25th July 2013
Concerns over high levels of fluoride consumption from drinking certain brands of tea have appeared in the media today.
The headlines are based on a recent study published in Food Research International . Researchers from the University of Derby assessed human exposure to fluoride from the consumption of tea in the UK. A selection of 38 tea products were analysed to determine the fluoride content in both the dry product and as a tea infusion (i.e. ready to drink). The level of fluoride in the infusions ranged from 0.43 to 8.85 mg/L. The lowest concentrations of fluoride were found in Oolong/Pu’er teas and pure blends (black teas from a specific geographical location such as Assam, Darjeeling), higher concentrations were found in black blends and green blends and the highest concentrations were found in economy blends of tea (range from 3.6 to 7.96mg/L). The average concentration overall was 3.85mg/L in a tea infusion (brewed for 2 mins).
Tea is one of the main sources of fluoride in the diet amongst adults. The issue of high levels of fluoride in tea has come up in previous studies. Most studies suggest that tea provides up to 5 mg/L for black tea. However, there have been studies showing levels up to 9mg/L.
The main role of fluoride in the body is in the mineralisation of bones and teeth. Low intakes are associated with an increased incidence of dental caries. Fluoride is found in fluoridated water, tea and fish. The diet provides only about 25% of total intake. The addition of fluoride to toothpaste is important in those areas where the water supply is low in fluoride.
In rare cases, very large amounts of (non-dietary) fluoride can cause fluorosis (giving rise to small white markings on the enamel surface of teeth). The period of particular vulnerability to excessive fluoride is between 2 and 5 years of age. Severe fluorosis is rare in the UK and incidences have usually been associated with excessive intakes of toothpaste or misuse of fluoride supplements (Moynihan 2005).
Tea is a very popular beverage in this country and around 77% of adults in the UK drink tea, with a mean consumption of 540ml (just over 2 mugs) per day (Henderson et al. 2002). So for an average tea consumer, this equates to an intake of 2.1 mg fluoride per day from tea. Consuming a tea brand containing the highest concentration of fluoride (7.96mg/L) would mean that average consumption of 540ml tea would equate to an intake of 4.3mg fluoride per day from tea.
With regard to what is a safe intake of fluoride, EFSA has set an ‘acceptable intake’ (AI) of 0.05mg/kg body weight per day, so a 70kg man would have an AI of 3.5mg. WHO recommends a fluoride exposure threshold for children of 2mg per day and adults 4mg. So consumption of tea containing average levels of fluoride, would mean that intake from tea is within acceptable levels. However, there may be an issue with consumers who drink a large amount of tea containing the highest levels of fluoride. Fluoride also comes from the water supply and is found in fish.
However, this information does needs to be put into context, as tea has a number of other known health benefits. Black tea infusions contain small amounts of minerals such as potassium and magnesium and if consumed with milk, a range of other nutrients are provided in small amounts, such as calcium. Tea drinking is associated with a decreased risk of coronary heart disease, possibly due to its polyphenol content. Tea has also been associated with reduced risk of cancer, dental caries and bone loss (see Ruxton 2008).
The article is available here:
Henderson L, Gregory J, Irvine K et al. (2002) The National Diet and Nutrition Survey: Adults aged 19-64 years: Summary Report. The Stationery Office: London.
Moynihan P (2005) Chapter 25: Dental disease. In: Human Nutrition, 11th edn (C Geissler, H Powers eds) pp 463-77. Elsevier: Philadelphia, PA.
Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (1997) Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington (DC): National Academies Press (US). Available at: http://www.ncbi.nlm.nih.gov/books/NBK109825/