We often hear that tea, especially green and white tea, is a healthy beverage to sip due to its high antioxidant content. Antioxidants are compounds that fight the constant oxidative stress that cells are under as they carry out their metabolic activities. But, for these free-radical fighters to have benefits, your body has to absorb them and absorb enough of them to have an impact. That means the antioxidants must be taken up by the digestive tract, enter the bloodstream and be delivered to cells and tissues where they can have an impact. How does this apply to tea? Is tea really a reliable source of antioxidants?
Source of Antioxidants in Tea
Non-fermented teas, like white and green tea, contain a variety of bioactive compounds. The most important of these are called catechins and the one we hear most about is called ECGC, short for epigallocatechin-3-gallate. Catechins, including ECGC, are part of a larger class of antioxidants called polyphenols. Green and white tea contain other catechins but researchers believe that ECGC is the most potent. The catechins in green tea are linked with antioxidant and anti-inflammatory effects. Some studies also show they improve insulin sensitivity and modestly boost fat oxidation. Scientists are also interested in the role green tea catechins play in cancer prevention. Some studies show that in a laboratory setting, they cause cancer cells to self-destruct through a process called apoptosis. Still, more research is needed.
Absorption and Bioavailability of Green Tea Catechins
For catechins to reach cells and tissues and offer benefits, multiple steps have to take place and the action starts in your digestive tract with absorption. How do you drink your green tea? With a meal? A study published in the journal Antioxidants found that ECGC in supplement form was best absorbed in the absence of food. Taking ECGC at the same time as food reduced how much was absorbed by the digestive tract. It’s possible that this also happens when you drink green tea with a meal. So, drinking green tea between meals rather than with a meal may improve bioavailability and how much benefit you get from it.
A study also found that adding milk to tea reduces the bioavailability of catechins in tea as the casein in milk binds to catechins. But, another study showed that the catechins in tea are still absorbed even in the presence of milk. However, a study published in the European Heart Journal found that adding milk to black tea may block its beneficial effects on the heart and blood vessels. Since the issue is unsettled, it’s probably not a good idea to add milk to tea or consume it with milk products when you’re concerned about maximizing its antioxidant power.
You might want to add a squirt of citrus juice to your tea. Studies show that vitamin C enhances the bioavailability of catechins in tea. In fact, in a study, adding citrus juice improved bioavailability of green tea catechins by five-fold! Citrus seems to work by stabilizing the catechins. So, if you like a squirt of lemon in your tea, so much the better. Lemon juice was best in the study for stabilizing the catechins followed by orange, lime, and grapefruit citrus juice.
Another problem with sipping green tea as a source of antioxidants is you have to drink a lot of it, at least three cups daily but some sources suggest that you need to drink up to six cups of day to get maximal benefits. That adds up to a fair amount of caffeine, more than caffeine sensitive folks can comfortably tolerate. That’s why some people turn to green tea extract in supplement form. However, there are have been a few cases of liver damage related to taking green tea in a concentrated, supplement form. Although rare, it’s something to be aware of if you’re considering taking a green tea or ECGC supplement.
Make Sure the Green Tea You Drink Actually Has Catechins
We know that black tea is fermented, and fermentation destroys most of the catechins. However, black tea, thanks to the fermentation process, contains other compounds called theaflavins that non-fermented teas don’t. It appears that theaflavins have potential health benefits as well. But, if you’re looking for the most catechin antioxidants, green and white tea are your best bets.
How you get your tea matters too. Studies show that many brands of bottled green tea contain few catechins. One exception is the brand Honest Tea that had substantial amounts based on independent testing. So, it’s best to brew your own tea at home. How long you steep tea at home and the temperature at which you steep it also impacts its antioxidant content – but it’s not straightforward. For black tea, antioxidant activity was greatest with short steeping times, whereas antioxidant content increased with longer steeping times for green and white tea. Cooler temperatures are best for maximizing the antioxidant content of green tea, as steeping green tea leaves for two hours at a cold temperature yielded the highest quantity of any source of antioxidants.
The Bottom Line
Your best bet for getting the most out of the green and white tea you drink is to brew your own and avoid bottled tea. Add a squirt of lemon or another citrus juice to boost absorption of the catechins. For green and white tea, steep at cooler temperatures for a longer period of time. You can buy green tea supplements that contain a concentrated source of catechins but be cautious if you take this route. Best to get your source of antioxidants from food and beverage sources rather than supplements.
References:
The FASEB Journal. Vol. 26 no. 1 Supplement 646.4. April 2012.
Am J Clin Nutr December 2004. Vol. 80 no. 6 1558-1564.
Antioxidants 2015, 4, 373-393; doi:10.3390/antiox4020373.
Eur Heart J. 2007 May;28(10):1265-6; author reply 1266-7. Epub 2007 Apr 28.
Science Daily. “Citrus Juice, Vitamin C Give Staying Power to Green Tea Antioxidants”
Mol Nutr Food Res. 2011 Jun; 55(6): 844–854. Published online 2011 May 2.
Science Daily. “Steeping temperature and time may affect antioxidants in tea”
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