BDental hygienists are pretty knowledgeable about fluoride. We apply fluoride treatments under ADA guidelines during recare appointments. We recommend different levels of at-home fluoride therapy depending on circumstances and need. We know the approved parts per million in community water supplies. Beyond that, we know which communities in our practice areas have fluoridated water supplies, and which do not have that benefit. We’re aware of fluorosis and its causes.
But did you know fluoride can be present in potentially toxic levels in tea? I was leafing through one of my mother’s less-than-reputable women’s magazines when I read that fluoride found in instant tea mixes can be more than 200% of the recommended safe level. According to the magazine, we should drink only green tea, because fluoride levels in green tea are much lower than in black and instant teas.
Being a typical hygienist, I went straight home to look it up. A cursory Internet search turned up PubMed studies, USDA research papers, and newspaper articles on high fluoride levels in tea. I started wondering about the possible links between tea’s high fluoride levels and fluorosis.
Suppose you have a tea-drinking patient who is in her 50s, with a family history of osteoporosis, and lives in a fluoridated community. On a daily basis, she drinks large quantities of iced tea made from mixes at her favorite coffee shop. This article will give you the background you need to discuss her tea consumption.
How Does it Get There?
How, exactly, does fluoride get into tea? It all starts with tea plants. Camellia sinensis (var. sinensis) and Camellia sinensis (var. assamica)are the varieties usually grown today. All types of tea—white, yellow, green, oolong, dark, black, and pu-erh—come from these two plants. (Remember that herbal teas are not made from tea plants, but from herbs.) The age of the tea leaves and the fermenting processing differ for each kind of tea. Dark, black, and pu-erh tea would typically be made from older leaves.1
Tea plants are known as fluoride hyperaccumulators, which means they absorb potential toxins and heavy metals to a greater concentration than is in the soil surrounding them.2 The older individual tea leaves get, the more fluoride they can absorb. The fluoride is then released during tea infusion. Bioavailability is close to 100%, because the GI tract readily absorbs soluble fluoride.3
Older tea leaves are also used to make less expensive tea.4 An article in ScienceDirect described a study in the United Kingdom of economy supermarket-branded teas. It was determined that drinking these cheaper teas made from older leaves carried a risk of high exposure to fluoride, up to 150% of the dietary reference intake level.5
Other Sources of Fluoride
Other fluoride hyperaccumulators include fruit juice, crab, fish, chicken, and rice, but the amounts of fluoride in those foods are much less than in tea.6
We already know our fluoride intake comes from naturally occurring and community fluoridated water, plus toothpastes and mouthwashes, plus recommended supplements. The Public Health Service recommends community water fluoridation at optimum levels ranging from 0.7 ppm to 1.2 ppm (1 ppm is equal to 1 mg/L). The U.S. Environmental Protection Agency has set maximum allowable fluoridation at 4 ppm with a secondary limit at 2 ppm. The American Dental Association, American Academy of Pediatric Dentistry, and the American Academy of Pediatrics jointly recommend guidelines that range from none for infants to 1 mg/day for adults, depending on availability of fluoridated water. The Institute of Medicine recommends a tolerable upper intake at 10 mg/day for those over nine years old.7
The USDA National Fluoride Database of Selected Beverages and Foods, Release 2, offers a comprehensive look at fluoride levels in foods and beverages.8 Here are some examples in parts per million:
- Strained applesauce baby food – 0.01
- Blueberry muffin – 0.39
- Light beer – 0.45
- Coffee, brewed – 0.91
- Chamomile herb tea, brewed – 0.13
- Black tea, brewed – 3.73
- Green tea, brewed – 1.15
- Instant tea powder, unsweetened, dry – 897.72
- Instant tea powder, unsweetened, prepared – 3.35
You can see that many foods and beverages have trace amounts of fluoride, but that there are frightening amounts in dry instant tea. Also notice the difference in black and green teas.
Effects of Excessive Fluoride
Now consider the effects of a heavy tea-drinking habit on fluoride accumulation in body tissues. We know that dental fluorosis caused by excess fluoride is a risk only in childhood, since fluorosis occurs during tooth formation. Children probably aren’t likely to drink tea in large amounts, so dental fluorosis from that source isn’t common. There have, however, been documented cases of skeletal fluorosis linked to tea. This type of fluorosis, caused by chronic consumption of fluoride, can be a crippling condition in which bones become weak and joints are stiff and painful. Deformities are seen in severe cases. There can also be neurological complications.9
A 2011 study in the Journal of Clinical Endocrinology and Metabolism concluded that skeletal fluorosis “can result from chronic consumption of large volumes of brewed tea” and that “daily consumption of 1-2 gallons of instant tea can lead to skeletal fluorosis.”10
A 2016 study done in the Republic of Ireland, home of serious tea drinkers, assessed the risks of fluoride intake in tea.3 The authors concluded that in all age groups, daily tea consumption can be higher than the maximum tolerable intake and result in chronic fluoride intoxication. That can contribute, they suggest, to the country’s high incidence of musculoskeletal disorders and undiagnosed skeletal fluorosis. Another concern they identified was for people with reduced renal function, since in that case fluoride can’t be easily excreted and is more damaging.
Tea is supposed to be good for us. It has flavonoids, a mild amount of caffeine, and has been shown to reduce risk for cardiovascular disease, high cholesterol, hypertension, and type 2 diabetes. It’s an anti-inflammatory and an antioxidant.11 Now, it appears, it could also be dangerous in certain circumstances. We, as hygienists, are the health-care workers patients trust to keep them informed about fluoride. When you discover a heavy tea habit in a patient, be sure they’re aware of the risks to their overall health.
For more information or to schedule your next visit, contact our team today.