Do antioxidants make tea healthier than water?
more cups a day could reduce the risk of a wide range of health
problems, ranging from cancer to heart disease, and may even be
healthier than water, says a review from Britain.
"Drinking tea is actually better for you than drinking water. Water is essentially replacing fluid. Tea replaces fluids and contains antioxidants so its got two things going for it," reviewer Dr Carrie Ruxton from Nutrition Communications told the BBC.
Interest in tea have mostly focusses on green tea, with consumption linked to a wide range of health benefits, including lower risk of certain cancers, weight loss, and protection against Alzheimer's.
The health benefits have been linked to the polyphenol content of the tea. Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
But Dr. Ruxton and her co-authors from King's College London report that black tea also had positive effects on general health.
"We found some research showing that black and green tea contained similar amounts of antioxidants but different types. This can be expected as they come from the same plant but go through different processing," Dr. Ruxton told NutraIngredients.com.
"Antioxidant activity in the blood is similar too so one could assume that both types of tea confer heart health benefits," she said.
The review, sponsored by the Tea Council and published on-line in the European Journal of Clinical Nutrition (doi: 10.1038/sj.ejcn.1602489), searcher databases for relevant epidemiological and clinical studies that were published between 1990 and 2004.
In terms of cardiovascular disease, the reviewers report that "clear evidence was found" to link drinking three of more cups per day could reduce the risk.
Cancer risk did seem to be reduced in experimental (in vitro and animal studies) said the reviewers, but these results were not backed up by epidemiological evidence, they said.
A small note of caution however was noted by the observation that a non-effect or slight increase in risk of colorectal cancer with consumption of black tea.
The researchers also tackled the old wives' tale that drinking tea leads to dehydration, due to the diuretic caffeine content of the beverage. This was not backed up by the science, said the reviewers, with normal levels of hydration maintained when the tea contained less than 250 mg per cup.
"Studies on caffeine have found very high doses dehydrate and everyone assumes that caffeine-containing beverages dehydrate. But even if you had a really, really strong cup of tea or coffee, which is quite hard to make, you would still have a net gain of fluid," Dr. Ruxton told the BBC.
The reasons for these benefits was proposed to be related to the antioxidant action of tea polyphenols, wrote the reviewers.
"There was sufficient evidence to show risk reduction for CHD at intakes of more than three cups per day and for improved antioxidant status at intakes of one to six cups per day," concluded the reviewers.
"A maximum intake of eight cups per day would minimise any risk relating to excess caffeine consumption. Black tea generally had a positive effect on health."
The global tea market is worth about €790 (£540, $941) million. Green tea accounts for about 20 per cent of total global production, while black tea (green tea that has been oxidized by fermentation) accounts for about 78 per cent.