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Herbal Tea Update: Rooibos & Nettle

Rooibos (red) tea may reduce stress levels by suppressing adrenal gland function. Nettle tea is mineral rich but may have estrogenic side effects.

March 8, 2013 |
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Supplementary Info

Sources Cited

T. Frank, G. Netzel, D. R. Kammerer, R. Carle, A. Kler, E. Kriesl, I. Bitsch, R. Bitsch, M. Netzel. Consumption of Hibiscus sabdariffa L. Aqueous extract and its impact on systemic antioxidant potential in healthy subjects. J. Sci. Food Agric. 2012 92(10):2207 - 2218

S. Fernández-Arroyo, M. Herranz-López, R. Beltrán-Debón, I. Borrás-Linares, E. Barrajón-Catalán, J. Joven, A. Fernández-Gutiérrez, A. Segura-Carretero, V. Micol. Bioavailability study of a polyphenol-enriched extract from Hibiscus sabdariffa in rats and associated antioxidant status. Mol Nutr Food Res 2012 56(10):1590 - 1595

J. Suliburska, K. Kaczmarek. Herbal infusions as a source of calcium, magnesium, iron, zinc and copper in human nutrition. Int J Food Sci Nutr 2012 63(2):194 - 198

A. Scholey, L. A. Downey, J. Ciorciari, A. Pipingas, K. Nolidin, M. Finn, M. Wines, S. Catchlove, A. Terrens, E. Barlow, L. Gordon, C. Stough. Acute neurocognitive effects of epigallocatechin gallate (EGCG). Appetite 2012 58(2):767 - 770

M. R. Safarinejad. Urtica dioica for treatment of benign prostatic hyperplasia: A prospective, randomized, double-blind, placebo-controlled, crossover study. J Herb Pharmacother 2005 5(4):1 - 11

Z. Caliskaner, M. Karaayvaz, S. Ozturk. Misuse of a herb: Stinging nettle (Urtica urens) induced severe tongue oedema. Complement Ther Med 2004 12(1):57 - 58

A. J. Cummings, M. Olsen. Mechanism of action of stinging nettles. Wilderness Environ Med 2011 22(2):136 - 139

L. Schloms, K.-H. Storbeck, P. Swart, W. C. A. Gelderblom, A. C. Swart. The influence of Aspalathus linearis (Rooibos) and dihydrochalcones on adrenal steroidogenesis: Quantification of steroid intermediates and end products in H295R cells. J. Steroid Biochem. Mol. Biol. 2012 128(3 - 5):128 - 138



Rooibos, or red tea, is anecdotally reported to aid stress-related symptoms, but has none of the mood-altering phytonutrients thought responsible for the increased calm and decreased stress after drinking green tea, so why do some people feel less stressed drinking red tea? Well researchers recently found human adrenal gland cells in a petri dish produce about 4 times fewer steroid hormones in the presence of red tea, yes this may possibly contribute to the alleviation of negative effects arising from elevated stress hormone levels" if it actually happened in real life, but the effect was so dramatic they were concerned it might adversely effect the production of sex steroid hormones as well, but that's not what they found when they tested it in human subjects. The same may not be true of nettle tea. Nettle is used to relieve the symptoms of prostate enlargement by boosting estrogen levels, but if men drink too much they may grow breasts and women may start lactating. It's safe as long as you don't drink too much, and as long as you don’t come down with atropine poisoning because you mistook it for this plant, deadly nightshade, and as long as you don't put the leaves in your mouth fresh. They don't call them stinging nettles for nothing. This is a picture of the impalement of a nettle spicule in the skin. Another thing nettle tea is touted for is being packed with minerals, which always seemed kind of strange to me. Yes, if you boil dark green leafy vegetables long enough, you do lose minerals into the cooking water, but how many minerals could we be getting if you just steep some tea? We never knew because it hadn't been tested, until now.  They compared the mineral content of nettle tea to chamomile tea, mint tea, St. John's Wort, and sage. Nettle tea didn't seem to have much more than any of the others, but maybe they're all really high? Well one cup of nettle tea has the iron of a dried apricot—that's more than I expected. The zinc found in a single pumpkin seed. One-twentieth of a mushroom's worth of copper, but 4 peanuts worth of magnesium and a fig's worth of calcium. I agree with the researchers that a cup of herbal tea may not be an important source of minerals, but it's not negligible. Greens are so packed with nutrition that they can just drink some hot water they've been soaking in a few minutes and get something useful.

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 Jonathan Hodgson.

To help out on the site please email

Dr. Michael Greger

Doctor's Note

I'm sorry this video had to be cut at the last minute from the volume 12 Latest in Nutrition DVD—I ran out of room!

My go-to herbal tea is hibiscus. See the previous video, Herbal Tea Update: Hibiscus, and an earlier one, Better Than Green Tea? Mint would also be an excellent choice: Antioxidants in a Pinch.

That micrograph of the nettle spicule made me think of the Migrating Fish Bones video—I think I'd take the nettles any day!

The fact that so much nutrition leaches into the water in nettle tea is a reason we don't want to boil greens unless we're making soup or something where we're consuming the cooking water. See Best Cooking Method for more tips on preserving nutrients.

Also, for more context be sure to check out my associated blog post: Rooibos & Nettle Tea

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

  • Veganrunner

    Good morning Dr Greger,

    Update! My sisters cardiologist agreed to work with her going vegan as an alternative to the angiogram and stint. As you would expect he said, “but that’s really hard to do.”

    Thanks again for giving my sister the needed encouragement.

    • Pat G.

      What’s to hard…? Cracking open and pulling apart the chest, which is next, of flooding the kitchen countertops and fridge with fruits and veggies, so the choice is evident? Carl Esselsteyn MD has achieved amazing results with putting all his patients on veg lifestyle. If you need help, go to PETA’s website and see if cruelty wil be convincing. It make take your whole being to make the switch, but it’s only for your WELL being.

      • Veganrunner

        Most doctors will say going vegan is hard to do. But we all know better.

    • Thea

      Veganrunner: Thanks for the update. The cardiologist may not be fully educated or 100% on-board, but it sounds like a good start. Better than other doctors out there. Good luck to your sister!

      • Veganrunner

        She wrote him a letter with all the experts referenced, including this website. How could he disagree!

        • Thea

          That’s SO cool. Good for your sister.

    • Stanley Guan

      Put it in a nutshell, today’s health care is disease care. It treats your symptoms, not causes.

  • Thea

    This is very good news about rooibus as I really, really like it. Thanks!

  • Marcel Vincent

    I think JUiCING nettle tea will deliver much more minerals ?!

    • Tree Ethington

      I bet that would taste GHASTLY….

  • galvanni

    What about the Fluoride levels?

  • Isabelle Langevin

    Thank you Dr Greger for giving us those sources of informations.

    Your impact travels aroud the wold.

    • basconesfalk

      i’m not so sure–a friend reported this morning that the lectures, Dr. Greger’s annual summaries of nutrition research are no longer on YouTube.

  • Isabelle Langevin

    In the video Herbal Tea Update: Rooibos & Nettle. Nettle leaf is the concern but is nettle roots (as it is given to man with prostate problem) the same action???

  • jenniferhope

    My Grandmother’s caregiver is from the Philippines and mentioned Guyabano fruit, saying that it is antibacterial, anti inflammatory and inhibits cancer cell growth. The fruit is expensive and a little hard to find. Was wondering if the tea offered health benefits.

  • LumLum2500

    I brag about this website so much, my friends made me a refrigerator magnet that says “WWMGE?” (What would Michael Greger eat).

    • Thea

      Too funny! Thanks for sharing.

    • Michael Greger M.D.

      Ooh, I want a picture! :)

    • balconesfalk


  • Nina Olofsson

    Im curious how the different infusions are made? Im talking about V1, H2 and K2? Assuming they are different types of infusions and not just same method done three times… Might as well make it the most powerfull way if I’m gonna get some minerals from it :)

  • Maria

    Dr. Greger,
    Could you do some investigating on nettle leaf tea for allergies? It is concerning that this type of tea might have estrogenic effects. thanks!

  • Lou Gaspard

    Is a little olive oil okay in a vegan diet? I am talking about a table spoon, maybe two table spoons daily.

    • Toxins

      1 tablespoon = 120 calories
      2 tablespoons = 240 calories
      You can see how this quickly can add up. Not to mention, olive oil is quite barren in nutritional value containing no fiber, minerals, vitamins or antioxidants.

      Would simply adding a small serving of olives suffice?

    • Jasmin

      Olive oil is absolutely fine. You don’t need to worry about its caloric content if you are not overweight and not overeating or gaining weight. It has a higher omega-3 content than many other vegetable oils too, which is great on a vegan diet.

      • JacquieRN

        Using 1-2 tablespoons/daily of any oil – depends on your health goals and health status. Why use any oil? Oil not only adds calories but is a source of inflammation therefore it wanting to avoid/arrest/reverse heart disease – the less oil the better.

  • Ann H

    Good Morning Dr. Greger,
    I live in Columbia, Marylalnd area. I am looking for Doctors who practice or are open to preventive health care using diet for CAD/ Heart disease. I have read Dr. Esselstyn/ Dr. Dean Ornish Prevent & Reverse Heart Disease. I have read their books and am changing my diet to reap the benefits. I have many questions. Please Help me find doctors in this area that I can work with.
    Ann H.

    • Michael Greger M.D.

      Dr. McDougall has a list:

    • Don Forrester MD

      I would also check with the Physicians Committee for Responsible Medicine in Washington DC to see if they have members in the Columbia area who might be able to help. Your health plan may be able to help either through the internet (when I worked at Kaiser Permanente I had a website which provided information about my interest in working with patients on a whole food plant based diet) or member services. Good luck.

  • Amy

    Good Afternoon, Dr. Greger,
    As a woman of 34 with Addison’s Disease (Adrenal Insufficiency), I’m concluding that based on this research, I should avoid drinking Rooibos Tea and other red teas. Would you agree, and if so do you have any further recommendations regarding adrenal support through nutrition.
    After considering your evidence to support Hibiscus tea, I’ve been drinking it daily. One tea bag a bedtime in a Nalgene bottle of water in the fridge, and enjoy it in the morning. Our kids prefer I dilute their apple juice by 50% with mixed berry zinger, as opposed to just using water.
    Thank you for supporting my families health with good, solid research.
    May your tribe increase.
    Washington State

  • CrazyMonkey CrazyMonkey

    How quickly do you have to drink the ice tea before antioxidants start to decrease or do they not decrease?

  • Tracy Taub

    The trouble with many scientific studies of medicinal plants is that they pay little or no attention to the traditional methods of gathering and steeping different teas for different purposes. Tests are run for nutritional values based on improper steeping methods.

    Nettles are supposed to be gathered in the Spring before flowering, steeped for four to eight hours a dry leaf-to-water ratio of one dry ounce of leaves (about 1-1/4C) per quart of water.

    Any word on the nutritional content of nettles gathered and steeped properly?