After a summer with plenty of outdoor play, the school year brings a major shift. Students suddenly spend more of their days indoors surrounded by other students. It’s usually only a matter of weeks before someone gets the sniffles. And that will kick off months of illnesses that circulate through students, teachers and their families.
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What can you do to stay healthy? Aside from doing your best to avoid germs, support your immune system. It can help you fend off illnesses before they take hold.
Our immune system is complex, but researchers are uncovering ways we can keep it running strong. The goal is to help us stay healthy.
When we hear about viruses and bacteria, we may think of runny noses and coughs. But the battleground for our immune system is not just in the nose and lungs. In fact, a whopping 80 percent of immune cells live in the gut. That’s not surprising, since it needs to be ready to spot germs every time we eat or drink.
The potentially harmful germs we swallow quickly enter a world chock full of other microbes. “We have many billions of bacteria living in our gut,” points out Caroline Childs. They’re part of our microbiome, the community of microbes that live in and on us. The “immune system is in charge of making sure that friendly ones are tolerated,” says this nutrition scientist at the University of Southampton in England. “But any harmful ones are rapidly dealt with.”
Immune cells patrol the walls of your gut. Some sense the different types of bacteria there, Childs says. They identify problematic invaders. Other immune cells stop the invaders from sticking to the gut’s wall, where they can start an infection. Still others “call for extra help from our whole-body immune system,” she explains.
Explainer: The body’s immune system
Keeping our gut microbes healthy is important to maintaining balance in the gut. A crowd of “good” germs means there’s no room for infectious ones to move in and take hold. Our guts host thousands of kinds of bacteria, viruses and fungi. Most of these microbes are good guys. Having a wide variety of them ensures no single type gets out of control to cause problems.
From supporting those gut microbes to moving our bodies and hanging out in nature, there are lots of ways to boost our immunity.
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Is diet the link between gut microbes and health?
Actions by the gut microbiome can be really important, even in fending off infections that don’t seem linked to the gut.
One 2023 review of COVID-19 studies found that the gut microbes of people hospitalized with COVID were different than those in healthy people. People with severe symptoms had high levels of infectious types.
Belly bacteria can shape mood and behavior
Kids who tested positive for COVID but didn’t show any symptoms also had different bacteria in their gut. They had high levels of good microbes.
It’s not clear if the gut microbes let COVID become severe or whether the COVID infection let bad bacteria take over. But clearly there’s a link between the two. Keeping our gut microbes in balance seems to help us fend off disease.
Whole foods — including fruits, vegetables and beans — provide fiber that’s important for a healthy gut.Paperkites/iStock/Getty Images Plus
That’s where diet comes in. Eating a variety of fruits, veggies and beans is “one of the best things we can do to help our microbiota flourish,” Childs says. (Microbiota is another name for that microbiome.) “The more varieties of foods we eat, the more varieties of gut microbes we will have in our gut.”
A varied diet also supports health overall. “There are a huge number of nutrients with important roles in our immune system which also have other jobs in keeping us healthy,” Childs notes. These include iron, which our bodies need to make red blood cells. Also vitamin D, which helps strengthen bones.
But there are other benefits from a healthy gut microbiome, too. A healthy gut is closely linked to mood and mental health. “I sometimes like to think of my gut microbiome as a little pet,” Childs says. “This helps me to consider how I can try to take good care of it and be sure to feed it well.”
Maximize movement
Exercise also improves the gut microbiome. So finds a 2019 study out of the University of Illinois Urbana–Champaign. Keeping active increases the number of good germs in the gut. That can help crowd out infectious ones.
Being physically active improves our immunity in other ways, too. It doesn’t have to be a specific type of exercise either, says Sebastien Chastin. He is a public-health researcher at Glasgow Caledonian University in Scotland. For instance, he notes, simply walking provides immune benefits.
Most research on exercise and health has focused on non-infectious diseases. Most have looked at its role on things such as type 2 diabetes, heart disease and cancer. But Chastin and his team were interested in how exercise might affect infectious disease. Will being more active make the immune system more efficient?
Outdoor activities not only reduce stress, but also could make you less likely to catch an illness.6okean/iStock/Getty Image Plus
To find out, the team reviewed 55 studies that included a total of more than 500,000 individuals. People who got at least 150 minutes of exercise a week were 31 percent less likely to get sick than people who exercised less, they found. These more active people also were 37 percent less likely to die from an infection.
Chastin and his team shared their findings in a 2021 paper.
Many of the studies they reviewed also measured how many immune cells were in the blood. These cells increased in people who exercised regularly. Their immune cells were therefore able to respond faster if and when they met up with invading germs.
How does exercise boost immunity? That’s not completely clear, Chastin admits. But he and others think one way is by reducing stress.
After the brain, the human immune system is the most complex system in the body. No wonder so few of us know how it works! Yet its roles are pivotal: It protects us from the billions of germs that want to feed off of us and from those cells inside us that can turn cancerous.
“Playing, being happy, being amongst friends, being physically active is a really great way to reduce stress,” he says. Stress can limit the immune system’s effectiveness. Stress triggers the body to release certain hormones. Long-term exposure to these can inflame body tissues. Stress also lowers the number of white blood cells, a type of immune cells, that patrol the bloodstream. That’s why people often get sick when they’re stressed. But if “we can reduce that, we can improve our immune response generally,” Chastin says.
What can you do to keep your immunity strong — and illness at bay? Walk, play sports and lift weights. All are types of immune-boosting exercise. “We need to be strong. We need to have good balance. We need to have good flexibility in our body,” Chastin says. “Some things are good for the immune system, but there [can be] multiple benefits to these movements.”
Many infections are likely to spread more easily as the planet warms. So in the future, keeping your immunity strong will be ever more important. Be active when you can, Chastin advises. “Every movement counts.”
Staying active doesn’t have to mean organized sports or going for a run. Even playing with friends can give the immune system a boost.monkeybusinessimages/iStock/Getty Images Plus
The nurture of nature
Chastin also says to get outside as much as you can. Emerging research is showing that natural spaces — such as parks, forests, rivers and lakes — can provide immune benefits. It’s a fairly new field of study. Liisa Andersen wanted to learn what’s known and what gaps in knowledge still exist. She looked into this while at the University of Copenhagen in Denmark.
Most studies finding health benefits from time spent in nature assigned those benefits to other things. Some highlighted physical activity or social interactions. Andersen wanted to know if there might be direct immune benefits as well. In a 2021 review, she turned up 33 studies that had exposed people or animals to natural spaces or natural chemicals (such as those released by trees). Those chemicals are known to stimulate immunity in some way. The studies also measured immune responses in the people who took part.
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Some of the studies reported measurable benefits here. Spending time in a forest, for instance, decreased allergic reactions, including itchy skin rashes and shortness of breath due to asthma. Two studies even found that breathing in the charged air particles near waterfalls improved breathing in kids with asthma.
What nature does to bring about these benefits “is completely unclear,” Andersen says. But even if we don’t know how it works, she says, it’s becoming increasingly clear that it does work.
There are so many ways to boost our immunity, Andersen says. In fact, she points out, we do it “all the time through our lifestyle — what we eat, the air we breathe and so on.”
Since the immune system is so important in keeping us healthy, it’s a no-brainer that we should do what we can to keep it running well. Getting outside is easy and costs little, Andersen says.
It can be even better if you’re running around with friends or perhaps enjoying a healthy snack. The combo can power you and your immune system, which can keep you feeling well for longer.
