Electronic 12-Hour Dietary Recall (e-12HR): Comparison of a Mobile Phone App for Dietary Intake Assessment With a Food Frequency Questionnaire and Four Dietary Records

Background: One of the greatest challenges in nutritional epidemiology is improving upon traditional self-reporting methods for the assessment of habitual dietary intake. Objective: The aim of this study was to evaluate the relative validity of a new method known as the current-day dietary recall (or current-day recall ), based on a smartphone app called 12-hour dietary recall, for determining the habitual intake of a series of key food and drink groups using a food frequency questionnaire (FFQ) and four dietary records as reference methods. Methods: University students over the age of 18 years recorded their consumption of certain groups of food and drink using 12-hour dietary recall for 28 consecutive days. During this 28-day period, they also completed four dietary records on randomly selected days. Once the monitoring period was over, subjects then completed an FFQ. The two methods were compared using the Spearman correlation coefficient (SCC), a cross-classification analysis, and weighted kappa. Results: A total of 87 participants completed the study (64% women, 56/87; 36% men, 31/87). For e-12HR versus FFQ, for all food and drink groups, the average SCC was 0.70. Cross-classification analysis revealed that the average percentage of individuals classified in the exact agreement category was 51.5%; exact agreement + adjacent was 91.8%, and no participant (0%) was classified in the extreme disagreement category. The average weighted kappa was 0.51. For e-12HR versus the four dietary records, for all food and drink groups, the average SCC was 0.63. Cross-classification analysis revealed that the average percentage of individuals classified in the exact agreement category was 47.1%; exact agreement + adjacent was 89.2%; and no participant (0%) was classified in the extreme disagreement category. The average weighted kappa was 0.47. Conclusions: Current-day recall, based on the 12-hour dietary recall app, was found to be in good agreement with the two reference methods (FFQ & four dietary records), demonstrating its potential usefulness for categorizing individuals according to their habitual dietary intake of certain food and drink groups.


Introduction
Many epidemiological investigations and intervention studies do not require a complete picture of the habitual diet (or average long-term consumption) [1], as it can represent both an unnecessary workload for study participants and an avoidable waste of the scarce resources available for research [2].The essential concept of these studies is to determine habitual consumption of specific key groups of food and drink (hereafter referred to as 'food') [3][4][5][6][7][8][9].Classifying individuals according to categories of habitual consumption of specific food groups is sufficient for identifying potential nutritional deficiencies [10] and for evaluating the relationship between relative ranking and disease [5,[8][9][10][11][12][13][14], and effectiveness of personalized methods that are implemented to promote changes in dietary patterns regarding selected food groups [1,5,[8][9][10]12].
The three principal and traditional self-reporting methods for determining dietary intake can be classified as follows: (1) Short-term methods: dietary record (DR) and 24-hour recall.
(2) Long-term methods: food frequency questionnaire (FFQ).These methods present significant and well-documented limitations [5,11,[15][16][17][18]. (1) DRs that require weighing food require too much preparation time and create a large workload for the study participants, which can lead to deviations in normal food intake (especially an underestimation of quantities), as well as both low participation and completion rates [5,11,[15][16][17]19,20].24-hour recalls require trained personnel and depend on the short-term memory of participants.Additionally, a proper picture of habitual diet using short-term methods requires methods to be repeated multiple times [16,19], which increases problems inherent in these procedures.(2) FFQs depend primarily on long-term memory of the interviewed subject, do not account for intrapersonal variation in recording the daily consumption of food during the study period, and do not allow a precise estimation of serving sizes of food consumed.Due to these limitations, results obtained by these inexact methods over both the short-and long-term could lead to inexact conclusions and incorrect decisions [18].
Newer alternatives for determining dietary intake include audio signal processing, inertial sensing, image processing, non-intrusive near-infrared scanning, and gesture recognition interfacing [21][22][23][24].Some authors maintain that more research is needed to develop these and other tools that are more objective and precise and that resources should be invested to this end [18].Until these alternatives are available, digital technologies for self-reporting methods can, and must, be developed and utilized [25], as an improvement in traditional self-reporting methods.This progress constitutes one of the most important challenges in the field of nutritional epidemiology [4,20].
For these reasons, the need is evident to develop better methods that can eventually replace current traditional self-reporting ones and provide better accuracy in measuring usual dietary intake of free-living individuals.This upgrade would represent a great boon not only to researchers [10] but also to society in general, considering the critical repercussions from both epidemiological investigations and interventional studies regarding the dietary intake of the population at large [25].
The objective of this study was to determine the relative validity of the new method known as current-day dietary recall (or current-day recall), based on a smartphone app called 12-hour dietary recall (e-12HR-previously known as e-Epidemiology [25]), utilizing reference methods, such as a semiquantitative FFQ and four estimated DRs, to verify the comparability of consumption data regarding a list of key food groups in the three methods.

Recruitment
Students of the Schools of Medicine and Pharmacy at the University of Seville (Andalusia, Spain, South of Europe) participated in this study.Two classes from each School were randomly selected and one member of the research team presented the project.Participant recruitment took place from January to December 2017.Participants were incorporated in the study progressively during the entire recruitment period so that every day of the week and every season of the year could be represented [26].Participation in the study was incentivized with a raffle that included school materials valued at 250 euros.

Study Sample
The study was presented to 219 students and of those, 26 were not interested, and 98 did not meet the inclusion criteria.Of the 95 individuals who signed the informed consent, 87 completed the study.Inclusion criteria: (1) Older than 18 years of age; (2) a student of the Schools of Medicine or Pharmacy (University of Seville); and (3) possesses a smartphone with internet access (3G/4G/Wi-Fi) and Android operating system.

First Interview: Participant Data Collection
The 95 students who were interested and met the inclusion criteria were scheduled for a first personal interview.The procedure of the interview was as follows: (1) the same research team member that presented the project personally explained the research protocol in detail; (2) each participant signed the informed consent form; (3) each participant was assigned a personal alphanumeric code; (4) each participant filled out an initial questionnaire (on paper) with date of birth, date of the interview, gender, and school; (5) each participant downloaded the e-12HR app for his or her personal smartphone; (6) the same member of the research team personally explained to each participant how to use the app with a practical demonstration before written instructions were given to the participants [14,27] to be consulted later, if necessary; (7) the same research team member personally gave each student detailed instructions on how to complete the four estimated DRs and how to estimate serving sizes consumed using an explanatory pamphlet that was also given to participants [12,13].
The researcher also insisted that participants maintain their habitual diet throughout the study.

Completing the 12-Hour Dietary Recall App
The e-12HR app was developed to record daily consumption of a list of 10 food groups.The list could not be too long to minimize the workload on participants as well as the research costs [28].These food groups were selected as they are XSL • FO RenderX indicators of health/disease and are considered protective factors (fruit, vegetables, legumes or fish) or risk factors (soft drinks, commercial baked foods, and precooked meals) for chronic illnesses [4,12,29].They also provide consumption patterns that range from almost every day for every inhabitant of the population to infrequently for the majority [4] (Textbox 1).
The first time the e-12HR app was used, the participants were required to introduce their personally assigned alphanumeric code and the e-mail of the researcher who would receive the data from the app.Participants were instructed to complete the app after consuming the last food of the day [14,27].The e-12HR app includes a notification option, so that the app can remind the participant, at the hour previously selected by the participant (between 20:00 h and 04:00 h), that it is time to complete the questionnaire.The app was structured according to food groups to facilitate completion of the e-12HR task.For each food group, the participant would choose the most appropriate image (or images) from a series of color photographs with 2-4 possible options, shown simultaneously [14,27], which illustrated the different serving sizes to assist with selecting the number of standard servings consumed [10,12,14,20,27].To further assist with estimating serving sizes, each photograph was accompanied by explanatory text and three objects of known/predictable size for the students [30,31] (fiducial markers): a commonly used pencil, pen, and a marker.For example, on the first screen of the app, the following would appear: How many pieces of fruit have you eaten today?, with the Rations button, and Next button and a box with the value set to 0 by default.Supposing that the participant had, throughout the day, consumed an apple and three mandarins, they would proceed as follows: (1) tap the Rations button; (2) a new window opens with different photographs of fruit, an Accept button, and a Cancel button; (3) tap once on the photo corresponding to the apple and tap three times on the photograph corresponding to the mandarin; (4) tap the Accept button; (5) the app returns to the previous window but the box now has, instead of the 0 value, the corresponding number of standard rations for the fruit selected with the photographs, in this example, a value of 2.5 (1 × 1 standard ration + 3 × 0.5 standard ration); (6) tap the Next button to access the next food group and proceed as before; (7) if an error occurs, the participant can tap the Cancel button instead of Accept in step 4, starting the process over again (Figure 1).The use of active images (accompanied by explanatory text and three reference objects of known/predictable size for the students [fiducial markers]) is the only modification of e-12HR regarding the previous version (known as e-Epidemiology).However, this single, apparently simple, modification to the app is actually an important evolution over the previous version.In fact, the inclusion of active images was designed with a double purpose: on the one hand, to facilitate completion of e-12HR (by tapping the images instead of directly introducing the number of standard servings consumed); and on the other to assist with estimating the quantity consumed (this new version of the app directly shows 2-4 possible options for serving sizes).
After completing the daily questionnaire with e-12HR, the information is automatically saved and sent, via 3G/4G/Wi-Fi, to the e-mail address of the research administrator (entered when first accessing the app).Once the questionnaire is completed and sent, the participant cannot change their responses or access the app until the following day.
The consumption record of the selected food groups on the app was performed for 28 consecutive days.The time interval selected is similar to other comparison/validation studies [8,12,[32][33][34].
The questionnaire and the size of the rations used in e-12HR are based on a semiquantitative FFQ previously validated for the population of Spain [35].

Completing the Four Estimated Dietary Records
During the 28-day period that e-12HR was in use for each participant, four estimated DRs (on paper) were scheduled on randomly assigned, non-consecutive days [9,32]: three days during the weekdays and one weekend day [9,12,13,32].The choice of between three and seven DRs is normally considered sufficient to evaluate food group intake [9,36].Four estimated DRs were chosen instead of weighed DRs for logistical reasons [9,12].In the daily life of the participants that made up the sample (university students who spend a large part of their days outside the home at their center of study), weighing food is not feasible and represents a great workload when compared with estimating servings consumed.
Each participant, during the first interview, received an explanation of how to use the estimated DRs and how to estimate the serving size consumed [12,13], using a pamphlet with a series of 2-4 color photographs [10, 13,14,27] (one series for each food group).To assist with estimating serving sizes, each photograph was accompanied by explanatory text and three reference objects of known/predictable size for the students [30,31] (fiducial markers): a commonly used pencil, pen, and a marker.
The DRs used were based on a DR previously validated for another European country [13], but structured according to the typical Spanish diet (breakfast, lunch, an afternoon snack, and dinner), and pre-codified with a column that included the same 10 food groups selected for the e-12HR.The serving sizes were based on a semiquantitative FFQ previously validated for the Spanish population [35].
Participants were told that they must record the consumption data on a separate page for each day [7], and immediately after consuming the food [7,13].

Second Interview: Completing the Semiquantitative Food Frequency Questionnaire
At the end of the e-12HR data collection period, each participant was scheduled for a second personal interview at their convenience.In this interview, the participant was required to fill out a structured, semiquantitative FFQ (on paper) that included the same 10 food groups selected for the e-12HR.The same research team member who performed the first interview then explained to each participant, in this second interview, the process for completing the semiquantitative FFQ, and provided them with an explanatory pamphlet to estimate what was considered a standard serving for each food group.This pamphlet contained a photograph of a standard serving for each food group along with explanatory text and three reference objects of a known/predictable size for students [30,31] (fiducial markers): a commonly used pencil, pen, and marker.The time period considered by the FFQ corresponded to the 28 days of the app.All participants completed the semiquantitative FFQ within the first week of finishing the e-12HR app with the exception of two participants, who completed the FFQ 8 and 11 days later.
The semiquantitative FFQ, as well as standard serving sizes, was based on a semiquantitative FFQ previously validated for the Spanish population [35].
Finally, in the second personal interview, participants were asked how much time, on average, was needed to complete the daily questionnaire on the app.Participants could choose between various options.Of the total participants, 11% (10/87) selected the option less than 1 minute per day; 36% (31/87) selected the option approximately 1 minute per day; 28% (24/87) chose approximately 2 minutes per day; 17% (15/87) chose approximately 3 minutes per day; 7% (6/87) chose approximately 4 minutes per day; and 1% (1/87) chose the 5 minutes per day or more option.Almost half of the participants, 47% (41/87) indicated that the task took 1 minute or less per day to complete and 75% (65/87) stated that it took 2 minutes or less.For this reason, the research team considers that the time necessary to complete the app is, normally, 2 minutes per day or less.

Legal Considerations
The study was carried out according to the rules established by the Declaration of Helsinki and the Law on Biomedical Research [37].
All of the personal information collected in this study was anonymized in accordance with current Spanish legislation [38].To achieve this, each participant was assigned a personal alphanumeric code that they had to enter into the e-12HR app (only when first accessing the app) and include on the different paper questionnaires that were provided: the initial questionnaire (personal information), on the four estimated DRs, and on the semiquantitative FFQ.The personal alphanumeric code was used to match all of the data pertaining to the participant while at the same time respecting their anonymity.

Data Conversion
Using the e-12HR app, each participant recorded the number of standard serving sizes consumed daily for each food group throughout the 28-day study period.With the four estimated DRs, each participant collected the number of standard serving sizes consumed daily for each food group on four different days throughout the 28-day monitoring period.On the semiquantitative FFQ, each participant selected the number of standard serving sizes habitually consumed for each food group throughout the 28-day monitoring period.
For each participant, the data from the e-12HR app, the four DRs and the FFQ had to be expressed in the same categories of habitual consumption to make comparisons: Less than once a week; Once or twice a week, 3-4 times a week, 5-6 times a week; Once or twice a day, and 3 or more times a day.On the FFQ, these different options for habitual consumption were already available for the participants to choose from and, as such, the FFQ data was not modified.Regarding the e-12HR app, the data needed to be transformed.As an example, one participant registered an average daily consumption of 0.52 standard servings of legumes over 28 days using the app.This average consumption represents 3.64 standard servings per week (0.52 × 7 = 3.64), which would be classified as 3-4 times per week [25].As for the four DRs, the information they contained also needed to be converted [9].As an example, one participant recorded consuming 0, 0.3, and 1 standard piece of fruit on the DRs during the weekdays and 1.5 standard pieces of fruit on the DR completed at the weekend.This consumption represents an average daily consumption during weekdays of: (0 + 0.3 + 1)/3 = 0.43 standard pieces.As for weekly consumption, the conversion was as follows: (0.43 × 5 weekdays) + (1.5 × 2 weekend days) = 2.17 + 3 = 5.17 standard pieces, which would then be classified as 5-6 times per week.
To enable making comparisons, the three tools registered the consumption of the same food groups, used the same standard servings as a reference and the intake record corresponded to the same time period, to avoid possible variations in the specific diets during different periods [20,32,39,40].

Statistical Analysis
In this study, when comparing e-12HR with the FFQ and the four DRs for each of the selected food groups, the association between the categories of habitual consumption was evaluated using the Spearman correlation coefficient (SCC) whereas the degree of agreement between the categories of habitual consumption was evaluated using cross-classification analysis and the weighted kappa index [1,41].For the cross-classification analysis, the percentage of participants classified in the same group was labeled exact agreement; in the same category or adjacent categories, exact agreement + adjacent; or in opposite categories, extreme disagreement, using different methods.For weighted kappa, partial values were assigned using the statistical program Stata: from 1.00 for an exact agreement to 0.00 for extreme disagreement.
The statistical analysis was performed utilizing STATA MP 13.1 (Stata Corp LP, College Station, Texas, USA), and a P value < .05 was considered statistically significant [42].

Overview
Of the 95 participants who signed the informed consent, 8 did not complete the study.Results of these individuals were not included in later statistical analyses.Participants who did not complete the study were those who performed the task fewer than 22 days, did not complete the FFQ and did not complete the four DRs.
The average age of participants was 19.2 years old; 64% (56/87) were women, and 36% were men (31/87), and 67% (58/87) were medical students and 33% (29/87) were pharmacy students (Table 1).No statistically significant differences in the variables studied were found among participants who completed the study and those who did not.

12-Hour Dietary Recall Versus Food Frequency Questionnaire
For all food groups: the average SCC was .70 (per food group, from .50

12-Hour Dietary Recall Versus the Four Dietary Records
For all food groups: the average SCC was 0.63 (per food group from 0.46 [legumes] to 0.83 [fruit]; Table 2).Cross-classification analysis showed that the average percentage of individuals classified in the exact agreement category was 47.1% (per food group, from 31.0%[chicken/turkey] to 66.7% [beer]); exact agreement + adjacent was 89.2% (per food group, from 83.9% [soft drinks] to 95.4% [legumes]; Table 3); and no participants (0%) were classified in the category of extreme disagreement.The average weighted kappa was 0.47 (per food group, from 0.26 [fish] to 0.72 [fruit]; Table 4).

Overview
Current-day recall is a modified 24-hour recall focused on a series of food groups and completed at the end of every day during the monitoring period.This method has been designed to classify individuals according to categories of habitual consumption of selected food groups and is not intended to be used to determine total food consumption for an individual [25].This study is the first time that current-day recall, based on the e-12HR app, has been compared with two different reference models, one long-term (the FFQ) and the other short-term (four DRs) to determine the utility of this new method as a tool for estimating the usual dietary intake of a series of food groups.

Reference Methods
Evaluating the true validity of a method requires measuring, with a high degree of accuracy, the habitual diet of free-living individuals during a prolonged period of time, which is not feasible [1].As a result, the researchers of this study have evaluated the relative validity of the method by comparing it with an alternative method of dietary assessment, with its own limitations [1].Given that none of the comparison methods are perfect [5,8,39,43], as all are subjective, it is of crucial importance for their errors to be as independent as possible to avoid falsely attributing validity to the method in question [5,6,8,16,20,34,44].For this reason, the research team considered the FFQ and DRs to be possible reference methods and not 24-hour recalls (current-day recall is a modified 24-hour recall).As neither the FFQ nor the DRs can be considered definitive reference methods, the research team selected both methods for this validation study.Aware that the quantity of work for participants could be excessive, a semiquantitative FFQ was selected (to be completed at the end of the e-12HR monitoring period) and four DRs (estimated).

12-Hour Dietary Recall Versus the Food Frequency Questionnaire
For all food groups: the average SCC was 0.70 (in 10/10 food groups SCC≥0.50 [1,32]).Cross-classification analysis showed that the average percentage of individuals classified in the category of exact agreement was 51.5% (in 5/10 food groups ≥50% [1]); exact agreement + adjacent was 91.8% (10/10 food groups ≥75% [32]); and no participants (0%) were classified in the category of extreme disagreement [1].The average weighted kappa was .51(in 8/10 food groups κ≥0.41 [1]).These values indicate good agreement between the two methods [1,32]).Values obtained were very similar to those from previous studies with the older version of the e-12HR app, which did not use photographs to facilitate estimation of servings consumed [45].

12-Hour Dietary Recall Versus the Four Dietary Records
For all food groups: the average SCC was 0.63 (in 8/10 food groups SCC≥0.50 [1,32]).Cross-classification analysis showed that the average percentage of individuals classified in the category of exact agreement was 47.1% (in 4/10 food groups ≥50% [1]); exact agreement + adjacent was 89.2% (10/10 food groups ≥75% [32]); and no participants (0%) were classified in the extreme disagreement category [1].The average weighted kappa was 0.47 (in 6/10 food groups κ≥0.41 [1]).These values indicate good agreement between the two methods [1,32]).This is the first time that the e-12HR app has been compared with the DRs and as such there are no prior results for reference.
It is important to note that the cross-classification analysis and k depend on the number of categories used [1].With the goal of reducing this dependence when evaluating the degree of agreement between different methods, the six original categories could have been reorganized into three [1,8,25], four [32,33] or five [46,47], as other authors have done.Notwithstanding, this research team preferred to maintain six categories for the statistical analysis [45] as a greater number of categories of habitual consumption provides compact information on the ability of methods to assign individuals according to agreement with the distribution of dietary intake [46].Comparison criteria applied to this study were also considered by Masson et al [1] and Forster et al [32].However, considering that these authors only used three and four categories of habitual consumption, respectively, the demands of this study are much more restrictive.In this study, the classification of the exact agreement categories suffered especially, whereas the criteria used by Mason et al (exact agreement ≥50%) was defined by three categories versus the six considered here.
The results demonstrate good agreement between e-12HR and both reference methods (FFQ and DRs).Nevertheless, certain disagreement was observed with the app.Regarding the FFQ: the average cross-classification analysis showed that 8.2% of participants were classified at a distance of 2-4 categories.As for the DRs: the average cross-classification analysis showed that 10.8% of participants were classified at a distance of 2-4 categories.The three methods (e-12HR, FFQ, and DRs) are all based on self-administered and anonymized questionnaires and use the same color photographs for directly estimating servings.Because these questionnaires were both self-administered and anonymized (with the use of alphanumeric codes), they enabled researchers to avoid information biases, such as obsequiousness bias and researcher bias in all three methods.Using the same photographs also favors the same precision in the three methods when estimating servings.In this sense, each participant serves as their own control, thereby minimizing differences when considering servings consumed.In any case, consumption frequency seems to have a greater impact on dietary intake than on serving size [5,9].However, differences between the three methods are factors that could potentially contribute to the discrepancies observed.The fundamental differences between the methods are centered on both the regularity in collecting data on dietary intake and the format used in the questionnaires.

Regularity in Collecting Data on Dietary Intake
With DRs, the collection of data was performed after consuming each food group throughout the four days selected; with the e-12HR app, data collection takes place at the end of each day during the 28-day monitoring period; in the FFQ, data was collected at the end of the monitoring period.These differences in regularity mean that the accuracy of the information depends on both the memory of the participant and the daily variation in dietary intake among free-living individuals.
With DRs, dependance on memory is not an issue [12]; the e-12HR app is short-term memory dependent; while FFQs depend on long-term memory.
The e-12HR does not interfere with daily variation as it is completed every day; however, an effect is seen on the FFQ, with only one point of data collected, and the DRs, where data is collected sporadically (only 4/28 days during the monitoring period).

Format Used in Questionnaires
The app is digital and both the FFQ and DRs are completed on paper.Paper formats are typically associated with errors such as unanswered questions, questions with multiple responses [10] (FFQ), and not registering the quantity consumed for some of the different food groups selected (DRs) [48].In addition, the information on paper questionnaires must be converted subsequently to digital format for analysis, which increases both the workload and costs for the research team [17,40].Online FFQs and DRs, or even smartphone apps, offer direct solutions to these limitations [10, 13,20,[30][31][32]40,[49][50][51][52][53], by reducing paper waste and mailing costs, and removing the need for secure storage space and organization inherent with paper documents [50].Additionally, online administrative methods can be used to gain access to specific population groups that would otherwise be difficult to study due to geography, for example, as they can be used remotely [32].Despite the potential advantages of utilizing FFQs and DRs in digital format, in the end it was decided to use paper formats in this study.The research team took into account that evidence shows that data collected from smartphone apps and both Web-based FFQs and DRs are comparable with data from paper formats [7,14,16,27,29,[31][32][33][34]40,46,54].The team also considered the characteristics of this study and the potential disadvantages of developing FFQs and DRs in a digital format that could outweigh the possible benefits.In fact, in this study, the paper-based FFQ and the DRs were very short and simple (they only contain 10 food groups), and the sample population is made up of students at the Schools of Medicine and Pharmacy at the University of Seville, which was easily accessible for the research team.
The simplicity of the paper-based FFQ and DRs minimized possible errors, the amount of paper used, problems with storage space, and costs associated with data conversion.These costs were minimal when compared with the potential costs of developing an online or smartphone-based FFQ and DRs.
Easy access to the sample made it possible to complete the paper FFQ in person, without the need for researchers or participants to travel or pay mailing costs [25].

Strengths and Limitations
The strengths of this study include that the e-12HR is a tool that depends only on short-term memory (the app is completed at the end of each day), it does not interfere with variability of dietary intake in daily life (the app is completed daily).In addition, it has a digital format (young people and adolescents have shown their preference for methods that use digital technology versus traditional methods [31,53]-improving motivation and completion rates [48]).These characteristics support greater accuracy in assigning the category of habitual consumption in those cases where the ranking assigned by current-day recall is different from that assigned by reference methods.Also, with the e-12HR app, data collection is performed digitally, eliminating the need for investigators to enter the data manually; it is a self-reporting tool, not requiring interviewers; it is both simple and intuitive to use, with photographs to assist with estimating servings consumed; and overall research costs are greatly reduced.

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Limitations of this study include that the sample used was extremely educated, which is a convenient sample and not representative of the youth population on the national level.Another limitation derives from the need to have a smartphone with an Android operating system.Access to these technologies is not universal and could exclude those students with less purchasing power [25].Also, even though two different reference methods were used for the e-12HR app, it is important to note that the high degree of association and agreement between the data collected when comparing different methods does not indicate that current-day recall is exact, as there is no true measurement of dietary intake [5,8,39,43].Ideally, validation studies should include the use of nutritional biomarkers, but currently there are few biomarkers for specific foods [12,43,44,55] and they cannot measure habitual intake [43].

Future Research
Future research will focus on the selection of other study samples, additional food groups, different monitoring periods for comparison, and with varying regularity for completing the app from daily, as in this study, to two days, three days, etc.

Conclusions
The good agreement between e-12HR and both reference methods, as illustrated by the results of various statistical analyses demonstrate the relative validity of current-day recall for determining categories of habitual intake for specific food groups, and even for those foods that are consumed infrequently.For large-scale epidemiological studies with samples of individuals who have grown up using new technologies and that do not require determining the complete diet, e-12HR can be a useful tool to replace other methods which are oftentimes longer, more expensive, and require a larger workload for both participants and researchers.Additionally, e-12HR can be a useful tool in a clinical context.Healthcare professionals can use the app with patients/users who are accustomed to new technologies.Individual information obtained through the app could be used as a baseline for health education and promotion activities: specific activities for each patient/user focused on those specific food groups that require a change in consumption patterns.
[legumes] to .86 [beer]; Table2).Cross-classification analysis showed that the average percentage of individuals classified in the exact agreement category was 51.

Table 1 .
Characteristics of study participants.
a N/A: not applicable.

Table 3 .
Cross-classification analysis derived from electronic 12-hour dietary recall (e-12HR) versus the food frequency questionnaire (FFQ) and from e-12HR versus the four dietary records (DRs).Exact agreement: % of cases cross-classified into the same category.Exact agreement + adjacent: % of cases cross-classified into the same or adjacent category.

Table 4 .
Weighted kappa derived from electronic 12-hour dietary recall (e-12HR) versus the food frequency questionnaire (FFQ) and from e-12HR versus the four dietary records (DRs).
a N/A: not applicable.