Why Do I Keep Getting Sick? 10 Hidden Reasons Your Immune System May Need More Support

Catching every cold that goes around? Feeling like you’re constantly fighting off another virus?

While getting sick occasionally is a normal part of life, frequent infections can sometimes be a sign that your immune system isn’t functioning at its best. Your immune system relies on adequate nutrition, quality sleep, regular movement, and healthy lifestyle habits to respond effectively to viruses, bacteria, and other pathogens.¹

If you find yourself asking, “Why do I keep getting sick?” These 10 factors may be worth considering.

1. You’re Not Getting Enough Sleep

Sleep is one of the most powerful regulators of immune health. During sleep, your body produces cytokines and other immune cells that help fight infection. Even a few nights of inadequate sleep can reduce immune defenses and increase susceptibility to viral illnesses.²

What you can do: Aim for 7-9 hours of quality sleep each night and maintain a consistent sleep schedule.

2. Chronic Stress Is Suppressing Your Immune System

Stress isn’t just mentally exhausting; it also affects your immune system. Long-term elevations in cortisol can reduce immune cell activity and make it harder for your body to respond to infections.³

What you can do: Prioritize stress-management strategies such as exercise, mindfulness, spending time outdoors, or talking with supportive friends and family.

3. Your Diet Is Missing Key Immune Nutrients

Your immune system depends on a wide variety of vitamins, minerals, and antioxidants to function properly. Nutrients including vitamin C, vitamin D, zinc, selenium, vitamin A, and folate all play important roles in supporting both innate and adaptive immunity.¹,⁴

What you can do: Eat a colourful, whole-food diet rich in fruits, vegetables, legumes, nuts, seeds, lean proteins, and healthy fats.

4. You May Have Low Vitamin D Levels

Vitamin D helps regulate immune responses and supports the body’s ability to defend against respiratory infections. Low vitamin D status has been associated with an increased risk of upper respiratory tract infections in many populations.⁵

What you can do: Ask your healthcare provider whether vitamin D testing or supplementation may be appropriate for you.

5. You’re Not Eating Enough Protein

Immune cells, antibodies, and many signaling molecules are made from protein. Inadequate protein intake can impair immune function and slow recovery from illness.⁶

What you can do: Include a quality source of protein with each meal, such as fish, poultry, eggs, dairy, tofu, beans, or lentils.

6. Your Gut Microbiome Needs Support

Approximately 70% of the body’s immune cells are located within the gut-associated lymphoid tissue. While this doesn’t mean 70% of immunity “lives” in the gut, it highlights the close relationship between gut health and immune function. A diverse gut microbiome helps regulate immune responses and supports the intestinal barrier.⁷

What you can do: Eat plenty of fibre-rich foods and include fermented foods such as yogurt, kefir, kimchi, or sauerkraut if tolerated.

7. You Rarely Exercise, or You Overtrain

Moderate, regular exercise supports immune surveillance and overall health. However, prolonged high-intensity training without adequate recovery may temporarily suppress immune function.⁸

What you can do: Aim for regular moderate physical activity most days of the week while allowing adequate time for recovery.

8. You Smoke or Drink Excess Alcohol

Smoking damages the respiratory tract’s natural defenses, while excessive alcohol intake can impair immune cell function and increase susceptibility to infections.⁹

What you can do: If you smoke, seek support to quit. Limiting alcohol intake may also help support overall immune health.

9. You’re Recovering From Illness Too Quickly

Returning to work, school, or intense exercise before fully recovering can prolong symptoms and leave your immune system under additional strain.

What you can do: Give your body adequate time to rest, stay hydrated, and gradually return to your normal routine.

10. An Underlying Health Condition Could Be Contributing

Frequent infections may sometimes be related to underlying conditions such as uncontrolled diabetes, autoimmune disorders, nutrient deficiencies, certain medications, or primary immune disorders.¹⁰

What you can do: If you’re experiencing frequent, severe, or unusually persistent infections, speak with your healthcare provider for a proper assessment.

Can Supplements Help Support Immune Health?

Supplements should never replace a healthy lifestyle, but they may help fill nutritional gaps when dietary intake is insufficient.

Several nutrients have been extensively studied for their role in immune function, including:

• Vitamin C
• Vitamin D
• Zinc
• Selenium
• Vitamin A
• Folate
• Vitamin B12

Some botanical ingredients, including green tea extract, medicinal mushrooms, and astragalus, are also being investigated for their potential to support normal immune function.¹¹⁻¹³

The Bottom Line

There’s rarely a single reason someone keeps getting sick. More often, immune health reflects the combined effects of sleep, nutrition, stress, physical activity, gut health, and overall lifestyle.

Supporting your immune system doesn’t require perfection. Small, consistent habits, such as improving your sleep, eating a nutrient-dense diet, managing stress, and correcting nutrient deficiencies, can help your immune system function at its best year-round.

References

1. Gombart AF, Pierre A, Maggini S. A review of micronutrients and the immune system—working in harmony to reduce the risk of infection. Nutrients. 2020;12(1):236. doi:10.3390/nu12010236
2. Besedovsky L, Lange T, Haack M. The sleep-immune crosstalk in health and disease. Physiol Rev. 2019;99(3):1325-1380. doi:10.1152/physrev.00010.2018
3. Segerstrom SC, Miller GE. Psychological stress and the human immune system: a meta-analytic study. Psychol Bull. 2004;130(4):601-630. doi:10.1037/0033-2909.130.4.601
4. Calder PC. Nutrition, immunity and COVID-19. BMJ Nutr Prev Health. 2020;3(1):74-92. doi:10.1136/bmjnph-2020-000085
5. Martineau AR, Jolliffe DA, Greenberg L, et al. Vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis of aggregate data from randomised controlled trials. Lancet Diabetes Endocrinol. 2021;9(5):276-292. doi:10.1016/S2213-8587(21)00051-6
6. Wu G. Dietary protein intake and human health. Food Funct. 2016;7(3):1251-1265. doi:10.1039/C5FO01530H
7. Zheng D, Liwinski T, Elinav E. Interaction between microbiota and immunity in health and disease. Cell Res. 2020;30(6):492-506. doi:10.1038/s41422-020-0332-7
8. Nieman DC, Wentz LM. The compelling link between physical activity and the body’s defense system. J Sport Health Sci. 2019;8(3):201-217. doi:10.1016/j.jshs.2018.09.009
9. Szabo G, Saha B. Alcohol’s effect on host defense. Alcohol Res. 2015;37(2):159-170.
10. Bonilla FA, Khan DA, Ballas ZK, et al. Practice parameter for the diagnosis and management of primary immunodeficiency. J Allergy Clin Immunol. 2015;136(5):1186-1205.e1-78. doi:10.1016/j.jaci.2015.04.049
11. Rondanelli M, Miccono A, Lamburghini S, et al. Self-care for common colds: the pivotal role of vitamin D, vitamin C, zinc, and Echinacea in three main immune interactive clusters. Evid Based Complement Alternat Med. 2018;2018:5813095. doi:10.1155/2018/5813095
12. Li X, Wang X, Chen D, Chen S. Antioxidant and immunomodulatory activity of polysaccharides from medicinal mushrooms. Int J Biol Macromol. 2021;168:641-651. doi:10.1016/j.ijbiomac.2020.12.108
13. Auyeung KK, Han QB, Ko JK. Astragalus membranaceus: a review of its protection against inflammation and gastrointestinal cancers. Am J Chin Med. 2016;44(1):1-22. doi:10.1142/S0192415X16500014