En español | Your mom swore by chicken soup whenever you were sick. And your doctor is always imploring you to eat more vegetables. But how much can a healthy diet contribute to keeping your immunity up?
According to experts, quite a bit. “Our immune system works most efficiently when lifestyle factors are in balance, and first and foremost is having the foundation of a healthy diet,” says Seema Bonney, an emergency room physician and founder of the Anti-Aging & Longevity Center of Philadelphia.
Diet has a huge impact on disease risk in general. “For example, as many as 30 percent of all cancers are linked to poor dietary habits,” says Anna Taylor, lead outpatient clinical dietitian at the Cleveland Clinic's Center for Human Nutrition. Specific foods have been shown to do everything from keeping your gut microbiome diverse to helping you ward off the occasional upper-respiratory infection — especially important during cold and flu season.
And while there are no foods that can directly prevent COVID-19, the common cold or flu, a diet rich in vitamins and minerals can help your body better prepare to fight off anything that may come its way. This is especially key as you get older. “Our immune response declines as we age, so it is important to consider every meal as an opportunity to nourish your body and support a healthy immune system,” Bonney says.
Here are eight superfoods to give your immune system a little TLC.
Superfood No 1: Yogurt
When it comes to regulating your immune system, keeping your digestive tract stocked with a variety of healthy bacteria that help make up what’s known as the gut microbiome has proven benefits. Research even suggests that probiotics have a modest effect on common cold reduction. “This makes sense, since eating foods rich in probiotics daily supports a healthy gut, supporting the microbiome where much of the immune system is housed,” Taylor says. You can give your gut a hearty dose of such live cultures by incorporating yogurt into your diet.
Start your morning with plain yogurt, add it to oatmeal or smoothies for a creamier flavor, or use it as a condiment in place of sour cream on chili or tacos. Avoid yogurts loaded with added sugars and opt for the Greek kind, which Taylor says contains over two times the protein of regular yogurt.
You can also get probiotics in foods such as kombucha, kimchi, kefir, sauerkraut and pickles. “Look for pickles made with salty water, as those in vinegar do not have the same probiotic effects,” says Michele Renee, director of integrative care at Northwestern Health Sciences University.
Superfood No 2: Garlic
Think of prebiotics as food for all that good bacteria in your gut. These nondigestible compounds (often fiber-rich foods) get metabolized by gut microorganisms and help maintain the balance of healthy gut flora. “So probiotics are live cultures, but it's the prebiotics that are allowing the good bacteria to grow,” says John Whyte, author of Take Control of Your Cancer Risk and chief medical officer at WebMD. “You do not need to take prebiotics for probiotics to work, but it could make probiotics work more effectively,” he says. One of these powerhouse forms of prebiotics is garlic.
In addition to helping your gut diversity thrive, garlic has additional immune-boosting properties. “Garlic contains a bioactive called allicin that has been shown in clinical studies to increase immune T cells and natural killer cells,” says William Li, a physician and author of Eat to Beat Disease: The New Science of How Your Body Can Heal Itself. A study by the University of Florida found that aged garlic extract supplements could significantly reduce cold and flu symptoms.
Additional forms of prebiotics include fiber-rich foods such as whole grains, onions, bananas, asparagus and ginger. Ginger in particular has also been shown to help alleviate clinical nausea of diverse causes.
Superfood No. 3: Blueberries
Part of the reason blueberries seem to make every list of superfoods is a flavonoid they contain called anthocyanin and its multiple immune-boosting properties. A study conducted by Appalachian State University, the University of Montana, Texas Woman's University and Vanderbilt University, for instance, showed that “eating blueberries can almost double the amount of immune natural killer cells in the bloodstream,” Li says. And additional research suggests the flavonoids found in blueberries may help decrease the incidence of upper respiratory tract infections due to such antiviral properties.
Berries, in general, are also loaded with antioxidants, which can help fight off free radicals that contribute to aging. Whyte suggests prioritizing berries of a darker hue, like blueberries or blackberries, as they are likely more antioxidant-packed.
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Superfood No 4: Kiwi
You know that oranges are rich in vitamin C, but there are non-citrus fruits that can also deliver an impressive dose. One medium kiwi contains 71 percent of your recommended daily intake of the key nutrient, which works to “ward off different pathogens by helping to augment production of white blood cells, which helps to prevent infection and inhibit disease,” says Lon Ben-Asher, a registered dietitian and licensed dietary nutritionist at Pritikin Longevity Center + Spa.
Kiwifruit also contains vitamin E, folate, carotenoids and polyphenols. And a small study of community dwelling seniors found that while eating four kiwis a day for four weeks did not significantly reduce the overall incidence of upper respiratory tract infections, it did greatly reduce the severity and duration of head congestion. It also helped participants heal faster from a sore throat.
Other foods you might be surprised to know contain high levels of vitamin C include parsley, thyme, bell peppers, broccoli and tomatoes. “Sprinkle parsley or thyme in your soups or add them to salad dressings,” Ben-Asher suggests.
Superfood No 5: Mushrooms
If you only eat mushrooms as a topping on pizza, you might also want to start working them into your regular rotation. These often-overlooked fungi contain a soluble fiber called beta-glucan, which research has suggested can stimulate the immune system to help it defend against bacterial or fungal infections, viruses and even parasites. Li notes that a study by the University of Western Sydney in Australia showed that eating white button mushrooms can increase protective immune antibodies called IgA in the saliva. Other foods rich in beta-glucan include oats and barley.
So strong are the potential immune-boosting effects of mushrooms that researchers at the University of California at San Diego (UCSD) and UCLA are running a clinical trial that looks at, among other things, whether the veggie can improve the body's response to the COVID vaccine. “We think that we may be able to help vaccines work even better when certain mushrooms are taken around the time of vaccination,” says Gordon Saxe, a physician who leads the Krupp Center for Integrative Research at UCSD and is the study's principal investigator.
Superfood No 6: Salmon
Fish has long been touted for its omega-3 fatty acids, which some studies have linked to better cardiovascular health. But fatty fish like salmon are also rich in vitamin D. And research suggests vitamin D supplementation is associated with lower rates of upper respiratory infections (and that, conversely, low vitamin D levels are linked to increased incidence of upper respiratory infections, Taylor notes.)
You can also get vitamin D from tuna, cheese, egg yolks, and of course through some selective time in the sun, via UV rays.
Superfood No 7: Beans and lentils
You've heard of blue zones — the areas of the world where people live the longest? As it turns out, beans are a diet staple of the centenarians living in these areas, and other research has tracked a drop in mortality with just over a tablespoon of fiber-rich beans and lentils that adults over 70 consumed daily.
Experts say zinc in these legumes may be part of their power, since the mineral helps boost the production of white blood cells, which protect the body against microbial invaders. (Similarly, deficiency in the nutrient is linked to immune dysfunction.) “Research suggests zinc supplementation may reduce the severity and duration of cold symptoms if started early in the infection,” Taylor says. Additional sources of zinc include lean beef, fortified breakfast cereal, pumpkin seeds and seafood, such as raw oysters.
Superfood No. 8: Tea
Curling up on the couch with a warm cup of tea is a great way to unwind. It may also help your body to ward off infections. One study found drinking five to six cups of tea a day boosted immune activity in the body. This did not occur in the study's coffee drinkers, though other research has linked coffee intake to a reduction in ailments as varied as Parkinson's disease, type 2 diabetes, depression and some forms of cancer.
Bonus: Add a scoop of honey to your mug. Its antimicrobial properties may help reduce symptoms of the common cold or flu. One study found that honey was better at easing nighttime coughs and improving sleep quality in children than drugs like cough-suppressing dextromethorphan and the antihistamine diphenhydramine (Benadryl).
Nicole Pajer is a contributing writer who covers health, culture and entertainment. She has also written for The New York Times, Parade, Woman's Day and Wired, among other publications.