Drinking
green tea BEFORE taking supplements may offer protection from toxicity
Penn State
As high doses of green
tea extract supplements for weight loss become more popular, potential liver toxicity becomes
a concern.
In the last decade,
dozens of people have been diagnosed with the condition.
However, drinking
green tea in the weeks before taking supplements likely reduces risk, according
to researchers in Penn State's College of Agricultural Sciences.
The
dosage was equivalent to the amount of the polyphenol found in some dietary
supplements taken by humans.
One group of mice was
pretreated with a diet containing a low level of ECGC for two weeks prior to
receiving high doses of the polyphenol. Another group was fed a diet that did
not include EGCG prior to receiving the high, supplement-like doses.
After three days of
high doses, the scientists tested the blood of the mice to determine how their
livers handled the EGCG. Pretreated mice had a 75 percent reduction in liver
toxicity compared to untreated mice.
The research data show
that dietary pretreatment with the green tea polyphenol protects mice from
liver toxicity caused by subsequent high oral doses of the same compound,
explained Josh Lambert, associate professor of food science.
He suggested that the
research has relevance to people who are taking or are considering taking
supplements containing green tea extract.
"We believe this
study indicates that those who are chronic green tea consumers would be less sensitive
to potential liver toxicity from green-tea-based dietary supplements," he
said. "If you are going to take green tea supplements, drinking green tea
for several weeks or months ahead of time may reduce your potential side
effects."
Lambert has another
suggestion for people considering green tea supplements -- drink green tea
instead.
"Drinking green
tea rather than taking supplements will allow you to realize the benefits and
avoid the risk of liver toxicity," he said. "The beneficial effects
that people have reported as being associated with green tea are the result of
dietary consumption rather than the use of supplements. The relative risk of
using supplements remains unclear."
Tea -- Camellia
sinensis -- is rich in catechins, polyphenols that are natural
antioxidants. A number of animal studies have shown the preventive effects of
green tea polyphenols against obesity.
And Lambert pointed
out that a recent analysis of 11 human trials with green tea preparations
reported a nearly three-pound average body weight loss in intervention groups
compared to control groups.
Green tea's effect on
weight loss may be more noticeable if a person exercises. In research published
last year, Lambert showed that mice on a high-fat diet that consumed
decaffeinated green tea extract and exercised regularly experienced sharp
reductions in final body weight and significant improvements in health.
Approximately 34
percent of adults in the United States are classified as obese, Lambert noted,
leading to a strong interest in the potential benefits of including green tea
and green tea supplements in weight-loss efforts.
The liver toxicity
research, recently published online in Food and Chemical Toxicology,
revealed a unique property of the green tea polyphenol EGCG.
"It appears that
EGCG can modulate its own bioavailability and that dietary treatment may reduce
the toxic potential of acute high oral doses of EGCG," said lead
researcher Sarah Forester, assistant professor of chemistry, California State
University, Bakersfield, a former Penn State postdoctoral fellow.
"These data may
partly explain the observed variation in liver toxicity response to dietary
supplements containing green tea."
Some people drink
surprisingly large volumes of green tea, according to Lambert, as much as 10-20
cups a day, but liver toxicity has never been reported in that context.
"No person can
sit down and drink 16 cups of green tea all at once," he said.
"However if you take a supplement you can get that type of green tea
extract dose, so there is some indication that the dosage form has an influence
on the potential to cause liver toxicity."
