health effects of tea health effects of tea although health benefits have been assumed throughout the history of using camellia sinensis as a common beverage, there is no high-quality evidence that consuming tea confers significant benefits other than possibly increasing alertness, an effect caused by caffeine in the tea leaves. in clinical research conducted over the early 21st century, tea has been studied extensively for its potential to lower the risk of human diseases, but there is no good scientific evidence to indicate that consuming tea affects any disease or improves health. 1912 advertisement for tea in the sydney morning herald, describing its supposed health benefits in regions without access to safe drinking water, boiling water to make tea is effective for reducing waterborne diseases by destroying pathogenic microorganisms. by constituents or substances aluminum, iron and other metals tea drinking accounts for a high proportion of aluminum in the human diet. the levels are safe, but there has been some concern that aluminum traces may be associated with alzheimer's disease. a 2013 study additionally indicated that some teas contained lead (mostly chinese) and aluminum (indian/sri lanka blends, china). there is still insufficient evidence to draw firm conclusions on this subject. most studies have found no association between tea intake and iron absorption. however, drinking excessive amounts of black tea may inhibit the absorption of iron, and may harm people with anaemia. concerns have been raised about the traditional method of over-boiling tea to produce a decoction, which may increase the amount of environmental contaminants released and consumed. fluoride exposure