Doctor's Note

Check out these videos on herbal teas:
Herbal Tea Update: Rooibos & Nettle
Is There Too Much Aluminum in Tea?
How Much Hibiscus Tea is Too Much?
Chamomile Tea May Not Be Safe During Pregnancy
Enhancing Athletic Performance With Peppermint

And check out my other videos on Yerba Maté

For more context, check out my associated blog post: Soy milk: shake it up!

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  • But is it bad and have the PAH’s because the Yerba Mate is smoked as part of the “drying” process?? Guayaki says that the Organic, Unsmoked, Air Dried Mate has less Pah’s then Green Tea. I know that they are selling the product, but I also really want to know what in the Mate is bad. For many years I drank the traditional blend, but in the last few years I have switched to Air Dried, Green, Organic Yerba Mate with water that is not terribly hot. And IF it is the “smoking” process that is bad, then are other teas smoked, like Lapsong? And then does it make my beloved Organic, Air Dried, Yerba Mate okay? It’s seriously a major happy tea………Please Miraculous Michael Gregor, do deliver good news to me.

    • Michael Greger M.D.

      That is an excellent question, and unfortunately the answer is that we just don’t know. A study of 8 different brands found “very high concentrations” of carcinogenic PAHs in all of them. As you’ll see if you have a chance to read it, they even go as far as to say suggest “that the benzo[a]pyrene intake associated with drinking mate may be comparable with that associated with smoking cigarettes.” Yikes! If you are going to drink it I’d recommend unsmoked varieties, but unfortunately we’re not sure how much better they are. I’ll definitely keep my eyes peeled for any new data–I used to love the stuff myself.

      • Brian Adams

        This piece of literature, on the other hand, is thought provoking indeed. I am amazed to see the hydrophobics making their greatest impact in the first 5 minute steep, and irrespective of temperature! So my 6g daily Mate is equivalent to 2.7 cigarretes’ worth of benzo- yeesh. I hope the antioxidants have been negating that….

      • Absolutely Stunned

        Does the study include the Organic, non-smoked version sold by Eco Teas,here?

        • Maria Schilling

          Still no studies about the non-smoked version of Mate after over 2 years?

      • Joey

        You’re right to claim that there are “high concentrations” in all 8 brands. But there’s a surprisingly wide variation — let’s compare ‘Brand 5’ against ‘Green Tea’.

        When you do so, you’ll see that Brand 5 only has twice the total level of PAHs compared to Green Tea. Moreover, a large number of Brand 5’s PAHs come in the form of Fluoranthene and Pyrene. Fluoranthene is classified by the International Agency on Cancer Research as “not classifiable as to its carcinogenicity to humans”.
        Pyrene is trickier. Maybe it’s bad for the liver and kidney. But the EPA has placed “pyrene in weight-of-evidence group D, not classifiable as to human carcinogenicity.”

        If we are willing to exclude Fluroanthene and Pyrene from our calculations, then Green Tea and Brand 5 are very similar ~330 vs. ~200.

        I’d guess that Brand 5 is an ‘unsmoked’ variety. The evidence here doesn’t seem damning — what do you think?

  • Yeah!! I know, I read some of that stuff. BUT, nearly all the mate in the world is consumed in South America and basically every brand I have ever seen there is Smoked. I think it isn’t very “porteno” to drink unsmoked. So I am assuming that all the varieties they tested were smoked. Maybe I can find out from Guayaki which study they are talking about. I ran into research on the web somewhere, but you had to pay for the rest of the paper. Yeah, I drink it from the gourd and quit a few times and may still because it does elevate the heart rate. We drink vats (well under the 60 cups a day :) of green tea as well, but I don’t feel complete without my Mate! Thanks for your answer!

    • nico_et

      hi, what have you done since this video? I also feel incomplete without mate.Do you keep drinking Organic mate?

  • Hey Dr. Greger.

    I take Vega Sport pre-workout drink (18g servings) five times a week. For each 18g of serving, there’re 167mg of yerba mate leaf.

    How much of a threat is yerba mate in this form and at the frequency I consume per week? Thanks.

  • DrDons

    Hi Tan Truong, Reviewing the product you consume shows it has many good components. However as discussed above it does contain a Mate which contains carcinogens plus a tropical oil(coconut seed oil see and another substance Kombucha see Although the dose is small I recommend avoiding carcinogens as much as possible.

  • Thanks DrDons for your time and research.

    I can’t imagine too many pre-workout drinks that don’t have carcinogens. I’m curious what Vega has to say about this.

    It’s just that it keeps me jacked and focused during workouts. I definitely will cut down on the consumption, and likely eventually eliminate it for good.

  • Ilana

    I’m so confused by this – so why aren’t Argentinians dropping like flies?

    • Argenrina

      I am from Argentina! This is TRAGIC NEWS for my country! lol

      • Anita

        me too! so tragic -.-

  • Brian Adams

    Hello Dr. Greger. The primary lit you quote in the video (Evaluation of the cyto- and genotoxic activity of yerba mate (Ilex paraguariensis) in human lymphocytes in vitro) is highly misleading, and using its results to validate the potential carcinogenecity of Y. Mate demonstrates poor interpretation of the data. The authors utilized caffeine as a control, and found it to perform worse than Y. Mate extract in the two ‘genotoxic’ assays of micro nuclear formation and aneugenic activity. Aside from yielding a non-result, the experimental design was flawed, as the Mate liquer produced was 4-8 times the strength of Mate produced in a normal kitchen (1-2 Tbsp per 8 oz cup yields 25.4-50.8g per Liter; compared to the 200g per Liter used in the experiment.). Couple this with the fact that the brewing method favors the extraction of more lipophilic molecules than would be encountered in normal brewing, (212 deg for 10 min vs 150 deg for 5-8 min) and the whole study is shot due to improper methods before we even get to discussing controls. Finally, the in vivo equivalent of bathing cells i

    • The Dude

      Old post i know, but there was a time when many supplements were claiming to “kill the AIDS virus in a petri dish.” Well, the FDA (not the most objective source it’s true) in order to get all of these fake AIDS cure off the market, showed how warm water kills the AIDS virus in a petri dish. A petri dish is not the human body!

      • Flaxflower

        Dude, what do you say about what grows in a petri dish?

  • fedex

    Yerba mate triggered my anxiety attacks I developed a week after taking it. Mate contains theobromine–a neurotoxin. Stay away as it messed up by adrenal glands.

  • Nassib

    Do you have an recent studies on Yerba?

  • Mark Hazell

    Dang it, and here I was thinking about using Yerba mate instead of coffee. Thanks for the update.

    • cin3

      I do not know ,but, I have heard of more health challenges with coffee. We drink Green Tea daily and have Yerbe Mate as a treat, after hearing about testosterone problems with Stevia , that has me concerned .

  • Tealover

    It seems to me that the problem with yerba mate is the SMOKING process of drying, rather than the leaves themselves. I hope research comes out soon on the effect of the NON-SMOKED yerba mate varieties. Please keep updating this topic! Thanks.

    • Charlotte

      I agree – please keep us posted on any updated research on the PAH levels of air-dried yerba.

  • Gaucho

    I’m from south brazil.
    Here we drink it every frakking day.
    Its a tradition and honestly is not because theres a vague relation to cancer we’ll start giving up this tradition.

  • Deborah

    For someone like myself, whose maternal family is Paraguayan, and drinks it daily, how can I flush my system of these carcinogens? I am 42 years old and thought it was a healthier option. Thank you!

  • Tired of this.

    What a reductionist vision. So, all this time.. it wasn’t the agrochemicals, nor the pollution or the synthetic poison added to our food. It was Mate! Thank you “Dr” for helping the sensationalism about health with this 0:30 seg. – explaining nothing – video about an historically used herb.

  • Andrea Rojas Molano

    Could you please share article based on this fact?

    • Thea

      Andrea: Look just below the video for the “Sources Cited” section. You can click that text to expand the section and see the reference.

  • Darren Sunderland

    Just couple of notes. I’ve noticed how caffeinated hot drinks react with my physiology over the last 5 to 10 years. A cup of coffee at night often resulting in waking with wet shins and a general sweat. Cocoa had a similar reaction but nowhere near to that extent. I still drink the cup of tea, and also note that when I do, it increases the BO from under my arm pits significantly. Be it green tea or black. Herbal teas I have no problem with, except for yerba mate, the potency of my BO level after drinking this forces me to the wash room and also to drink water to help flush it out. The other thing I find with Yerba Mate is that it stains the cup like no other herbal/tea I’ve encountered. Dave explained this was due to the Chlorophyll and Tannins which he says is not unusual. Dave also cites an article and video of his that considers the Yerba Mate and Cancer issue: – Please let me know your thoughts anyone. I wonder for example to what extent the study of 8 brands of Yerba rules out the confounding variables of smoking, alcohol consumption, drinking it hot, and meat consumption: – Many thanks

  • esther4

    Ever so grateful, Dr. G. Trendy has no place in good health.

  • Gareth

    I make ‘tea’ simply with hot water and lemongrass. Is this an issue? What about eating lemongrass? I make my own curry pastes which usually have a fair amount. The lemongrass is from our own garden and all organic.

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