacteria, these immune defenses will be compromised.10

You can support your gut health by drinking more water and eating more fiber to help keep things moving through the digestive tract and flush out waste and toxins. You can also support your friendly bacteria by taking probiotics and by feeding them with prebiotics, a type of indigestible fiber found in foods such as asparagus, onion, apples, and mushrooms. Avoiding simple sugars will also help starve the unfriendly bacteria which thrive on them. 

5. Too Much Time Indoors

As modern life moves increasingly online, we’re all spending less time outdoors. We’ve become so used to it that we may not even realize how the lack of sunshine, fresh air, and exposure to nature is affecting our mental and physical health – from our stress levels and sleep patterns to our immune health.

For starters, an indoor lifestyle can lead to an increased risk of vitamin D deficiency, since we need direct sunlight in order for our skin to make vitamin D. Vitamin D plays an important role in activating immune responses, and lack of vitamin D is linked with a weaker immune system.11,12 Sunlight also helps regulate our circadian rhythms, which is important for healthy sleep patterns.

But that’s not the only reason to spend time outdoors. Simply breathing in fresh air increases oxygen, which helps cleanse the lungs and supports healthy white blood cell activity. If there are trees nearby, even better: not only is the air quality cleaner, which supports respiratory health, but being near trees has actually been shown to help reduce stress and boost immunity. One study found that spending at least 2 hours per week in nature was associated with good health and well-being.13

Make a habit of getting outside for a walk a few times a week, preferably in a natural setting. You’ll move your body, breathe fresh oxygen, soak up the sun, clear your mind, and refresh your mood. Not only will you feel better afterward, you’ll likely sleep better, stress less, and support your immunity, too.

Of course, in the winter, this is more easily said than done: bad weather may keep you indoors, and you may not be able to get enough vitamin D from the available sunlight anyway. You may want to consider vitamin D supplements during those colder months. Consult your health provider about how much vitamin D is right for you.


[1] Pietrangelo, Ann and Watson, Stephanie. “The Effects of Stress on Your Body.” Healthline, March 2020.

[2] Kress, Robert. “Stress, Inflammation, Immunity.” RN.com.

[3]What Happens When Your Immune System Gets Stressed Out?” Cleveland Clinic, March 2013.

[4] Auddy, Biswajit & Hazra, Jayaram & Mitra, Achintya & Abedon, Bruce & Ghosal, Shibnath. (2008). "A Standardized Withania Somnifera Extract Significantly Reduces Stress-Related Parameters in Chronically Stressed Humans: A Double-Blind, Randomized, Placebo-Controlled Study. "Journal of American Nutraceutical Association. 11. 50-56.

[5]Micronutrient Inadequacies in the U.S. Population: An Overview.” Linus Pauling Institute, Oregon State University.

[6]Nutrition and Immunity.” Harvard T.H. Chan School of Public Health.

[7] Danziger, Lucy. “Eat Protein to Boost Your Immunity.” The Beet, Sept 2020.

[8] Olson, Eric J. “Lack of sleep: Can it make you sick?” Mayo Clinic, Nov. 2018.

[9] “Data and Statistics: Short Sleep Duration Among US Adults.” Centers for Disease Control and Prevention.

[10] Wiertsema, S.P.; van Bergenhenegouwen, J.; Garssen, J.; Knippels, L.M.J. “The Interplay between the Gut Microbiome and the Immune System in the Context of Infectious Diseases throughout Life and the Role of Nutrition in Optimizing Treatment Strategies.” Nutrients 2021, 13, 886.

[11] Leavy, O. “Immune-boosting sunshine.” Nat Rev Immunol 10, 220 (2010).

[12] Aranow, Cynthia. (2011). “Vitamin D and the Immune System.” Journal of investigative medicine : the official publication of the American Federation for Clinical Research. 59. 881-6. 10.2310/JIM.0b013e31821b8755.

[13] White, M.P., Alcock, I., Grellier, J. et al. “Spending at least 120 minutes a week in nature is associated with good health and wellbeing.” Sci Rep 9, 7730 (2019).