Chinese green tea, like other plants, can accumulate fluoride, an essential trace element in the human diet. While fluoride is necessary for human health, excessive intake can be harmful. Thus, monitoring the fluoride content in tea products has been a focus of national regulations. The fluoride content in tea is specified in Chinese standards, with a limit of 150 milligrams per kilogram (mg/kg) for green tea and 200 mg/kg for black tea.
First, let’s take a closer look at what fluoride is. Fluoride is a substance that you may frequently encounter in daily life, such as fluoride toothpaste and the refrigerant freon used in air conditioners. Fluoride is an essential trace element for the human body, and it promotes the calcification of bones and teeth, contributing to increased bone strength and the prevention of tooth decay.
In the human body, about 2.6 grams of fluoride is found, with the majority distributed in bones and teeth, where it accounts for approximately 90% of total body fluoride. In the blood, fluoride concentrations range from 0.04 micrograms to 0.4 micrograms per milliliter. Fluoride in the human body is derived from various sources, primarily water, food, and air. However, chronic fluoride toxicity can occur when daily intake exceeds 4 milligrams, leading to clinical manifestations such as dental fluorosis, skeletal fluorosis, and increased urinary fluoride levels.
The World Health Organization (WHO) recommends an adequate daily intake of fluoride for individuals ranging from 2.5 to 4.0 milligrams. Of this, 0.8 to 1.8 milligrams can be obtained from drinking tea, and a total intake of 2.7 to 5.9 milligrams from tea is considered potentially toxic.
Now, let’s explore the presence of fluoride in tea. Fluoride in the environment primarily originates from fluorine-rich minerals such as fluorite, cryolite, and fluorapatite. In essence, fluoride is naturally occurring in soil and water. Tea plants, being able to accumulate fluoride, absorb fluoride from the soil and water.
Currently, China has established a maximum acceptable limit of 300 mg/kg for fluoride contamination in tea. In the past, a standard of 200 mg/kg was also utilized.
Research reports have investigated the fluoride content in teas. Notably, a report titled “Fluoride in Dark Teas and Progress in Low-Fluoride Dark Teas” co-authored by renowned experts in the dark tea industry, Dr. Liu Zhonghua and Dr. Xiao Lizheng, was published in the December 2007 issue of “Tea Communication.” Additionally, experts from Zhejiang University and the Ministry of Agriculture’s Key Laboratory of Tea Chemical Engineering, such as Ma Lifeng and Shi Yuanzhi, published the research article “Study on the Fluoride Content of Tea in China” in the 2002 “Agricultural Environmental Protection” journal.
The fluoride content in green tea can vary widely. Different studies have reported fluoride contents ranging from 4.81 to 349.56 mg/kg. Among tea types, black tea tends to have the highest fluoride content, with an average of 196.14 ± 246.07 mg/kg.
Numerous studies have shown that the fluoride content in tea is closely related to the brewing method. As the brewing time increases, the amount of fluoride dissolved in the tea also rises. For instance, when tea leaves are steeped for 5 minutes, approximately 60% of the fluoride in black tea is released into the tea liquor. After 30 minutes of steeping, about 90% of the fluoride can be dissolved into the tea liquor. Using traditional methods of boiling tea can result in a high extraction rate, with up to 98% of the fluoride being leached out.
If we use a typical gaiwan (lidded bowl) brewing method, with an average steeping time of around 20 seconds and ten consecutive infusions, the fluoride content in the tea is only about 50% dissolved into the tea liquor. This significantly reduces the intake of fluoride into the body. Therefore, gaiwan brewing is much safer in terms of fluoride content compared to boiling tea.
To prevent chronic fluoride poisoning:
- Avoid tea products from areas with high fluoride content, especially those made from mature leaves.
- For safety, choose tea leaves with fluoride content below 200 mg/kg, with particular attention to the fluoride content in dark brick teas.
- Select tender and high-grade tea leaves, and avoid consuming teas made from older leaves or low-grade teas.
- Minimize the use of traditional tea boiling methods and opt for gaiwan brewing.
- Diversify the types of tea you consume to avoid long-term consumption of dark brick teas.
- If you enjoy dark brick tea, it is recommended not to exceed a daily consumption of 10 grams.
- In areas with low fluoride content, consume teas with high fluoride content, and vice versa.
In summary, by using tea that complies with national production standards and adopting appropriate brewing methods, you can both supplement the body’s fluoride needs and avoid the problem of excessive fluoride intake due to tea consumption.
