Most of us drink hot tea in hopes of soothing a sore throat or avoiding the common cold.
The concept of tea as medicine is nothing new. The Chinese have used this method for centuries to alleviate ailments and improve the immune system, says Paulina Lee, RD, a registered dietitian in Houston, who employs both Western medical practices and alternative and integrative therapies to help patients address the root causes of their health issues.
Despite the widespread use of tea for immunity, there is little solid scientific evidence to demonstrate that tea offers these types of benefits. Read on to find out what doctors have discovered about how tea may or may not help maintain a strong immune system.
How Tea Can Support Immune Health
Most of the immune and general health benefits of tea are linked to a group of antioxidants known as polyphenols. A significant amount of epidemiological data has shown that a diet rich in polyphenols protects against chronic health conditions such as cardiovascular diseases and type 2 diabetes, says Megan Meyer, PhD, senior director of scientific communications for the International Food Information Council in Durham, North Carolina. Her previous research has examined the effects of nutritional antioxidants on the immune system’s response to the flu.
Dr. Meyer points to a review published in September 2017 in Nutrition Bulletin, which found that teas are particularly rich in polyphenols known as flavonoids. These plant chemicals have been shown to help lower blood pressure and cholesterol levels.
Regarding your immune system, antioxidants (such as the flavonoids in tea) can help protect the body against free radicals generated by pollution, cigarette smoke, and ultraviolet rays, according to Harvard Health. Free radicals can have damaging effects on the body, including a weakened immune system, according to a previous analysis.
There are many varieties of tea that can support your immune health. Popular options like green, black, white, and oolong tea all come from the same plant, Camellia sinensis, according to Harvard T.H. Chan School of Public Health. What makes them distinct is how they are processed, says Meyer. Differences in processing, geographical location, and plant varieties provide the unique flavors and nutritional compositions of tea, meaning some teas offer more immune benefits than others.
More research is needed on tea and immune health
While research on tea and immune health is promising, studies so far either do not involve humans or the research is conducted on a relatively small number of people. Many studies also use tea in the form of capsules or tablets, which usually contain a much higher dose of plant compounds than found in a cup of tea. Given these limitations, it is difficult to know if and how a cup of tea will benefit the immune health of an average person. More extensive studies on humans consuming brewed tea are needed.
That said, health experts generally agree: brewed tea without sweeteners is a healthy beverage choice.
1. Green Tea
Green tea, with its bittersweet flavor, is a rich source of catechins. Catechins are polyphenols that have a generally positive benefit on well-being and are known antioxidants, says Lee. Epigallocatechin gallate (EGCG) is one of the most abundant and well-known catechins in green tea. It also offers benefits for your immune system.
For example, one study found that treating mice with EGCG increased the number of regulatory T cells in the spleen and lymph nodes. Regulatory T cells modulate the immune response, helping the system remain balanced and preventing it from attacking healthy cells.
Research suggests that EGCG may affect immune function in humans. In a study published in April 2021 in Biochemical and Biophysical Research Communications, researchers treated T cells taken from 20 healthy adult males with EGCG isolated from green tea dissolved in water. They found that EGCG prevented T cells from producing pro-inflammatory proteins known as cytokines, suggesting that the plant compounds in green tea may help regulate the immune system.
While these results provide clues about the link between green tea and immunity, more research on humans, particularly those with weakened immune systems and larger populations, is needed.
2. Turmeric Tea
Turmeric, the yellow-orange spice that gives curry its vibrant color, has been shown to be beneficial for your immune system when enjoyed in tea. Research indicates that turmeric can reduce inflammation and contains high levels of antioxidants, both of which support overall immune function, says Lee.
The main active compound in turmeric is curcumin. According to a review published in Foods, curcumin effectively eliminates various types of free radicals, controls enzymes that neutralize free radicals, and helps prevent the formation of free radicals. Given the role that free radical damage can play in many diseases, the antioxidants in turmeric can make this spice a useful addition to your immune health.
Curcumin may play an important role in the immune response. For example, a study using cultured spleen cells from mice showed that curcumin could regulate T cells and B cells, two lymphocytes that recognize and respond to foreign substances in your body. In the aforementioned study, curcumin helped regulate the immune response to prevent immune cells from attacking healthy tissues. Researchers concluded that curcumin may be a promising therapy for keeping the immune system in check.
3. Black Tea
This type of tea gets its dark color from a group of polyphenols known as theaflavins. Research supports the antioxidant potential of theaflavins, even in comparison to EGCG, says Lee, highlighting a study that found these two types of polyphenols are equally effective antioxidants.
However, the antioxidants in black tea may have unique effects on the immune system. For example, a clinical study found that healthy individuals (without major illnesses and with normal to slightly elevated systolic blood pressure) who drank three cups of black tea daily for six months showed increased immune activity.
Researchers analyzed three markers indicating that the immune system had been activated: neopterin, kynurenine, and tryptophan. While black tea did not have a significant effect on neopterin or tryptophan levels, it increased kynurenine, suggesting that the polyphenols in black tea help activate the immune response in healthy individuals.
4. Ginger Tea
As a close relative of turmeric, ginger may offer benefits for immune health.
Gingerol is the main active compound responsible for the spicy, peppery flavor and medicinal properties of ginger. According to a previous analysis, gingerol not only provides antioxidant and anti-inflammatory effects but may also treat infections.
In addition to gingerol, ginger contains other antiviral compounds that are effective in combating colds, notes a previous research paper. These compounds are associated with a reduction in pain, fever, and coughing related to the common cold.
That said, few studies have analyzed the effects of ginger on the immune system, particularly the effects of ginger tea.
5. White Tea
Due to minimal processing, white tea is one of the lightest and most delicate varieties on the market. Like green tea, white tea offers high levels of catechins, according to a previous review. In fact, previous research suggests that white tea has antioxidant benefits similar to green tea, although the antioxidant potential of green tea is higher, notes Lee.
As an added benefit, white tea may offer antimicrobial benefits. For example, researchers tested the antimicrobial effects of white tea leaves against the bacteria Streptococcus mutans and Streptococcus sobrinus, two microorganisms that contribute to dental cavities. After a 72-hour incubation period, researchers found that white tea extracts exhibited significant antibacterial effects against Streptococcus mutans, suggesting that white tea extract may help protect against dental cavities. The findings were published in Materials Today: Proceedings.
While such test-tube studies can yield interesting results, they do not provide a complete picture. More studies on humans who drink brewed tea are needed to understand how white tea affects the immune system. A plant or supplement that passes through our digestive systems must be absorbed into the bloodstream, processed in the liver, and still be effective when diluted in the body, explains Lee.
