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Michael Greger MD

Michael Greger MD

Posted September 5, 2013

Published in Health

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Latest Science on Rooibos & Nettle Tea

Read More: calcium, chamomile tea, copper, estrogen, green tea, hibiscus, iron, magnesium, minerals, mint tea, nettle tea, phytonutrients, prostate enlargement, red tea, rooibos, sage, St. John's Wort, steroid hormones, steroids, zinc

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Rooibos, or red tea, is anecdotally reported to aid stress-related symptoms, but it has none of the mood-altering phytonutrients thought responsible for the increased calm and decreased stress after drinking green tea (see Dietary Brain Wave Alteration). So why do some people feel less stressed drinking red tea?

Researchers recently found that human adrenal gland cells in a petri dish produce about 4 times fewer steroid hormones in the presence of red tea. This could certainly result in lower stress hormone levels if it happened within the body, but the effect was so dramatic the researchers were concerned it might adversely effect the production of sex steroid hormones as well. Thankfully, that's not what they found when they tested it in human subjects. The same, however, may not be true of nettle tea.

Nettle is used to relieve the symptoms of prostate enlargement by boosting estrogen levels, but case reports show men drinking too much may grow breasts and women may actually start lactating. Nettle tea is safe as long as you 1) don't drink too much, 2) don't mistake it for deadly nightshade if you forage it, and 3) don't put the leaves in your mouth fresh. They don't call them stinging nettles for nothing! In my 3-min video Herbal Tea Update: Rooibos & Nettle I show a close-up of the impalement of a nettle spicule in the skin.

My go-to herbal tea is hibiscus (see my last post Hibiscus Tea: The Best Beverage?). But nettle tea is touted for being packed with minerals. This always seemed a bit 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.

Researchers 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?

One cup of nettle tea has the same amount of iron in a dried apricot, the zinc found in a single pumpkin seed, one-twentieth of a mushroom's worth of copper, and 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 we can benefit by just drinking some hot water they've been soaking in for a few minutes.

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 otherwise consuming the cooking water. See Best Cooking Method for more tips on preserving nutrients.

-Michael Greger, M.D.

PS: If you haven't yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death and More Than an Apple a Day.

Image credit: chumsdock / Flickr


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