by By Rina Shaikh-Lesko
C.K. Ho et al., “Effects of single dose and regular intake of green tea
(Camellia sinensis) on DNA damage, DNA repair, and heme oxygenase-1
expression in a randomized controlled human supplementation study,” Mol Nutr Food Res, doi:10.1002/mnfr.201300751, 2014.
Researchers have long reported that green tea drinkers have better
health outcomes, but why that is has been unclear. To get to the
cellular roots of these observations, Iris Benzie of the Hong Kong
Polytechnic University and her colleagues monitored the activity of DNA
repair enzymes in lymphocytes shortly after people drank a cup of green
tea and after a week of drinking two cups of tea each day.
An enzyme critical for fixing DNA damage from oxidation, hOGG1, and
another that protects against such damage, heme oxygenase-1 (HMOX-1),
were more active after the 16 study participants drank tea, compared to
when they drank water. The team also found 30 percent less DNA damage in
lymphocytes 60 minutes after a cup of tea. Benzie says the finding
“opens up a whole new avenue to look at the molecular mechanisms” of
green tea’s effect on cells.
Genes coding for hOGG1 and HMOX-1 did not show an increase in
expression. The authors speculate that green tea triggers
posttranslational changes that prolong the enzymes’ half-lives or their
ability to protect and repair DNA. There’s also the possibility that
increased HMOX-1 could be a sign of oxidative stress induced by green
tea that prompts antioxidant defense and enhanced DNA repair.
“It’s a good preliminary study,” says Susanne Henning of the University
of California, Los Angeles. She recommends studying animal models for a
clearer understanding of the molecular mechanism in all tissue types.
It also remains to be seen whether the changes Benzie observed actually
correspond to any health benefits.