The statement, published on FDA's website last Thursday, could surprise the increasing number of consumers, both in the US and Europe, buying green tea for its widely reported health benefits.
A number of studies in recent years have revealed that compounds in green tea slow growth of cancer cells in the lab, while epidemiological studies have shown an association between green tea drinking and lower risk of breast and prostate cancer.
Reports on these studies are thought to be responsible for the increased consumer interest in the traditionally Asian beverage.
Recent research from Zenith found that consumption of green tea products in the UK had increased 87 per cent between 2000 and 2003, contrasting sharply with the downward trend in hot drink consumption across Europe.
"The health issue is probably the most important factor behind this growth," Zenith analyst Anya Bourke told NutraIngredients.com.
Much of the science on green tea has focused on its potential to help prevent cancer but last week the FDA said there was little science to support this link.
"Two studies do not show that drinking green tea reduces the risk of breast cancer in women, but one weaker, more limited study suggests that drinking green tea may reduce this risk," said the statement.
"Based on these studies, FDA concludes that it is highly unlikely that green tea reduces the risk of breast cancer."
Likewise, only one "weak and limited" study shows that drinking green tea can reduce the risk of prostate cancer, the FDA said, and existing evidence does not support qualified health claims for green tea consumption and a reduced risk of any other type of cancer.
However the FDA did not comment on green tea extracts nor purified epigallocatechin gallate (EGCG), an antioxidant found in the tea that is often studied for its anti-cancer effects in the lab.
The scientist who submitted a request with the FDA for a green tea health claim noted that the studies assessed by the authority may not have had access to populations consuming sufficient amounts of the beverage.
Dr Sin Hang Lee, who markets a green tea health drink through his company Fleminger, claims a qualified health claim should be based on a National Cancer Institute (NCI) recommendation on the amount to be studied in anti-cancer research - daily consumption of 40 ounces of typical green tea containing 710(mu)g/mL of the antioxidant compound epigallocatechin gallate (EGCG).
The NCI standard, published in 1996, is based on the traditional green tea drink consumed by the residents living near tea plantations in China and Japan, said Dr Lee.
The "lack of ready access likely prevented the studies from utilizing the standard recommended by both the NCI and our efforts forevaluating health benefits of green tea", he said.
Most producers in Europe market the antioxidant potential of the beverage as there is currently no health claims legislation permitting disease risk reduction claims.