The immune system plays a key role in both the development of cancer and the effectiveness of many treatments. A well-functioning immune system can help the body respond better to therapies and may even help keep the cancer in check. Understanding how your immune system works, how to support it, and how to monitor and optimize its function is an important part of comprehensive cancer care.
Certain cancers have been directly linked to impaired immune function. These include cancers of the bladder, kidney, and skin (melanoma). Immune-mediated illnesses such as Crohn’s disease, celiac disease, or asthma can also increase cancer risk, both in the affected organs such as the colon or lung, and in other areas of the body. In addition, some viral infections are also known to cause cancer. These include cervical cancer, some head and neck cancers, liver cancer, and some types of lymphoma.1He MM, Lo CH, Wang K, Polychronidis G, Wang L, Zhong R, Knudsen MD, Fang Z, Song M. Immune-Mediated Diseases Associated With Cancer Risks. JAMA Oncology. 2022 Feb 1;8(2):209-219; Hanahan D, Weinberg RA. Hallmarks of cancer: the next generation. Cell. 2011 Mar 4;144(5):646-74.
What is your immune system?
Your immune system is your body’s defense team, on the lookout for infections caused by bacteria and viruses, as well as abnormal cells that aren’t behaving as they should. As with inflammation ›, the immune system uses cytokinessmall proteins that helps cells in the immune system communicate with each other. They act like messengers, telling immune cells when to start or stop fighting infections, inflammation, or diseases. to “talk” to each other.
The immune system has two main lines of defense:
- Innate immunity is your first line of defense. It’s the system you are born with. It acts like a team of security guards, using barriers like skin, mucus, stomach acid, and white blood cells to block or neutralize threats quickly.
- Adaptive immunity is your second line of defense. It learns from experience, developing the ability to recognize and respond more effectively to previously encountered threats. This system includes specialized immune cells such as B cells, T cells, and memory cells.
Together, these systems normally help prevent the formation and spread of cancer. However, under certain conditions, these immune defenses can become less effective, which may lead to cancer.
These systems also normally prevent you from getting infections. Many cancer treatments can weaken your immune defenses and increase your chances of getting a serious infection.
Symptoms of a weakened immune system
Although your immune system typically works quietly in the background, certain signs may indicate it’s not functioning at its best. If you notice any of the following, it may be worth exploring your immune health further.
- Frequent colds and infections: If your immune system is underpowered, you may notice that you catch everything that comes along, or have a much longer or severe illness than those around you.
- Slow wound healing: In addition to inflammation, immune health plays an important role in wound healing. Aging and chronic illnesses such as diabetes are often associated with delayed wound repair.
- Fatigue: Immune cells require significant energy to fight infections and maintain cellular health. When your system is actively using immune cells, your body may redirect energy from elsewhere, leaving you feeling drained.2Chapman NM, Chi H. Metabolic adaptation of lymphocytes in immunity and disease. Immunity. 2022 Jan 11;55(1):14-30.
- Digestive issues: The largest reservoir of the immune system lies in your gut. The gut microbiome and the food you eat influence immune function. Because the gut is a key frontline barrier for the immune system, any compromise can weaken your overall immune defense.3Takiishi T, Fenero CIM, Câmara NOS. Intestinal barrier and gut microbiota: Shaping our immune responses throughout life. Tissue Barriers. 2017 Oct 2;5(4):e1373208.
How do you know if your immune system is working well? What to ask your doctor
Ask your doctor about how your immune health might be affecting your cancer treatment along with tests to assess the current state of your immune system.
Common tests to discuss with your doctor:
- Complete blood count shows both the total number of white blood cells along with a ‘differential’ or a breakdown of different types of cells
- Neutrophils are a marker of the innate immune system
- Lymphocytes are an indicator of the adaptive immune system
- Elevated C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-α (TNF-α), or transforming growth factor-β (TGF-β) are associated with alterations in immune function.
- Other tests that may help further understand immune health include looking at specific populations of cells: B cells, T cells, and ratios of neutrophils to lymphocytes.
There may be specific tests for different cancer types. Ask your doctor what might be appropriate for your case.
Improving your immune health with evidence-based therapies and practices
Supporting immune health through evidence-based therapies, including lifestyle changes and complementary therapies, can help improve outcomes and overall well-being during and after cancer treatment.
Optimizing other terrain factors is also important. High-quality research about your immune system links it to other body terrain factors. The most well-researched body terrain factor with links to immune health is the microbiome ›, which is often closely linked to diet. Additional terrain factors include inflammation › and oxidative stress. You might notice that the practices and therapies that support immune health are also helpful in supporting other aspects of the body’s terrain. Supporting one aspect can have bountiful impacts on other areas of your overall health.
Top therapies and practices to improve your immune health
1. Sleeping Well
While many of us can’t just order up a great night’s sleep, we can do things to ensure better sleep. Make time for your sleep health, and if you snore or have risk factors for sleep apnea, ask your care team for an evaluation by a sleep medicine specialist.4Besedovsky L, Lange T, Haack M. The sleep-immune crosstalk in health and disease. Physiological Reviews. 2019 Jul 1;99(3):1325-1380. See our guide to Sleeping Well ›
2. Eating Well
The influence of nutrition on the immune system and even on cancer treatment outcomes is becoming increasingly clear. The relationship between gut health, immune function, and overall health highlights how powerful our daily food choices can be. Several different diets have been studied including the Mediterranean diet ›, the ketogenic diet, and others. A hallmark of all of them? They emphasize whole, diverse foods, avoiding ultra-processed foods, and eliminating sugar-sweetened beverages. More information about specific diets and cancer can be found on our Eating Well › page. Most studies have focused on how these diets impact inflammation, a key factor affecting immune function. For more information on how diet impacts inflammation (and some excellent suggestions on foods and supplements!), see our terrain article about inflammation ›.6Nguyen NA, Jiang Y, McQuade JL. Eating away cancer: the potential of diet and the microbiome for shaping immunotherapy outcome. Frontiers in Immunology. 2024 May 30;15:1409414; Tan IJ, Parikh AK, Cohen BA. Melanoma metabolism: molecular mechanisms and therapeutic implications in cutaneous oncology. Cancer Medicine. 2024 Nov;13(21):e70386.
3. Managing Stress
Talk with your care team about your mood and stress symptoms, and treat them if they are persistent. Having cancer is stressful. Finding your center, supporting your mood, and monitoring yourself for symptoms that have gone from short-term to persistent or chronic is an important way to support your immune system. Mood and stress symptoms are both a risk factor for cancer and a symptom that can follow a cancer diagnosis, triggering changes in the nervous system that affect the function of the immune system. These changes include over- or underproduction of immune cell signalling molecules. Stress directly affects the performance and number of white blood cells, which are essential tools for fighting infections and tumors. Many of the practices we suggest here (sleep, diet, exercise, sauna, qigong) are known to positively impact mood, so as you combine these approaches, take note of how you feel overall.7Berk M, Köhler-Forsberg O et al. Comorbidity between major depressive disorder and physical diseases: a comprehensive review of epidemiology, mechanisms and management. World Psychiatry. 2023 Oct;22(3):366-387; Elkhatib SK, Case AJ. Autonomic regulation of T-lymphocytes: Implications in cardiovascular disease. Pharmacological Research. 2019 Aug;146:104293; Alotiby A. Immunology of stress: a review article. Journal of Clinical Medicine. 2024 Oct 25;13(21):6394; Klein PJ, Schneider R, Rhoads CJ. Qigong in cancer care: a systematic review and construct analysis of effective qigong therapy. Supportive Care in Cancer. 2016 Jul;24(7):3209-22.
Meditation for immune health: Many people with cancer face a baseline hum of stress that may be supported through regular meditation practices. While not for everyone, people who feel drawn to meditation may be able to influence several immune system parameters, including the number of immune cells, the ability of immune cells to make antibodies, and the production of cytokines.8Black DS, Slavich GM. Mindfulness meditation and the immune system: a systematic review of randomized controlled trials. Annals of the New York Academy of Sciences. 2016 Jun;1373(1):13-24.
Qigong: People who feel drawn to a movement-based exercise may benefit from exploring qigong ›, an ancient Chinese practice that combines physical movements with breathing techniques and mindfulness. In many randomized controlled trials, qigong has led to higher markers of cancer-specific immune function among people with cancer.9Klein PJ, Schneider R, Rhoads CJ. Qigong in cancer care: a systematic review and construct analysis of effective qigong therapy. Supportive Care in Cancer. 2016 Jul;24(7):3209-22.
4. Moving More
Even a single session of physical exercise can produce measurable changes in innate immune function. Regular physical activity has been shown to positively impact both innate and adaptive immunity by supporting antibody production for mucosal defense, improving immune cell function, and increasing overall immune cell counts.10Yu X, Pei W, Li B, Sun S, Li W, Wu Q. Immunosenescence, physical exercise, and their Implications in tumor immunity and immunotherapy. International Journal of Biological Scienes. 2025 Jan 6;21(3):910-939. See our guide to Moving More ›
5. Acupuncture
Higher markers of immune function during cancer treatment have been observed among people with lung cancer treated with acupoint stimulation. Moxibustion › has evidence for promoting immune activation as well, and is offered by acupuncture practitioners.11Sun H, Zhang B, Qian HH, Chen ZC. [Effect of warm-needle moxibustion intervention on immune function and intestinal flora in patients after colorectal cancer radical operation]. Zhen Ci Yan Jiu. 2021 Jul 25;46(7):592-7. Chinese; Chen HY, Li SG, Cho WC, Zhang ZJ. The role of acupoint stimulation as an adjunct therapy for lung cancer: a systematic review and meta-analysis. BMC Complementary and Alternative Medicine. 2013 Dec 17;13:362; Li WT, Liu YH, Pet al. [Effects of “Tiaoyi Sanjiao” acupuncture and moxibustion on cancer-induced fatigue and immune function in patients with advanced non-small cell lung cancer]. Zhen Ci Yan Jiu. 2020 Dec 25;45(12):1000-5; Liu L, Xing XY, et al. [Effect of moxibustion on clinical symptoms, peripheral inflammatory indexes and T lymphocyte subsets in COVID-19 patients]. Zhongguo Zhen Jiu. 2020 Dec 12;40(12):1271-5; Chen HY, Li SG, Cho WC, Zhang ZJ. The role of acupoint stimulation as an adjunct therapy for lung cancer: a systematic review and meta-analysis. BMC Complementary and Alternative Medicine. 2013 Dec 17;13:362; Sun H, Zhang B, Qian HH, Chen ZC. [Effect of warm-needle moxibustion intervention on immune function and intestinal flora in patients after colorectal cancer radical operation]. Zhen Ci Yan Jiu. 2021 Jul 25;46(7):592-7. Chinese. See our review of Acupuncture ›
6. Several supplements to support immune function
- Astragalus › Studied as a part of a traditional Chinese medicine formula called Kangai, which also includes ginseng and matrine, astragalus has shown specific benefits in immune parameters in patients with non-small cell lung cancer undergoing platinum-based chemotherapy treatment.12Zhu D, Xu Y, Feng F, Wang Z, Han D, Zhou X. Effect of kangai injection combined with platinum-based chemotherapy on the immune function of patients with advanced non-small-cell lung cancer: A meta-analysis. Phytomedicine. 2022 Jun;100:154088.
- Reishi Mushroom › Across a few studies, there is good evidence of higher markers of immune function among people with cancer taking reishi mushrooms.13Zhong L, Yan P, Lam WC, Yao L, Bian Z. Coriolus versicolor and Ganoderma lucidum related natural products as an adjunct therapy for cancers: a systematic review and meta-analysis of randomized controlled trials. Frontiers in Pharmacology. 2019 Jul 3;10:703; Mohammed Ali NAK, Saeed HA, Othman RT. Immunostimulatory and anti-inflammatory effect of Ganoderma lucidum on breast cancer patients. Asian Pacific Journal of Cancer Biology. 2018;3(2):51-57; Henao SLD, Urrego SA, Cano AM, Higuita EA. Randomized clinical trial for the evaluation of immune modulation by yogurt enriched with β-glucans from lingzhi or reishi medicinal mushroom, Ganoderma lucidum (Agaricomycetes), in children from Medellin, Colombia. International Journal of Medicinal Mushrooms. 2018;20(8):705-716; Jin X, Ruiz Beguerie J, Sze DM, Chan GC. Ganoderma lucidum (reishi mushroom) for cancer treatment. Cochrane Database of Systematic Reviews. 2016 Apr 5;4:CD007731.
- Turkey Tail Mushroom › In a small study, higher blood lymphocyte and neutrophil counts were observed when a group of people with advanced non-small cell lung cancer took a turkey tail extract (PSP) after completing conventional treatment.14Tsang KW, Lam CL et al. Coriolus versicolor polysaccharide peptide slows progression of advanced non-small cell lung cancer. Respiratory Medicine. 2003 Jun;97(6):618-24.
- Turmeric › In a small study, a higher immune response was observed among people with advanced colon cancer treated with 3g oral curcumin for 1 month compared to placebo.15Xu B, Yu L, Zhao LZ. Curcumin up regulates T helper 1 cells in patients with colon cancer. American Journal of Translational Research. 2017 Apr 15;9(4):1866-1875.
7. Hyperthermia
Emerging evidence has shown improvements in outcomes for patients with cancer who are able to combine modalities such as radiation therapy, immunotherapy, or chemotherapy with hyperthermia ›. This approach may trigger improvements in T cell function, changes in the function of cells in the innate immune system, or variations in cell signalling that improve immune function. The approach involves raising the whole body’s temperature to at least 40oC or 104oF for a certain length of time. Different protocols have used combinations of treatments with various success rates.16Atanackovic D, Nierhaus A, Neumeier M, Hossfeld DK, Hegewisch-Becker S. 41.8 degrees C whole body hyperthermia as an adjunct to chemotherapy induces prolonged T cell activation in patients with various malignant diseases. Cancer Immunology, Immunotherapy. 2002 Dec;51(11-12):603-13; Ahlers O, Hildebrandt B et al. Stress induced changes in lymphocyte subpopulations and associated cytokines during whole body hyperthermia of 41.8-42.2 degrees C. European Journal of Applied Physiology. 2005 Oct;95(4):298-306; Logghe T, van Zwol E et al. Hyperthermia in Combination with Emerging Targeted and Immunotherapies as a New Approach in Cancer Treatment. Cancers (Basel). 2024 Jan 24;16(3):505.
8. Fasting
Fasting › is an ancient practice rooted in many cultural and religious traditions. It includes time-restricted eating (limiting your food intake to a set daily window), the fasting-mimicking diet (typically 5 days of low-calorie, low-protein and low-carbohydrate intake), or longer water fasts combined with fiber-rich diets. These methods have shown emerging evidence to improve several markers associated with immune function. Ongoing clinical trials are being designed to assess if these changes are also associated with improvements in treatment response. Note that fasting isn’t right for everyone. Discuss with your oncologist or primary care doctor before beginning a fasting program to make sure it is safe for you.17Vernieri C, Fucà G et al. Fasting-mimicking diet is safe and reshapes metabolism and antitumor immunity in patients with cancer. Cancer Discovery. 2022 Jan;12(1):90-107.
9. Hyperbaric oxygen therapy
Emerging research shows that oxygenating therapy like hyperbaric oxygen therapy may help boost the effects of radiation and chemotherapy. This is because the high-pressure oxygen can improve how immune cells work in the tissue around tumors. Particularly in glioblastoma, hyperbaric oxygen appears to be a low-risk modality to combine with radiation therapy, making it better tolerated and improving overall survival rates.18l Wang P, Wang XY, Man CF, Gong DD, Fan Y. Advances in hyperbaric oxygen to promote immunotherapy through modulation of the tumor microenvironment. Frontiers in Oncology. 2023 Sep 15;13:1200619; Alpuim Costa D, Sampaio-Alves M et al. Hyperbaric oxygen therapy as a complementary treatment in glioblastoma-a scoping review. Frontiers in Neurology. 2022 Jul 1;13:886603.
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Therapies mentioned in this article
References