This study was a 5-week randomized controlled, within-subject crossover study, consisting of two 2-week intervention periods with a 1-week of washout in between (Figure 1). For each intervention period, participants were instructed to consume NVSFs (novel) or control staple foods (control) in mixed meals for breakfast, lunch, and dinner. The sequence of intervention for each participant was generated using a randomization software. For each participant, a total of three one-to-one interview sessions were conducted before the study commencement and after each intervention period. Continuous glucose monitoring was also employed during both intervention periods. Additionally, food diaries were provided for each intervention where participants were instructed to annotate the time at which each test meal was consumed during the day, and for any snacks which were consumed in between meals. Participants were also advised to consume the test meals within 15 min and to fast 2 to 3 h prior to consuming the test meals and after consumption to ensure accuracy of their postprandial glycemic responses. They were allowed to snack on foods of their choice after the fasting window, with the exception of anthocyanin-containing foods or supplements, which they were required to abstain from for at least 1 week before the study period. They were instructed to take a photograph of their empty food container after each meal and send it to a study coordinator to verify their compliance with the meal plan. This study was approved by the National Healthcare Group Domain Specific Review Board (Reference No. 2019/00952) and registered at ClinicalTrials.gov (NCT05399134). Participants gave written informed consent before enrolling into the study.

Twenty Chinese participants with T2D were enrolled into the study. Recruitment was conducted via poster advertisements displayed at the National University Hospital, Singapore, and through local newspaper. Participants initially approached study coordinators to express their interest through a phone call and/or email. Participants who met the recruitment criteria were eligible to attend a screening session conducted at the Department of Medicine, National University of Singapore. The recruitment criteria excluded participants who were smokers, those receiving prandial insulin therapy, individuals with unstable medical conditions, and those who had allergies to the test meals. Inclusion criteria included participants who were English-speaking, aged between 21 and 70 years old, and clinically diagnosed with T2D with a HbA1c of less than 10%. Three of the participants dropped out due to personal reasons, and one participant was excluded from analysis as the participant did not follow the meal sequences provided. The remaining 16 participants completed the study and were included for analysis. Figure 2 portrays the Consolidated Standards of Reporting Trials (CONSORT) diagram of the participants in the study.

Each staple food was served with standardized side dishes in mixed meals for breakfast, lunch, and dinner (Table 1). Microfluidic gel noodles were consumed for dinner every other day and were replaced with control beehoon (rice vermicelli) noodles for the other days throughout the 2-week novel intervention period. This was done with the aim of enhancing compliance with the microfluidic gel noodles, which were expected to be less palatable compared to the other two NVSFs. Chicken broth was also added to the microfluidic gel noodles to improve the overall meal’s palatability.

The jasmine white rice, fiber-fortified rice, beehoon noodles, and chicken and spinach side dishes were prepared by a food caterer licensed by the Singapore Food Agency (Creative Eateries Pte. Ltd.). Fiber-fortified rice was prepared by incorporating a novel fiber composition blend (5ibrePlus™, Alchemy Foodtech Pte. Ltd., Singapore) into uncooked white rice before cooking it with water. The quantity of fiber blend added was 20% of the mass of the uncooked rice. Soymilk reduced sugar (NutriSoy, Fraser and Neave Pte. Ltd., Singapore), extra virgin olive oil butter (SCS Dairy, DKSH Marketing Services Pte. Ltd., Singapore), and chicken broth (Swansons, Campbell Soup Company, New Jersey, United States) were purchased from a local supermarket (NTUC Fairprice Cooperative, Ltd., Singapore).

The anthocyanin-fortified bread, white bread, and microfluidic gel noodles were produced in a food processing facility at the Department of Food Science and Technology, National University of Singapore. Anthocyanin-fortified bread and white bread were prepared according to methods described by Sui, Zhang and Zhou (19) and Ou, Yu (20) (Supplementary material 1). Microfluidic gel noodles were produced following the techniques described by Lin, Yang (18) (Supplementary material 2). Microfluidic gel noodles are a novel food format produced via an extrusion process, where a soy protein isolate solution is encapsulated within a gel matrix formed by the interaction of sodium alginate and calcium chloride, resulting in noodle-like structures. Unlike commercial noodles, these gel-based noodles are engineered to promote satiety while eliciting a lower postprandial glycemic response.

Table 2 shows the nutritional compositions of each meal containing the staple foods. Nutritional compositions of the test meals were analyzed by an external laboratory (TÜV SÜD PSB Pte. Ltd., Singapore).

The interview sessions were conducted in a private room with an interviewer (the first author) and a note-taker (the third author). All authors had no prior relationships with the study participants. Interviews were conducted in English, audio recorded, and subsequently transcribed verbatim. Interview transcripts were qualitatively analyzed through an inductive approach. Initially, line-by-line coding was used to generate codes by closely examining the content of the transcripts. Codes that were related were then organized into sub-themes, and these sub-themes were further grouped into overarching themes by the first author. The themes were refined through consistent review and validation by the first, third, and sixth author before being finalized. Any discrepancies were discussed until a consensus was reached. NVivo (QSR International Pty Ltd., Melbourne, Victoria, Australia) was used for data management and organization.

A total of three interviews were conducted for each participant: (1) pre-intervention; (2) post-intervention (novel); and (3) post-intervention (control). The pre-intervention interview focused on the introduction to the NVSFs with the presentation of food samples. In contrast, the post-intervention interviews centered around gathering feedback on the staple foods, including participants’ thoughts on regular consumption considerations, cost considerations, any challenges faced, and their personal experiences with diabetes. The interview guide was co-developed by the third and sixth author with a key focus on understanding participant’s lived experiences with the foods in reference to Lim, Ting (16). A sample of the interview guide is shown in Supplementary material 3, Table S1. The qualitative data is reported following the Consolidated Criteria for Reporting Qualitative Studies (COREQ) guidelines.

Continuous glucose monitoring (CGM) was conducted during both 2-week intervention periods. Before the start of each intervention, a CGM device (FreeStyle Libre Pro, Abbott Diabetes Care Inc., Netherlands) was inserted at the back of the participant’s upper arm following instructions provided by the manufacturers. The CGM device was removed after the intervention period and scanned using a reader to retrieve the raw glucose readings recorded over the 2-week period. Subsequently, the 2-h postprandial glucose readings for the meals were extracted, based on the times of meal consumption reported by the participants in their food diaries. The incremental area under the curve (iAUC) over the 2-h postprandial period was then calculated. The iAUC quantifies the total rise in glucose concentration above the pre-meal (fasting) baseline, providing a measure of the net postprandial glycemic excursion attributable to each test meal.

Sample size calculation was based on a study conducted by Rieder, Knutsen (21), which reported a significant decrease in iAUC for white bread when fortified with 3.8 g of beta-glucan fiber from 165.8 ± 20.4 to 106.8 ± 13.9 mmol/L.min (mean ± SEM). Using a 0.05 significance level (α = 0.05) and a power of 0.8, at least 16 participants were required to observe a reduction in iAUC after staple food fortification.

The sample size for the qualitative aspect of the study was guided by the principle of saturation which describes a point at which further data collection would not yield additional insight (22). Based on studies by Hennink, Kaiser and Marconi (23) and Hennink and Kaiser (24), ‘meaning saturation’ which relates to a comprehensive understanding of issues raised in interviews, required 16 to 24 interviews. Based on this range and the sample size calculation above, a minimum of 16 participants were required for this study. To account for attrition, a total of 20 participants were recruited.

Postprandial glycemic responses were presented as 2-h iAUC. Data was checked for normality using the Shapiro–Wilk test before performing a paired t-test to analyze for any differences in 2-h iAUC values between the novel and control meals. Significance was defined as p-value < 0.05. Additionally, 95% confidence intervals (CI) were calculated for the mean differences between meals. Effect size was measured using Cohen’s d, calculated as the mean difference between the two groups divided by the pooled standard deviation. Cohen’s d values were interpreted as small (0.2), medium (0.5), or large (0.8). The difference in postprandial blood glucose concentrations from baseline over 2 h was also presented as a ‘change in glucose’ graph. GraphPad Prism Version 8.0.2 (GraphPad Software Inc., California, United States) was used to conduct the statistical tests. Values were presented as mean ± standard error of mean (SEM) unless otherwise stated.

A convergent parallel structure was utilized for this mixed methods study, where the qualitative and quantitative data were separately analyzed before they were merged for interpretation to allow for a cross-validated understanding of the study results for each of the NVSFs (25, 26). Both datasets were integrated together following a four-step approach by Skamagki, King (27) which encompasses (1) the creation of a joint display table; (2) linking activity; (3) establishing relationships; and (4) interpretation of data. Qualitative and quantitative datasets for each NVSF were merged using this approach to derive meaningful interpretations regarding the acceptance and feasibility of these NVSFs.

Twenty participants diagnosed with T2D were enrolled into the study. Of these participants, three dropped out due to personal reasons. One participant was excluded from analysis due to non-compliance while the remaining 16 participants completed the study and were included for analysis. These participants were also asked about the types of staple foods commonly consumed in their households. Majority of the participants reported more than one type of staple food typically being consumed in each household (i.e., bread, rice, and noodles). The baseline characteristics of the participants are shown in Table 3. The weight and HbA1c of participants across the study timepoints were also measured and presented in Supplementary material 4, Table S2, however there were no significant changes.

From the qualitative analysis of interviews, seven key themes were identified related to the acceptance of NVSFs: prior dietary choices as individuals with T2D; prior perceptions and expectations of NVSFs pre-tasting; visual first impressions of NVSFs; trade-off between sensory and health properties; price and willingness to pay; modification methods; and other socio-economic factors for regular consumption. A summary of themes, sub-themes, and their illustrative quotes are presented in Table 4 for participants’ initial perceptions of NVSFs and their dietary choices prior to the study, and Table 5 for their perceptions post-intervention.

The 2-h iAUC values, derived from CGM data, are presented in Figure 3. It summarizes the postprandial glycemic responses to each NVSF and its corresponding control. Figure 3A displays the iAUC values for the breakfast meal, showing that anthocyanin fortified bread (347.9 ± 44.5 mmol/L.min) and white bread (345.9 ± 40.0 mmol/L.min) elicited similar glycemic response. The difference was not statistically significant based on a paired t-test (p = 0.921, 95% CI = -41.22 to 45.31, Cohen’s d = 0.025). Corresponding glucose curves and peak times are shown in Figure 3B, where both breads reached their peak glucose concentration at 90 min. For the lunch meal, fiber-fortified rice (240.2 ± 41.9 mmol/L.min) and jasmine white rice (242.8 ± 40.4 mmol/L.min) also produced comparable glycemic responses, with no significant difference observed (p = 0.907, 95% CI = -50.71 to 45.35, Cohen’s d = −0.030; Figure 3C). Their respective glucose time curves are presented in Figure 3D, with both peaking at 75 min. Overall, no trend toward glycemic improvement was observed for the fortified bread or rice products, as evidenced by negligible effect sizes and non-significant differences. In contrast, the dinner meal (Figure 3E) showed a statistically significant (p = 0.046, 95% CI = −90.86 to −0.92, Cohen’s d = −0.544) reduction in 2-h iAUC with microfluidic noodles (114.3 ± 12.2 mmol/L.min) compared to beehoon noodles (160.2 ± 17.6 mmol/L.min). The effect size for this difference is considered medium, suggesting a meaningful practical difference in glycemic response between the two noodle types. Additionally, glucose peaked earlier and at a lower level with the microfluidic noodles—at 60 min with a change of 0.776 mmol/L—compared to beehoon noodles, which peaked at 90 min with a larger glucose change of 1.36 mmol/L (Figure 3F).

Table 6 presents a joint display of both qualitative and quantitative findings for each NVSF, integrating participants’ interview responses with CGM-derived glycemic data. This side-by-side format facilitates clearer interpretation of how participants’ subjective experiences align with their physiological glycemic responses, illustrating the value of the mixed methods approach.

The expectations and perceptions of individuals with T2D toward NVSFs and their feasibility as alternative staple foods were explored and examined in this study. The qualitative analysis of interviews revealed that participants’ acceptance of the NVSFs was primarily influenced by their prior dietary choices as individuals with T2D, prior perceptions, expectations, and their visual first impressions of the NVSFs. The trade-off between sensory and health properties, price and willingness to pay, NVSF modification methods, as well as other socio-economic factors for regular consumption also influence acceptance. However, postprandial glycemic responses from 2-h iAUC of the test meals revealed only the meal with microfluidic noodles exhibited a significant improvement in 2-h iAUC relative to its control meal.

Fundamentally, the staple foods preferred to be modified by the participants represented the staple foods commonly consumed in their households: bread, rice, and noodles. This was expected, as modifications of these staples may improve their carbohydrate quality and allow for their continued consumption while promoting the participants’ well-being as individuals with T2D (4, 28). Additionally, rice was the top choice of staple food for majority of the participants. This also provided insight into the type of staple foods that should be targeted for modifications for health purposes.

When first introduced to the NVSFs, participants often related them to everyday foods they regularly consumed. Familiarity of foods may impact an individual’s attitude toward the foods, shaping values, beliefs, and norms relating to the food item. Therefore, NVSFs maintaining familiarity with minimal changes in sensory properties tended to be more attractive (29–31), and any sensory changes from conventional staples in NVSFs may evoke skepticism among the participants. Interestingly, a small subset of participants embraced the novelty of the anthocyanin-fortified bread, viewing its dark color as a positive attribute that set it apart from typical staple foods, signifying healthfulness and uniqueness. In contrast, the ‘normal’ appearance of fiber-fortified rice was also linked to the ‘bad’ reputation of white rice which was considered by many as one of the main causes of blood glucose surges. This finding was unexpected since the novel appearance of the anthocyanin-fortified bread was expected to potentially evoke feelings of uncertainty and doubt, while the conventional appearance of the fiber-fortified rice was expected to elicit feelings of security and comfort. These responses also reflected participants’ perceptions of existing conventional staples and how they believed these staples would impact their blood glucose levels.

Notably, in post-intervention interviews, a trade-off between sensory and health properties was observed, a common conflict in numerous studies (32–35). Prior to the study, participants reported difficulties in restricting carbohydrate intake, suggesting that this may not be a sustainable diet approach for individuals with T2D. The introduction of NVSFs, on the other hand, was presented as diabetic-friendly alternatives of staple foods, potentially resolving the challenges associated with carbohydrate restriction. Furthermore, health claims made on conventional carbohydrate-rich staple foods which may have a ‘reduced health image’ may be inherently portrayed as ‘healthier’ choices, suggesting that the type of product featuring the health claim may also play a role in influencing an individual’s trust toward the claim or perceived health image (36). Thus, foods like NVSFs with health images or claims that address experienced diseased states may appear more attractive (37).

However, their consideration for NVSF regular consumption was still hindered by its taste and texture, in particular that of the microfluidic noodles. This further reiterates taste and texture as crucial sensory properties in the acceptance of new or novel foods and for their continued usage (16, 38–40). Despite some of their initial expectations to compromise on taste, participants remained highly critical of sensory properties (for microfluidic noodles), illustrating the extent to which such compromises in taste would be tolerated despite their perceived health properties, as similarly reported by others (41, 42). The implications of this trade-off for product formulation and consumer integration warrant further discussion and are explored in greater detail in Section 4.5.1.

Continuous glucose monitoring revealed only the meal with microfluidic noodles, but not anthocyanin-fortified bread or fiber-fortified rice, had exhibited a significant improvement in postprandial glycemic responses. We had initially hypothesized that the combination of macronutrients and functional ingredient fortification (i.e., anthocyanin- and fiber-fortification) could be an efficacious dietary strategy to affect postprandial glucose outcomes. This was based on existing studies that had demonstrated the impact of individual dietary constituents on postprandial glycemic responses. Proteins had exhibited an insulinotropic effect which accelerated the rate of glucose clearance in the blood (43). Dietary fibers and fats were noted to delay gastric-emptying rate and release the gastric inhibitory peptide (GIP) which promoted insulin secretion (44–46). Existing postprandial studies have also demonstrated improved glycemic responses through the intake of anthocyanin- and fiber-rich carbohydrate challenges in vivo (47–49). Unlike these studies that have only focused on individual food items, we evaluated the test foods as a mixed meal comprising standardized side dishes of protein, dietary fiber and fat—a more realistic setting akin to daily diets. The lack of efficacy of anthocyanin- and fiber-fortification in our study could be attributed to the confounding effect of macronutrients on postprandial glucose homeostasis when consumed as a meal. While Meng et al. (50) had initially hypothesized that additional macronutrients would impact postprandial glycemic responses, the investigators had concluded largely no significant changes to postprandial glucose outcomes when carbohydrate-rich foods are consumed as mixed meals of varying protein, fat, and fiber contents. Beyond meal compositions, Song et al. (51) highlights that individual responses to carbohydrates and mixed meals could vary greatly based on physiology, reporting coefficient of variances up to 68% for postprandial glycemic responses to different carbohydrate-rich mixed meals. These findings collectively indicate not only the confounding effects by macronutrients and individual variability which remain partially unaddressed in literature but also suggest potential challenges in postprandial glycemic predictions of actual eating occasions.

Despite this, a significant decrease in postprandial glycemic responses was still observed for microfluidic noodles. This can be attributed to its modification method involving the reduction of available carbohydrates, which would result in a lower amount of carbohydrates being metabolized in the test meal, in contrast to the anthocyanin-fortified bread and fiber-fortified rice meals which contained similar amounts of available carbohydrates as their respective controls. The amount of available carbohydrates has also been reported to be associated with T2D (52) and decreasing carbohydrate intake in a low-carbohydrate diet has been shown to improve glycemic control among individuals with T2D (53–55).

In Singapore, several diabetes-friendly products, such as AuroraFood’s low-GI baked goods and Glucerna nutritional products, are marketed to support glycemic control. Moreover, the fiber-fortified rice used in this study is already commercially available, while the anthocyanin-fortified bread has comparable alternatives in the market. However, broader consumer adoption of all these diabetes-friendly products remains limited, potentially due to factors such as cost, unfamiliarity, and suboptimal sensory appeal, as highlighted in our findings. The microfluidic noodles, while still under development, represent an innovative approach to glycemic management but require significant improvements in palatability to enhance consumer acceptance. While the growing availability of diabetes-friendly products reflects market interest, our findings suggest that availability alone is insufficient. Therefore, successful integration of these diabetes-friendly foods requires strategies that address key barriers, as discussed in Section 4.5.

The strength of this study is derived from the utilization of a mixed methods approach, which acknowledges both the subjectivity of qualitative analysis and the objectivity of quantitative analysis, thereby facilitating the mutual reinforcement of the two datasets. This amplifies the interpretations derived, contributing to a comprehensive understanding of the acceptance and feasibility of NVSFs among individuals with T2D. Furthermore, the crossover design of this study also minimizes potential confounding and variability factors that may arise among participants. Participant compliance to test meals was also improved through the provision of the meals free of cost and the submission of a photograph of their empty food containers following meal consumption.

However, several limitations must be acknowledged to contextualize our findings. First, this study had a relatively small sample size (n = 16). While appropriate for an exploratory study, this limits the generalizability of the results to the broader population of individuals with T2D. Nonetheless, the outcomes provide valuable preliminary insights and lay the foundation for future larger-scale trials. The study duration was also relatively short (5 weeks), and no follow-up was conducted to explore whether participants would continue consuming NVSFs beyond the study period. As such, future research should explore the long-term sustainability, adherence, and metabolic impacts of incorporating NVSFs into habitual diets.

Second, certain aspects of the intervention design may have shaped participant experiences. The use of standardized side dishes across both intervention periods, which was implemented to control for macronutrient consistency, was noted by some participants as reducing meal variety and flavor. This lack of variety may have undermined the participants’ overall experiences and perceptions toward the NVSFs. Similarly, the absence of restrictions during the snacking window—aimed to mirror real-world behaviors—may introduce potential second-meal effects (71). Participants were also not blinded to the intervention, which may have influenced subjective feedback regarding their perceptions and experiences of the NVSFs and their dietary habits during the novel intervention. However, postprandial glycemic responses were objectively measured using continuous glucose monitoring, minimizing reporting bias. Novelty bias may have also played a role in shaping participants’ reactions—both positive and negative—to the intervention foods, as their unfamiliarity or uniqueness may have temporarily influenced perceptions of palatability or acceptability. This effect may not fully represent sustained preferences over time.

Third, the demographic profile of the participants may limit broader applicability of the findings. The average age of the recruited participants was 57.9 ± 9.45, with younger adults underrepresented. This is noteworthy, as age differences may influence food preferences and openness to NVSFs. For example, generational food habits may shape familiarity and comfort with traditional staples, with older adults potentially showing greater resistance to change (72, 73) compared to younger individuals. Nonetheless, evidence also suggests that older adults often prioritize health benefits and may therefore be more receptive to functional foods that address specific health concerns (74). Additionally, all participants were of Chinese ethnicity, which helped minimize potential ethnicity-related confounding effects associated with postprandial glycemic responses. However, this limits the applicability of the findings to other cultural groups, particularly within Singapore’s multi-ethnic context. Individuals from other ethnic backgrounds may exhibit different glycemic responses based on genetic variation (75), and may hold differing perceptions of the NVSFs shaped by cultural food practices. For instance, staple food preferences, food preparation methods, and broader dietary norms can vary significantly among ethnic groups in Singapore (76), all of which can affect both attitudes and preferences toward NVSFs. Future studies involving more diverse populations would provide richer insight into how age and cultural-related differences could affect NVSF acceptance and feasibility.

Finally, other demographic factors such as education level, socioeconomic status and marital status were not collected. While not central to the present analysis, these variables may provide valuable context regarding dietary behavior and openness to novel foods and could be included in future studies to inform more tailored interventions.