Common Habits That Undermine Your Immune System
Most people don’t give their immune system a second thought until it’s struggling to keep up. When you’re battling your third cold of the season, dealing with yet another sinus infection, or confined to bed with the latest bug doing the rounds, it’s easy to blame external factors. Perhaps you attribute it to bad luck, crowded commutes, or the unpredictable British weather. But what if the real reason your body keeps succumbing to illness isn’t lurking “out there,” but rather hidden within the daily habits you barely even notice?
Your immune system is your body’s dedicated, round-the-clock defence network. And like any system, its effectiveness depends on the inputs it receives. Nutrition, sleep patterns, stress management, and even your social life all play a vital role. However, many of the most damaging behaviours to your immunity are the very ones we rarely question.
Here’s a look at some common culprits – six everyday habits that can weaken your immune defences, along with practical steps you can take to reverse the trend.
1. Skimping on Sleep
While you sleep, your body releases cytokines, crucial proteins that help fight infection and reduce inflammation. Regularly failing to get enough sleep disrupts this vital process, leaving your immune system vulnerable when viruses or bacteria strike.
Studies have shown that individuals who consistently sleep fewer than six hours a night are more susceptible to catching colds compared to those who get seven hours or more. Sleep deprivation also impairs your immune memory – the way your body remembers and fights off viruses it has encountered previously. When you cut back on rest, your immune response becomes sluggish and less effective.
Try this:
- Establish a consistent bedtime routine, even on weekends.
- Ensure your bedroom is dark, quiet, and cool.
- Avoid screens for at least an hour before bed, as the blue light emitted can interfere with melatonin production.
- Consider using a sleep tracker to identify patterns and potential interruptions.
2. Too Much Sitting, Not Enough Moving
Modern life often confines us to a seated position, whether we’re working, relaxing, or travelling. However, prolonged sitting has a detrimental impact on your lymphatic system, which plays a vital role in circulating immune cells and removing toxins. Even if you manage a 45-minute workout, extended periods of sitting throughout the rest of the day can still suppress immune activity. A sedentary lifestyle slows down circulation, limiting the efficiency with which immune cells travel through the body.
Movement acts as a pump, facilitating the movement of lymph fluid throughout the body.
The NHS recommends that adults aim for at least 150 minutes of moderate-intensity physical activity per week.
Research has linked regular moderate movement to improved immune surveillance, particularly in older adults. It doesn’t require intense training. Simple activities like walking, stretching, cycling, or light strength training a few times a week can help keep your system active and responsive.
Try this:
- Break up long periods of sitting with short movement breaks. Even two minutes of standing or walking every hour can make a difference.
- Incorporate walking into meetings or phone calls.
- Add low-impact activities like yoga or walking after meals.
- Use a step counter or fitness tracker to encourage activity throughout the workday.
3. Chronic Low-Level Stress
You might not feel overtly “stressed,” but ongoing deadlines, constant news updates, financial worries, or even constant multitasking can trigger a steady release of cortisol, the stress hormone. Chronically elevated cortisol levels can suppress the immune system’s ability to respond effectively to infections.
It also prolongs inflammation. While short-term inflammation is a natural response to infection, chronic inflammation (driven by long-term stress) weakens your body’s ability to defend itself, leading to more frequent colds, slower recovery times, and even increased vulnerability to autoimmune flare-ups.
Research has shown that prolonged stress can shrink lymphoid tissue (where white blood cells are produced) and reduce your antibody response after vaccinations.
Try this:
- Take proper breaks (even just five minutes to step outside or practise deep breathing).
- Practise breathing exercises or gentle movement techniques.
- Identify your main stress triggers and develop strategies to manage them.
- Limit your exposure to stressful digital content.
4. Skipping Meals or Mindless Eating
It’s easy to grab processed foods when you’re busy. However, ultra-processed foods like packaged snacks, sugary cereals, and ready meals are often low in the essential nutrients your immune system needs. Your body requires a consistent supply of vitamins and minerals to produce antibodies, repair tissues, and regulate inflammation.
Diets high in refined carbohydrates, sugar, and processed fats tend to cause blood sugar spikes and increase inflammation – both of which strain immune regulation and weaken your body’s natural defences. Research links excessive sugar intake to reduced immune cell function and an increased risk of infections. Conversely, a diet rich in whole foods like leafy greens, citrus fruits, oily fish, legumes, and fermented foods supports immune resilience.
Try this:
- Base your meals around whole foods: leafy greens, legumes, whole grains, and lean proteins.
- “Eat the rainbow” – consuming a variety of colourful fruits and vegetables provides a wide range of antioxidants.
- Replace fizzy drinks or sweetened beverages with water, herbal tea, or kombucha.
- Minimise ultra-processed “meal substitutes” like bars, energy drinks, and pre-packaged snacks.
Eating at regular intervals is also important. Skipping meals or eating erratically can lead to cortisol spikes and nutrient deficiencies. Prioritise balance: avoid overeating and under-fuelling.
For additional support, nutrients like vitamin D, zinc, and omega-3 fatty acids are consistently linked to improved immune responses.
5. Neglecting Hydration
Dehydration is often associated with fatigue or headaches, but it also affects your immune system. Fluids help your body flush out waste products and transport nutrients. The lymphatic system, in particular, relies on adequate fluid intake to function properly. If you’re not drinking enough water or are over-consuming caffeine or alcohol, you may be quietly compromising your immune health.
Even mild dehydration can cause the barriers that protect your body from infection to become dry and less effective, making it easier for pathogens to enter. A well-hydrated body also allows immune cells to move more efficiently and communicate effectively.
Try this:
- Aim for approximately 3.7 litres of water per day for men and 2.7 litres for women.
- Increase your fluid intake if you’re very active or live in a hot climate.
- Add electrolytes if you sweat a lot or drink a lot of coffee.
- Eat hydrating foods like cucumber, melon, and citrus fruits.
- Pay attention to your thirst – by the time you feel thirsty, you’re already dehydrated.
6. Insufficient Social Connection
Social isolation, especially when prolonged, has a significant physiological impact. Research has shown that social connection directly influences immune function, reducing inflammation and supporting antibody responses.
People who feel lonely or emotionally unsupported are more likely to experience immune dysregulation, making them more vulnerable to both infection and chronic disease.
Connection doesn’t require a busy social calendar. A meaningful conversation, regular check-ins with a friend, or even shared laughter can make a difference. If in-person contact isn’t always possible, video chats or phone calls still count. The body responds to the feeling of connection, not just physical proximity.
7. Lack of Natural Light and Fresh Air
Many people spend the vast majority of their time indoors, which isn’t beneficial for immunity. Sunlight helps your body produce vitamin D, a crucial nutrient for immune regulation. Low vitamin D levels are associated with increased susceptibility to respiratory infections.
Fresh air, particularly when combined with exposure to nature, can also lower stress levels, reduce blood pressure, and improve mood – all factors that support immune function.
Try this:
- Aim for 15–30 minutes of sun exposure per day (without sunscreen during off-peak hours).
- If you can’t get outside, work or take breaks near windows.
- Incorporate walks into your routine, especially in green spaces like parks or nature trails.
- Consider taking a vitamin D supplement if sunlight is scarce in your area.