White tea
White tea consists of young leaves (new-growth buds) that have undergone no oxidation; the buds may be shielded from sunlight to prevent formation of chlorophyll. White tea is considered to contain the most powerful cancer-preventing properties of all teas. One recent study demonstrated that it removes or prevents even more tumors from the stomachs of specially bred cancer-susceptible rats than green tea, or caffeine alone (athough all three were shown to have benefit). Produced almost entirely in China, white tea is steamed and dried almost immediately after harvesting (in some situations in the fields themselves). It is possible that this method of minimal processing accounts for this tea's added benefits. Roderick H. Dashwood, an Oregon State biochemist has theorized that the polyphenols, called catechins, are destroyed through the processing used with other teas. Another possiblity of why white tea may be especially beneficial is its high caffeine content--higher than that of other teas.Kit Chow notes in All The Tea In China that in hard times, very poor Chinese homes would serve guests boiled water when they could not afford tea. Host and guest would call the water "white tea" and act as if the tradition of serving guests tea had been carried out as usual.
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Reference
Chow, Kit with Ione Kramer (1990). All The Tea In China. San Francisco: China Books and Periodicals. ISBN 0835121941.