Green tea extract (INCI: Camelia sinensis) is manufactured by steaming and drying the leaves at a high temperature to ensure the phenolic compounds do not oxidize. It contains about 2 to 4% caffeine, 0.15% to 0.25% Vitamin C, a whole bunch of polyphenolic compounds - with tannins, proanthocyanidins, and other flavonoids - at about 10 to 25% or 30%. It also contains minerals like zinc, magnesium, selenium, and chromium. And it contains some polyphenols we've met before like quercetin and rutin.
Oh, how we love caffeine, found as theophylline and theobromine in green tea. It behaves as an anti-oxidant on our skin, and can offer anti-inflammatory properties. Let's take a look at the claims made about this wondrous alkaloid for our skin!
Cellulite reduction: There have been many studies about caffeine in the role of reducing cellulite. One study showed that a cream with caffeine used twice a day on the 55 subjects' hips and thighs for 28 days did result in a decrease in cellulite. Another study showed a cream with caffeine used once a day by 27 female subjects on their thighs showed a reduction in the thickness of subcutaneous fat beneath the skin.
However, it seems that these studies are countered by the myriad studies showing the benefits of anti-cellulite treatments containing caffeine may come from massaging in the cream, not the cream itself. Caffeine might penetrate our skin through the hair follicles - as demonstrated by a small study of six male volunteers who had a solution of 70% propylene glycol and 30% alcohol with 2.5% caffeine dissolved therein applied to their arms - but it cannot go very far. Certainly not far enough to the fatty layer under our skin!
Anti-inflammatory: Caffeine has been demonstrated to be a good anti-inflammatory, encouraging blood vessels to constrict and, therefore, appear smaller. Studies have shown it works well for acne and rosacea prone skin to reduce the redness, and it is effective for post-sun exposure creams (more about this in a moment).
Anti-aging: Caffeine is an anti-oxidant, which means it will fight free radicals on our skin. In addition, it is showing great promise in fighting UVB radiation damage when applied 30 minutes before sun exposure and immediately after exposure, killing off the damaged cells but keeping the undamaged skin cells alive. (These studies were on rats, but scientists are happily replicating these effects on human volunteers.)
Sun exposure: I did see a claim that caffeine can have an SPF of 50, but I did not see any evidence for this, indications of how much we should use or how we should use it, so I would take this claim with a grain of salt. You can see, however, there are studies showing how awesome it is for damaged cells, so don't use it in place of a sunscreen, but consider using it in a lotion for during or post sun exposure.
Hair growth: Some in lab studies show caffeine applied topically can increase hair growth, but there is no evidence of this in humans.
Psoriasis: There have been a few studies showing a lotion with 10% caffeine can help improve psoriasis. This cream, applied three times a day for 28 days, showed it was more effective than a placebo at reducing psoriasis symptoms. There was the annoying side effect of mild itching.
The downside of using green tea extract solely for the caffeine content is the large amount you'd have to use to get the required amounts. To get 10 grams of caffeine in 100 grams of lotion, you'd have to include 200 grams of green tea extract or more. To get 2.5 grams in 100 grams of lotion, you'd have to include at least 100 grams of green tea extract! Obviously, this isn't an option.
But you can get the goodness of caffeine using low levels of green tea for anti-inflammatory purposes. This is one of the reasons I use it in my toner and like to use it in my face moisturizers. I have Northern European skin - I don't tan, I burn, and I get red easily - so an anti-inflammatory containing caffeine is a nice bonus for me. You also get the benefits of a lovely anti-oxidant!
But there's more to green tea than just the caffeine! Join me tomorrow for fun with green tea's polyphenols!