Reducing stress, sleeping enough, exercising and getting sunlight are all known strategies for improving the body’s ability to protect itself from harm. However, the most important factor in building a rock-star immune system is nutrition. Here is a guide to the care and feeding of the inner fortifications that fight off disease, supporting long-term wellness.

Ground Zero: The Gut

About 70 percent of the immune system resides in the gastrointestinal tract—home to a microbiome that contains trillions of bacteria. It works as a complex ecosystem in which the good bacteria prevent the bad bacteria from taking hold and causing illness or disease.

Eating plants promotes the robust growth of that good bacteria. “The GI microbiome evolved closely with our immune systems and under the influence of the plants our ancestors ingested,” says Holly Poole-Kavana, who practices herbal medicine in Washington, D.C. Yet about 90 percent of Americans don’t eat enough fruits and vegetables, according to the U.S. Centers for Disease Control and Prevention. The consequent weakening of the microbiome is a double-edged sword, because the processed foods Americans commonly consume promote the growth of harmful microbes. The 2015-2020 Dietary Guidelines for Americans indicates that added sugars, saturated fats and sodium eaten by most Americans are far above recommended amounts. This tipping of the scales causes weight gain, toxin buildup and immune system dysfunction.

What Not to Eat

Plants and grains on grocery shelves today are typically processed into bread, cereal, pasta, desserts and snacks, abundant in added sugars, salt, detrimental fats and chemical additives. These altered foods slam the gut’s immune protection and increase the risk of chronic disease. A Czech Republic study on food additives found that gut microbes that fought inflammation were harmed by additives. According to the research, “Permanent exposure of human gut microbiota to even low levels of additives may modify the composition and function of gut microbiota, and thus influence the host’s immune system.”

And of course, be wary of sugars. Anything that turns into sugar in the system—think carbs like refined bread products and pasta, not just sweets—is an immune-depressing culprit, says Heather Tynan, a naturopathic doctor at Evergreen Naturopathic, in San Diego. “The level of germ-fighting activity your immune system is able to maintain after a sugary meal decreases for a number of hours.” Saturated fats also alter immune cells, disrupting their functions and triggering inflammation.

Getting away from processed food cravings can be a challenge, because the foods provide a temporary energy boost. Dorothy Calimeris, of Oakland, California, a certified health coach and author of three anti-inflammatory cookbooks, suggests that cravings mean the body needs something, but it may be rest or water. “By focusing on eating higher-quality nutrients, we can limit and eventually eliminate the cravings.”

Eat the Rainbow

Fruits and vegetables get their colors from phytochemicals, which provide the human microbiome with antioxidants, minerals and vitamins that keep the gut healthy and help the immune system combat cellular damage. National guidelines suggest Americans eat 10 servings of plants a day, ideally two each from the green, red, white, purple/blue and orange/yellow categories. But data from the National Health and Nutrition Examination Surveys show that eight out of 10 people in the U.S. don’t get enough of any color category.

  “A good strategy is to add one new vegetable a week to your grocery cart,” suggests Canadian nutritionist Lisa Richards, founder of TheCandidaDiet.com. “Blending fruits and vegetables into shakes or smoothies is also an effective way to eat the rainbow for those who are busy.”

Whatever goes into the grocery cart should be certified organic, the only sure way to avoid ubiquitous genetically modified organisms (GMOs) in the food chain, which animal studies have linked to immune system damage.

Herbs are also helpful to boost the body’s inherent ability to protect itself. Poole-Kavana points to medicinal herbs like astragalus and reishi mushroom, which support immunity and balance gut bacteria; antimicrobial herbs like garlic, thyme and oregano; and elderberry, an anti-inflammatory fruit that boosts the body’s ability to identify and eliminate viruses and bacteria.

“The single greatest thing anyone can do for their health is to eat whole foods, including organic vegetables, fruits, high-quality proteins, whole grains and healthy fats,” says Calimeris.

Julie Peterson writes from rural Wisconsin and can be reached at [email protected].

Published in the January 2020 issue of Natural Awakenings.