Opting for cheap supermarket tea bags over artisan blends could have long-term health consequences, according to new research.
A study published in the journal Food Research International has found that cheap tea bags from supermarkets including Asda, Sainsbury's and Tesco can push a person's fluoride intake over daily recommended levels and put them at a higher risk of bone and dental disease.
Experts have now called for supermarkets and tea manufacturers to consider stating fluoride concentration as part of the nutritional information found on food packaging.
Levels of fluoride found in 38 tea products were compared by PhD student Laura Chan, Professor Aradhana Mehra and Professor Paul Lynch from the University of Derby.
Using Ion Selective Electrode analysis - which analyses trace elements, such as fluoride, in a liquid - of the dry tea, and of the tea infusions brewed with boiling water for two minutes, the researchers compared the fluoride levels consumed by someone drinking the average intake of four cups or a litre of tea a day.
It is recommended that an adult does not consume more than three to four mg of fluoride per day.
Yet researchers discovered that economy blends of tea contained between 75 per cent and 120 per cent of the recommended daily intake.
On average, a litre of cheap supermarket tea contained six mg of fluoride.
Excessive intake of fluoride can cause a variety of health problems.
In addition to tea, fluoride can be found in some seafood, fluoride-enriched toothpaste, drinking water in some areas of the country and in processed foods using fluoridated water.
Less seriously dental fluorosis can occur, which causes white and brown spots appear on the enamel of the teeth, and results in an unsightly 'mottled' effect.
This can be the first sign that fluoride has poisoned enzymes in the body.
But it can also cause skeletal fluorosis, a crippling disease that causes symptoms including bone and joint pain, muscle weakness and gastrointestinal disorders.
This tends to occur in people who have routinely consumed 10 to 20mg of fluoride per day for 10 to 20 years or 2.5 to five mg per day for at least 40 years. In the most severe cases, the spine becomes completely rigid.
Excessive fluoride consumption has also been linked to osteoporosis.
A higher incidence of kidney stones has also been recorded in areas with high fluoride levels in drinking water.
Research has also linked excessive fluoride exposure to bone cancer in young men. A 1992 study found that osteosarcoma rates were three to seven times higher in fluoridated water areas than non-fluoridated areas.