Thee een gezonde drank.*
Als conclusie van een evaluatie van relevante studies van de laatste 15 jaar over thee blijkt dat thee wellicht nog wel beter is dan water. Door thee is vooral de kans op hart- en vaatziektes duidelijk wat minder. Omdat koffie sterk vochtafdrijvend werkt bestaat er de mythe dat thee, waarin ook cafeïne zit, dat ook zou doen. Doch dat is niet juist thee is net als water vocht aanvullend.
Drinking
three or more cups of tea a day is as good for you as drinking plenty of water
and may even have extra health benefits, say researchers.
The
work in the European Journal of Clinical Nutrition dispels the common belief
that tea dehydrates.
Tea
not only rehydrates as well as water does, but it can also protect against heart
disease and some cancers, UK nutritionists found.
Experts
believe flavonoids are the key ingredient in tea that promote health.
Healthy
cuppa
These
polyphenol antioxidants are found in many foods and plants, including tea leaves,
and have been shown to help prevent cell damage.
Public
health nutritionist Dr Carrie Ruxton, and colleagues at Kings College London,
looked at published studies on the health effects of tea consumption.
They
found clear evidence that drinking three to four cups of tea a day can cut the
chances of having a heart attack.
Some
studies suggested tea consumption protected against cancer, although this effect
was less clear-cut.
Other
health benefits seen included protection against tooth plaque and potentially
tooth decay, plus bone strengthening.
Dr
Ruxton said: "Drinking tea is actually better for you than drinking water.
Water is essentially replacing fluid. Tea replaces fluids and contains
antioxidants so it's got two things going for it."
Rehydrating
She
said it was an urban myth that tea is dehydrating.
"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.
"Also,
a cup of tea contains fluoride, which is good for the teeth," she added.
There
was no evidence that tea consumption was harmful to health. However, research
suggests that tea can impair the body's ability to absorb iron from food,
meaning people at risk of anaemia should avoid drinking tea around mealtimes.
Dr
Ruxton's team found average tea consumption was just under three cups per day.
She
said the increasing popularity of soft drinks meant many people were not
drinking as much tea as before.
"Tea
drinking is most common in older people, the 40 plus age range. In older people,
tea sometimes made up about 70% of fluid intake so it is a really important
contributor," she said.
Claire
Williamson of the British Nutrition Foundation said: "Studies in the
laboratory have shown potential health benefits.
"The
evidence in humans is not as strong and more studies need to be done. But there
are definite potential health benefits from the polyphenols in terms of reducing
the risk of diseases such as heart disease and cancers.
"In
terms of fluid intake, we recommend 1.5-2 litres per day and that can include
tea. Tea is not dehydrating. It is a healthy drink."
The
Tea Council provided funding for the work. Dr Ruxton stressed that the work was
independent.
Abstract
Objective:
To
consider whether consumption of black tea has a positive or negative impact on
health.
Design:
Databases
were searched for relevant epidemiological and clinical studies published
between 1990 and 2004.
Results:
Clear
evidence was found for coronary heart disease (CHD), where an intake of >=3
cups per day related to risk reduction. The mechanism could involve the
antioxidant action of tea polyphenols. While experimental models have suggested
that flavonoids attenuated cancer risk, epidemiological studies failed to
demonstrate a clear effect for tea, although there is moderate evidence for a
slightly positive or no effect of black tea consumption on colorectal cancer.
Studies on cancer were limited by sample sizes and insufficient control of
confounders. There is moderate evidence suggestive of a positive effect of black
tea consumption on bone mineral density although studies were few. There is
little evidence to support the effect of tea on dental plaque inhibition but
evidence to support the contribution of tea to fluoride intakes and thus
theoretical protection against caries. There was no credible evidence that black
tea (in amounts typically consumed) was harmful. Normal hydration was
consistent with tea consumption when the caffeine content was <250 mg
per cup. A moderate caffeine intake from tea appeared to improve mental
performance, although sample sizes were small. There was no evidence that iron
status could be harmed by tea drinking unless populations were already at risk
from anaemia.
Conclusions:
There
was sufficient evidence to show risk reduction for CHD at intakes of >=3 cups
per day and for improved antioxidant status at intakes of one to six cups per
day. 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.