An old Chinese proverb goes, “Better to be deprived of food for three days, than tea for one.”
For centuries, people have consumed green tea for its health benefits. But it’s only in the past couple of decades that a handful of researchers have put the question, “Is green tea good for your immune system?” to the test.
Let’s consider some of their efforts.
Six Studies Ask, “Is Green Tea Good for Your Immune System?”
Green Tea Supplements vs. Cold and Flu in Adults:
In 2007, researchers led by Cheryl A. Rowe conducted a trial to understand better if green tea can help prevent or reduce cold and flu symptoms.
The team split the trial’s 124 adult recruits (aged 18 to 70) into two groups. Every day for three months, the first group consumed green tea supplements equivalent to drinking ten cups of green tea.
The second group took placebo (fake) supplements.
During the trial, the difference between the two group’s cold and flu symptoms was striking:
- Thirty-two percent fewer green tea group participants had symptoms.
- Twenty-three percent of the green tea group had fewer bouts of flu lasting more than two days.
- As a whole, the green tea group had 36 percent fewer days with any cold or flu symptoms.
To discern the reason for the difference, the researchers examined the participants’ immune systems. Sure enough, they’d responded positively to the green tea with:
- Twenty-eight percent higher T-cell growth.
- Twenty-six percent higher IFN-gamma secretion
Green tea and L-theanine vs. flu in healthcare workers:
Published in 2011, this trial headed by the University of Shizuoka’s Keiji Matsumoto also tackled the question, “Is green tea good for your immune system?”
The Japanese research team separated nearly 200 healthcare workers into two groups and followed them for five months.
One group took a combination of green tea and L-theanine (an amino acid found in tea leaves) capsules, and the other group took placebos.
Four (4 percent) of the green tea group came down with “laboratory-confirmed” influenza during the trial. So how did the placebo group do?
Not so hot! Thirteen of them (13 percent or over three times more than the green tea group) developed influenza.
Green tea, anyone?
Green tea gargling vs. flu in nursing home residents:
What can green tea do for the immune systems of elderly nursing home residents?
According to another University of Shizuoka study, just gargling it has flu-fighting benefits!
Researchers led by Hiroshi Yamada had 76 of their 124 enrollees gargle with green tea extract three times daily for three months.
The remaining 48 used other gargling solutions.
Only one tea gargler became ill with flu during the study. Compare that to five of the residents who used other solutions – a five-fold increase in flu frequency!
While this could have been a random result, the fact that other studies have duplicated it makes me believe green tea could have been the deciding factor.
Green tea gargling vs. flu in healthy adults:
A larger trial, also headed by Hiroshi Yamada, recruited more than 400 healthy adults aged 20 to 65. The team assigned half to gargle three times daily with green tea extract and half to gargle with a placebo.
After three months, two (1 percent) of the green tea group and four (2 percent) of the placebo group had contracted flu. However, the researchers decided the result wasn’t significant enough to be conclusive.
Green tea gargling vs. respiratory-related fever in nursery school kids:
For a more definitive study, we have to jump to a different institution. The Hamamatsu University School of Medicine’s Tatsuya Noda ran a green tea gargling trial on nearly 20,000 nursery school children aged 2 to 6.
For 20 days, the three groups of children either gargled with green tea, gargled with water, or didn’t gargle. Imagine being one of the nursery workers charged with getting a toddler to gargle with green tea for 20 days!
But it seems their efforts paid off. The green tea garglers came down with only one-third of the respiratory infection-related fevers of the non-garglers!
Balancing the Admittedly Limited Evidence
Other than these trials, there’s not an abundance of research on which to base an answer our question, “Is green tea good for your immune system?” That said, the results of these six studies consistently point to the likelihood that it is.
If I’d been a participant in any of them, I would’ve definitely wanted to be in the green tea group. The one with better odds of not getting a cold or fever!
Time for my daily cup of green tea!