Erosive Potential of Various Beverages in the United Arab Emirates: pH Assessment

Today’s market has a wide array of drinks that are available for everyday consumption targeting almost all age groups. It has been reported that the United Arab Emirates (UAE) residents consume an average of 103 L of soft drinks a year [1]. Studies have shown that more than 4 out of 5 Emirati students consume energy drinks, and about 1 out of 5 does so on daily basis [2]. The UAE is one of the top 5 countries in the world in terms of juice consumption per capita [3]. A study that followed dietary habits of Emirati citizens concluded that their daily caloric intake consisted of 8–14% from beverages [4]. In addition, the average yearly sugar consumption per capita in the UAE topped 38.5 kg and much of it is probably coming from liquid sources [5].

A combination of increased income and decreased prices has made beverages more affordable to the public, which in turn makes these drinks more prevalent in the community [6]. The rising consumption of sweetened beverages is a major contributor to a plethora of diseases. Studies showed that people who increased their sugary drink consumption gained more weight over time and those with frequent consumption of sugary drinks are at high risk of developing type II diabetes. Furthermore, soft drinks have been strongly linked to altered levels of blood calcium and higher urinary calcium excretion, which may lead to osteoporosis later in life [7, 11].

Along with the growing health risks of sweetened beverages, a new problem surfaced that consumers would now encounter due to the acidity of these drinks that is dental erosion as beverages with a pH of less than 4.0 are likely harmful to tooth structure [12, 13]. Tooth erosion is the irreversible loss of tooth structure due to acids in the absence of bacterial organisms [14, 15]. Erosion starts on enamel surfaces and progressively advances to dentine where it dissolves the hydroxyapatite crystals and exposes the organic matrix. The most common extrinsic trigger of erosion is acidic foods and drinks. The increase in hydrogen ion concentration in beverages causes loss of tooth structure as a result of erosion and softening of the inorganic component [16].

The low pH value of commercially available beverages promotes dental erosion. Carbonated and energy drinks, iced tea, and fruit juices are some examples of a long list of these drinks. Acids are either naturally occurring or artificially added to the product. Manufacturers add acids to beverages to enhance the flavor and prolong their shelf life [17]. Citrus fruit juices have naturally occurring citric acid; however, this acid is also added by the manufacturer to impart a tangy flavor and preserve the product. Phosphoric acid is added to soft drinks for similar reasons [18].

The increased intake of acidic drinks among different age groups in the UAE has a noted impact on the population’s dentition. 58.8% of 5-year-old preschoolers have some sort of dental erosion, and 55.09% exhibited signs of enamel dissolution [19]. As primary dentition is more susceptible to rapid erosion of dentine [16], those findings are considered remarkable representation of subsequent dental challenges that the younger generation will encounter in the future. Dental erosion leads to hypersensitivity in the teeth and might affect the overall quality of life. Previous studies have been conducted in different regions of the world, including the study by Reddy et al. [20] carried out in the USA. They tested the pH of 380 beverages which were then classified into 3 groups: minimally erosive (pH ≥ 4.0), erosive (pH 3.0–3.99), and extremely erosive (pH < 3.0), and they reported that 93% are potentially erosive to tooth structure.

The objective of our study was to determine the pH value of beverages available for consumers in the UAE and identify the most commonly added acids. The significance of this study lies in increasing the awareness of the public regarding the choices available for drinks that will have the least impact on the tooth structure and will also enable better patient counseling by dental clinicians and nutritionists regarding dietary beverage suggestions.

The Research Ethics Committee at the University of Sharjah exempted the study of pH assessment of commercially available beverages from requiring ethics approval according to the decision number REC-23-01-22-01-F. This study included non-alcoholic and non-dairy beverages available in the UAE. Three hundred six drinks were tested and categorized into different groups. The groups were carbonated drinks, energy drinks, sparkling water, iced teas, juices, malt beverages, coconut water, and sports drinks. The pH of each drink was tested using an LAQUA pH meter (Horiba, Tokyo, Japan). Each drink was tested three times at room temperature immediately after opening, and the mean value and standard deviation of the triplicate readings were calculated using the Microsoft Excel application package. The type of added acid to each selected drink was identified through information labels printed on each container.

The pH data of each drink were expressed as mean ± standard deviation. Seventy-seven carbonated drinks were evaluated (Table 1). The pH range of this category was 2.32–4.99 and the mean pH value was 3.01 (±0.46). Sixteen energy drinks (Table 2) had a pH range of 2.68–3.67 and a mean value of 3.24 (±0.32). Twenty-one sparkling waters (Table 3) had a pH range of 2.60–5.28 and a mean value of 3.72 (±0.86). Sixteen iced teas (Table 4) had a pH range of 2.88–5.48 and a mean value of 3.33 (±0.61). One hundred and twenty-five juices (Table 5) had a pH range of 2.32–5.86 and a mean value of 3.43 (±0.69). Twenty-nine non-alcoholic malt beverages (Table 6) had a pH range of 2.54–4.10 and a mean value of 2.99 (±0.53). Twelve coconut drinks (Table 7) had a pH range of 3.91–5.53 and a mean value of 4.64 (±0.59). Ten sports drinks (Table 8) had a pH range of 2.69–3.97 and a mean value of 3.30 (±0.41). Most beverages tested had a pH less than 4.0 (269 of 306; 88%). This study indicated that 37% of the beverages (114 of 306) tested were extremely erosive (pH < 3.0), 51% erosive (pH 3.0–3.99), and 12% (37 of 307) minimally erosive (pH ≥ 4.0). Bickford’s Classic Cola and Tesco Lemon Juice were the most acidic beverages (pH < 2.4). The most identified acids in the tested beverages were citric, phosphoric, ascorbic, and malic acids.

Extrinsic factors involved in dental erosion are vast; however, diet and lifestyle have the greatest contribution. Indeed, consumption of acidic beverages has been reported as the most common extrinsic factor for the development of dental erosion [21]. Children and adolescents experience dental erosion as a result of the increased consumption of acidic drinks in these age categories [22]. A proton-promoted mechanism of dissolution is responsible for erosion of the dentition. In this mechanism, the hydrogen ions interact with inorganic part of tooth structure represented by the hydroxyapatite [23]. Research argued that titratable acidity is more important than the pH in assessing the erosive potential of beverages [24]. Nonetheless, these hypotheses have been challenged after findings that considered the initial pH of the consumed products as another main chemical factor associated with erosion of teeth [24, 25]. Furthermore, dental erosion is not only governed by titratable acidity as the acidic liquid is usually in contact with the teeth during consumption for a short period of time [24, 28]. Enamel surface demineralization starts when the pH drops to 5.5 or lower; however, teeth erode when pH reaches to less than 4.0 [29]. A logarithmic rise in the solubility of apatite has been observed as pH plummets under laboratory conditions [30].

As proposed by Larsen and Nyvad, enamel solubility increases by 10-fold with each one unit decrease in the pH, and under conditions of a pH of 2, enamel demineralization proceeds at an amplified rate. Thus, according to the apatite solubility curve, beverage erosiveness is categorized into the following [13, 20, 30]: (i) extremely erosive, pH lower than 3.0; (ii) erosive, pH: 3.0–3.99; and (iii) minimally erosive, pH more than or equal to 4.0. In this study, 37% (114 of 307) of the beverages were extremely erosive (pH < 3.0), 51% were erosive (pH 3.0 to 3.99), and 12% (37 of 307) were minimally erosive (pH ≥ 4.0). The varying concentrations of acids added or naturally occurring in the beverages gave rise to different range of pH values. The results of this study are consistent with those Reddy et al. [20] obtained which reported that the majority of beverages purchased from corner shops, supermarkets, petrol stations, and venders in the Alabama area in the USA were potentially erosive. In their study, 39% (149 of 379) of the beverages tested were extremely erosive, 54% (205 of 379) were erosive, and 7% (25 of 379) were minimally erosive. The majority of the most acidic beverages tested were soft drinks and lemon-based drinks.

Only slight variations in pH values were found in our study compared to values obtained with other studies from different regions. For instance, Schweppes Tonic Water which was 2.62 as compared to 2.54 (Reddy et al.) [20] and 2.50 (Lussi et al.) [21]; Red Bull – original was 3.42 as compared to 3.43 (Reddy et al.) [20], 3.05 (Zimmer et al.) [10], 3.50 (Enam et al.) [31], and 3.37 (Jain et al.) [32]. Coca-Cola was 2.62 as compared to 2.37 (Reddy et al.) [20], 2.45 (Lussi et al.) [33], 2.46 (Hara and Zero) [34], 2.53 (Attin et al.) [35], 2.47 (Zimmer et al.) [10], and 2.50 (Enam et al.) [31]. Coca-cola light was 2.72 as compared to 2.59 (Zimmer et al.) [10]. The pH of Pepsi was 2.92 as compared to 2.39 (Reddy et al.) [20], (Lussi et al.) [35], 2.90 (Enam et al.) [31], and 2.53 (Larsen et al.) [30]; the pH of Sprite was 3.03 compared to 2.68 (Zimmer et al.) [10] and 3.10 (Enam et al.) [31]; the pH of Fanta Orange was 2.86 compared to 2.90 (Enam et al.) [31]; the pH of Mirinda Orange was 2.95 compared to 2.90 (Enam et al.) [31]; the pH of 7 UP was 3.23 compared to 3.40 (Enam et al.) [31]; and finally, the pH of Mountain Dew was 3.14 compared to 3.00 (Enam et al.) [31]. The ingredients of the same product might be different from one region to another to suit the palate of the targeted population of a certain nation, and this might result in some differences in the pH value.

Zimmer et al. [10] carried out a distinctive method of comparison where extracted bovine incisors were collected, and after introducing each respective beverage, the amount of hard tissue loss of both enamel and dentine was calculated. Coca-Cola with a pH of 2.47 caused a loss of 7.5 mg of enamel and 6.6 mg of dentine, whereas Sprite with a pH of 2.68 caused a loss of 26.1 mg of enamel and 17.7 mg of dentine. Ehlen et al. [36] compared the effects of popular beverages around the USA (100% Apple juice, Coke, Diet Coke, Gatorade, and Red Bull) by testing the effects of their respective pH and titratable acidities and recording the resultant demineralization depth in tooth structure after being exposed to these liquids. It was concluded that tooth structure erosion does not only depend on the beverage’s pH or titratable acidity. Other factors might also play a role such as the type of acid added or naturally occurring in the drink. For instance, citric acid in beverages was found to be more aggressive than phosphoric acid. The molecular shape of citric acid and the presence of three carboxylic groups in the chemical structure give it an immense ability to chelate with calcium which is translated clinically into a great erosive potential [37, 41]. In the present study, citric, phosphoric, ascorbic, and malic acids were the most identified acids according to the ingredients label. Phosphoric acid was found in both carbonated and energy drinks. Citric acid combined with pantothenic acid was found in energy drinks. Malic acid was mainly identified in sparkling water and in combination with citric acid in juices, while ascorbic acid was identified more in malt beverages and juices.

Knowledge of pH beverages is a necessity for the development of prophylactic measures and strategies to guide patients with clinical erosion [42, 44]. Preventive measures include the elimination or reduction of acidic drinks; however, the success of this approach is vastly dependent on patient compliance and may be difficult to implement in young individuals. This remark is crucial as the greatest increase in soft drink consumption has been among children and adolescents, who tend to develop irreversible tooth structure loss because of the consumption of these drinks between meals rather than with meals [45]. A survey conducted by Melbye et al. [46] revealed that 221 of 850 (26%) Norwegian students consumed acidic beverages on a daily basis, further highlighting the lack of knowledge about dental erosive wear.

Kamal et al. [47] revealed more surfaces with tooth wear in overweight participants than in those with normal body size, disclosing a directly proportional association between body size and indulgence with high calorie acidic drinks with the amount of tooth wear. Patients should be advised to avoid acidic drinks close to bedtime where the mouth is xerostomic [48, 49]. Since dental erosion is associated with the drinking method, the latter should be modified to decrease the potential erosiveness of beverages. For instance, an acidic drink should not remain inside the oral cavity for more than a few seconds before swallowing and using a straw would help direct the drink away from the teeth; however, this method might be destructive if the straw was placed labial to the anterior teeth; thus, proper sipping technique using the straw must be demonstrated for patients by dental practitioners and nutritionists. Athletes should be warned that ingestion of sports or energy drinks when they are dehydrated may double the chances of dental erosion since saliva flow is remarkably decreased after and during exercise. The use of abrasive products to brush the teeth can also contribute to further irreversible loss of tooth structure [50]. Sports drinks are also quite popular among the general public. Despite the claimed benefits of these drinks, the low pH values contribute to dental erosion [51].

An important prophylactic measure is identifying individuals at risk through proper diagnosis and evaluation of different etiological factors which will aid in tailoring a preventive program [52]. Al-Ashtal et al. [53] assessed the awareness and knowledge of Yemeni dental professionals and students about the topic of dental erosion, and it was reported that thorough understanding of dental erosion diagnosis, prevention, and contributing factors was lacking among 50% of the participants. It seemed obvious that there is an immediate need for improving awareness about this topic.

Altering the chemical composition of beverages may decrease their erosiveness; replacing citric and phosphoric acid with malic acid, since the latter is less damaging to enamel, can prove to be a prudent solution [21, 54]. Calcium fortification in beverages has been suggested as a mean to limit dental erosion in high-risk patients; however, it salient to carefully weigh the risks and benefits before establishing a recommendation [41]. It is also important to instill healthy oral hygiene habits; for instance, one of the most overlooked instructions given by dental clinicians to their patients is brushing prior to or 30–60 min after consumption of an acidic drink rather than immediately [55].

It should be noted here that the use of in vitro experimental condition, such as the one used in this study, contributes to only limited answers to more complex problems. Moreover, although the clinical relevance of the pH of consumed beverages is indisputable, it is never the sole determinant of the propensity of a drink to cause tooth structure erosion as various other parameters are involved, including but not limited to titratable acidity, adhesiveness and displacement of the liquid, mineral content of the drink, components and flow rate of saliva, and the composition of the inorganic part of tooth structure [56].

Beverage’s erosive potential is influenced by its pH. The study included 306 non-alcoholic and non-dairy beverages that were assessed for relative erosivity by assessment of the pH. The present study showed that 37% of the beverages tested were extremely erosive (pH < 3.0), 51% were erosive (pH 3.0–3.99), and 12% (37 of 307) were minimally erosive (pH ≥ 4.0). The most acidic beverages were Bickford’s Classic Cola and Tesco Lemon Juice with pH values lower than 2.4. Information obtained will increase the awareness of the public on the available choices and enable better patient counseling regarding dietary beverage suggestion.

The Research Ethics Committee at the University of Sharjah exempted the study of pH assessment of commercially available beverages from requiring ethics approval according to the decision number REC-23-01-22-01-F.

The authors have no conflicts of interest to declare.

No funding was received.

Conceptualization: Mohannad Nassar; methodology: Noor Hasan, Ahmed Al-Khazraji, and Mohannad Nassar; software, formal analysis, and writing – original draft: Mohannad Nassar and Noor Hasan; validation and supervision: Mohannad Nassar and Md Sofiqul Islam; investigation, data curation, and writing – review and editing: all authors; resources: Mohannad Nassar, Ahmed Al-Khazraji, and Md Sofiqul Islam; visualization: Husain Maki, Noor Hasan, and Ahmed Al-Khazraji; and project administration: Mohannad Nassar and Husain Maki. All authors have read and agreed to the published version of the manuscript.

The authors confirm that the data supporting the findings of this study are available within the article.