As flu season heightens, it's important to prioritize immune system support, which includes eating a balanced diet of nutrient-dense foods, experts say.
The immune system is directly connected to the gut, so consuming the right nutrients can positively affect both.
"If we're not getting enough fiber, fermented foods or the right nutrients, we can get that imbalance in the gut environment, and that's going to impact the immune system," New Jersey-based registered dietitian Erin Palinski-Wade told Fox News Digital.
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There were an estimated 51 million flu-related illnesses during the 2024-25 flu season, according to the Centers for Disease Control and Prevention (CDC).
There are plenty of foods and beverages that support the immune system and may help protect against illness.
"Eat the rainbow, especially when it comes to produce," Palinski-Wade said. "So those bright colors, things like bell peppers, kiwis, citrus fruits, broccoli, they're all an excellent source of vitamin C," plus a wide range of other nutrients.
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Aside from fruits and vegetables, it's beneficial to eat fermented foods like yogurt, kefir and sauerkraut because they help support the gut microbiome, according to Palinski-Wade.
Fiber also plays a big role in supporting gut health and the immune system, she noted, adding that beans, nuts and seeds are great options for increasing fiber intake.
Only 6% of American adults consume enough fiber daily, according to a report published in September by the American College of Cardiology.
Make sure to get enough protein and zinc, Palinski-Wade added, "because these are really the building blocks our body needs to build the immune cells."
She listed lean meats, shellfish, eggs, pumpkin seeds and chickpeas as good sources of protein and zinc.
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Lauren Manaker, a South Carolina-based registered dietitian, touted dairy milk as an immune-supporting beverage due to its vitamins and hydrating benefits.
"Several of the essential micronutrients found in milk, including vitamin A, vitamin D, zinc and selenium, support a healthy immune system," Manaker told Fox News Digital.
A common misconception is that milk increases mucus and phlegm production and, therefore, should be avoided during a cold.
There's little scientific evidence to support that theory, although one reason people might associate dairy with higher mucus production is the sensation it causes when consumed, according to the Mayo Clinic.
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"When you take milk products and you mix them with saliva, it can feel like a thicker coating in your throat, and that's why you can feel like you have more phlegm or more mucus," Palinski-Wade said. "It doesn't really mean you're producing more, but it can make you feel that way."
Those who are lactose intolerant can opt for lactose-free milk, "because it offers the same key nutrients as regular dairy milk, just without the lactose," Manaker noted.
Hydration is crucial for immune support, as well.
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"The hydration helps you feel your best, but what's also interesting about hydration is it keeps your airways moist, and that's actually part of your body's first line of defense against catching a cold or a flu," Palinski-Wade said, suggesting people sip on water, broth, green tea and ginger tea.
Getting adequate sleep, managing stress and being physically active are also important for maintaining a healthy immune system, Manaker added.
Regarding supplements, Manaker said they can be helpful for people struggling to meet all of their nutrient needs through food alone.
However, it's best to ask a health-care provider for guidance and to be thoughtful about dosages, "because more is not always better," she said.