Green tea is a form of traditional tea made from the Camellia sinensis plant. Green tea has become a popular health supplement and is now widely available from health food stores. This relates to research showing beneficial effects for green tea consumption. In particular, green tea has been shown to provide a significant concentration of antioxidants, and these may have health effects that include protection from weight gain, cardiovascular disease and cancer. The traditional way to consume green tea is as a decoction is hot water and this is the way that green tea has been consumed throughout recorded history. However, recently technology has allowed the creation of green tea tablets and capsules, and to some, these are more convenient than consuming tea. Not surprisingly therefore researchers have had a desire to investigate whether green tea supplements still retain the health effects of green tea as a decoction and whether label claims are accurate for the amounts of nutrients contained within the tea capsules or tablets.
Green tea capsules and tablets appear to vary in their polyphenol content. It is true that tea can also vary in its nutrient content and so one could argue that this is a moot point. However, many supplements of green tea make label claims for the concentrations of polyphenols contained within the tablet or capsule and this may not be an accurate representation of the actual content. In particular, large variations within supplements can be found for total polyphenol, caffeine and total antioxidant levels. As most studies have shown that the beneficial effects of green tea come from drinking the tea, this is still the recommended way to benefit from the health effects of the Camellia sinensis plant. This is certainly how the Japanese and Chinese have traditionally obtained the benefits of green tea.
The main phytochemicals in green tea are a group of polyphenols called flavan-3-ols (catechins). These include epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate. The alkaloid caffeine is also present in green tea. Studies that have measured the caffeine, epigallocatechin gallate and total polyphenol content of green tea supplements and found that they varied from label claims by between 28 to 183 %, 12 to 143 % and 14 to 36 %, respectively. It is likely the antioxidant capacity of tea that provides its health benefits, but the level of antioxidants in green tea supplement may vary widely from label claims. For example, the antioxidant capacity of green tea has been shown to vary from between 167 to 15340 and 166 to 13690 μmol/g trolox equivalents in green capsules and tablets, respectively. This would suggest that green tea supplements as capsules or tablets are not uniformly consistent in their supply of polyphenols. Green tea as a decoction may therefore be a better way of ensuring health effects.
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RdB
