Shedding light on fluoride in tea: a roadmap to safer brews
image: Fluoride absorbed by the leaves is transferred to the leaf tips and edges, chelates with metal ions, and the complexes are deposited in the leaves. Fluoride can be transferred from old leaves to new tips. Fluoride from soil and water can form complexes with organic acids and aluminum, which are stored in the leaves of tea plants. Fluoride from soil and water can also be individually absorbed and transported for storage in the leaves.
Credit: The authors
The researchers examine how environmental factors and plant genotypes influence fluoride uptake and identify molecular pathways and transporter proteins involved in fluoride movement. The study also reviews how fluoride stress affects tea plant growth, photosynthesis, and the formation of quality-related metabolites such as polyphenols and theanine. Finally, it evaluates current strategies—such as breeding low-fluoride cultivars, adjusting cultivation practices, and improving processing and brewing methods—to mitigate health risks and improve tea safety.
Tea (Camellia sinensis) is consumed by billions globally and is celebrated for its antioxidant-rich profile. However, tea plants are known to accumulate fluoride, a naturally occurring element that, in excess, can lead to chronic health issues like skeletal fluorosis. This is especially relevant for dark tea, which is often brewed from mature leaves with higher fluoride content and consumed via boiling methods that increase fluoride leaching. Despite its potential harm, the biological and environmental mechanisms governing fluoride uptake and tolerance in tea plants remain poorly understood. Due to these challenges, a deeper understanding of the fluoride-accumulation process in tea plants is urgently needed to reduce health risks while maintaining tea’s nutritional value.
A study (DOI: 10.48130/bpr-0024-0010) published in Beverage Plant Research on 4 June 2024 by Lanting Zeng’s team, South China Botanical Garden, Chinese Academy of Sciences, summarizes decades of findings on how fluoride enters, moves through, and affects tea plants—and how this knowledge can inform tea safety strategies.
To investigate how tea plants absorb and transport fluoride, researchers reviewed studies examining both environmental and molecular mechanisms. Using physiological, biochemical, and molecular approaches, these studies revealed that tea plants primarily absorb fluoride in its water-soluble form through the roots, with active uptake occurring at low concentrations (0.1–10 mg/L) and passive uptake at higher levels. This process is mediated by ion pump proteins like H⁺-ATPase and Ca²⁺-ATPase, as well as ABC transporters that help sequester fluoride into vesicles to reduce toxicity. Passive absorption involves water and ion channels, including the CLCF and FEX protein families. After uptake, fluoride is transported upward through the xylem, sometimes as aluminum-fluoride complexes, and accumulates mainly in mature leaves. Key transporter genes such as CsFEX2, CsCL667, and CsABCB9 are differentially expressed in response to fluoride stress and help regulate internal fluoride levels. Environmental factors like soil pH, atmospheric fluoride levels, and the presence of ions such as Ca²⁺ and Mg²⁺ influence fluoride uptake. Organic acids secreted by roots can further facilitate fluoride absorption. Additionally, the fluoride content varies with tea variety, plant organ, and season—older leaves and spring harvests often show higher levels. These findings highlight the complex interplay of environmental conditions and genetic factors in fluoride accumulation and offer insights for developing low-fluoride tea varieties and cultivation practices to ensure safer tea products.
Fluoride accumulation in tea is a complex, multi-dimensional challenge that affects both public health and the tea industry. By understanding the molecular, physiological, and environmental mechanisms that drive fluoride uptake and tolerance in tea plants, we can begin to design more targeted and effective defluorination strategies. These include breeding low-fluoride varieties, optimizing soil and fertilizer use, and refining tea processing and brewing practices—all aimed at ensuring that tea remains a safe and beneficial beverage worldwide.
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References
DOI
Original Source URL
https://doi.org/10.48130/bpr-0024-0010
Funding information
Part of the research aspects carried out by the authors are supported by the financial support from the Key-Area Research and Development Program of Guangdong Province (2023B0202120001), the Guangdong Natural Science Foundation for Distinguished Young Scholar (2023B1515020107), Tea garden standardized production and processing project of Yigong tea farm in Nyingchi City, the South China Botanical Garden, Chinese Academy of Sciences (QNXM-202302), the fund for China Agriculture Research System (CARS-19), Chinese Academy of Sciences Specific Research Assistant Funding Program (2021000064, 2023000030), the Science and Technology Project of Guangzhou (202206010185), the Guangdong Provincial Special Fund for Modern Agriculture Industry Technology Innovation Teams (2023KJ120), and the Science and Technology plan Project of Qingyuan (220804107510735).
About Beverage Plant Research
Beverage Plant Research (e-ISSN 2769-2108) is the official journal of Tea Research Institute, Chinese Academy of Agricultural Sciences and China Tea Science Society. Beverage Plant Research is an open access, online-only journal published by Maximum Academic Press which publishing original research, methods, reviews, editorials, and perspectives, which advance the biology, chemistry, processing, and health functions of tea and other important beverage plants.