When the going gets rough, the English offer each other tea. Maybe it helps. What is sure is that tea consumption changes the expression of genes associated with cancer and estrogen metabolism – in women.
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Whether the change is good, bad or neutral remains to be seen. Either way, men are epigenetically unaffected by a tea habit, according to new research.
Tea and coffee can affect health in similar ways, says the team from Uppsala University University in collaboration with scientists around Europe. But coffee had no such epigenetic effect, the researchers observe.
Genetic sequencing has become, if not trivial, at least widespread, yet we have little idea what genes we really have and how they work – how they are regulated. One method of genetic regulation we have discovered is epigenetic modification: Some genes are regulated (turned on and off) by adding or removing methyl groups to the DNA.
Moreover, geneticists suspect that epigenetics is inheritable: that parents can "pass on" the state of a gene being turned-off or turned-on to the kids.
Modulating disease risk
Both coffee and tea have been found to affect the risk of disease, for instance by suppressing tumor progression and decreasing inflammation, and also through influencing the estrogen metabolism. (More precisely: coffee consumption has been associated with lower risk of oral, pharynx, liver, colon, prostate, endometrial cancer and melanoma – but increased lung cancer risk.)
Now tea has joined the growing list of substances, from foods to marijuana to soaps to tobacco, that lead to epigenetic changes – but only in females, says the team, in the journal Human Molecular Genetics.
The new study does not purport to say whether the epigenetic changes are beneficial, neutral or otherwise – meaning, whether drinking tea is healthy or not. Or doesn't matter. It just says that drinking tea causes changes to certain genes in women, but not men.
The scientists, led by Weronica Ek, say that caffeine in general reduces estrogen levels in women. (Other research has actually indicated different effects in women of different race. Asian women who averaged two cups of caffeine a day presented somewhat elevated estrogen levels compared to women who drank less, research has shown; but white women who drank that amount had slightly lower estrogen levels than women who don't indulge. The results regarding black women were inconclusive.)
The new research encompassed just over 3,000 Europeans and involved meta-analyses of the results. Ek also notes that more women were studied than men, making it harder to find significant associations for the male component.
"Estrogen" is a catchall for three basic hormones, estrone, and estradiol, which women make chiefly in the ovaries in women, men in the testes, and both sexes in the adrenal gland and fat tissue.
People usually call estrogens "female" hormones, and they are key to female development and pregnancy. But estradiol, the predominant form of estrogen, also plays a critical role in male sexual function: the male has receptors for the hormone in the penis, testes and brain. No estrogen, no procreation. Estrogen is also key to a host of physical functions that exist in both genders, including bone metabolism and even mood.
Open questions abound. The researchers did not narrow their study to a specific type of tea, or even quantities of tea that would have epigenetic effect on women.
Homo sapiens didn't evolve drinking tea. Like peering into the future, the estrogen metabolism cannot possibly rely on tea leaves. But clearly, the habit has an effect.