Is it possible to boost your immune system? Overall, it does a great job of protecting our bodies from microorganisms. However, sometimes it fails — a microbe manages to breach the defenses and brings along a disease. Can we intervene in this process and strengthen the immune system? What about improving our diet? Taking vitamins or supplements? We’ll tell you what really helps and what you can safely skip
The idea of boosting immunity sounds appealing but is impractical for several reasons. The immune system is just that — a system, not a single organ. For it to function well, it needs balance and harmony. Researchers still don’t fully understand the intricacies of the immune response and how different parts are interrelated. Currently, there is no scientifically proven direct link between lifestyle and enhanced immune function.
However, this doesn’t mean that lifestyle’s impact on immunity isn’t worth studying. Scientists are exploring the effects of diet, exercise, age, stress, and other factors. General healthy lifestyle strategies are likely beneficial because they may support immune function and offer other health advantages.
If you want your immune system to stay strong as you age, you should focus on balance — it’s better to have a balanced immune system rather than a stronger one.
What can help?
1. A balanced and varied diet
An immune-boosting diet should be diverse. Every stage of the immune response relies on different nutrients. Studies highlight the importance of a plant-based diet, particularly the Mediterranean diet, which includes plenty of whole grains, fresh vegetables, fruits, nuts, and olive oil.
Such foods provide not only essential nutrients but also fiber, which is crucial for gut health. The gut is a key player in immunity, as it is the body’s largest immune organ. To function properly, the gut’s lining must be intact, and the gut flora should be diverse.
Soluble fibers, like pectins, are essential food for bacteria. Microbes break down polysaccharides into short-chain fatty acids that regulate immune cells’ activity, as explained by a team led by Marco Aurelio Vinolo at the State University of Campinas in São Paulo in 2016.
These acids promote the formation of regulatory T-cells, which in turn have an anti-inflammatory effect. Acute inflammation is a natural response of our immune system aimed at destroying pathogens. However, chronic inflammation drains the immune system’s energy, leaving less for other important tasks. Additionally, chronic inflammation activates the stress axis, triggering disease-promoting processes. Some fatty acids produced by bacteria can also reprogram killer cells to better fight tumors, as reported by Maik Luu’s team from the University of Würzburg in Nature Communications in 2021.
It’s worth nourishing our gut bacteria by consuming dairy products (like natural yogurts) with probiotics and fermented foods (like sauerkraut and pickles), which are good for gut microbiota. In contrast, a typical Western diet rich in red meat, sugar, and highly processed foods with modified starch and additives can disrupt the gut microbiota’s balance.
2. Exercise
Regular physical activity can protect against infections, cardiovascular diseases, and cancer. Exercise enhances the ability of natural killer cells to destroy infected or malignant cells and helps counter chronic inflammation. WHO recommends at least 150–300 minutes of moderate-intensity exercise per week.
According to the U.S. National Library of Medicine, physical activity also helps flush bacteria out of the lungs and airways.
Outdoor exercise provides a double immune-boosting effect, as it also increases vitamin D production. However, don’t overdo it — excessive exercise can weaken the immune system due to stress.
3. Adequate hydration
Water supports the innate immune system. This is because mucous membranes are an effective barrier against microbes. For these natural barriers to stay intact and not dry out, you need to stay hydrated. Otherwise, viruses and bacteria can more easily take hold. This is particularly important in colder months when heated air dries out mucous membranes even more. What you drink matters too: water and unsweetened tea should be prioritized over sugary drinks, as high sugar content can negate efforts to maintain a healthy immune system.
4. Quality rest
As the saying goes, sleep is the best medicine. The National Sleep Foundation recommends 7–9 hours of sleep for adults and up to 11 hours for school-aged children. Adequate sleep is crucial for the immune system’s functioning.
Why?
Firstly, when muscles are still and bodily functions slow down, more energy is available for the immune system. Secondly, sleep directly boosts the body’s defenses by stimulating immune cells. In 2019, scientists from the Universities of Tübingen and Lübeck identified a potential mechanism for this. They conducted a 24-hour experiment with participants: one group slept for eight hours, while the other stayed awake. After just three hours of sleeplessness, the T-cells’ ability to adhere to other cells significantly decreased.
“T-cells continuously circulate in the bloodstream searching for pathogens. Adhesion to other cells allows them to move around the body and attach, for example, to infected cells to later destroy them,” explained the study’s lead author Stoyan Dimitrov.
People who sleep less than six hours a night are four times more susceptible to cold viruses, as shown in a 2015 study led by Sheldon Cohen from Carnegie Mellon University in Pittsburgh.
Sleep also supports the development of immune memory — the body’s ability to recognize and fight pathogens after the first encounter. Therefore, it’s important to get good sleep after vaccination, as shown by researchers studying the hepatitis vaccine. Those who didn’t sleep the night after vaccination had half as many immune cells against the virus after a year compared to those who rested.
5. Vitamin supplements for the elderly
Most people don’t need dietary supplements unless they have a real deficiency. According to studies, nearly 42% of U.S. adults are deficient in vitamin D, a figure that rises to almost 63% among Hispanic adults and 82% among African-American adults.
The National Institutes of Health (NIH) recommends a daily intake of 15 mcg of vitamin D for most adults, with increased intake of 20 mcg for those over 70.
These recommendations assume minimal sun exposure, as vitamin D is produced in the skin when exposed to sunlight. It is also vital for bone metabolism and the immune system.
As people age, their immune system weakens, making them more susceptible to severe illnesses, such as after a coronavirus infection. Therefore, the International Society for Immunonutrition advises older adults to increase their intake of zinc, vitamins E, C, and D. However, this should only be done after consulting a doctor.
What can harm?
1. Smoking
The substances in cigarette smoke (nicotine, ammonia, formaldehyde, carbon monoxide, and tar) throw the immune system out of balance. Their effects are complex and somewhat paradoxical. On the one hand, smoking enhances autoimmunity, meaning the body’s defenses attack its own cells. On the other hand, it weakens the body’s defenses against pathogens, making smokers more susceptible to infections and causing them to take longer to recover. Nicotine and tar likely have the most immunosuppressive effects.
Additionally, cigarette smoke damages the mucous membranes of the respiratory tract, which are key elements of innate immune defense. Over time, the cilia that capture microbes and expel them from the body are also destroyed. Smokers are more likely to have severe pneumonia than non-smokers and are at higher risk for severe cases of COVID-19, according to recent studies.
2. Alcohol
The U.S. National Institute on Alcohol Abuse and Alcoholism warns against excessive alcohol consumption. Excessive drinking is defined as more than three drinks per day for women and more than four for men.
In 2015, researchers from the University of Maryland School of Medicine confirmed that even one serving of alcohol can have a lasting impact on the immune system. They had volunteers drink several shots of vodka in 20 minutes, then took blood samples at regular intervals. After two hours, the number of T-cells in the blood had significantly decreased, meaning they were less capable of protecting the body. The effect was still noticeable five hours later. According to research, only those with autoimmune diseases like multiple sclerosis or rheumatoid arthritis may benefit from alcohol’s immunosuppressive effects.
3. Dietary supplements
There are situations when dietary supplements can be helpful. When needed, it’s essential to consult a doctor. However, most people don’t need supplements despite the booming market. Mainstream medicine asserts that healthy individuals who eat a balanced diet and spend time outdoors do not require any supplements.
In reality, many people suffer from an overactive immune system, which reacts to harmless substances or their own body cells. This leads to allergies and autoimmune diseases.
For example, an adult’s daily requirement of 100 mg of vitamin C can be easily met through diet. The recommended dose is roughly half a bell pepper or two oranges. There is no evidence that high doses of vitamin C supplements protect against colds — except for extreme athletes. And its impact on the duration of illness is minimal, as demonstrated by Harri Hemilä and Elizabeth Chalker from the University of Helsinki in a systematic review.
Dietary supplements can also cause harm. For instance, vitamin D can be overdosed, unlike vitamin C. In a 2012 review, researchers concluded that oral zinc intake could shorten cold duration. However, high doses of zinc should never be taken for long periods. Overdosing can cause poisoning symptoms and anemia.
4. Systematic Stress
How our health reacts to stress depends on how long it lasts. If stress is short-term, it can stimulate the innate immune system. The body prepares to prevent physical damage: the hormone cortisol is released, and immune cells are mobilized. On the other hand, constant stress over weeks, months, or years weakens the entire immune system. Cortisol levels in the blood remain elevated during this time. The stress hormone suppresses immune cells and prevents them from multiplying. As a result, those who experience constant stress get sick faster. Moreover, wounds heal slower, and vaccines work less effectively. But there’s good news: positive thinking, despite stress, can strengthen the immune system.
