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The #1 Thing You Can Do for Immunity, Says Science 

Start now and protect yourself from "twindemic."

The COVID-19 pandemic has continued into its second autumn, the traditional start of flu season, causing experts to warn about a potential "twindemic" as the two potentially serious respiratory viruses spread among people who increasingly spend time indoors. Many of us are wondering how we can support our immune systems to fend off potential threats old and new. Experts say there is one thing that is probably the most important step you can take to protect your immunity. Read on to find out more—and to ensure your health and the health of others, don't miss these Sure Signs You May Have Already Had COVID.


How to Improve Immunity

exercise lunges

Experts like Harvard Medical School say there are many things you can do to bolster the immune system. These include:

  • Get regular exercise
  • Reduce stress
  • Maintain a healthy weight
  • Avoid smoking or other tobacco use
  • Drink alcohol only in moderation
  • Get good quality sleep

But there's one thing that's probably the most important.

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The #1 Thing You Can Do for Immunity

healthy foods

The #1 thing you can do to bolster your immune system is to eat a healthy diet — one that's low in processed foods and added sugar, while being high in fruits and vegetables, lean proteins, and healthy fats.

By eating a varied diet that's high in fruits and vegetables, you'll consume micronutrients that support the immune system, including two of the most important: vitamin D and vitamin C.

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The Evidence for Vitamin C

citrus fruit juice

Although it's not a magic pill—no supplement is—vitamin C is one of the immune system's bodyguards. "Vitamin C contributes to immune defense by supporting various cellular functions of both the innate and adaptive immune system," wrote researchers behind a 2017 study published in the journal Nutrients. "Vitamin C deficiency results in impaired immunity and higher susceptibility to infections … supplementation with vitamin C appears to be able to both prevent and treat respiratory and systemic infections." 

Good food sources of vitamin C include citrus fruits, peppers, berries and cruciferous vegetables like broccoli and brussels sprouts.

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The Evidence for Vitamin D


Good sources for Vitamin D include fatty fish like salmon, herring and mackerel; egg yolks; liver; and fortified milk.

"Laboratory studies show that vitamin D can reduce cancer cell growth, help control infections and reduce inflammation," says the Harvard T.H. Chan School of Public Health. The National Institutes of Health notes that vitamin D helps regulate immune function.

It can be hard to get enough vitamin D entirely through food, so you might want to consider taking a vitamin D supplement in addition to your healthy diet. (It's a good idea to consult your doctor first, though.) One review of studies published in BMJ looked at more than 11,000 people and found that those who took weekly or daily vitamin D supplements were less likely to develop respiratory tract infections than those who didn't. 

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Other Benefits of a Healthy Diet


Vitamins D and C aren't the only micronutrients important to immunity. The immune system is exactly that—a system of complicated processes, which are supported by various nutrients in complex ways. Eating a varied diet rich in plant foods, healthy proteins and good fats can help ensure you're getting all those nutrients. Plus, eating healthy can lower your risk of chronic conditions that tax immunity, including obesity, diabetes and heart disease.

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How to Stay Safe Out There

Woman in medical protective mask getting injection in arm vaccination.

Follow the fundamentals and help end this pandemic, no matter where you live—get vaccinated ASAP; if you live in an area with low vaccination rates, wear an N95 face mask, don't travel, social distance, avoid large crowds, don't go indoors with people you're not sheltering with (especially in bars), practice good hand hygiene, and to protect your life and the lives of others, don't visit any of these 35 Places You're Most Likely to Catch COVID.

Michael Martin
Michael Martin is a New York City-based writer and editor. Read more about Michael