Ive written lots about my favorite drink, green tea. For years, its been the only drink besides water and fresh raw veggie juices that I would recommend. Its just loaded with wonderful plant chemicals that can protect you from many illnesses — and even treat some of them. But we now have evidence that the source of these nutrients is not limited to just green tea.
New research now shows that black tea is equally effective in improving endothelial cell function in humans. These cells line your blood vessels and protect them from plaque and other damage.
But that is not all. Both teas significantly increase nitric oxide. Nitric oxide dilates your blood vessels. Its the end target for erectile dysfunction drugs. Getting an increase in nitric oxide in your arteries then results in improvement in a circulation parameter called flow mediated dilation. This means your vessels are dilated better and allow for better circulation.
Ive always thought the processing of black tea destroyed most of the beneficial nutrients. You see, black, oolong, and green teas all come from the leaves of the Camellia sinensis plant. A different processing of the leaves creates the different teas.
To make green tea, you have to heat the leaves to kill enzymes that might otherwise alter the leaf. You then dry the leaves. This preserves its very delicate flavor and all of its nutrients.
For black tea, you simply lay the leaves out and leave the enzymes intact. As they dry, they react with air, which induces oxidation. This process is called fermentation. This oxidation process causes darkening of the leaves and provides the robust flavor as well.
Oolong tea follows the black tea path. However, the difference is that you allow the leaves to oxidize for only a very short period of time.
Knowing this, Id expect green tea to be a superior source of intact phytochemicals. I believe that it is. Studies do show a superior effect of green tea on cancer prevention, and function of beneficial polyphenols. The oxidation process may damage some of these compounds in the black and oolong teas.
However, this new information tells us that beneficial chemicals do make it through the oxidation process into black tea, at least for your vascular system.
So, while I suggest sticking with green tea, with the most preserved polyphenols for overall health and wellness, black tea is no slouch either. Look for organic tea and be sure your drinking-water source is chlorine, floride and aluminum free.
Ref: Br J Nutr, 2007 October 5; Am J Clin Nutr, 2007; 86(4): 1243-7.