Doctor's Note

Also see: Update on Yerba Maté.

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  • 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 update on yerba maté. Also, there are 1,449 other subjects covered in the rest of my videos–please feel free to explore them as well!

    • John Bull

      Hi Dr. Gregor, I stopped drinking Yerba Matė a while back after seeing one of you videos on it. I keep waiting for more research. On Guayaki’s sight they talk about how they have the air dried style and they have cut the PAH’s down by 80% with it. I am wondering if you know of any more updates on it or your latest scientific opinion.

  • Whoa! Really?! It seems there must be a lot of problems for the South Americans who consume loads of this daily? I haven’t read anything negative — any other info on how this is affecting people who have been drinking it for years?

    • Toxins

      We should all strive to reduce our carcinogenic intake as much as possible. People in south America get cancer still, the continent is not barren of this degenerative disease. The less carcinogens we expose our bodies too, the better chance we have of not developing a form of cancer.

    • Michael Greger M.D.

      The latest review suggests that the drying method (using firewood) may be to blame for the high levels of carcinogenic polycyclic aromatic hydrocarbons found in maté drinks, so a different production method may obviate this problem. That would be great since new evidence suggests that yerba maté may protect bone strength and improve blood sugar and cholesterol control in diabetics. I’ll let you know if I find more research in this evolving area.

      • John Bull

        Hi Dr. Greger, I stopped drinking Yerba Matė a while back after seeing one of you videos on it. I keep waiting for more research. On Guayaki’s sight they talk about how they have the air dried style and they have cut the PAH’s down by 80% with it. I am wondering if you know of any more updates on it or your latest scientific opinion.

  • GetSkinnyGoVegan

    The man from Guayaki will talk with you regarding the studies they have done. Also, even though there are several brands “air dried”, apparently there can be differences in how “air dried” they are. So apparently, their brand may have a drying process (ONLY for the San Mateo Air Dried) that is truly at low temps and is supposed to have the same or lower PAH’s than green teas (which I am sure vary quite a bit as well). I know I drank the “hard” stuff for years, Suave & Fuerte, of Rosamonte, and HOPE that that did not harm me. But I do wonder as well, as MOST of Argentina & Uruguay take this all day long, in major doses….
    I guess it is more difficult to do studies here or other places where beef consumption isn’t sky high, in addition to pollution. Most Americans only drink Mate in tea bags, or very small doses. I guess I will be the vegan human guinea pig, because I have not yet given it up. Even though I do the whole green tea bit & all, I love my gourd and am either in denial or not convinced. I don’t know which one, but I guess if I felt 100% that it was harmful, I would have to stop. I do know that my last blood test-after eating tons of bananas & drinking mate (A LOT) & about one pound of greens a day (being nice to my stressed out gut), my blood sugars were good………but I have never had glucose and fats tested RIGHT after drinking it. Or Insulin. I hope that this stuff comes out “okay” in the long run. I have already put the kabosh on avocados & coconut oil (for all practical purposes, but I don’t turn down raw cheezecake). I think Mate is kind of an anti-depressant & I think that somehow it may help your weight. Either because you have something in your mouth other than food all day, or it actually helps you feel fuller. Maybe a myth, but there seems to be a grain of truth to it…..

  • guest

    shut the fuck up man

  • fedex

    I also believe that mate is harmful. After taking it for a week, I developed anxiety attacks.

  • Resa

    please help I have leaky gut what should I do for it im dairy free gluten free no caffeine,im in so much pin I tae probiotics, digestive enzymes is yerba mate,peppermint leaves, cayenne , tumeris,cinnamon,cloves ginger,and black pepper its called Hieronymus life elixir wellness tea is it good for leaky gut

  • Resa

    I also take gi-revive,lglutamine,zinc,amino acids, fiber, omegas ,,I eat beef,chicken lots of fish cabbage,brussel sprouts berries,spinach,i drink coconut milk and cook with coconut oil please help can’t take the pain,,how long does it take to heal leaky gut

    • Veganrunner

      Resa I recommend you watch the videos from beginning to end. They will answer the questions about your diet.

  • TraPerson

    How about Guayusa? is it safe to consume?

  • DStack

    I became aware of the yerba carcinogen issue in the last year and started buying “unsmoked” varieties of the tea. I love the stuff, it’s a great performance enhancer for any kind of physical or mental test (as a musician, it really helps staying focused in auditions). I hear the antioxidant levels are great, so I hope that drinking unsmoked makes it a positive presence in my diet. GetSkinnyGoVegan, it’s funny that you say it’s an antidepressant, I have always wondered if I was the only one who felt like a million bucks after drinking a cup.

    I don’t drink it regularly, only when I need it, and I drink it in the traditional gourd + bombilla fashion. I suspect that if the unsmoked varieties are harmless, it could potentially be an antioxidant powerhouse. If it has anywhere near the amount of antioxidants in green tea, that amount must surely be multiplied at least 50 fold when consumed in the traditional way. Depending on the gourd/mate size, that’s a whole lot of leaves packed into one drink.


  • TheLance3185 .

    Shit! I just finished a large bag I bought at Whole Foods. It had such a high OREC rating, it seemed the way to go. I”m disappointed but thanks doc.

  • sylviecha

    This disturbed me for a few days , since I’ve switched from coffee to Y.Mate 4 years ago, for health reasons. I’ve been drinking certified organic (and mostly unsmoked) brands for a few years, made in the french-press (press pot). Not ready to let go of my favorite morning drink, soooo, I’ve spent a few hours researching the association of Y.Mate with cancer. And I am really glad of what I found.

    Recent advances on Ilex paraguariensis research: minireview.
    “A review on the evidence implicating Ilex paraguariensis (Yerbba mate) heavy consumption with some neoplasias show data that are inconclusive but indicate that contamination with alkylating agents during the drying process of the leaves should be avoided.” and “Although we are still waiting for the double-blind, randomized prospective clinical trial, the evidence seems to provide support for beneficial effects of mate drinking on chronic diseases with inflammatory component and lipid metabolism disorders.” The source: Us National Library of Medecine National Institute of Health -nov.2011.