Tea and health--a review of the current state of knowledge.

Until recently, tea has been numbered among stimulants, i.e. products of no nutritional value. Nowadays, with advance of research studies, the amount of data suggesting beneficial effect of tea on health is increasing. Polyphenols are the basic tea ingredients to which positive effect on human body is attributed. Their wide spectrum of biochemical activity, including a strong antioxidant potential, contributes to the situation in which tea may have various beneficial functions in the body. Research studies focus mostly on green tea which is believed to reduce the risk of many modern diseases. However, so far the preventive effect of tea has not been confirmed yet. Despite it being a natural product, too much tea in a diet carries the risk of excessive caffeine intake and decreased absorption of non-heme iron which may be of detrimental consequences for some groups of consumers.