We selected widely used apps from 2 distinct regions, Taiwan and the United States, to represent linguistic and cultural differences. Specifically, we chose the academic app Formosa FoodApp [14] and the commercial app COFIT [24] given their widespread clinical and educational acceptance in Taiwan. In addition, we also explored 2 commercial US-based apps—MyFitnessPal and Lose It!—based on their broad acknowledgment, dominant presence in both clinical settings and among consumers, and citations in earlier literature [10,15,19]. The primary sources for nutrient data included the Taiwan FCD, US Department of Agriculture (USDA)–Food and Nutrient Database for Dietary Studies (FNDDS), and US food manufacturers and restaurants. Notably, MyFitnessPal and LoseIt! make user-generated food entries available to all users (Table 1).

Figure 1 shows the flowchart of the food item and food code selection process. Briefly, data from our Formosa FoodApp validation study were used for the analyses [14], which involved 86 healthy adults aged 19-26 years who tracked their daily diet using the Formosa FoodApp. To identify food items that contributed to high cholesterol and saturated fat intake, a nutrition-trained investigator ranked frequently consumed, saturated fat– and cholesterol-containing items from our prior study. The initial assessment generated 2 lists of 50 food items each. After eliminating duplicates and similar entries, we finalized a list comprising 42 unique food items.

To mitigate potential biases from initially using data from the Formosa FoodApp, which may predominantly reflect Taiwanese dietary preferences, we verified the availability of these 42 food items across all apps selected for this study. The comprehensive list of these food items is provided in Multimedia Appendix 1 for reference. We further grouped these 42 food items into broader categories—such as eggs, beef, pork, chicken, dairy, seafood, and prepackaged and processed foods—to enhance the representativeness of our analysis across diverse national diets.

Food items were entered using the search feature for the free versions of Formosa FoodApp, COFIT, MyFitnessPal, and Lose It!. Searches were performed across Formosa FoodApp and COFIT in Chinese and LoseIt! in English. To explore MyFitnessPal’s reliability across different national contexts, searches were conducted in both Chinese and English, and we compared the errors in nutrient data from its English and Chinese versions. To ensure a clear distinction between MyFitnessPal in Chinese and English, we refer to them as MyFitnessPal-Chinese and MyFitnessPal-English, respectively, throughout the manuscript. Given the vast array of food codes that appeared in the search results and to make the analysis more manageable and representative, we selected the top 5 relevant food codes that appeared first in the search results for each item as representative subsets. Energy contents and nutrients including total carbohydrate, protein, total fat, saturated fat, and cholesterol values were extracted from the apps (Figure 1). The selection process underwent a review and confirmation by a second investigator. Portion sizes for the selected food codes were standardized at 100 g across all databases. Data from all selected apps and reference databases were documented for each food code and entered into a Microsoft Excel dataset.

We calculated the mean percentage error for energy, total carbohydrate, protein, total fat, saturated fat, and cholesterol values as the difference between the nutrient intake values from the apps and the corresponding values from the reference databases, expressed as a percentage error. This error, calculated for each food code in each app, is given by the following:

We focused on 2 key components of variability for saturated fats and cholesterol: missing nutrient data and inconsistencies of nutrient data for the same food item across 5 codes. Missing nutrient information for each food item was determined as the ratio of missing nutrient information to the total selected food codes for that item, presented as a percentage:

We calculated coefficients of variation (CVs) to address nutrient data inconsistencies across 5 food codes for the same item within an app. CVs were obtained by taking the square root of the average reporting variance within a food item, divided by the mean of the items (app values over food codes). A CV was calculated for each food item, and then mean CVs were determined based on the food group and app. Our analysis involved paired 2-tailed t tests for app-to-reference comparisons (paired within food codes) and a 1-way ANOVA for app-to-app variations. A linear regression analysis was used to assess the factor associated with the percentage of underestimated error of nutrients compared to reference databases. To assess the reliability of a commercial app universally used in different national contexts, we conducted a cross-national analysis, comparing errors in both MyFitnessPal-Chinese and MyFitnessPal-English against the USDA-FNDDS and Taiwan FCD reference databases. All analyses were performed in SPSS (version 23; IBM Corp) and GraphPad Prism 8 (GraphPad Software), with P values of <.05 considered statistically significant.

This study conducted a secondary analysis of data previously collected in an earlier study [14], which received approval from the Taipei Medical University Institutional Review Board (N202101046). Written informed consent was obtained from all participants. The data used in this analysis were deidentified.

Among the selected nutrition apps, Formosa FoodApp is an academic mobile nutrition app, while COFIT, MyFitnessPal-Chinese, MyFitnessPal-English, and LoseIt! are all commercial apps (Table 1). Figure 1 details the distribution of 42 food items across 7 main food categories. The dominant food groups were prepackaged processed foods (15 items), seafood (6 items), and pork and egg (5 items each).

Figure 2A presents the mean percentage errors of app nutrient data against national reference databases. Most apps showed no differences in energy or macronutrients compared to their respective national references, with the exception of LoseIt!, which underestimated protein by −1.3% and fats by −22.4% compared to the USDA-FDNSS. COFIT, MyFitnessPal (in both languages), and LoseIt! underestimated saturated fats with errors ranging from −16.3% to −40.3% (all P<.05). All apps underestimated cholesterol, with errors ranging from −26.3% to −60.3% (all P<.05).

Figure 2B displays the mean percentage errors in MyFitnessPal-Chinese and MyFitnessPal-English using the USDA-FNDSS and Taiwan FCD. The Chinese version underestimated saturated fats by around −40% (−43.2% for the Taiwan FCD and −39.4% for the USDA-FNDSS) and cholesterol by −60% (−58.2% for the USDA-FNDSS and −60.3% for the Taiwan FCD). In contrast, the English version showed −10% errors for saturated fat (−16.8% for the USDA-FNDSS and −4.3% for the Taiwan FCD) and −40% for cholesterol (−40.4% for the USDA-FNDSS and −38.8% for the Taiwan FCD). Notably, these discrepancies, significant at P<.01 for both nutrients, remained unchanged regardless of the reference database used.

Omission rates for different nutrients considerably varied. Total fats exhibited the lowest omission range, spanning from 0% to 21%. In comparison, saturated fats and cholesterol showed higher rates of omission, ranging from 19% to 47% and from 21% to 62%, respectively (data not shown). COFIT showed the highest missing information for saturated fats at 47% (Figure 3A), while MyFitnessPal-Chinese recorded the highest omission at 62% for cholesterol (Figure 3B).

For saturated fats, both COFIT and MyFitnessPal-Chinese showed substantial omissions, especially for beef (60% and 56%, respectively), pork (80% and 28%, respectively), and dairy (50% and 43%, respectively). For cholesterol, there were significant differences in omission rates between MyFitnessPal-Chinese and MyFitnessPal-English (62% vs 32%; P<.05), notably for beef (67% vs 11%), pork (56% vs 16%), dairy (80% vs 53%), and prepackaged processed foods (84% vs 39%).

We calculated CVs to address saturated fat and cholesterol data consistencies, by assessing 5 food codes for identical items within a given app (Figure 4). For saturated fats, the lowest mean CVs were observed in Formosa FoodApp (23.8%) and COFIT (38.9%). The highest mean CVs were observed in MyFitnessPal-Chinese (96.7%) and LoseIt! (83.6%). A similar trend was also observed for cholesterol.

Saturated fat variability was high for beef (78%-145%), chicken (74%-112%), and seafood (97%-124%) among MyFitnessPal-Chinese, MyFitnessPal-English, and LoseIt!, respectively. Cholesterol variability was high for dairy (71%-118%) and prepackaged foods across all apps (84%-118%; Figure 4).

To the best of our knowledge, this is the first study to critically examine the reliability of mobile nutrition apps’ reported data on saturated fats and cholesterol against 2 different national FCDs. We found significant errors up to −40.3% for saturated fats and −60.3% for cholesterol, suggesting that these apps may provide unreliable data when assessing diets, particularly in the context of CVD prevention. These findings align with the findings by Shinozaki and Murakami [25] on MyFitnessPal’s nutrient underestimation of saturated fats and cholesterol (85.1% and 97.6%, respectively). Similarly, Siniarski et al [16] also reported errors up to 57.3% in mobile app predictions for saturated fats compared to Polish reference data. Furthermore, our results demonstrate that errors in MyFitnessPal’s nutrient reporting are consistent across different national FCDs (USDA-FNDDS and Taiwan FCD). Such errors remained statistically significant, regardless of the FCDs used as a reference. This problem suggests that the errors are not merely due to mismatches or variations in external FCDs but are rooted in the app’s core database.

Data inconsistencies within consumer-grade apps, evidenced by significant omissions and variability, compromise their reliability. For instance, saturated fat variability was notably high across different food groups, with beef ranging from 78% to 145%, chicken from 74% to 112%, and seafood from 97% to 124% among MyFitnessPal-Chinese, MyFitnessPal-English, and LoseIt!, respectively. Similarly, cholesterol variability was consistently high in dairy (71%-118%) and prepackaged foods (84%-118%) across all apps. COFIT lacked almost 50% of its saturated fat data, and MyFitnessPal-Chinese was missing over 60% of its cholesterol information. This is concerning as food labeling regulations require clear disclosure of these nutrients [6], yet many entries incorrectly list these values as zero, deviating from standard guidelines [26]. This issue is even more pressing in the context of prepackaged foods. Previous research from our team emphasized this challenge, revealing that data omissions related to prepackaged foods significantly impact the reliability of mobile dietary assessments [14]. This emphasizes the urgency for databases to stay updated with new market introductions.

The lack of transparency in food sourcing within consumer-grade apps, particularly when combined with the extensive volume of FCDs [11,27], can significantly confuse users during food logging [28,29]. As consumer-grade apps allow for a vast array of food items to be listed—often without clear sourcing information, users face the daunting task of navigating through numerous results to find the most accurate match for their consumed foods. The entries frequently do not specify their nutritional data sources. Our data showed that only a fraction of the analyzed food codes transparently disclosed their sources. Specifically, just 51.5% (n=105) of MyFitnessPal-English’s 204 food codes and 43.7% (n=87) of its Chinese counterpart’s 199 food codes provided clear sourcing information. Meanwhile, LoseIt! transparently sourced only 37.4% (n=71) of its 190 codes. Formosa FoodApp led with 78.2% (n=115) for its 147 codes, while COFIT lagged at 61% (n=57) for its 94 codes. This lack of clarity can lead to confusion and inaccuracies, underscoring the need for improved transparency in food sourcing to facilitate more precise dietary tracking.

Our analysis also delved into the complexities of maintaining accuracy within multilingual universal apps, using MyFitnessPal as a case study. Although errors in MyFitnessPal’s nutrient reporting are consistent across different national FCDs (USDA-FNDDS and Taiwan FCD), it is important to note that the larger errors observed in MyFitnessPal-Chinese, as opposed to the English version, highlight another challenge for universal apps: ensuring uniform accuracy across different languages and, by extension, cultural contexts. Several factors may contribute to the discrepancies observed in MyFitnessPal. First, the integration of multiple FCDs combined with user-generated content without stringent quality control can introduce variability in nutrient data [27]. Second, nutritional composition can also vary by region due to differences in food production, processing, and preparation practices, further complicating accurate nutrient estimation [30]. Lastly, user-generated content can exacerbate inaccuracies, as this content may not undergo rigorous verification processes, leading to inconsistencies in nutrient reporting [27]. Together, these factors highlight the complexities of providing accurate, universal dietary tracking tools and the critical need for app developers to address these challenges to enhance the reliability and global applicability of their platforms.

This study has highlighted significant errors and inconsistencies in various consumer-grade apps. Academic apps such as Formosa FoodApp, which show fewer reporting errors and greater transparency in nutrient sourcing, are crucial for health professionals who require precise and validated data to make evidence-based dietary recommendations, particularly for CVD prevention. However, these apps encounter financial and regional limitations that restrict their usability. As academic apps are usually funded by research grants or academic institutions for specific purposes, their development and maintenance are often constrained, limiting updates and expansion. Moreover, many academic apps are tailored for specific regional diets, such as the Taiwanese focus of Formosa FoodApp, which narrows their international relevance. Additionally, these apps often lack engaging user interfaces and features that are essential for widespread user adoption [14]. Innovative funding models supporting extensive food databases and multilingual capabilities are needed to make these tools globally accessible and competitive with commercial apps. Khazen et al [11] suggested that an ideal dietary tracking tool would combine the features of commercial apps with the accuracy of academic apps, increasing their utility in global research and public health initiatives.

Our study contributed to the current literature by critically examining how accurately mobile apps can estimate the intake of saturated fats and cholesterol in different national contexts. Additionally, by investigating the consistency of data within and across the apps, we have highlighted several challenges these apps face in providing reliable nutritional information in the context of CVD prevention. Nonetheless, our methodology has inherent limitations. The data from a young demographic may introduce bias, potentially limiting the applicability of findings across all age groups. By focusing on only the top 5 food codes per item, we might not have captured the full extent of the data variability within each app. This strategy, although deliberate, possibly overlooked broader inaccuracies or consistencies in less frequently selected food items. Our cross-national examination predominantly relied on MyFitnessPal’s performance, potentially narrowing the applicability of our findings to other multilingual apps. Furthermore, the discrepancy in the number of selected food codes across apps—with MyFitnessPal at 204 and COFIT at 94, for instance—introduces bias when comparing results across platforms. Additionally, we did not factor in user behaviors such as app update frequencies, which can intermittently influence data accuracy. The evolving nature of these apps, with ongoing food item additions and updates by developers and users alike, suggests that database accuracy might shift over time. As the landscape of mobile health apps is dynamic, future studies would benefit from broader sampling and recognizing of these continual database evolutions, ensuring a more encompassing perspective on app reliability.

Our study reveals substantial inaccuracies and inconsistencies in mobile nutrition apps’ reporting of saturated fats and cholesterol, highlighting challenges in ensuring data reliability across different national contexts and within the apps themselves. As digital tools are increasingly incorporated in CVD prevention and care, rigorous assessments and continuous refinements are crucial to ensure that they serve as dependable resources for both professionals and the public.