Folate is indicated by the World Health Organization (WHO) [1
] as a nutrient especially important for women of reproductive age, in particular during pregnancy. A deficiency of this nutrient is associated with neural tube defects in progeny, and also with anemia in young women [2
]. Considering both neural tube defects and anemia prevention in pregnant women, it is recommended to implement folic acid supplementation as early as possible, while supplementation before conception is indicated as the best option [2
In terms of WHO’s global targets to be achieved by the year 2025 [3
], the role of folate is also undeniable. Regarding the global target of the reduction of anemia in women of reproductive age and of the reduction of low birth weight, there is direct evidence of the effect of daily iron and folic acid supplementation during pregnancy, from the review and meta-analysis of Peña-Rosas et al. [4
]. In terms of the global target of the reduction of the number of children who suffer from stunted growth, as well as the reduction of childhood wasting, there is no direct evidence for the link between supplementation during pregnancy and the achievement of these goals, but the pooling analysis of longitudinal birth cohorts conducted by Christian et al. [5
] enabled conclusions to be drawn about existing associations [6
However, it must be indicated that in Western countries, both before and during pregnancy, a number of women do not take adequate folic acid supplements, and this is especially alarming, if in a given country there is no mandatory folic acid fortification [7
]. Among countries without such fortification requirements are the Netherlands and Norway, where the frequency of non-adherence to recommended supplementation in the preconception period is, respectively, 45–63% [8
] and 70% for women of European ethnicity [10
Among countries with obligatory folic acid fortification are the United States of America and Canada [11
], which is noted as a positive example of a decreased frequency of neural tube defects in progeny [7
]. However, in Canada 40% of women still do not achieve the recommended folate blood levels [12
]. Taking this deficiency into account, in Canada not only is fortification mandatory and supplementation recommended, guidelines for pregnant women also include dietary counseling associated with the food sources of folate [13
Such nutritional counseling may be of great value for young women, not only to indicate necessary dietary modifications, but also to make women aware of the need for supplementation, due to their insufficient dietary intake. Especially in non-pregnant women of reproductive age, such education could be valuable to ensure necessary understanding before conception [14
]. Considering the fact that the number of unplanned pregnancies is still high [15
] and such pregnancies are the main reason for a lack of folic acid supplementation [16
], properly planned education should be conducted not only for pregnant women but for all women of reproductive age.
In assessments of folate [17
] and vitamin B intake [18
] in countries with no folate fortification [19
], food frequency questionnaires are suggested as a good option. However, the majority of folate food frequency questionnaires validated so far consist of a large number of questions, and as a result, are time consuming [20
]. Simultaneously, brief questionnaires are indicated as especially valuable, as they enable immediate feedback to respondents, indicating their required dietary goals, as well as may be positively validated [21
The aim of the presented study was to design a brief folate-specific food frequency questionnaire, as well as to assess the validity and reproducibility of the designed Folate-Intake Calculation-Food Frequency Questionnaire (Fol-IC-FFQ) on a group of Polish women aged 20–30 years.
Among the factors that influence folate status, as indicated by WHO [1
], are diet, physiological status (age, pregnancy or lactation), as well as co-morbidities or socioeconomic status. However, low dietary intake and lack of supplementation are the prime reasons for folate deficiency. Consequently, tools enabling a rapid assessment of intake may be of great value for public health purposes.
Comprehensive questionnaires enabling the assessment of the intake of a few nutrients or many nutrients are commonly designed for B vitamins, including folate. However, the number of food products included in such questionnaires may be very high. Such questionnaires, covering inter alia folate intake assessment, commonly include over 100 items [42
], or even over 200 items, while it is stated that completing a 235-item questionnaire adapted by Fayet [20
] from the 145-item Blue Mountain Eye Study Food Frequency Questionnaire [47
] takes approximately 45 min [20
In order to ensure brief assessment, fewer questions must be included, as is in brief food frequency questionnaires that in general include less than 50 food products [48
]. For the 19-question, one-page Block Dietary Folate Equivalents (DFE) Screener, designed to assess folate intake based on the intake of food products contributing to the top 60% of folate intake [49
], it is estimated that 6–12 min is enough time to complete the questionnaire [50
]. The 19 food product groups of the DFE Screener is similar to the number in conducted own study, as 25 food product groups were included in the Fol-IC-FFQ, but a different approach was applied, as all food products characterized by a folate content no lower than 0.1 µg per 100 g were included and clustered into groups.
The lower number of questions included in brief food frequency questionnaires is also essential to obtain a lower level of overestimation, as was emphasized by van de Rest et al. [45
], who stated that a higher number of questions is associated with a higher level of overestimation. As a result, in their food frequency questionnaire applied to assess folate intake, indicated authors included 89 questions, but did not ask about specific vegetables, fruits and beverages intake, but rather asked about total intake of food products from the mentioned groups [51
]. The clustering of products from groups characterized by a similar folate content was applied in presented own study for the Fol-IC-FFQ, but for vegetables, three separate groups were identified, based on varying folate contents. It may be stated that the general low number of questions in the Fol-IC-FFQ was the reason for the observed slight underestimation.
In spite of the number of questionnaires designed and validated so far, no similar brief questionnaire for folate intake has been designed for and validated in the countries of Central or Eastern Europe. The majority of brief questionnaires have been validated elsewhere—United States of America [50
], Canada [52
], Mexico [53
], Japan [55
], Iran [56
]. Among European countries, they have been validated for the countries of Northern Europe (Great Britain [57
], Norway [35
]), Southern Europe (Serbia [17
], Croatia [33
]), as well as Western Europe (The Netherlands [51
]), but not for the countries of Central or Eastern Europe.
The lack of a food frequency questionnaire aimed at Central and Eastern European populations may be an important limitation for folate intake assessment in these populations. Folate is indicated as a nutrient especially prone to error in the estimation of its intake, and that is influenced by the fact that there are many plant and animal products which are folate sources and so food product lists applied in such questionnaires must be specific for the population [55
]. In various populations, there are some similarities, but also differences in food product choice, and the products commonly consumed in the countries of Western Europe may be different than those in the countries of Central or Eastern Europe. This is especially so for vegetables, which are the main contributor to folate intake, and where the region may be an important influencing factor.
Moreover, while a food frequency questionnaire is designed to assess the intake of only one nutrient (as for brief questionnaires, including Fol-IC-FFQ), it is possible to include the major sources that are most important for a given population [57
]. The inclusion of fewer food products in a brief food frequency questionnaire designed to assess the intake of a single nutrient may be better than a higher number, as can be observed in the study by French et al. [52
] for folate intake assessment, where a questionnaire including 81 questions produced a higher correlation than did a 140-question questionnaire.
The need for a carefully planned food product list is especially evident while considering the Japanese women population, as among the products that contribute to folate intake in these population are green tea, rice, young shoots of bracken, natto, miso, soy sauce, and purple laver, all foods that are consumed only rarely or not at all by European populations [55
]. However, also in comparison with questionnaires applied for other European populations, there are products not consumed in countries of Central and Eastern Europe, such as Bovril and Marmite, which are included in questionnaire applied in Great Britain [57
]. This case indicates the need to apply dedicated food frequency questionnaires for each population, such as Fol-IC-FFQ designed for a Polish population, and which may be also used for other countries of Central or Eastern Europe, after the necessary adjustments, if needed.
The possibility of using a questionnaire designed for another population is limited especially if there are different products contributing mainly to folate intake and responsible for variation of the folate intake in the population. In the study by Ishihara et al. [55
] focusing on a group of Japanese women, depending on the assessed cohort, either green tea or spinach leaves were demonstrated to be the most important source of folate, while green tea contributed to the highest variation of its intake, and this was dependent on the individual preference for this product. At the same time, in the study by Bacardí-Gascón et al. [53
] conducted in Mexico, among the most important predictors of folate intake were corn tortillas and papayas, rarely consumed by European populations, as in the case with green tea. As a result, green tea, corn tortillas and papayas were not included in Fol-IC-FFQ, but the spinach leaves were, as in Poland they are chosen more frequently than the other products indicated above.
Except for the length of the form and included food products, the observed validity and reproducibility are the most important issues. Considering the methods applied in the assessment of validity and reproducibility, it must be emphasized that the Bland-Altman method is the primary one [57
]. When comparing obtained results with results of other studies, the majority of these did not include the Bland-Altman method, but only the kappa statistic [33
], analysis of correlations [33
], as well as assessment of individual distributions into tertiles [57
] or quartiles [33
In the own study, the analysis of the kappa statistic, analysis of correlations, as well as assessment of individual distributions into tertiles were also applied. Moreover, the share of individuals classified into the same and into the conflicting folate intake adequacy category were analysed. It was observed that for the analysis of the folate intake adequacy, the Fol-IC-FFQ may be a good method, both in the assessment of validity and reproducibility, as for over 70% of individuals, the results were valid in comparison with the reference method, and for almost 90% of individuals, they were reproducible. As a result, it must be indicated that the designed Fol-IC-FFQ may allow to indicate, in the population, individuals characterized by adequate folate intake and by inadequate folate intake.
The Bland-Altman method was applied by Galván-Portillo et al. [54
] in the assessment of the reproducibility of a 127-item food frequency questionnaire to assess folate intake, as well as by Zekovic et al. [17
] in the assessment of the validity of a 90-item food frequency questionnaire for folate (F-FFQ). In the study by Galván-Portillo et al. [48
], the number of individuals observed to be within the LOA value was 45 out of 48, which confirmed a Bland-Altman index of 6.25%, higher than the value of five percent which is commonly assumed as a maximum value for the positive validation of a method of measurement [33
]. Simultaneously, in the study by Zekovic et al. [17
], a Bland-Altman index of 3.98% indicated a good agreement between methods in the comparison of the F-FFQ and three 24-h dietary recalls. The results observed in the own study in the assessment of the Fol-IC-FFQ are comparable with the results of Zekovic et al. [17
] and Galván-Portillo et al. [54
], but the reproducibility in own study was observed to be higher (Bland-Altman index of 2.7%), while the validity was stated to be borderline significant (Bland-Altman index of 5.3%). The results must be recognized as promising also for other countries of Central and Eastern Europe. Not only quite good validity is indicated, but also very good reproducibility.
The results were also confirmed using in the assessment of reproducibility other methods than the Bland-Altman plot. The share of individuals classified into the same tertile was almost 75%, while weighted κ statistic indicated substantial agreement (0.67) and the correlation was significant (p = 0.0000; R = 0.7995). At the same time, in the assessment of validity, the share of individuals classified into the same tertile was lower, at 40%, while weighted κ statistic indicated a slight agreement (0.19).
The reproducibility higher than validity, indicates that the obtained Fol-IC-FFQ may be a valuable method especially while the repeated measurements are conducted. It may be used, for example, during nutritional education, while the results of education must be verified, in order to indicate if the individuals sufficiently increased their folate intake. Similar conclusions were drawn for the Block DFE Screener to assess folate intake in the United States of America population assessed by Owens et al. [50
], as it was demonstrated that the Block DFE Screener is especially useful in the repeated measurement of single nutrient intake.
However, not all studies of other authors have revealed such a good agreement for folate-specific food frequency questionnaires. For example, the food frequency questionnaire validated by Pufulete et al. [57
] was stated to be a useful method for assessing folate intake, but mainly in male, not female respondents. Considering the fact that for female respondents, folate intake assessment is especially needed, questionnaires enabling reliable estimation of folate intake for women, such as Fol-IC-FFQ, are of great value. In the future, further analysis of the Fol-IC-FFQ may be needed, while food products that are consumed by a small number of respondents and that do not contribute high levels of folate may be excluded to simplify the questionnaire, as is also recommended by authors of other questionnaires [58
The need for efforts to increase folate intake among all young women is also emphasized by other authors and dedicated food frequency questionnaires are considered valuable tools in the assessment of folate intake [53
]. This is especially important, given that independently from the applied recommended level, folate intake in developed countries is insufficient in many young women.