Expanding the food database with values of FODMAP content
The process to expand the food database with values of FODMAPs is illustrated in Fig. 1. First the five groups of FODMAPs; fructose, fructan, lactose, GOS and polyols, were added to the list of nutrients within the software program Dietist XP (version 3:2, Kostdata.se). Dietist XP is a nutrition calculation software program widely used in Sweden and is based on the official food database from the Swedish National Food Agency (2012-03-19). Second, all the existing 2039 food item or dishes in Dietist XP was manually checked against published peer-reviewed papers containing FODMAP-data using enzymatic -and chromatographic methods and reports containing FODMAP-data from Swedish National Food Agency published in year 2007 to 2014. In addition, food items missing from the database but reported in the food-diaries (see below) were added (Table 1). Non carbohydrate food such as meat, fish and egg were not included in the database as they consequently contain no FODMAPs. Baby food was not included as the database is intended for assessment of FODMAP intake in adults. Nordic sources were used when possible.
Table 1
Main peer- reviewed papers used as source for FODMAP values.
References | Analysed food-item/ product/ raw material | Analysed value added in database | Food sampling/biological variation | Analytical method |
(16) National Swedish Food Agency 2007–2013 | One hundred and nineteen vegetables, cereal products and other food items | Fructose and lactose | Purchased in grocery chains, small food stores, and vegetable retailers and from casual trading area. • If possible a minimum of ten samples of each food item | •Gas- chromatographic method (46). •Result presented in fresh weight g/100 g food item |
(9) Muir et al.2007 | Sixty vegetables and 43 fruits | Free fructose and fructan | Approximately 500 g (edible weight) of each food item from respectively five grocery stores and five green grocers, Australia, Melbourne | • Analyses made of pooled samples •Enzymatic analyse and spectrophotometry (47) •Triplicate analysis •Result presented in g/ 100 g “as eaten” in fresh weight |
(10) Muir et al.2009 | Forty-five vegetables and 41 fruits | Fructose, fructan | Approximately 500 g (edible weight) of each food item from each of five grocery stores and five green grocers, Australia, Melbourne | • Analyses made of pooled samples •HPLC with ELSD •Triplicate analysis •Result presented in g/ 100 g “as eaten” in fresh weight |
(8) Biesiekierski et al. 2011 | Fifty- five grains and cereals | Fructose, FOS (nystose, kestose). Total fructan, lactose, GOS (raffinose, stachyose) sugar polyols (sorbitol, mannitol) | Approximately 500 g (edible weight) of each food item from Supermarkets, market- places and health stores in Melbourne, Australia, One to 9 products/ brands of each food item, 500 g of each product edible weight | • Analyses made of pooled samples • HPLC • Total fructan via enzymatic analyses (48) •Result presented in g/ 100 g “as eaten” in fresh weight. |
(17) Whelan et al.2011 | Nine categories of bread | Fructan | Five brands of each bread category and 500 g of each category of bread from Supermarkets was pooled together to 2500 g | • Analyses made of pooled samples • Fructan via enzymatic and spectrophotometry method (47) Triplicate bread samples were extracted and analyzed in duplicates. • Result presented as content g/100 g fresh weight (‘as consumed’) |
(13) Andersson et al.2009 | Rye kernels and five kind of whole grain rye soft- and crispbread baked on one type of rye kernels | Fructan | Rye kernels 18 samples from an experimental field, Sweden | • Fructan via enzymatic and spectrophotometry method (47) • Result presented in dry weight • Duplicate analysis |
(14) Haskå et al. 2008 | Two cultivars of wheat grain and five milling fractions of the wheat | Fructan | Two cultivars, one sample conventionally and organically grown. One cultivar conventionally grown in Sweden | •Enzymatic (47) •Duplicate analysis •Result presented in dry weight |
(26) Yao et al. 2014 | Seventy three food items | Sorbitol and mannitol | Five grocery stores, five green grocers, Australia Melbourne | •HPLC with ELSD •Triplicate analyses • Result presented in fresh weight |
High performance liquid chromatography (HPLC) |
Evaporative light scattering detection (ELSD) |
When a relevant FODMAP value was available it was assigned to the food item or dish in the database in Dietist XP. White bread is given as an example here: values per 100 g white bread: 0.27 g fructose (16), 1.02 g fructan (17) and 0.20 g GOS (8) were added to the database. All values assigned to the database are in fresh weight. A few values in dry weight have been converted to fresh weight using the data on water content from the food composition tables from Swedish National Food Agency (Swedish food composition tables, SFCT).
Single ingredient food items
The majority of the food items in the database are single ingredient food such as fruits, fruit-juices, vegetables, root-vegetables, milk-products as well as couscous, rice, oatmeal, pasta, potato- chips, rice cakes (plain or flavoured), and legumes. When FODMAP-content data was missing the food item was assigned with the same value as a similar food item in Dietist XP, such as fresh broccoli and frozen broccoli. Similarly, brown beans and white beans originate from same plant family as kidney beans and were assigned the values for kidney beans, and bulgur was assigned with the same value as couscous.
Composite food items
The FODMAP values for composite foods, consisting of several FODMAP containing ingredients, were obtained through a recipe calculation procedure (18). The ingredients list from the data sources were matched with the most similar food item in the SFCT on which the database is built. As neither the SFCT nor the articles presenting data on FODMAP content present the exact amount of ingredients the food items were matched based on quantity of content. This was true for bread in particular, see section “Fructan” below.
Fructose
Fructose is jointly absorbed with glucose using GLUT-5 and GLUT-2 (19) transporters and fructose in excess of glucose is more likely to be malabsorbed (7). Fructose will be fermented whenever not properly absorbed. When calculating the total FODMAP value, fructose in excess of glucose is approximated by taking the monosaccharide content from the food records, in most foods free fructose is accompanied by glucose in various proportions (7). If the glucose content was higher than the fructose content the excess fructose value is 0 (20). Values for free fructose analyzed with different HPLC techniques and fresh weight was the preferred sources of food composition data. (8–10, 16) and if not available, fructose values from an appendix from the Swedish National Food Agency (15) and Finnish food composition database Fineli (21) were used. Fructose values from Muir and co-authors (10) were assigned but when a fructose value was analyzed for the same food-item in Muir and co-authors (9) a mean value was assigned.
Fructans
Values from different chromatographic methods or enzymatic analyses were the firsthand choice. Swedish values for food items in dry weight were chosen for whole grain rye, soft and- crispbreads as well as values for wheat flour and other milling fractions of wheat (13, 14, 22, 23). Analytical values of fructan content of Swedish sources were transformed from dry weight to fresh weigh using the water content in food items from Swedish food composition tables (16). Values from Australia (8–10) and U.K were also used (17).
Values from enzymatic analyzes of total fructan were first choice and when not available HPLC values from separate fructo-oligosaccharides e.g. nystose (GF2), kestose (GF3) and 1F-β- fructofuranosylnystose (GF4) were summed up to give a fructan value (12). When there were discrepancies between papers regarding presence of fructan in the food item, the paper detecting fructan was chosen as the source of the assigned value to a few food items such as banana to ensure that all fructan content in food was captured.
Breads from SFCT were divided in groups depending on their main type of flours e.g. white bread, granary bread, whole grain/meal wheat bread, sifted rye breads containing both rye and wheat flour, whole meal/grain rye breads and yeast fermented crisp bread with sourdough or non-leavened, non-yeast crisp bread. Content of yeast or sourdough was one of the main factors to take into account in the matching as fermentation is known to influence the fructan value (13). A white bread in Sweden generally contains wheat flour, water, wheat gluten, yeast, with or without sourdough, and differs slightly from the Australian bread which often contains added soy flour (8). The ingredients were matched to the description of bread type in published data and/or the company’s website to see the type of ingredients and type of flours in the product and the mean value was assigned, such as the values for gluten-free breads from Whelan (17) and Bieseikierski (8).
The majority of the analyzed Australian cereals and muesli tend to come from large multinational companies that are sold internationally, e.g. Kellogg’s cornflakes, Weetabix, All-Bran and Rice Crispies. Other cereals and muesli was matched based on the description of the product (8), especially noting if the muesli contains dried fruit which largely impact of the fructose value in the food item. The same procedure was used for biscuits.
The values for composite foods containing wheat flour were calculated with 1.3 g of fructan/100 g wheat flour, the mean value from three wheat cultivars analyzed in Sweden (14).
Lactose
Most values for lactose were derived from Swedish (24) and Finnish (25) dairy companies who have comprehensive data of lactose content in their products although a few Swedish values came from the Swedish National Food Agency.
GOS and polyols
Australian data regarding GOS and polyols in fruits, vegetables and chewing gum (8, 10, 26) were used as no data from Europe was available. Carbohydrates separately analyzed with HPLC e.g., raffinose and stachyose were summed up to give a value of GOS. Sorbitol and mannitol were summed up and called polyols. Values for composite meals containing GOS were calculated by using information about components from food-business sites. Values for cough-drops were found on business websites (27).
Calculation of FODMAP intake from food diaries
Collection of food records
The present study includes 117 estimated four-day food records randomly selected from the Swedish nationwide diet survey Riksmaten (30) performed from May 2010 until July 2011. Sample size was determined based on constraining the uncertainty around the estimated mean of a key parameter (fructan) to within 10% of the expected mean value. This ensures sufficiently precise estimates of average intake. Assuming an SD of 2.5 and a 95% confidence interval, approximately 110 individuals were required. The achieved sample size slightly exceeds this requirement at 117.
Eligible participants of Riksmaten, 5000 randomly selected Swedish adults aged 19–80 years, were sent a letter with written information about the study and were phoned a few days later by a trained interviewer from Statistics Sweden and asked if they wanted to participate in the Riksmaten study. A total of 1797 persons chose to participate. Participants in the present study were selected to serve as matched healthy controls for 117 patients in another study not yet published and individuals with diabetes, kidney-disease, lactose intolerance or celiac disease had been excluded (28).The mean age was 39 years (range 18 to 70 years), 89 were women (76%). Body Mass Index (BMI) was on average 24.8. The study Riksmaten was approved by the Regional Ethical Review board at Uppsala University (registration number: 2010/060). All participants gave oral consent.
All participants received written and oral information about keeping a food diary. Food intake was estimated using a portion size guide to facilitate the recording. Participants were instructed to record their food intake immediately after every meal and encouraged to eat as they normally do. Food intake was entered on a website belonging to the Swedish National Food Agency. If a participant was unable to use the computerized web log, a trained person at Statistics Sweden phoned the participant and recorded the food intake during the call. The food records covered all weekdays and seasons on a group level to cover weekday versus weekend and seasonal variations in food intake.
Calculation of FODMAP content in food records
The 117 four-day food records were entered into Dietist XP, version 3:2, with the expanded database, by a registered dietitian. Composite dishes were entered when available in the database and otherwise broken down into their ingredients. Each food record was summarized in Dietist XP and the average intake in grams per day and 95% confidence interval per FODMAP was calculated. Each FODMAP was tabulated by magnitude of most common eaten food item, see supplementary files.
Patient and public involvement
Patients or representatives from the public were not involved in the planning or execution of this research project.