Thursday July 25 2013
Tea also contains caffeine, so it's best to drink it in moderation
Tea drinkers who opt for cheaper supermarket blends could be at a higher risk of bone and teeth problems, The Daily Telegraph reported today. The story comes from a study looking at fluoride levels in different brands of tea, including leading supermarket economy products.
Fluoride is a mineral that is needed for healthy teeth and bones, although excess fluoride can lead to a condition called fluorosis. Fluorosis causes discoloration of the teeth, and bone pain and stiffness.
The study found that economy ‘own-brand’ supermarket tea contains, on average, higher levels of fluoride than more expensive brands.
The researchers calculate that an adult regularly consuming one litre (just under two pints) of economy tea daily could be consuming more fluoride than is recommended by US experts. This could be bad for health.
However, fluorosis, which can damage bones and teeth, usually only occurs in countries where there are high natural levels of fluoride in drinking water. It is rare in the UK.
The study is of interest, but it does not show that people using economy teas are putting their health at risk from consuming too much fluoride. Regularly drinking one or more litres of any caffeinated product is not recommended, as high levels of caffeine can cause irritability and trigger insomnia.
Where did the story come from?
The study was carried out by researchers from the University of Derby and the former Health Protection Agency (now part of Public Health England). The study was published in the peer-reviewed journal Food Research International.
It was covered widely and uncritically in the media. Headlines claiming that cheap tea bags may make you ill are alarmist and not supported by this study.
The study does provide a case report of a US woman who experienced significant bone damage due to tea consumption. However, this woman had been drinking 3.8 litres (around 6.5 pints) of tea daily since the age of 12.
What kind of research was this?
This was a study of fluoride levels in 38 teas, mainly bought from UK supermarkets. The authors point out that fluoride is an essential micronutrient, needed to prevent dental decay and promote healthy bone growth. However, consumed in excess it can lead to a condition called fluorosis, which can damage both teeth and bones.
The authors say that previous research has found that consuming tea with high levels of fluoride has been associated with dental and bone problems. Their aim in this study was to assess people’s exposure to fluoride from their consumption of tea in the UK, by analysing fluoride concentrations in a range of products and their infusions.
What did the research involve?
The researchers bought 35 teas from UK supermarkets and a further two from India and one from Sri Lanka. Depending on their origin and method of processing, the teas were classified as black blends, green blends, pure blends, oolong/pu’er and economy blends. Economy blends were black blended teas, labelled as essential economy brands by UK supermarket chains.
In the laboratory, they used a method called ion chromatography to analyse the fluoride concentrations in dry tea products.
They then measured the fluoride levels in typical infusions of each tea, adding 100ml of boiling water to each 2g sample. These were analysed at two, 10 and 30 minutes for fluoride levels using sensors called ion selective electrodes. These can detect the presence of trace elements such as fluoride in a liquid.
What were the basic results?
- The average fluoride concentrations in dry teas ranged from 103 to 839 milligrams (mg) per kilogram (kg).
- On average, economy blends had the highest fluoride concentrations, at about 580mg per kg.
- The green teas averaged about 397mg per kg and pure blends had the lowest concentrations on average of 132mg per kg.
- Overall, fluoride levels in the infusions ranged from 0.43 to 8.85mg per kg.
- There was little difference in fluoride levels between the two and 10 minute infusions or between the 10 and 30 minute infusions but an “extremely significant” difference between the two and 30 minute infusions, with infusion time increasing fluoride levels.
- Economy blends had the highest fluoride levels, with an average 6mg per litre in a two minute infusion. Economy blends included Asda Smart Price, Sainsbury’s basics, Morrisons and Tesco value.
- Pu’er and oolong tea infusions had the lowest levels of fluoride, followed by pure blends, black blends and green blends.
How did the researchers interpret the results?
The researchers point out that US experts recommend 4mg of fluoride daily for adults, with an “upper tolerable intake” of 10mg daily. They calculate that an adult consuming one litre of economy tea daily, containing 6mg per litre of fluoride, would be getting 75-120% of the recommended fluoride allowance. Economy teas may use the older leaves on the tea plant, which may contain higher levels of fluoride, they suggest.
The fluoride intake of people drinking cheap tea may exceed recommended levels, they argue. All tea products should be considered as a source of fluoride and supermarkets and manufacturers of tea should consider stating fluoride concentrations on food packaging.
This study suggests that people drinking economy brands of tea may be exposed to high levels of fluoride, which can cause dental and bone problems. The researchers calculate that people drinking 1 litre of cheap tea a day may be consuming more fluoride than the daily recommended amount, as advised by US experts. However, as the authors themselves say, in the US the “upper tolerable limit” of fluoride is 10mg of fluoride daily. The researchers’ calculations are not based on this maximum limit – but on recommended daily intake.
In some parts of the world the natural fluoride levels in water are excessive and this is known to cause serious dental and bone problems.
In the UK, severe fluorosis is rare, although mild fluorosis, in which the teeth become stained, may occur in children given fluoride supplements.
If your budget can only stretch to economy teabags then there is no real cause to worry as long as you limit your tea consumption.
While there is no official guidance, most experts recommend drinking no more than three mugs of tea a day on a regular basis.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.