The Health Benefits of Black and Green Teas

Today, we look at why the tea plant has a singular effect on our brain and body.

Teas, whether white tea, green tea, oolong, or black—are all made from the tea plant, Camellia sinensis. That’s different from herbal tea, which is defined as pouring hot water over any plant in the world, other than this particular plant.

There are at least 287,655 different plants that we know of on this planet. Why is this one plant the most popular beverage in the world? It’s not the caffeine; the coffee plant has more caffeine, but more people drink tea than coffee. It’s probably not the taste; most people would probably prefer peppermint or some of the fruity berry teas to be better tasting. It’s a pretty enough plant, but why do we drink literally billions of cups a day of this particular plant?

It turns out there’s something in this plant that’s found concentrated in only two places in nature—in the tea plant, and in an odd mushroom called the bay bolete, which has these little holes instead of gills. Scientists figured this one might not pair as well with crumpets, so they called the compound theanine. What does it do that’s got billions of people hooked on it? We weren’t quite sure, until we hooked people up to an EEG.

An electroencephalogram measures the activity of our brain waves, which are split into four major bandwidths: we have delta waves, theta waves, alpha waves, and beta waves. Delta waves, where basically our brain is electrically pulsing very slowly at about one wave per second, are seen primarily in deep sleep. Then, there are theta waves—at about five cycles per second—typically seen when we’re drowsy or in early sleep.

The two waking states are alpha and beta. We have alpha brain waves when we’re relaxed, aware, attentive, like when we close our eyes and meditate. And beta waves are more when we’re stimulated with increased alertness, in a hustle-and-bustle state where most of us live our lives. How can we get more in that alpha state—that wakeful relaxation—fully alert and focused but calm?

Well, if we relax in a nice peaceful place, after about 90 minutes, we can start to see some significant alpha activity, which is this yellow and red. Now, practicing meditators, like Buddhist monks, can achieve this state earlier, and even maintain alpha activity with their eyes open. And the deeper the meditation, the higher the alpha waves. So, we can meditate for 30 years, or just drink some tea.

That is why people drink tea from the tea plant.

What else can green tea do? How about using it as a mouthwash?

Tea is the second most widely consumed beverage in the world, after water, to the tune of billions of pounds every year.

There have been a lot of studies on the effect of green tea on other aspects of oral health. For example, green tea appears to work as well as chlorhexidine for reducing plaque, and chlorhexidine is like the gold standard. Green tea is safer too. Chlorhexidine has so many side effects you’re not supposed to use if for more than a short time period––side effects like discoloration of the teeth, increased formation of tartar, impairment of taste sensation, and occasionally damage to the inner lining of your mouth, whereas, if anything, drinking green tea appears to have good side effects.

Tea consumption is associated with living a longer life thanks to links to less cardiac death, heart disease, stroke, and type 2 diabetes—and not just by a little. A three-cup (720 ml) a day increase in tea consumption per day is associated with a 24% decreased risk of premature death from all causes put together––the equivalent of adding about two years onto your lifespan. The longevity link extends to both green tea and black, though the per cup effect appears greater with green.

If you compare the anti-microbial efficacy of green tea and chlorhexidine mouth rinses against the bacteria associated with tooth decay in children with severe early childhood cavities, this study found that a green tea mouth rinse was superior to chlorhexidine. But this study found the opposite. Chlorhexidine wiped out like 95% of the decay bacteria, versus more like 70% for green tea. But just rinsing with water alone can cut levels in half. So, in terms of protecting teeth, the effectiveness of green tea as a mouth rinse agent has not been proven. But what about for bad breath?

The effect of green tea on halitosis has evidently been well known from early times, perhaps due to the deodorizing activity of certain antioxidant polyphenols. But you don’t really know until you put it to the test.

This study found that sucking on green tea tablets reduced stinky breath compounds. But who sucks on tea tablets? Here, green tea was compared to breath mints, chewing gum, and parsley oil, and green tea seemed to help. But it did not reach statistical significance. But again, this wasn’t drinking or swishing with green tea, but rather some green tea power sprinkled on people’s tongues. This study used actual tea, and found that one minute later, swishing with green tea was no better than swishing with water.

Okay, but what about chronic use over time? This is the study I had been looking for. A randomized, double-blind, placebo-controlled trial in which people rinsed their mouths twice a day for a month with a green tea mouthwash, or a similar looking and tasting placebo mouthwash. And at the end of the month, the stinky bad breath compounds were reduced nearly 40% in the green tea group, versus closer to only 10% in the placebo group.

Bottom line: a systematic review on the effect of the tea plant on decreasing the level of halitosis concluded that green tea mouthwash can indeed reduce bad breath––though they don’t feel the evidence is sufficiently robust for dentists to start recommending it on its own, due to lack of enough randomized clinical studies. But green tea mouthwash can be a good treatment of choice beside other halitosis treatments, like tongue scraping, to achieve better clinical results.

Finally today, unlike most antiviral drugs, green tea appears to work by boosting the immune system. Here’s the story.

“The belief of green tea as a ‘wonder weapon’ against diseases dates back thousands of years.” I’ve talked about it in relation to chronic disease, but what about infectious disease? Interest in the antimicrobial activity of tea dates back to a military medical journal in 1906, suggesting that servicemen fill their canteens with tea to kill off the bugs that caused typhoid fever. However, this effect of tea was not studied further until the late 1980s, when tea compounds were pitted against viruses and bacteria in test tubes and petri dishes.

But, what we care about is do they work in people? I had dismissed this entire field of inquiry as clinically irrelevant—until genital warts. “External genital warts,” caused by human wart viruses, “are one of the most common and fastest-spreading venereal diseases worldwide.”

“Patients with [external genital warts] present with one or several cauliflower-like growths on the genitals and/or anal regions,” considerably impairing people’s “emotional and sexual well-being.” But, rub some green tea ointment on, and you can achieve “complete clearance of all warts” in more than 50% of cases.

Wow. If it works so well for wart viruses, what about flu viruses? Works great in a petri dish, but what about in people? Tea-drinking schoolchildren do seem to be protected. But, you don’t know until it’s put to the test. If you give healthcare workers green tea compounds, they come down with the flu about three times less often than those given placebo. In fact, just gargling with green tea may help. While a similar effect was not found in high school students, gargling with green tea may drop the risk of influenza infection seven- or eight-fold, compared to gargling with water, in elderly nursing home residents, where flu can get really serious.

Unlike antiviral drugs, green tea appears to help by boosting the immune system, enhancing the proliferation and activity of gamma delta T cells, a type of immune cell that acts as “a first-line defense against infection.” “Subjects who drank six cups of tea per day had up to a 15-fold increase in [infection-fighting] interferon…production in as little as one week”—but why?

There’s actually a molecular pattern shared by cancer cells and pathogens with “edible plant products, such as tea, apples, mushrooms, and wine.” And so, eating healthy foods may help maintain our immune cells on ready alert, effectively priming our gamma delta T cells “that can then provide natural resistance to microbial infections, and perhaps tumors.”

I guess I shouldn’t have been so surprised—tea, after all, is “a vegetable infusion.” You’re basically drinking a hot water extraction of a dark green leafy vegetable.