The health and environmental benefits of plant-based protein foods (PBP) are well documented. Indeed, PBP consumption has been associated with improved cardiovascular health(Reference Blanco Mejia, Messina and Li1,Reference Balakrishna, Bjørnerud and Bemanian2) , lower all-cause mortality(Reference Balakrishna, Bjørnerud and Bemanian2,Reference Naghshi, Sadeghi and Willett3) and a reduced environmental footprint compared to animal-based protein foods(Reference Poore and Nemecek4). As a result, many food guides and dietary recommendations worldwide are now promoting PBP consumption(Reference James-Martin, Baird and Hendrie5). For instance, the latest version of Canada’s food guide (CFG), published in 2019, recommends choosing PBP more often as an alternative to animal protein(6) and the EAT-Lancet Commission’s proposed diet emphasises the consumption of plant-based foods(Reference Willett, Rockström and Loken7).
While adequate protein consumption is essential for healthy ageing, intakes tend to decrease with age and may fall below the recommendations(Reference Auclair and Burgos8). For instance, according to the 2015 Canadian Community Health Survey, nearly 10 % of women aged 71 years and older in Canada had protein intakes below the Estimated Average Requirement, which is 0.66 g/kg per d(Reference Auclair and Burgos8). Although several advantages of PBP over animal proteins have been raised by older adults, including better digestibility and affordability(Reference Drolet-Labelle, Laurin and Bédard9), the vast majority of protein foods consumed by Canadian older adults in 2015 were from animal sources(Reference Brassard and Chevalier10). Greater inclusion of PBP in older adults’ diets could therefore contribute to this age group’s overall protein intake while adhering to current recommendations and promoting health. We recently conducted a study in the province of Quebec (Canada) in which we identified older adults’ barriers to introducing PBP, such as lack of knowledge about how to prepare these foods(Reference Drolet-Labelle, Laurin and Bédard9), which will help inform future interventions to increase PBP consumption in the older adult population. To accurately assess the impact of such interventions, a questionnaire specifically designed for older adults that rigorously and accurately assesses PBP consumption is needed. To our knowledge, no such tool exists yet.
Dietary assessment in the older adult population presents several difficulties. Challenges with short-term memory tasks, for instance, can make 24-h recalls less suitable for this age group(Reference De Vries, De Groot and Van Staveren11). In addition, 24-h recalls often require significant technical or human resources and multiple administrations to better reflect habitual diet(12). Longer questionnaires, such as diet histories or food recalls, may also be challenging for older adults, as they require more time and effort(12). Therefore, shorter questionnaires may be more appropriate for older adults as they reduce the fatigue and burden associated with completion(12,Reference Volkert and Schrader13) . Although food-frequency questionnaires (FFQ) also rely on memory, several studies have shown that they are appropriate tools for assessing older adults’ food and nutrient consumption and for ranking older adults according to their intake(Reference Eysteinsdottir, Thorsdottir and Gunnarsdottir14,Reference Yaghi, Boulos and Baddoura15) . Therefore, using a brief FFQ designed to specifically assess PBP intake may be appropriate for this population, especially since our focus is not on the total diet(16).
Cognitive testing is a method for improving and adapting questionnaires by allowing respondents to verbalise their cognitive processes. For self-administered questionnaires, a pretesting step using probes and think aloud approaches can help identify problematic questions and understand how instructions and questions are interpreted(Reference Miller17,Reference Collins18) . Pretesting and refining a questionnaire based on feedback can also help improve the questionnaire to reduce the cognitive load associated with its completion(Reference Townsend, Ganthavorn and Neelon19). Previous studies have demonstrated the effectiveness of cognitive testing in improving the clarity and comprehension of FFQ or other types of questionnaires(Reference Hutchinson, Williams and Westaway20–Reference Subar, Thompson and Smith22). The current study aimed to develop a web-based FFQ that specifically assesses the level of consumption of PBP in the older adult population from the province of Quebec, Canada. This paper describes the development process, the face and content validity evaluation by a panel of experts, and the cognitive testing conducted to assess whether the questions were clear and well understood by the target population.
Methods
Development of the questionnaire
An existing 136-item self-administered FFQ validated among adults from the province of Quebec, Canada(Reference Labonté, Cyr and Baril-Gravel23), was used to develop our web-based PBP-FFQ. The questionnaire was adapted by a graduate student in nutrition (VDL), and two researchers with expertise in questionnaire development (AB and SD). From this 136-item FFQ, the development team identified items related to PBP products and modified or added items to ensure that the questionnaire adequately represented the PBP products currently available in grocery stores in the Quebec market, particularly processed products, which were less captured in the original questionnaire. To properly estimate the amount of PBP consumed, foods with similar protein content were grouped in the same questions. This resulted in a twenty-six-item PBP-FFQ.
The frequency of consumption of individual food items or groups of foods, in terms of day, week or month, remained the same as in the initial questionnaire (i.e. frequency of consumption in the past 30 d: never, once a month, 2–3 times per month, 1–2 times per week, 3–4 times per week, 5–6 times per week, 1 time per d and 2 times per d or more). Existing images from the 136-item FFQ were used to illustrate four different portion sizes, embedded within images of negative and positive signs to denote smaller and larger portion sizes, respectively. Figure 1 shows the visual of one of the questions. The images represented the exact food/food group questioned or a similar food item/food group, depending on the images available. All products were unbranded.
Question example (translated from the original French questionnaire).
Evaluation by an expert panel
An expert panel consisting of four researchers (SL, VD, LV and DL) with diverse conceptual and methodological expertise (PBP, questionnaire development and validation, cognitive testing and epidemiology), and with knowledge of our target population (older adults), evaluated the face and content validity of our initial questionnaire, to assess the extent to which the questions provided a good measure of PBP consumption, and whether the measures were well constructed and easy to understand. The development team presented the PBP-FFQ to the expert panel to obtain their general thoughts and comments. The revised questionnaire was then submitted to the experts for a more in-depth evaluation. Specifically, each expert was asked to evaluate whether the questions adequately and comprehensively measured PBP consumption, as well as the relevance and clarity of each question on a scale from 1 to 4. A score of 1 meant that the item was not relevant or not clear; 2, that it needed a major revision; 3, that it needed a minor revision and 4, that it was perfectly relevant or clear. To determine the content validity index, we calculated for each question the percentage of experts who rated the item’s relevance as 3 or 4, as suggested by Di Iorio (2005)(Reference Di Iorio24). A content validity index below 90 % suggests that the question should be modified or deleted(Reference Di Iorio24). The experts were also asked to provide their general comments on the instructions, answer options, question order and whether some questions should be added or removed.
Cognitive testing interviews
Participants
Recruitment of participants began in June 2022. Newsletters featuring the project recruitment advertisements were sent to several older adults and retirees organisations and associations in the province of Quebec, Canada, as well as to participants from a study conducted by our team who agreed to be recontacted for another study(Reference Drolet-Labelle, Laurin and Bédard9). Inclusion criteria were to (1) be 65 years of age or over, (2) reside in the province of Quebec, (3) live at home (i.e. not in a retirement home or long-term care) and (4) be able to read and understand French. Purposive sampling was used to maximise variation in sociodemographic characteristics, including gender, age, education level and PBP consumption, which ensured that a greater diversity of cognitive processes would be captured(Reference Miller17). Specifically, we sought to recruit a sample that included as many men as women, with a well-balanced number in each age group (65–69 years, 70–74 years, 75–79 years and 80 years and older), and with at least one-third of the sample having not completed post-secondary education, as a proxy for lower literacy levels(25). In addition, we sought to recruit a greater proportion of PBP regular consumers (PBP consumption in main meals ≥ 2 times /week) than PBP non-regular consumers (PBP consumption in main meals < 2 times/week), to obtain greater feedback on the consumption frequency options, the suggested serving sizes and the images used to represent food items/food groups. Participants did not receive compensation but were eligible to win one of the two $25 gift cards. The project was approved by the ethics committee of Université Laval (#2022-153/23-05-2022).
Procedure
Cognitive testing interviews were conducted in three phases from July to October 2022, which allowed for the refinement of our PBP-FFQ (see Fig. 2). Each phase of cognitive testing involved 6–7 participants. The interviews were conducted in French, and an observer was present at each interview to take notes and to discuss the participants’ behaviour and responses with the interviewer afterwards. Participants had the choice between an online Zoom and face-to-face interview at the research centre. Before starting the interview, participants gave verbal consent to the project and the video recording. Interviews were not transcribed, but recordings were available if needed.
Development process.
After consent was obtained, we shared a screen with a PowerPoint presentation explaining the main purpose of the project, the concept of cognitive testing and the think-aloud approach(Reference Collins18) using an example. The PBP-FFQ instructions were then given to the participant, followed by the PBP-FFQ questions. Each slide of the presentation covered one food item/food group, and the visual was representative of the future web-based self-administered questionnaire. For each food item/food group, participants were first asked about the frequency of consumption in the past 30 d and then about the serving size usually consumed. If participants selected ‘never’, they were not subsequently asked to report a serving size. Participants responded aloud and were encouraged to verbalise their thoughts by the interviewer who asked probes(Reference Collins18) to elicit more information, such as: ‘How did you reach this answer? Are you confident of your answer? Did you have any difficulty answering this question?’. Finally, at the end of the interview, participants were asked if they consumed PBP that were not included in the PBP-FFQ to confirm its exhaustiveness, as well as general questions about the ease of completing the questionnaire, difficulties encountered, redundancy of questions and household situation.
Analyses
After each interview, the interviewer and the observer met to discuss the participant’s challenges and identify potential changes that could be made to the questionnaire to address the issues identified. At the end of each phase, elements of the questionnaire and instructions were modified based on participants’ feedback and discussions with the development team. The modified elements were then carefully monitored in subsequent phases to assess improvements in understanding. When clarification was needed, recordings were reviewed to ensure an accurate understanding of the difficulties encountered.
Results
Experts panel
All questions were deemed relevant, with a score of 3 or 4 given by all experts. The content validity index score for each question was therefore 100 %, which is higher than the recommended 90 %(Reference Di Iorio24). All the experts considered the questionnaire to be exhaustive and did not suggest adding or removing any questions. However, the experts suggested some minor changes to the order, presentation and wording of the questions, to make the questionnaire easier to understand. Instructions were also slightly reformulated. Finally, to confirm if the reported intakes were representative of usual intakes, the experts recommended adding a question at the end of the PBP-FFQ to document whether a situation or event has significantly affected the participant’s eating habits in the past month: ‘In the past 30 d, did you have to make any changes to your usual diet for any reason (e.g. illness, travel, etc.)? (yes/no; if yes please specify)’.
Cognitive testing
The three phases of cognitive testing conducted, for which we recruited a total of twenty participants (seven participants for phase 1; seven participants for phase 2; and six participants for phase 3), allowed for continuous improvement of the questionnaire. Only one of the twenty interviews was conducted in person and the others were conducted online. Participants’ characteristics are presented in Table 1. After the third phase of interviews, only few minor modifications were suggested by participants. Consequently, a fourth phase was not required. The issues raised during the three phases of cognitive testing were grouped into three themes, which are described below. Table 2 presents in more detail the changes made to the questionnaire.
Sociodemographic characteristics
PBP, plant-based protein foods.
* CEGEP (Collège d’enseignement général et professionnel) offers pre-university and technical programmes and is unique to the province of Quebec.
† PBP non-regular consumers were defined as participants who consumed PBP less than twice a week at main meals, and PBP regular consumers as participants who consumed PBP two times or more per week at main meals.
Summary of the issues and modifications
PBP, plant-based protein foods.
Lack of clarity in the instructions
Some issues were raised regarding the clarity of the instructions. First, there was some confusion about the overall definition of PBP, which could lead to misinterpretation throughout the questionnaire. To address this ambiguity, a list of foods included and excluded from the PBP definition was added at the beginning of the questionnaire (see example 1 in Table 2). Second, some participants found it difficult to precisely report consumption frequency and serving size, especially because of the close-ended, multiple-choice style response options. Many wanted to be precise in their answers, leading to more laborious response processes. Therefore, at the beginning of the questionnaire, we included examples of responses to FFQ-PBP questions that addressed these issues (see example 2 in Table 2). Nevertheless, we asked participants in phase 3 which response option style they preferred, and closed response choices were indeed preferred to open response options. Finally, given the confusion between the number of times a food was purchased and the number of times it was consumed, a sentence was added to the instructions after phase 3 stating that the questions were about frequency of consumption, not frequency of purchase. This sentence will be added to each question in the final web questionnaire.
Wording and content of the questions
The cognitive testing revealed issues related specifically to the questions. First, participants were unsure about the types of foods that needed to be reported in some questions. We therefore added definitions and exclusions to these questions, making it easier to identify which foods should be included in their answers (see examples 3 and 4 in Table 2). Second, some questions were added, combined or split following participants’ feedback about incorrect groupings or missing foods (see examples 5, 6 and 7 in Table 2). Third, the order of some questions was changed to make the questionnaire more coherent, consistent and easier to complete (see example 8 in Table 2). Fourth, for processed products that have homemade and commercial versions, the word ‘commercial’ (in French: du commerce) was added to indicate the origin of the product and to reduce confusion (see example 9 in Table 2). Finally, the wording of some questions was changed to shorten the questions and to make them more readable for participants (see example 10 in Table 2).
Issues related to the serving size
Several changes have been made to the serving size sub-questions. First, to improve the readability and simplify the visual, we removed the amounts in ounces and millilitres, leaving only cups, teaspoons/tablespoons and grams (see example 11 in Table 2) and we confirmed with participants in subsequent phases that they were comfortable with this change. Second, the ‘more’ and ‘less’ options, which were initially quite small, were enlarged to improve their visibility (see example 12 in Table 2). It should be noted that serving size options were considered, for the most part, adequate. Only two questions required the modification of the serving size options with the addition of an intermediate option. Finally, although they were considered useful, the quality and representativeness of the images of certain food items/food groups were considered sub-optimal (see example 13 in Table 2), highlighting the need to create new images for some items.
Other comments and observations
When participants were asked at the end of the interview if they had experienced any difficulty in remembering what they had eaten in the past month, the vast majority reported no difficulty. Nonetheless, their answers still need to be validated. However, difficulties were raised regarding unfamiliarity with certain foods, particularly processed foods, which led to confusion among participants as to whether they had consumed the food in question. The addition of definitions resulted in less confusion and helped participants confirm that they had not consumed the food in question, and thus the frequency choice ‘never’ was selected. In addition, when asked at the end of the interview whether they had consumed any PBP other than those listed in the questionnaire, most participants responded that the questionnaire was exhaustive, but some mentioned non-PBP, reinforcing the need for the definition of PBP in the instructions (see example 1 in Table 2). We also decided to keep the question about missing PBP in the final PBP-FFQ, to ensure that all PBP are captured, including recently available products on the market that were not covered in the survey.
Final version of the questionnaire
The final version of the PBP-FFQ included twenty-eight questions, in addition to the questions about missing PBP and about situations or events that could have influenced the participant’s eating habits in the past month and was presented to and approved by the expert panel. The final questions are shown in Table 3.
Food items/food groups included in the final PBP-FFQ
PBP, plant-based protein foods.
Discussion
This study is the first to detail the development process of a FFQ focused on PBP and tailored to the older adult population. The three phases of cognitive testing conducted with adults over 65 years old in the province of Quebec resulted in a final PBP-FFQ consisting of twenty-eight questions that may support a better assessment of the amount and frequency of PBP consumed by older adults. Feedback from our expert panel suggested that the questionnaire was comprehensive and relevant and allowed us to improve the clarity of the questions asked. Cognitive testing with our target population further enhanced the comprehensiveness of the questionnaire, confirmed its exhaustiveness and played a key role in improving the FFQ-PBP. Indeed, feedback from participants allowed us to make progressive changes that would otherwise have led to misreporting of food consumption, which could have jeopardised the accuracy of the future questionnaire. By reporting aloud the difficulties they encountered, participants highlighted which elements of the instructions and questions were ambiguous, allowing us to clarify them. Using probes also helped us to gain a deeper understanding of participants’ responses and to identify questions that had been misunderstood, unbeknownst to the participants. These findings highlight the value of cognitive testing in identifying small changes that can have a major impact on questionnaire comprehension and accuracy. Overall, the PBP-FFQ was well understood by older adults. Most changes were minor and were tested in at least one phase following their modification. The issues raised were mainly related to comprehension, for example, instructions, wording, content of the question and serving size sub-questions. Most participants also indicated that the questionnaire was not cognitively demanding in terms of their ability to recall information or the length of the questionnaire. However, whether the questionnaire can adequately report the correct amount and frequency of PBP consumed has yet to be validated.
Many of our modifications were similar to other studies that used cognitive testing. For example, Hutchison et al. also raised the issue of lack of clarity as to which foods to include and exclude in each question in their screener assessing adults’ alignment with the 2019 CFG recommendations. To address this issue, they added details and changed the sequence of some questions, which improved the clarity of their questionnaire(Reference Hutchinson, Williams and Westaway20). In the current PBP-FFQ, the definitions and exclusions proved to be very effective and allowed participants to quickly know whether the item had been consumed or not, especially for ambiguous questions such as the one about nutritional yeast shown in Table 2. Similar to our study, Subar et al., who conducted cognitive testing with older adults, found that open-ended response choices in FFQ were not ideal for self-administered questionnaires and could lead to errors, compared to closed-ended choices(Reference Subar, Thompson and Smith22). This suggests that closed-ended response choices are likely to be preferred in this population. Other authors have also shown that cognitive testing can be useful in identifying unfamiliar concepts/words for participants(Reference Spark and Willis21). In our case, some PBP or foods derived from them were unknown to the participants, which justified the addition of definitions. However, our results contrast with a previous study in which older adults reported lower serving sizes than younger individuals, suggesting that portion size adjustments are needed in FFQ(Reference Shahar, Fraser and Shai26). Indeed, although our PBP-FFQ was developed based on a questionnaire validated in the adult population, we did not have to adjust the serving sizes downwards.
This project has several strengths. Our approach used both an expert panel and cognitive testing with our target population, resulting in a more thorough improvement of our questionnaire. We used the think aloud and probing approaches, which allowed for an in-depth study of participants’ thinking processes. Also, the baseline FFQ had been previously validated in the adult population of Quebec, and our sample was diverse in terms of sociodemographic characteristics which ensured that we captured a diversity of cognitive processes and literacy levels.
Our project also has some limitations. First, some of the foods in our questionnaire, mostly processed foods (i.e. meatless chicken, meatless nuggets, etc.), were not consumed by any of the participants in the cognitive testing. As a result, we were unable to determine if the serving sizes were appropriate for these foods. Nevertheless, these serving sizes were inspired by those of comparable foods already included in the PBP-FFQ, which may suggest that they are adequate. Second, the foods included in this questionnaire were representative of what was on the market in 2022, but the availability of PBP products is constantly evolving, which may result in missing foods and consequently in an underestimation of PBP intakes. However, adding the question inviting participants to report foods not included in the questionnaire could help in this regard, allowing us to adjust our questionnaire over time. Third, it should be noted that completing this type of questionnaire requires memory skills(12). As we conducted our cognitive trials among individuals with no apparent cognitive impairment, the generalisability of our results and use of this questionnaire with individuals with cognitive decline may be limited. A different type of dietary assessment may be necessary for this population. Our sample also consisted of volunteers who were responsible for meal planning, potentially introducing a bias as they might have a heightened interest in food and nutrition. Results may differ in other population subgroups. Additionally, the generalisability of our findings may be limited to individuals within the province of Quebec, as the questionnaire is in French and the availability of PBP in grocery stores may differ elsewhere. Fourth, we made some minor changes to the questionnaire after the final round of testing, which we were unable to evaluate (i.e. more representative images, improved serving sizes, splitting of one question and other minor changes in question wording and exclusions). However, these changes were suggestions from participants to clarify some minor remaining issues and did not represent significant changes to the questions.
Implication for research and practice
This PBP-FFQ represents a potential tool for assessing PBP consumption among older adults and, ultimately, for evaluating the effectiveness of an intervention. Compared to a comprehensive FFQ assessing total dietary intake, its concise format makes it easier for older adults to complete. In addition, the cognitive testing we conducted improved the understanding of the tool among this population, further increasing the reliability of the data collected. This step was particularly relevant considering their lack of familiarity with PBP(Reference Drolet-Labelle, Laurin and Bédard9) and the decline in protein consumption with age(Reference Auclair and Burgos8). Our PBP-FFQ can also help researchers, policymakers and healthcare providers better understand the current state of PBP consumption among older adults and help develop targeted interventions to improve consumption. Finally, as we are still in the development phase, further validation steps, including comparison of our final PBP-FFQ to a food record and assessment of its reproducibility, will be necessary to complete the validation process.
Conclusion
A comprehensive twenty-eight-item PBP-FFQ was developed through a rigorous process that included collaboration with an expert panel and cognitive testing with older adults. A validation study assessing the reliability and validity of our PBP-FFQ will be conducted as the next step. The development of such a questionnaire will support rigorous evaluation and monitoring of the PBP consumption habits among older adults.
Acknowledgements
The authors would like to thank Laurie Miville-Deschênes for her contribution to the interviews and participants for their time.
Authorship
V.D-L., A.B. and S.D. developed the initial questionnaire. V.D-L. conducted the interviews with A.B. S.L., V.D., L.V. and D.L. formed our expert panel. V.D-L. drafted the manuscript and was supervised by S.D. All authors read, critically revised and approved the final manuscript.
Financial support
This work was supported by the Centre Nutrition, santé et société, Université Laval, which had no role in the design, analysis or writing of this article
Competing interests
None declared.
Ethics of human subject participation
This study was conducted according to the guidelines laid down in the Declaration of Helsinki, and all procedures involving research study participants were approved by the ethics committee of Université Laval (#2022-153/23-05-2022). Verbal informed consent was obtained from all subjects. Verbal consent was witnessed and formally recorded.
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