On the green tea debate:
I understand that the much quoted 10-(small)cups-a-day thing comes from the author of one of the most publicised toxicology studies in this area. BUT he also stressed that the
main risk to liver/kidneys/intestines in this context is from taking
supplemements containing polyphenols (in green tea = catechins type) which contain up to 50 times the amount as found in a single cup of green tea (
http://pubs.acs.org/doi/full/10.1021/tx7000515 = original research which is worth a read for any heavy drinkers
http://www.newscientist.com/article/dn11786-green-tea-can-be-harmful-in-large-quantities.html = New Scientist comment). The study/review was initiated from some pretty ground-breaking research in early 2000's which raised concerns about potential pro-oxidant effects of green tea (so it's not a stand-alone finding), but Yang also concluded with a recommendation for further research on the effects in humans...still, it feels significant to me.
Of course, the polyphonols found in dietary consumption of green tea in the correct dosage & form, i.e. moderate consumption of a few cups a day can be tremendously beneficial for health...that's toxicology for you
...hence the controversy...but overall another reason IMHO to steer clear of supplements unless there is a nutritional void which needs to be filled. And to take medical advice before taking high-dosage of any supplement in case a) it's attached to a toxicity concern, b) it's not compatible with a medical condition 3) it interacts with any other medication...and probably more stuff too...(the problem comes when people don't know how high *high* is tho'
but I digress....)
When it comes to the usage of green tea to make your
skin look smooth & flawless, things change a bit though. The "good for skin" bit of green tea catechins is a components referred to as EGCG (epigallocatechin-3-gallate) which has been shown to help alleviate some of the damage from UVB rays (sunburn & dna damage). It's found in small quantities in a cup of green tea so I would guess that an enormous amount (probably waaaay over the supposedly "safe" limit) would need to be consumed in order to reach the skin in any meaningful concentration, if at all. Which is probably why skincare manufacturers use a concentrated green tea extract of EGCG as a topical ingredient instead (it's pretty good at penetrating the skin when applied from the outside).
In any case, green tea and rather the active catechins / EGCG component is clearly powerful stuff and ongoing research (another 20+ great scientific papers published this month on this ingredient
) suggests it can do both good and, potentially, in high doses, bad things to the organs of living creatures.
I can't stand the taste of green tea
but I used to have a 12-a-day coffee habit which is another story...
Even if I did like it though, I wouldn't drink more than a few cups of green tea per day. And for any skin benefits I'll stick to putting green tea extract directly on my face through a cream.