Epidemiological evidence linking tea consumption to human health: a review

Tea has been widely consumed around the world for thousands of years and drinking tea is a daily habit for people of all ages. Tea is a major source of flavonoids, which have become well known as antioxidants. Tea also contains caffeine and theanine, which have been found to associate with health benefits. Many animal and epidemiological studies have been conducted to investigate the link between tea consumption and human health. However, common questions that arise about tea consumption include: whether all teas are the same, why drinking tea is linked with health benefits, how do the different ways of tea preparation impact on availability of tea components, how much and how long a person should consume tea to obtain health benefits, and whether there is any negative health effect associated with drinking tea. To answer these questions, this paper outlines the tea components and their link to human health, discusses major factors affecting availability of tea components in a tea cup, and reviews the latest epidemiological evidence linking tea consumption to human health.