What to Know About Your Immunity

Melissa Eide

For decades, many of us have thought we could “boost” our immune systems with vitamin C or herbs, which would fight contagious illnesses, such as colds and the flu. But in reality, there are no quick fixes for better immunity, and little can replace the benefits of fresh food, fresh air, stress management, and loving relationships. And as researchers learn more about the immune system, we learn more ways in which it can extend our lives and improve our health.

For example, one thing that has changed in our knowledge of the immune system is just how big a role it plays in the body and how it works at an optimal level. “We used to think that the immune system was made up of white blood cells, the thymus, spleen, lymphatic system, and bone marrow,” biochemist Jeffrey Bland, Ph.D., who has studied immunity for more than 40 years, tells Bicycling. “Now we understand it is a supersystem of interconnected organs, and that 60 percent of our immune system is in our digestive system.”

Furthermore, researchers now say that many “lifestyle” diseases, such as cardiovascular disease, and neurodegenerative diseases including Alzheimer’s, relate to the immune system.


In a recent study published in The Lancet, Boston University researchers revealed that people who live to be 100 are part of an elite group whose immune systems remain “highly functional” even at “extreme old age.” The researchers compared the cells of 14 centenarians to younger people to determine if something set the older people apart from those aged 20 to 89.

While small, the study suggests that people who live to old age can stave off illness because of “unique, highly functional immune systems that have successfully adapted to a history of insults.” In other words, it’s not that people who live to be 100 are not exposed to disease, but that their immune systems respond appropriately.

While researchers continue to study the intricacies of immunity, they’ve also cleared up a few common immune system myths. Here’s what we’ve gotten wrong over the years, plus key facts to understand so you can better support your immune system function.

Myth 1: You can “boost” your immune system

Truth: Your daily habits create a healthy immune system over a lifetime.

You basically have two immune systems: An innate immune system and an adaptive immune system. That means your immune system is both something we’re born with, and something that interacts with the environment.

The innate immune system is the first line of defense against disease or illness, and it includes stomach acid, coughing, tears, mucus, and your skin, all of which protect you against diseases and injuries.

The adaptive system is clustered in our intestinal and respiratory systems, and it calls on T and B cells to fight invaders. When we get vaccinated, we provoke these cells to do their work and fight infections.

Together, the innate and adaptive systems make up our overall immune system, and while you can’t necessarily change what you’re born with, you can support the adaptive system with a healthy lifestyle.

In fact, because the immune system adapts to food, the environment you live in, and your life experiences, it’s almost as if you get a new immune system every three months, says Bland. He calls it “rejuvenation.”

To support this “rejuvenation,” it’s helpful to know what injures the system and what improves it, Bland says. For example, you can take away sugar, fried foods, and plastic residues, which may injure the immune system. And you can add in sleep, fermented and plant foods, and things that bring you happiness and joy, such as meaningful work and strong relationships, to improve its function. However, all of this takes time to improve your immune system—it’s not an overnight fix.

Also, you want your immune system to respond to illnesses or injuries, but at just the right level. For example, let’s say you get a papercut. You want your white blood cells to clot so that the cut heals, but you don’t want it to respond so much that you get a giant scar that changes the shape of your finger. Therefore, instead of finding instant ways to “boost” the immune system, it’s more helpful to recognize that you want to keep your immune system responsive and in balance.

Part of good health is having an immune system that learns to respond to common germs and allergens. “When you’re a little kid in your first years in school, you get sick a lot, and your body develops protective antibodies through those illnesses,” Sandra M. Gawchik, D.O., an allergist-immunologist in Chester, Pennsylvania tells Bicycling. Those illnesses, with their symptoms like sneezing, coughing, and running a fever, are signs of inflammation—your body is trying to fight the bug. As you get older, you may get colds, but it’s unusual for an adult to become chronically ill as a more robust immune system regulates those responses and fights off future infection.

This is also why you need some exposure to allergens and germs, so the adaptive immune system learns to fight potential irritants. “The cleanest environments don’t train our bodies to mount an appropriate immune reaction,” Bland says.

Myth 2: If you eat right and exercise, you won’t get sick

Truth: Don’t ignore cold symptoms. Instead, consider them a clue that you need to rest.

When your immune system is busy responding to germs, it may send you signs that you need to step in and change some of your habits (at least temporarily) to help it do its work. Taking time off, resting, and consuming nutrients that support immunity, like vitamin A and zinc, will help your immune system fight off bugs.

Good health doesn’t mean you will never have to use medicine to help your immune system function at its best. Just because you eat right and exercise doesn’t mean you won’t suffer from allergies or get sick, says Gawchick. The important thing is to pay attention to symptoms and figure out what you can do to address them.

Also, as a cyclist who probably spends lots of time outside on your bike, you may be more exposed to allergens. “Some people are highly allergic and highly reactive to environmental allergies, and that means they’ve inherited a genetic prototype,” Gawchik says. “Cyclists are inhaling more pollen than someone who is sitting [inside] with air conditioning, but that doesn’t mean it’s healthier to stay indoors.”

People with seasonal allergies have immune systems that “overreact” to pollen, and medicine can help you minimize that reaction—another example of when you need to take steps beyond exercise and eating well to feel good.

Myth 3: Exercise is always good for your immune system

Truth: Overtraining may leave you vulnerable to illness.

In the same way that some foods—fresh fruit and vegetables, for example—can help create a healthy immune system, while others, such as processed meat, can make it not as responsive, the same is true of exercise. Do too little, and research has shown you may be more likely to develop illnesses, such as diabetes, now known to be related to immune system dysfunction. Do too much over a long period of time and—you guessed it—you may also suppress your immunity.

One research review published in the Journal of Sport and Health Science in 2019 says that overall, exercise supports immune system function. However, high training periods or competition (like running a marathon) can lead to immune disturbances and increased inflammation, which ups illness risk. This is especially true if you go through repeated cycles of heavy training or stress the immune system in additional ways, like also skimping on sleep or not eating enough calories to support training. Researchers do point out that your nutrition strategy—including taking in enough carbs and polyphenols, found in plant foods—can help tame the inflammation and other damage done by intense workouts.

“Exercise can increase inflammation if it exceeds the exercise tolerance of an individual,” Bland explains. “In general, exercise at a level of intensity and duration that is within an individual’s fitness level improves immune function and lowers inflammation.”

Therefore, it’s important to pace your training in order to work your way up to longer, harder rides, says Bland. Likewise, you need rest and recovery after exertion to let that postworkout inflammation lower and to support a healthy immune system.

Keep an eye on symptoms of overtraining to know whether you need to pull back on exercise.

Myth 4: Your stomach isn’t an immune system organ

Truth: Gut health plays a leading role in immune system function.

“We eat between five and 10 tons of foreign molecules over the course of our lifetimes,” says Bland. “Our digestive system translates that from the intestinal level to the brain and the rest of the body to determine if we need to fight those molecules or not.” In other words, your gut helps to determine how your body will respond to food.

One thing that messes with that communication: chronically taking antibiotics, which wipes out your gut microbiome, says Gawchik. That’s why she recommends eating fermented foods such as like kimchi and sauerkraut. “These help rebalance the microbiome of the gut,” she explains.

Research also shows the importance of pre-, post-, and probiotics found in foods, like yogurt, for balancing out your gut bacteria and helping to regulate the immune response.

Both doctors also suggest eating less sugar and white flour, both of which may increase inflammation.

According to a research review, published in Nutrients in 2021, nutrition is actually one of the most important environmental factors that affects the gut microbiota and immune system. The review authors suggest following a Mediterranean diet approach to eating, as it focuses on polyunsaturated fatty acids, fiber, vitamins, antioxidants, and plenty of anti-inflammatory foods. They also suggest avoiding a more Western approach to eating, which is usually described as high in carbs, saturated fat, ultra-processed foods, and added sugars and other additives.

Myth 5: Emotions don’t affect the immune system

Truth: Love and friendship may lead to longevity.

Bland says that of all the things he has learned over the last 40 years about the immune system, his thinking has evolved most around emotional health. “I’m a biological scientist by training and I had a very stereotypical bias toward the hard sciences, but that model was all wrong,” he says. Your emotions are just as much a part of your immune system as your reaction to allergens and germs.

Science has come to recognize that if you live with fear, trauma, and isolation, those emotions send signals to the genes of your immune system to begin a response just as if your cells were being targeted by a virus. How we think about ourselves and how we gain support from people who see our value are real markers of health.

In fact, a 2019 study published in PLOS One looked at 2,057 participants, ages 18 to 65, to study how their moods affected both immune system and thyroid function. According to the researchers, your mood communicates with both your innate and adaptive immune systems. Negative emotions can harm the systems, while positive emotions and close connections are connected to healthy outcomes.

So what emotions help boost immunity? Those feelings that are associated with belonging and friendship, according to Bland. In fact, people who are part of close, engaged communities have been shown to live longer. Chances are, cycling with friends and sharing your passion for the road is one of the greatest benefits for your immune system.

Headshot of Donna Raskin

Donna Raskin has had a long career as a health and fitness writer and editor of books and magazine articles. She bikes in a nearby county park, lifts weights, takes Zumba, and loves to walk/run with her dog, Dolly. 

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