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| "Decallerate" your life - drink tea!? |
After a couple of database searches, I did eventually have to realize that the most recent study by Schloms et al. is only the tip of an ice-, or rather "paper-berg" discussing various beneficial health effects of Aspalathus linearis infusions (aka Rooibos [/ˈrɔɪbɒs/], "the red bush" tea) that range from anti-viral to anti-cancer and pro-liver to pro-lung effects.
From South Africa to the Netherlands
In view of the fact that even I, as a German am more or less lucky to know what Rooibos is and you (mostly US and UK citizens) are only slowly catching up with my countrymen and our Western neighbors, the Dutch, as far as Rooibos imports and consumption is concerned, I just want to clarify that we are talking about a "popular tisane or herbal tea made from the stems and leaves of the fynbos plant, Aspalathus linearis, which is unique to the Western Cape region of South Africa" (Schloms. 2013).
What else can Rooibos do for you? Decreased incidence of herpex simplex + beneficial effects on other skin diseases (1.5l tea, orally; Shindo. 1991); liver protectant (Bosek. 2003); no inhibition of iron absorption (Hesseling. 1979; Breet. 2005; no ADHD?). Anti-cancer effects (Marnewick. 2005 ⇋ fermented = more effective; Sissing. 2008); antidiarrhoeal activity (Gilani. 2006); bronchodilator and antispasmodic (Khan. 2006); increased CYP3A activity (metabolizes caffeine, for example; Matsuda. 2007); anti-estrogenic effects in breast cancer ➙ reduced growth (Verhoog. 2007b; note: low estrogenic activity of its ow ➙ SERM)... there is more (mostly on anti-oxidant activities), but I think this should suffice.
Rooibos is sold as fermented and unfermented tea. While the latter has a higher anti-oxidant capacity, the former containing unique byproducts of the oxidation process. Contrary to the common perception these molecules are neither metabolic waste nor dangerous toxins, but can have a distinct set of beneficial metabolic effects of their own (Joubert. 2008).The good thing: Unfermented Rooibos tea increases the testosterone to cortisol ratio
For the study at hand, Schloms et al. used unfermented Rooibos from the South African
Rooibos Council. We can thus exclude any processing specific effects and simply assume that the results the scientists from the Stellenbosch University in South-Africa observed, when they administered the chloroform-methanol extract from the fresh tea leaves (1g of Rooibos leaves yielded 0.158 g extract) to their "subjects" - male Wistar rats.
The dosage the rodents received by oral gavage, was chosen to contain the rodent equivalent of the amount of soluble solids from one infusion with 15 g Rooibos leaves (six cups of fermented Rooibos per day). This means: If we discard inter-species differences, every serious Rooibos drinker should see changes in his (cortico-)steroid levels which resemble those you see in Figure 1:
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| Figure 1: Deoxycortisol (precursor), corticosterone (active), 11-dehydrocorticosterone (inactive corticosteroid) and testosterone levels after 10 days on rodent equivalent of six cups of Rooibos tea that was prepared with 15g of unfermented leaves; all values expressed relative to inter-group averages (Schloms. 2013) |
"In the adrenal, the biosynthesis of glucocorticoids, min eralocorticoids, and adrenal androgens from the com mon precursor, cholesterol, is catalyzed by the cytochrome P450 (P450) enzymes and 3 -hydroxysteroid dehydrogenases (3 HSD), with cytochrome P450 11 -hydroxylase (CYP11B1) catalyzing the production of corticosterone (CORT) and cortisol from their respective precursors, deoxycorticosterone (DOC) and deoxycortisol." (Schloms. 2013)Ok, of the hormones mentioned in this explanation you have both, cortisol and deoxycorticosterone in Figure 1. As you can see,...
the consumption of the Rooibos tea lead to a significant reduction of DOC;![]()
Illustration 1: Interconversion of cortisol and cortisone as well as CORT and 11-DHC by 11 HSD-type-1 and type-2 - the inactive CORT metabolite 11- dehydrocorticosterone (11-DHC), on the other hand did not change much;
- the latter would yet have been the case if the reduction in cortiosterone was a result of an increased metabolism of this rodent-specific corticosteroid
Rooibos tea is a 11 HSD1 inhibitor
In plain English you would probably say: Some of the active ingredients in Rooibos tea have the marvelous ability to block the enzyme that's responsible for the conversion of in-active to active corticosteroids.
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| Figure 2: In the corresponding 6-week (6 cups of tea per day) human study, none of the measured sex- nor corticosteroids changed significantly (Schloms. 2013) |
While there were significant decreases in the cortisone : cortisol (active : inactive corticosteroid) levels in both, men and women, there were no significant changes in cortisol, alone, testosterone, or the testosterone : cortisol ratio. With to the large inter-subject variations for testosterone, there is yet a chance that it worked for some, but not all male study participants.
References:
- Bosek, P., and M. Nakano. "Hepatoprotective effect of rooibos tea (Aspalathus linearis) on CCl4-induced liver damage in rats." Physiol. Res 52 (2003): 461-466.
- Breet, P., Kruger, H. S., Jerling, J. C., & Oosthuizen, W. (2005). Actions of black tea and Rooibos on iron status of primary school children. Nutrition Research, 25(11), 983-994.
- Gilani, Anwarul Hassan, et al. "Antispasmodic Effects of Rooibos Tea (Aspalathus linearis) is Mediated Predominantly through K+‐Channel Activation." Basic & clinical pharmacology & toxicology 99.5 (2006): 365-373.
- Hesseling, P. B., J. F. Klopper, and P. D. R. Van Heerden. "The effect of rooibos tea on iron absorption." (1979).
- Joubert, E., et al. "South African herbal teas: Aspalathus linearis, Cyclopia spp. and Athrixia phylicoides—A review." Journal of Ethnopharmacology 119.3 (2008): 376-412.
- Khan, Arif-ullah. "Selective bronchodilatory effect of Rooibos tea (Aspalathus linearis) and its flavonoid, chrysoeriol." European journal of nutrition 45.8 (2006): 463-469.
- Marnewick, Jeanine, et al. "Inhibition of tumour promotion in mouse skin by extracts of rooibos (< i> Aspalathus linearis</i>) and honeybush (< i> Cyclopia intermedia</i>), unique South African herbal teas." Cancer Letters 224.2 (2005): 193-202.
- Matsuda, Kazuhiro, et al. "Effects of continuous ingestion of herbal teas on intestinal CYP3A in the rat." Journal of pharmacological sciences 103.2 (2007): 214-221.
- Schloms, Lindie, et al. "Rooibos influences glucocorticoid levels and steroid ratios in vivo and in vitro: A natural approach in the management of stress and metabolic disorders?." Molecular nutrition & food research (2013).
- Shindo, Y., and K. Kato. "Effect of rooibos tea on some dermatological diseases." Proceedings of the international symposium on tea science. 1991.
- Sissing."Investigations into the cancer modulating properties of Aspalathus linearis (rooibos), Cyclopia intermedia (honeybush) and Sutherlandia frutescens (cancer bush) in oesophageal carcinogenesis." M.Sc. (Physiology) Thesis. University of the Western Cape, Bellville, South Africa (2008).
- Verhoog, N. J. D., E. Joubert, and Ann Louw. "Screening of four Cyclopia (honeybush) species for putative phyto-oestrogenic activity by oestrogen receptor binding assays." (2007).