How to Support Your Immune System with a Plant-Based Diet

You can’t always control whether you get sick. But by understanding how your immune system works, what hurts it and what helps it, you can learn to take steps to stay as healthy as possible. (Spoiler alert: Some of the biggest influencers on your body’s natural defense system are the foods you put into your mouth.)

The immune system is our defense against illness. Our bodies are regularly exposed to challenges, such as mutated cells, and invaders, such as bacteria and viruses. Immune cells act like a security system to clear them before they can lead to problems. 

The immune system is made up of two parts. The innate immune system senses general threats and fights off pathogens before they can settle into the body and start a full-blown infection. The adaptive, or acquired, immune system can create a memory of past invaders so that it can personalize the attack against them and protect us from future threats.

The immune system is expansive and complex. There are numerous kinds of immune cells, and they are housed everywhere from your skin all the way to the marrow inside your bones. They also circulate throughout your bloodstream to patrol for problems, so even your heart plays an integral role by transporting them where they need to be. “There are all sorts of different factors and cells working together in a symphony,” says Matthew Lederman, MD, cofounder of Kinectin and coauthor of The Forks Over Knives Plan and The Whole Foods Diet: The Lifesaving Plan for Health and Longevity. “It’s a big, intricate system that works together to fight invaders.”

Contrary to popular belief, we don’t want a boosted immune system or more white blood cells. We want an optimal system where the immune cells that we do have work really, really well. “We want the right cells going to battle and fighting for our health,” says Will Bulsiewicz, MD, MSCI, a gastroenterologist in Charleston, South Carolina, and author of the upcoming book Fiber Fueled. “And we want the rest of our cells to cool off and not get trigger-happy.” 

A hyperactive immune system can lead to problems like autoimmune disease, where the immune system decides your own body is the enemy and goes on the attack, and even acute respiratory distress syndrome, one of the major lung complications of viruses like COVID-19, created by an exaggerated immune response.  

Left to its own accord, the immune system is quite proficient at its job. Things go wayward when it gets hampered by any number of insults: environmental toxins; smoking; excessive alcohol; sleep deprivation; chronic stress; social isolation; lack of exercise; vitamin D deficiency; and a diet heavy in sugar, fats, animal products, and processed foods. 

“When you take something that functions well and put all of this weight on it, you impair a normally robust immune system,” says Lederman. Forget taking an “immune-boosting” supplement or incorporating a vitamin-packed superfood to counteract lifestyle choices that are bogging it down: Immune health doesn’t work that way. “We have to remove the weight so that the immune system can slingshot back into this amazing, powerful thing,” says Lederman.

An astounding 70 to 80 percent of your immune system resides in your gut. The immune system is separated from the 39 trillion microbes of your gut microbiome by a single layer of cells a fraction the width of a strand of hair. The two are in constant communication. “A strong microbiome empowers the neighboring immune cells for optimal function,” says Bulsiewicz. “When you benefit the gut you also benefit the immune system.”

The foods that are highest in fiber are whole plant-based foods, including vegetables, fruits, whole grains, legumes, nuts, and seeds. Instead of focusing on a single micronutrient, like vitamin C, it’s important to eat a wide variety, since they contain different vitamins, minerals, antioxidants and phytochemicals that work in synergy. 

Eating a whole-food, plant-based diet does not make you bulletproof. By combining a diverse plant-based diet with plentiful sleep, regular exercise, stress management, social connection, and good hygiene, you increase your odds of staying healthy. These healthy lifestyle practices can also lessen the intensity and duration of your symptoms when you do catch a bug.  

“Getting sick and getting better is part of a healthy life,” says Lederman. “The more you can build up that memory of different viruses, the more likely your sickness is to be uneventful.”

Ready to get started? Check out our Plant-Based Primer to learn more about adopting a whole-food, plant-based diet.