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Dietary Brain Wave Alteration

A neurological basis for humanity’s love affair with Camellia sinensis?

September 3, 2009 |
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Supplementary Info

Sources Cited

A. C. Nobre, A. Rao, and G. N. Owen. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr, 17(suppl - 1):167-168, 2008.

Cancer Epidemiol Biomarkers Prev. 2008 Mar;17(3):712-6.Coffee, tea, colas, and risk of epithelial ovarian cancer. Song YJ, Kristal AR, Wicklund KG, Cushing-Haugen KL, Rossing MA.

S. E. McCann, M. Yeh, K. Rodabaugh, and K. B. Moysich. Higher regular coffee and tea consumption is associated with reduced endometrial cancer risk. Int. J. Cancer, 124(7):1650-1653, 2009.

M. B. de Santana, M. G. Mandarino, J. R. Cardoso, I. Dichi, J. B. Dichi, A. E. I. Camargo, B. A. Fabris, R. J. Rodrigues, E. C. S. Fatel, S. L. Nixdorf, A. N. C. Sim~ao, R. Cecchini, and D. S. Barbosa. Association between soy and green tea (camellia sinensis) diminishes hypercholesterolemia and increases total plasma antioxidant potential in dyslipidemic subjects. Nutrition, 24(6):562-568, 2008

K. Maruyama, H. Iso, S. Sasaki, and Y. Fukino. The association between concentrations of green tea and blood glucose levels. J Clin Biochem Nutr, 44(1):41-45, 2009.

K. C. Maki, M. S. Reeves, M. Farmer, K. Yasunaga, N. Matsuo, Y. Katsuragi, M. Komikado, I. Tokimitsu, D. Wilder, F. Jones, et al. Green tea catechin consumption enhances exercise-induced abdominal fat loss in overweight and obese adults. Journal of Nutrition, 139(2):264, 2009.

S. I. Lee, H. J. Kim, and Y. C. Boo. Effect of green tea and (-)-epigallocatechin gallate on ethanol-induced toxicity in hepg2 cells. Phytother Res, 22(5):669-674, 2008.

T. P. Ng, L. Feng, M. Niti, E. H. Kua, and K. B. Yap. Tea consumption and cognitive impairment and decline in older chinese adults. American Journal of Clinical Nutrition, 88(1):224, 2008.



Tea, black tea/green tea/white tea, is made from the tea plant. That’s different from herbal tea, which is defined as pouring hot water over any plant in the world other than the tea plant. There are 287,655 different types of plants on the 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 as better tasting. I mean it’s a pretty enough plant, but why do we drink literally billions of cups a day—of this one?
Well, I think we just figured it out. It turns out there’s something in this plant that’s basically found in only two places in nature—here, and in a weird blueish mushroom called the bay boleet, which has these little holes instead of gills. Scientists figured this one might taste better with crumpets, and so they called the unique substance theanine. What does this stuff do that it has billions of people hooked on it? We weren’t quite sure, until last year.
When you hook up people to an EEG to measure their brain wave activity, you find that human beings essentially have four mental states—two while sleeping and two while awake. Delta waves, where your whole brain is basically electrically pulsing very slowly at about a wave a second, are only seen in deep sleep. Then there’s theta wave sleep, when you’re dreaming, at about 5 cycles per second.
The two waking states are alpha and beta. Alpha is relaxed, aware, attentive, like when we close our eyes and meditate; and beta is more the stimulated, hustle-and-bustle state where most of us live our lives.
Alpha is where we want to be, fully alert and focused, but calm. How do we get there? Well if you relax in a nice peaceful place, after about 90 minutes you 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 maintain it even with their eyes open.
So you can meditate every day for a few years, or just drink some tea. This is the amount of theanine that enters your brain after you drink about two cups of tea. Look closely, compare, and see if you detect a difference. That, is why people drink tea from the tea plant.
But are their side-effects to so dramatically altering our brain on a daily basis? Well if seen my previous years’ lectures, you know that the side effects of daily tea consumption include things like less breast cancer risk, and living a significantly longer life.
Here are the new side-effects we just learned about in the last 12 months: Drinking tea from the tea plant halves your risk of getting ovarian cancer. Halves your risk of getting endometrial cancer. Can lower our cholesterol, our blood sugars, and our weight. Protect our liver. And protect our brain. Drink green tea every day.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by veganmontreal.

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Dr. Michael Greger

Doctor's Note

Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other videos on tea. Also, there are 1,449 other subjects covered in the rest of my videos--please feel free to explore them as well!

Also, for more context be sure to check out my associated blog posts: Breast Cancer and DietIs Caffeinated Tea Really Dehydrating?Stool Size and Breast Cancer RiskSoymilk: shake it up!Increasing Muscle Strength with FenugreekHibiscus Tea: The Best Beverage?, and Rooibos & Nettle Tea.

If you haven't yet, you can subscribe to my videos for free by clicking here.

  • Michael Greger M.D.

    Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other videos on tea. Also, there are 1,449 other subjects covered in the rest of my videos–please feel free to explore them as well!

    • t091582

      one comment and one question:
      1. Dr. Blaylock says NEVER squeeze lemon in tea as it brings out the aluminum.
      2. question: about 10 years ago there was much comment about white tea having even more antioxidants than green tea. But in recent years I have not seen anything else about this.. Just wondering if you feel white tea is better than green??
      thank you.

      • Thea

        t091582: I think you will be interested in the following video which compares green tea to white tea.

        The thing about the lemon makes no sense to me (as a lay person). But if squeezing lemon concerns you, then you would want to stick with green tea. (You’ll see why I say that after watching the above video.

        Good luck.

        • t091582

          Thanks for that!!!

  • Laura Scalia

    Hi Doc
    Two questions: with fibromyalgia, I am constantly waking up in the night – is there a way to know whether I have reached the delta sleep?
    Also, I have always read that meditation is a deeper sleep than what sleep is – so, are you saying that drinking tea will actually restore the brain patterns that loss sleep caused and that there is no benefit to meditation?

  • wickedchicken

    Wow. I meditate and have drank a lot of tea in my time…. no comparison, meditation gets my high score.

  • Michael Greger M.D.

    Also be sure to check out my associated blog post Breast Cancer and Diet!

  • Phil

    Have the Monks been briefed? =D

  • Gabrielle

    Is this the same tea plant (and effect) in black tea? or is it just green tea?

    • Mark R. Mach

      Both black tea and green tea come from the same plant, as well as oolong and white tea. I don’t how these particular effects vary between the different types of tea.

  • Stephen Lucker Kelly

    Is Hibiscus Tea better than Green Tea? Or do both have different effects?

  • Johnny T.

    What about decaf green tea? Just as effective as regular?

  • Eva

    Wouldn’t the caffeine counteract the relaxing effects of the theanine? I’m very sensitive to caffeine; it makes me anxious. How could I get the benefits of green tea without the effects of caffeine? Is that at all possible?

    • Toxins

      If you are sensitive to caffeine, you can always find decaffeinated green tea.

  • Cynthia C

    How quickly does the effect dissipate after drinking a cup of tea? Basically, how often to I need to drink it to keep up the effect all day! I need this!

  • Tobias Brown

    I started drinking green tea based on the reports here and I plan to continue doing so. However, in my enthusiasm, spurred by the more recent video on cold brewing green tea, I recently started drinking half a pitcher a day. But I’m quite sure I had a strong reaction against this which caused my eyes to be very heavy upon waking in the morning as well as a general feeling of sinus congestions, and a bit like feeling “hung over.” My research suggested that it was likely the histamine in tea or possibly the caffeine which would have a dehydrating effect. I stopped with the tea and the sensation went away within a couple of day. So, is there anything to this? Should we limit tea to 2-3 cups per day? This video suggests that 2 cups is enough for this considerable impact so… is more always better?

  • Analisa

    Dr. Greger, what about the high concentrations of aluminum in green and black teas? According to the NCI, “aluminum can accumulate in the body and cause osteomalacia
    and neurodegenerative disorders, especially in individuals with renal failure” — not to mention, Alzheimer’s disease. While NCI also states that it’s not clear how much of the aluminum in tea is bioavailable, wouldn’t it be better to stick with herbal teas (like Hibiscus) just to be safe?

  • k

    hi dr. greger, and thank you for the wealth of information you provide here!

    on the question of green tea, i am wondering how white tea stacks up?

    white tea seems not to have been as widely studied and the only information i can find is that it’s antioxidant content is higher than green tea or other teas. is it possible that the fermentation process yields benefits in green tea that are not present in white tea, since it is not fermented?

    i’ve been drinking organic pai mu tan for years now but now i’m wondering if that is the right choice. any thoughts would be welcome!

  • tavit

    I wander can I drink green tea safely if I’m 22 and have per-hipertension (133/75).

  • ReluctantVegan

    I’m in the USA. Anyone ever noticed that in British films, whenever a situation becomes emotionally difficult for someone, they are always offered tea? (In addition to the requisite tea drinking at every possible juncture of the day.) I also noticed this when I visited England. I always thought it was because the English were uncomfortable expressing or talking about emotions – and uncomfortable being around someone who might be about to lose their composure (even if for a good reason). Is it possible that this emotional-tea-offering is NOT because they can’t stand emotive situations, rather, should it be seen like offering someone an aspirin for a headache?

    If you are from The Commonweath, I invite your comment.

    • Thea

      ReluctantVegan: I’m from the USA too, so I can’t meet your request.

      But I wanted to say that I thought it was an interesting post and that it reminded me a bit of the Big Bang Theory — a TV show. One of the main characters in the Big Bang Theory has trouble with social skills. But he is able to remember rules. One of the rules his mom taught him was to offer friends hot beverages for various emotional situations. In the show, there is a different, specific hot beverage for specific emotions. Ahh. If only life were really that easily fix-able.