The FiberTAG repertoire is a new DF composition database detailing soluble versus insoluble DF, ITF, FOS, GOS content in addition to the total DF content of food products based on scientific recognized methods. An exhaustive literature search has been performed to deeply complete the database with prebiotic (oligo)saccharide levels (ITF, FOS, GOS) in food products using scientific published data. However, even we found values of total DF for most of the food items, this repertoire highlighted several gaps for some categories of fiber (mostly FOS and GOS) and encouraged further additional analysis of prebiotic (oligo)saccharides. FFQ was chosen to assess DF intake in general population because it is inexpensive, simple to complete, and provide an overview of long-term food habits, widely used as the primary dietary assessment tool to epidemiologic studies [26]. By using the FiberTAG repertoire in a small group of healthy young Belgian subjects, data obtained from the FiberTAG FFQ indicated a total DF intake of 38 g/d in a small group of healthy young Belgian subjects. This value is higher than the estimated contribution for the average Belgian in the 2014–2015 Food Consumption Survey (18 g/d) and higher compared to previously reported intake for adults in Europe ranging from 16 to 24 g/d based on 24 h-recall or 3–7 days records. This estimation is also closer to the European (EFSA) and Belgian (CSS) recommendations, which ranges from a minimum of 25 g to ideally 30 g of fiber per day, in order to have significant health benefits [2]. This difference might be explained by a more adequate inclusion of fruits and vegetables intake in FFQ than with other methods, as previously reported [25]. To date, four studies have quantified dietary inulin and oligofructose intake: two studies were from the 1990’s using food composition data from Van Loo et al.[15, 22] whereas two studies were from the 2010’s using 23-item short FFQ developed to measure short-term inulin and oligofructose intake over the same 7 days [27, 1]. ITF and FOS intakes were 5.1 and 2.2 g/day, respectively whereas GOS intake was 0.9 g/d. Even it is determined in a limited sample size, this is the first study reporting GOS intake in a population. FOS intakes were already estimated in 4 studies [15, 22, 28, 27]. American diets provided on average 2.5 g of oligofructose estimated from 24-h dietary recalls from 15,000 Americans and using only ITF contents given by Van Loo et al (1995) [15]. It was reported in the recent study performed on 44 subjects in New Zeeland that inulin or oligofructose intakes were around 3 g/d.[28] Here, intakes of FOS (2.2 g/d) were lower than in the US (2.5 g/d) [22]. ITF or FOS intakes estimated in the present study were at the lower end of the range of intakes across Europe (3.2–11.3 g/d) [15, 27]. Our results are in accordance to those already reported for Belgium (ranging from 2.8 to 10.4 g /d) [15].
Our approach has the advantage and the drawback of all FFQ: the FiberTAG questionnaire requires an average of one hour to complete the form and it takes into account the eating habits over the year and the seasonality. A 24 h-recall or 3–7 days records could be more precise but also could lead to many biases, requires discipline and is time-consuming. Its great advantage was the ability to characterize precisely the DF intake. We were thus able to highlight in this small population that when consumption of food is accounted for, vegetables are the most important sources of total DF, followed by cereal products (flour-based products). In line with previous studies reporting that wheat was the largest contributor to inulin and oligofructose intake [22, 15, 27], we have shown in the present study that cereal products are the principal contributors of FOS. When considering ITF intake, condiments in particular onions and garlic (and in at a lesser extent chives and shallots) are the principal contributors of this prebiotic DF fibers assessed using the FiberTAG FFQ and the new FiberTAG database. This result may be explained by the high concentration of fructans in onions (average of 4.5 g/100 g) and garlic (16.7 g/100 g) versus their contents in cereal-based products (average of 1.6 g/100 g). The differences between studies may also relate to real differences in dietary intake between the populations linked to different dietary habits reported but also to differences in dietary assessment used, with the most comprehensive being the FiberTAG FFQ covering a large period (12 months) used here.
Our aim was to build a new tool for evaluation of prebiotic dietary fibers. Since the questionnaire has been submitted to a small cohort of healthy subjects, the interpretation of the data must be kept with caution. The use of a university population, with a potentially higher education level and health conscious, and therefore is unrepresentative of the entire Belgian population. Despite this limitation, the (in)soluble DF intakes and prebiotic (oligo)saccharides intakes are intensively recorded and the first reported in Belgian population. The FiberTAG FFQ should be tested in other and larger cohorts, and be adapted to specific dietary habits of populations following the aim of the studies.
Strengths of the present study include the development of the FiberTAG repertoire with a deep characterization about DF, in particular DF with prebiotic properties known to maintain health and to manage non-communicable diseases. This repertoire should be completed in the future by new analyses of prebiotic content in some food products. The FiberTAG FFQ was built using the gold standard described in the recent review aiming to identify methods to assess fruits and vegetables intake among children and adults in pan-European studies [25]. The present FFQ provides a tool with possibility to associate specific fiber sources with outcomes since it focused on the main prebiotic (oligo)saccharides. A section of the FFQ details typical French and Belgian cooked meals since the questionnaires have been tested in those two countries as first intend; this section is adaptable for DF intake estimation in another country. The FFQ, evaluated in the present study, is applicable for the Belgian adult population but might also be relevant for adult populations in other European countries with similar food patterns, in particular neighboring countries (Germany, France, Luxembourg, Netherlands). Prebiotic are now used as functional ingredients in yoghurts and breakfast cereals. The formulation, use and availability of such food products vary between different countries [29]. Therefore, those wishing to use the FiberTAG FFQ should first identify this kind of fortified food products and record their intake to ensure accurate assessment of prebiotic (oligo)saccharides intakes [27].