Scientists at the Laboratory for Cancer Research at Rutgers University report that tea has anticancer benefits and can slow the rate of tumour development. They determined that a daily dose of tea solids decreases the number of tumours and also lowers the levels of tissue fat surrounding those tumours. They believe these two properties of tea drinking are linked.
In this study, mice were given 6 mg of tea solids for 23 weeks. Researchers used both regular and decaffeinated versions of green tea and black teas as well as decaffeinated teas with caffeine added back in. Interestingly, they found that decaffeinated teas had little or no effect compared to the regular versions, but that adding caffeine back into the mix restored the positive anticancer effects.
Black and green teas are rich sources of flavonoids, catechins and antioxidants and have also been studied in relation to heart disease prevention. At the Erasmus Medical Center in the Netherlands, researchers found that an increased intake of tea may contribute to the prevention of heart attacks. Using a Dutch population-based study of 4,807 men and women 55 years and older, who had never had a heart attack before, researchers found a distinct correlation between tea drinking and reduced risk of heart attack. In fact, researchers noted that the less tea a subject drank, the greater likelihood existed that his or her heart attack could be fatal.
Black and green teas are derived from the same plant; however, black teas have gone through a fermentation process. Green tea extracts are also available in capsule form, for those who may not be tea drinkers but still desire its health benefits.
Sources: Am J Clin Nutr 2002 May;75(5):880-6; Cancer Res 2001 Jul 1;61(13):5002-9