Nutrients, Vol. 18, Pages 895: Development and Evaluation of a Functional Food Consumption Index (FunFoCI) in Adults
Nutrients doi: 10.3390/nu18060895
Authors:
Gülden Arman
Aslı Akyol
Background/Objectives: Functional foods are widely discussed in nutrition research, yet their consumption is rarely quantified using a standardized, food-based metric. We developed the Functional Food Consumption Index (FunFoCI) and conducted an initial evaluation of its performance in adults. Methods: In this cross-sectional study, 500 adults (≥18 years, 286 women, 214 men) were assessed using a 210-item quantitative food frequency questionnaire (FFQ) and a 3 day food record (FR). Candidate index foods were evaluated by five experts, using a 4-point Likert scale to establish content validity, and the finalized FunFoCI comprised 100 foods across nine groups: fruits; vegetables; whole grains; legumes; nuts and oilseeds; fermented foods and products; animal-based foods; functional oils; and spices, herbal teas, and functional beverages. FunFoCI scoring used a sample distribution-based percentile approach, including modifications for zero-inflated or sparsely consumed items, followed by group-level normalization (0–1), equal weighting across nine groups, and rescaling to 0–100. FR data were used to examine the between-method feasibility of the scoring approach. The convergent validity was assessed via correlation analyses, with the Diet Quality Index-International (DQI-I) and Healthy Eating Index-2015 (HEI-2015) derived from both FFQ and FR data, and additional correlation analyses and robustness checks were conducted to examine associations among key study variables. Known group patterns were examined across sociodemographic, lifestyle, and anthropometric characteristics. Results: Content evaluation supported index coverage (S-CVI/Ave = 0.912; S-CVI/UA = 0.877; mean modified kappa = 0.899). The mean FunFoCI total scores were 32.68 ± 11.92 (FFQ) and 13.29 ± 4.65 (FR). Participants were classified into low (32.8%, n = 164), moderate (33.0%, n = 165), and high (34.2%, n = 171) FunFoCI categories. FunFoCI correlated with FFQ-derived DQI-I and HEI-2015 (r = 0.367 and r = 0.368; both p < 0.001), and both indices increased across ascending FunFoCI total scores (p < 0.001). The FFQ-derived FunFoCI total score was correlated with the FR-derived FunFoCI score (r = 0.294; p < 0.001). FunFoCI scores showed differences across participant sociodemographic, lifestyle and anthropometric characteristics. Conclusions: FunFoCI is a newly developed, expert-reviewed, food-based index with transparent, sample distribution-based scoring and normalized aggregation. Its initial evaluation supports its use for the standardized quantification of relative functional food consumption in adults, while further studies should assess the reliability and external validation criteria in other populations and study designs.
Background/Objectives: Functional foods are widely discussed in nutrition research, yet their consumption is rarely quantified using a standardized, food-based metric. We developed the Functional Food Consumption Index (FunFoCI) and conducted an initial evaluation of its performance in adults. Methods: In this cross-sectional study, 500 adults (≥18 years, 286 women, 214 men) were assessed using a 210-item quantitative food frequency questionnaire (FFQ) and a 3 day food record (FR). Candidate index foods were evaluated by five experts, using a 4-point Likert scale to establish content validity, and the finalized FunFoCI comprised 100 foods across nine groups: fruits; vegetables; whole grains; legumes; nuts and oilseeds; fermented foods and products; animal-based foods; functional oils; and spices, herbal teas, and functional beverages. FunFoCI scoring used a sample distribution-based percentile approach, including modifications for zero-inflated or sparsely consumed items, followed by group-level normalization (0–1), equal weighting across nine groups, and rescaling to 0–100. FR data were used to examine the between-method feasibility of the scoring approach. The convergent validity was assessed via correlation analyses, with the Diet Quality Index-International (DQI-I) and Healthy Eating Index-2015 (HEI-2015) derived from both FFQ and FR data, and additional correlation analyses and robustness checks were conducted to examine associations among key study variables. Known group patterns were examined across sociodemographic, lifestyle, and anthropometric characteristics. Results: Content evaluation supported index coverage (S-CVI/Ave = 0.912; S-CVI/UA = 0.877; mean modified kappa = 0.899). The mean FunFoCI total scores were 32.68 ± 11.92 (FFQ) and 13.29 ± 4.65 (FR). Participants were classified into low (32.8%, n = 164), moderate (33.0%, n = 165), and high (34.2%, n = 171) FunFoCI categories. FunFoCI correlated with FFQ-derived DQI-I and HEI-2015 (r = 0.367 and r = 0.368; both p < 0.001), and both indices increased across ascending FunFoCI total scores (p < 0.001). The FFQ-derived FunFoCI total score was correlated with the FR-derived FunFoCI score (r = 0.294; p < 0.001). FunFoCI scores showed differences across participant sociodemographic, lifestyle and anthropometric characteristics. Conclusions: FunFoCI is a newly developed, expert-reviewed, food-based index with transparent, sample distribution-based scoring and normalized aggregation. Its initial evaluation supports its use for the standardized quantification of relative functional food consumption in adults, while further studies should assess the reliability and external validation criteria in other populations and study designs. Read More