What Happens to Your Immune System When You Drink Green Tea

Reviewed by Dietitian Jane Leverich, M.S., RDN

Key Points

• Green tea contains catechins, including EGCG, that may support antioxidant defenses.

• Research on green tea and inflammation is mixed, and it’s unclear whether drinking tea can prevent illness.

• Green tea can be part of an overall immune-supporting routine.

As we move closer to cold and flu season, you may start thinking about things that can support your immune system. Green tea has generated online buzz for possibly supporting immune health, and it can seem like an easy addition to your routine. But its reputation for immune support can leave you with expectations that go well beyond enjoying a cup of tea.

Before you add another box to your grocery cart, it may help to understand what green tea can actually offer your immune system. We asked health experts to explain what happens after you drink it and whether making it a daily habit is worth considering for your immune system.

How Green Tea May Affect Your Immune Health

It May Support Your Antioxidant Defenses

Your immune cells produce reactive molecules as part of the body’s response to destroy invading germs. But when these molecules build up beyond what your antioxidant defenses can manage, they can also damage your own cells and tissues. This imbalance, called oxidative stress, can contribute to ongoing inflammation. Antioxidant defenses help limit that damage while allowing your immune system to do its job.

“Some oxidative stress is a normal part of immune activity, but too much can damage cells and contribute to chronic inflammation,” says Serena Pratt, M.S., RDN.

Green tea contains plant compounds called catechins, including epigallocatechin gallate, or EGCG, that may support those antioxidant defenses. Research suggests that green tea may improve some measures of antioxidant activity and reduce markers of oxidative damage.

The research has included a mix of green tea beverages and extracts, as well as people with different health conditions, so the findings can’t predict exactly what your daily cup will do. But, green tea’s potential antioxidant effects may be one way it could support the body’s defenses against oxidative stress.

Its Effects on Inflammation Are Mixed

Inflammation is part of your immune response to injury or infection. It helps your body respond to a threat and begin healing, although an excessive or prolonged response can also damage tissue. Researchers have investigated whether green tea can influence that response. Research suggests that green tea may affect some markers of inflammation, but the findings are mixed.

“Human studies have found improvements in some inflammatory markers but not others, so I wouldn’t say that drinking green tea broadly ‘reduces inflammation,'” Pratt says.

That means an anti-inflammatory label on your green tea likely needs some context. A change in one blood marker doesn’t tell researchers that your daily tea will improve immune function in a meaningful way.

It May Affect Some Respiratory Symptoms

Some research suggests that tea catechins may help ease certain cold-like symptoms, including runny nose, nasal congestion and headache. However, the evidence is limited, and research has not found consistent improvements across all respiratory symptoms, including cough, sore throat and fever.

The amounts of catechins studied can also vary considerably, and some research has used beverages or concentrated extracts with controlled doses. So, the findings don’t tell you whether your home-brewed tea would have the same effect. They also don’t establish that green tea prevents the infections behind cold and flu symptoms.

That distinction is reflected in the broader research, explains Nagi Kumar, Ph.D., RD, FADA. Kumar says human evidence is stronger for changes in oxidative stress and related biological markers than for preventing colds, influenza or other infections. Green tea may have a role in easing some symptoms, but you shouldn’t count on it to keep you from getting sick.

Its Compounds May Support Your Gut’s Protective Barrier

Your intestinal lining helps keep bacteria and their potentially harmful components inside your gut and out of your bloodstream. Keeping that barrier working well helps limit what your immune system needs to respond to.

Green tea compounds may help support this protection. Research suggests that green tea catechins may influence intestinal barrier function and reduce exposure to bacterial compounds that can trigger inflammation.

However, much of the research has examined concentrated green tea extracts rather than brewed tea. “Brewed tea should not be equated with concentrated supplements of green tea,” Kumar says. More research is needed to understand whether the amounts of catechins found in a typical cup of green tea have meaningful effects on gut barrier function and immune health. Even so, current evidence offers a promising explanation for how green tea compounds could support immune health by strengthening your gut barrier.

Ways to Enjoy Green Tea

Finding a preparation you enjoy can make green tea an easy addition to your routine. Here are a few ways to try it:

• Enjoy a warm cup. Follow the brewing instructions on the package. Pratt recommends using those directions instead of steeping longer to extract more plant compounds, which can make your tea bitter.

• Serve it iced. Brew green tea, let it cool and pour it over ice. Pratt notes that serving it cold doesn’t remove its beneficial compounds.

• Add plant-based flavor. Try a squeeze of lemon, a few mint leaves or sliced ginger, all additions Pratt suggests.

Other Tips for Supporting Your Immune System

Think of green tea as fitting into your routine alongside daily habits that support immune function and help reduce your exposure to infections. Start with these:

• Eat a variety of foods. Pratt recommends getting enough food overall and including protein, fruits and vegetables. A varied diet helps you get nutrients your immune system needs, including vitamin C, vitamin D, selenium and zinc.

• Wash your hands regularly. Use soap and water, especially before eating and after coughing, sneezing or blowing your nose, to help prevent germs from spreading.

• Stay current on recommended immunizations. Vaccines help your immune system recognize specific infections and prepare to respond, reducing your risk of severe illness.

Our Expert Take

You don’t need proof that green tea prevents colds to enjoy a daily cup. Though the research is mixed about whether it will support common cold symptoms, it still provides beneficial plant compounds. If you like green tea, keep drinking it. If you’re curious, try it hot or iced and see which you prefer. Just remember to give the rest of your routine—including eating regular, varied meals, getting enough sleep and staying up to date on recommended immunizations—the same attention you give what’s in your mug.

Read the original article on EatingWell