Anticarcinogenicity

Tea is one of the most widely consumed beverages, with potential health benefits against such chronic diseases as cardiovascular disease and cancer. Green tea is more effective in its anticarcinogenic benefits than black tea, because green tea has a higher level of catechins and other polyphenols . White tea has high levels of polyphenols, even more than green tea, and might have the strongest potential of all teas for fighting cancer. 14

Heterocyclic amines are procarcinogens generated from sugars, amino acids, and creatinine during the cooking of foods .15 They occur widely in meats and fish. Certain heterocyclic amines can induce the multiplication of tumors in the small intestine and colon in experimental animals .15 Recent studies have shown that four grades of white tea have marked antimutagenic activity in the Salmonella assay against heterocyclic amines, particularly in the presence of S9 mix (microsome fraction of rat liver) .16 The most active of these teas, Exotica China white tea, was significantly more effective than the premium green tea (Dragonwell special grade) against 2-amino-3-methylimidazo[4,5-f] quinoline (IQ) and four other heterocyclic amines 16 These results also suggest that the greater inhibitory potency of white tea in the Salmonella assay might be related to catechins and caffeine, perhaps acting synergistically with other minor constituents to inhibit mutagen activation as well as scavenging the reactive intermediates The mixture prepared from the combination of major constituents of white tea or green tea, consisting of catechins and caffeine according to their relative levels in teas, exhibited less antimutagenic and anticarci-nogenic potency than with white and green teas 16

Orner et al .17,18 examined the relative effectiveness of white and green teas in suppressing heterocyclic amine-initiated intestinal tumorigenesis in Apc(min) mice . After 12 weeks of treatment, mice given white tea, green tea, or sulindac, a nonsteroidal anti-inflammatory drug known to be highly effective in Apc(min) mice, had significantly fewer tumors than the controls (p < 0 . 05) . The protection provided by 1 . 5% green or white tea was comparable to that provided by 80 ppm sulindac. Mice treated with a combination of white tea and sulindac had significantly fewer tumors than either treatment alone This research provided evidence that teas, particularly when administered in combination with sulindac, were highly effective in inhibiting intestinal neoplasia in mice via direct or indirect effects on the beta-catenin-APC pathway, and are also effective against intermediate and late stages of colon cancer, via effects on the beta-catenin-Tcf signaling pathway Consistent with the findings from in vivo studies, in vitro cell model studies also suggested the suppression of intestinal polyps by white tea via an apparent downregulation of beta-catenin and Wnt target genes 19

In another study, Santana-Rios et al . 20 found 5 . 65 ± 0 . 81 and 1 . 31 ± 0 . 27 aberrant crypt foci (ACF) per colon in groups of rats given 2-amino-1-methyl-6-phenylimid-azo[4,5-b]pyridine (PhIP) and PhIP + white tea, respectively, during 8 weeks of study. White tea also inhibited cell proliferation and suppressed early lesions in the colon 21

Although no changes were detected in N-acetyltransferase or arylsulfotransferase activities compared with controls, there was marked induction of ethoxyresorufin O-deethylase, methoxyresorufin O-demethylase, and UDP-glucuronosyltransferase after treatment with white tea . Results from PCR assays showed that the inhibition of white tea in PhlP-induced ACF might be due to the altering of the expression of carcinogen-metabolizing enzymes . These data provide additional support for the possible chemopreventive role of white tea against cancer of the large bowel

Although there were many studies on white tea as a potential anticarcinogen, these data are highly preliminary and cannot be extrapolated to human cancer prevention or treatment Further studies with white tea in animal models and in human trials are needed

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