# Identification of Factors Influencing Fluoride Content in Tea Infusions: A Systematic Review
## 3 Results
### Main Study Outcomes
#### 3.3.5 Impact of Brewing Temperature and Water Composition  
Several physicochemical parameters of the brewing process also affect fluoride concentrations. Lower pH values have been associated with increased fluoride release [55; 56; 58; 59; 67], although [PERSON] et al. [51] did not find a consistent pH effect, suggesting that its influence may depend on other variables.  
Repeated brewing of the same tea leaves typically results in decreased fluoride release with each successive infusion [56; 63; 68; 69]. Furthermore, the fluoride content of the brewing water itself plays a critical role: [PERSON] et al. [22], [PERSON] et al. [63], and [PERSON] et al. [65] demonstrated a positive correlation between fluoride concentrations in water and tea infusion. Interestingly, [PERSON] et al. [54] observed that tea leaves can adsorb fluoride from high-fluoride water, occasionally resulting in lower concentrations in the infusion than in the original water.  
Water hardness and ion content further modulate fluoride extraction. High calcium carbonate concentrations significantly reduced fluoride release [32; 48]. Likewise, elevated  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Author** & **Tea Mass/Form** & **Granules and Tea Bags Had the Highest Fluoride Levels.** \\ \hline [PERSON] et al. [28] & 2 g; leaves, bags, granules & Granulated and tea bag samples had higher fluoride content than loose-leaf tea. \\ \hline [PERSON] et al. [31] & 2 g (leaves and bags); bottled teas analyzed directly & Tea bags contained higher fluoride concentrations than loose-leaf and bottled tea. \\ \hline [PERSON] et al. [32] & 1 g; leaves and bags & Tea bags released more fluoride than loose leaves; extraction efficiency reached up to 73.5\%. \\ \hline [PERSON] et al. [49] & 1 g powder, 1.75–2.25 g bags & Highest fluoride concentrations were found in black tea, followed by green and herbal teas. \\ \hline [PERSON] et al. [52] & 2 g; leaves and bags & Fluoride content was highest in economy blends, followed by green and black teas. \\ \hline [PERSON] et al. [54] & 1 g; powder and bags & Black tea powder released more fluoride than tea bags; values varied with water fluoride content. \\ \hline [PERSON] et al. [58] & 1 g; leaves and bags & Loose green teas showed higher fluoride levels than bagged herbal teas. \\ \hline [PERSON] et al. [63] & 2 g; loose vs. packed tea & Loose tea had higher fluoride concentrations than bagged tea. \\ \hline [PERSON] et al. [50] & 2 g; bags, leaves, granules & Granules \textgreater{} leaves \textgreater{} bags in fluoride content. \\ \hline [PERSON] et al. [19] & 2 g; leaves and bags & Fluoride content was highest in black tea bags and increased with brewing time. \\ \hline [PERSON] et al. [55] & 500 mg powder & Traditional powdered teas showed elevated fluoride levels (up to 6.9 mg/L); herbal teas contained significantly less. \\ \hline [PERSON] et al. [56] & 2.0 \(\pm\) 0.5 g bags & Fluoride levels varied by tea origin and were negatively correlated with the pH of brewing water. \\ \hline \end{tabular}
\end{table}
Table 2: Influence of Tea Mass and Leaf Fragmentation on Fluoride Content.  
levels of aluminum and iron (III) ions were found to bind fluoride and reduce its availability in the infusion [67]. (see Table 3).