Black tea contains more fluoride than ever thought

Black tea may contain a higher concentration of fluoride  than previously thought, accoridng to a new study cited in a press release by Medical College of Geogia.

Dr. Gary Whiteford of the School of Dentistry, co-author of the study, suggests that heavy tea drinkers could get in trouble even though drinking a couple of tea a day may not pose a risk.

Early studies found black tea contains 1 to 5 milligrams of fluoride per liter, but the new study showed fluoride in black tea can be up to 9 milligrams per liter, almost doubling the early estimate.

The findings were presented yesterday at the 2010 International Association of Dental Research Conference in Barcelona, Spain.

Fluoride is believed to help prevent dental cavities, but over-exposure to it or long term ingestion of excessive amounts is considered a risk.  According to the release, an average person can safely ingest 2 to 3 milligrams a day through fluorinated drinking water, toothpaste and food. However, serious bone health can result from ingesting about 20 milligrams a day over a period of 10 or more years.

The findings came after Dr. Whitford examined four patients who suffered advanced skeletal fluorosis - a condition caused by excessive ingestion of fluoride and characterized by joint and bone pain and damage.  These patients had one thing in common: they drank 1 to 2 gallons of tea every day for 10 to 30 years.

Certain tea leaves contain fluoride at a level ranging from 600 to more than 1,000 milligrams per kilogram of leaves, Dr. Whitford found.  Tea leaves also contain similarly higher levels of aluminum, which is considered neuron-toxic.

The detection method makes a difference.  Early methods could account for the amount of fluoride as aluminum fluoride. Dr. Whitford's method can measure that amount of fluoride as aluminum fluoride.

The take-home message is that excessively drinking black for a long term can cause fluoride poisoning.

By David Liu