Prolonged consumption of tea,especially the oolong and black variety,could weaken human bones due to the presence of toxic fluorine in tea beverages,Japanese researchers say.
The researchers,including Tetsuo Shimmura,who is senior research scientist of Toyama Institute of Health in Toyama Prefecture,reported the existence of the chemical in beverages such as oolong tea and black tea at a meeting of Japan Society for Biomedical Research on Trace Elements in Tokyo recently,Kyodo news agency reported.
They confirmed that the fluorine content in tea exceeds the standard for tap water in terms of density in about 70 per cent of the 130 instances they analysed.
There is no criterion for the amount of fluorine in green tea,black tea and oolong tea beverages,but for raw water and tap water it is under 0.8 milligrams per liter and for mineral water it is under 2 milligrams per litre.
“In our study of people’s health in the Inner Mongolian Autonomous Region (in China),we found that the bones of those who consumed water and beverages containing high fluorine density over a long time could develop a propensity to break,” Shimmura said.
“They are not in any immediate risk. However,it is desirable that a standard be set and displayed for tea drinks.”
Shimmura,who is also an honorary professor of Inner Mongolia Medical College in China,and his research group analysed exuded matter from tea beverages,from tea leaves grown in China and from tea bags not originating in China.
They found that oolong tea came out top in terms of fluorine content,with an average fluorine density totaling 1.1 milligrams per litre,followed by green tea with 0.9 milligram and black tea with 0.7 milligram.
They also studied fluorine exuded by Chinese tea leaves in a cup of tea. They found that the fluorine density in oolong tea was high,on a par with tea beverages. Meanwhile,fluorine discharged from tea bags containing non-Chinese-made black tea totaled 4 milligrams per litre,or double the amount in tea refreshments.
“This is caused by fluorine contained in tea leaves. More fluorine is contained in ripening leaves than in stems and young leaves,” Shimmura said.
It is estimated that to avoid tooth decay,no more than 1 milligram per litre of fluorine a day should be consumed. A volume of 2 milligrams per litre per day could lead to dental fluorosis,or mottled teeth.
The Japan Soft Drink Association,meanwhile,said,”There is no problem with soft drink beverages made from natural materials such as tea leaves because they include natural ingredients. They are the same as general foodstuffs.”