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        Intake estimation of total and individual flavan-3-ols, proanthocyanidins and theaflavins, their food sources and determinants in the European Prospective Investigation into Cancer and Nutrition (EPIC) study
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        Intake estimation of total and individual flavan-3-ols, proanthocyanidins and theaflavins, their food sources and determinants in the European Prospective Investigation into Cancer and Nutrition (EPIC) study
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        Intake estimation of total and individual flavan-3-ols, proanthocyanidins and theaflavins, their food sources and determinants in the European Prospective Investigation into Cancer and Nutrition (EPIC) study
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Abstract

Epidemiological studies suggest health-protective effects of flavan-3-ols and their derived compounds on chronic diseases. The present study aimed to estimate dietary flavan-3-ol, proanthocyanidin (PA) and theaflavin intakes, their food sources and potential determinants in the European Prospective Investigation into Cancer and Nutrition (EPIC) calibration cohort. Dietary data were collected using a standardised 24 h dietary recall software administered to 36 037 subjects aged 35–74 years. Dietary data were linked with a flavanoid food composition database compiled from the latest US Department of Agriculture and Phenol-Explorer databases and expanded to include recipes, estimations and retention factors. Total flavan-3-ol intake was the highest in UK Health-conscious men (453·6 mg/d) and women of UK General population (377·6 mg/d), while the intake was the lowest in Greece (men: 160·5 mg/d; women: 124·8 mg/d). Monomer intake was the highest in UK General population (men: 213·5 mg/d; women: 178·6 mg/d) and the lowest in Greece (men: 26·6 mg/d in men; women: 20·7 mg/d). Theaflavin intake was the highest in UK General population (men: 29·3 mg/d; women: 25·3 mg/d) and close to zero in Greece and Spain. PA intake was the highest in Asturias (men: 455·2 mg/d) and San Sebastian (women: 253 mg/d), while being the lowest in Greece (men: 134·6 mg/d; women: 101·0 mg/d). Except for the UK, non-citrus fruits (apples/pears) were the highest contributors to the total flavan-3-ol intake. Tea was the main contributor of total flavan-3-ols in the UK. Flavan-3-ol, PA and theaflavin intakes were significantly different among all assessed groups. This study showed heterogeneity in flavan-3-ol, PA and theaflavin intake throughout the EPIC countries.

Flavan-3-ols or flavanols, terms used interchangeably, are compounds that belong to a polyphenol subclass called flavonoids, which share a common C6–C3–C6 skeleton. Flavan-3-ols are perhaps the most structurally complex in the flavonoid subclass ranging from simple monomers (such as catechin and its isomer epicatechin) to oligomers (from dimers to decamers), polymers (>10mers) and other derived compounds (e.g. theaflavins and thearubigins). The oligo and polymers of flavan-3-ols are also referred to as condensed tannins or proanthocyanidins (PA), named for their ability to yield anthocyanidins when heated in acidic media(1). Enzymatic and non-enzymatic oxidation of (gallo)catechins, reactions characteristic of green tea fermentation, results in flavanol-derived compounds: theaflavins and high-molecular-weight thearubigins(1, 2). Being much larger molecules, PA and flavanol-derived compounds tend to be less bioavailable and have different functional properties; therefore they are often considered as separate groups of flavonoids(1, 3). Although their average degree of polymerisation can be estimated, the structures of some high-molecular weight polymers of PA and of most of the thearubigins have not been well defined due to inadequate analytical methods(1).

Flavan-3-ol monomers are found ubiquitously in plants as secondary metabolites(4). Flavan-3-ol monomers are most abundant in fruits (e.g. berries, apples/pears, stone fruits), barley, cocoa beans, nuts(5) and their derived products(6). Gallocatechins are found, almost exclusively, in green tea infusions(2, 7) while flavanol-derived compounds, theaflavins and thearubigins, are abundant in fermented black and oolong teas(2). Common PA-rich foods are cocoa, berries, nuts and some raw beans(5, 8). Transformations and losses of some flavonoid compounds during processing and cooking are common and vary for different subclasses and even for the individual compounds(911).

Total and individual compounds of flavan-3-ols have been studied extensively in vitro for their antioxidant, anti-inflammatory, immunomodulator and anti-carcinogenic effects(1214). A plethora of human intervention studies currently available strongly suggests beneficial effects on human health, particularly the effects of flavan-3-ol-rich foods, such as tea, cocoa and chocolate(7, 15, 16). Intervention studies involving various PA-rich sources such as red wine, grape, pomegranate, chocolate and cranberry juice showed numerous positive effects on antioxidant, CVD and endothelial maintenance biomarkers(3). Given the limited reported bioavailability of PA, particularly those having a high degree of polymerisation (>3)(17), the observed action of PA-rich foods in the body, with the exception of perhaps the intestinal lumen, may be attributed to flavan-3-ol monomers, which are systematically associated to PA and comprise 5–25 % in these foods, or to other yet unidentified PA(3, 18). Furthermore, PA may also exert their action after their degradation by the colonic microbiota and subsequent absorption(19). Indeed, two Italian case–control studies suggested inverse associations between PA, but not flavan-3-ol monomer, intake and gastric and colorectal cancers(20, 21). Furthermore, the inverse association augmented with increasing degrees of polymerisation of PA in colorectal cancer cases(20) despite their observed decrease in absorption. Further research, particularly in prospective studies, on individual flavan-3-ol and PA compounds is clearly needed to clarify and confirm these potential effects.

Total intake of any nutrients is usually related to sex, cultural, lifestyle and socio-economic factors that may affect accessibility to and habitual consumption of health-promoting foods. Studies in European Prospective Investigation into Cancer and Nutrition (EPIC) Spain and the USA found significant differences in total flavonoid intake between sexes and among different age groups, socio-economic levels and ethnic groups(22, 23). Therefore, these factors need to be taken into consideration when looking into associations of these compounds and their dietary sources in disease prevention. To our knowledge, there are few data on individual flavan-3-ol intakes in the European population. The present study aims to evaluate total, subclasses and individual dietary intake of flavan-3-ols and their main food sources by EPIC centre and geographical region, while taking into account lifestyle, anthropometric and socio-demographic factors.

Materials and methods

Study population

EPIC is an ongoing prospective cohort study designed to investigate the associations between diet, lifestyle and cancer throughout ten Western European countries: Denmark, France, Germany, Greece, Italy, Norway, Spain, Sweden, The Netherlands and UK(24). The cohort includes approximately 366 000 women and 153 000 men, most of them aged 35–74 years, who were enrolled between 1992 and 2000 by twenty-three centres. Some differences in methods of recruitment exist between centres. Part of the Oxford (UK) cohort was recruited from subjects who consumed a vegetarian-type diet. This was designated a ‘Health-conscious’ group and shall be distinguished from the UK General population cohort which is a combined group of the UK Cambridge and UK Oxford general population. The female part of the cohort in Florence (Italy) and Utrecht (The Netherlands) is composed of women who underwent breast cancer screening. The French cohorts recruited women only, but from the members of the health insurance scheme for the state-school employees. The centres in Italy and Spain recruited mostly blood donors. For the purpose of dietary consumption patterns analysis, the initial twenty-three centres were later redefined by geographical areas into twenty-seven centres(25). The calibration subsample of the EPIC cohort study composed of 36 994 subjects (8 % of the whole EPIC cohort), who were recruited to be a random sample stratified by age, sex and centre, and weighted for expected cancer cases in each stratum of the main EPIC cohort study, was considered herein. After exclusion of 945 subjects under 35 or over 74 years of age because of low participation in these age categories, and sixteen subjects without baseline dietary data, a total of 36 037 subjects were included. Approval for the study was obtained from the ethical review boards of all local recruiting research institutions. All participants provided written informed consent.

Measurements of diet and other lifestyle factors

Dietary intake was measured with a standardised 24 h dietary recall (24-HDR) administered via a computerised interview programme (EPIC-SOFT) developed specifically for the EPIC calibration study(25, 26). The 24-HDR was administered in a face-to-face interview, except in Norway where it was obtained by telephone(27). A detailed description of the rationale and methodology of the 24-HDR calibration study in the EPIC cohort has been described elsewhere(24, 2830). Data on socio-demographic and lifestyle factors, including educational level, physical activity and smoking history were collected at baseline through standardised questionnaires and clinical examinations for the calibration sample(3134). Age as well as body weight and height were self-reported by the participants during the 24-HDR interview. The mean time interval between these baseline questionnaire measures and the 24-HDR interview varied by country, from 1 d to 3 years(24).

Flavonoid Food Composition Database

The US Department of Agriculture (USDA) released a PA database in 2004 and an updated flavonoid database in 2007, with more analytical values for raw, cooked, canned and commercially processed foods(35, 36). In the process of combining the two USDA databases, we observed data duplicity of the monomers. Since flavan-3-ols monomers (USDA database on flavonoids)(35) and PA monomers (USDA database on PA)(36) are the same molecules, the PA monomer data was removed. We expanded these databases with analytical values from the Phenol-Explorer database released in 2009(37). Approximately, 6·5 and 0·6 % of our database came from USDA and Phenol-Explorer, respectively. Thus far, these databases are the most complete and updated databases on flavonoids/polyphenols and they evaluate and compile the most worldwide food composition data published. We further expanded our EPIC-specific food composition database (FCDB) by estimating values for foods not present in either of the two databases, but that had occurred in the 24-HDR. Therefore, for our FCDB, we calculated estimated values (92·9 %) including logical zeros (25·3 %), estimations based on similar food items (22·5 %), application of retention factors (27·7 %) and recipes (17·3 %). When there were no analytical data provided for cooked foods by either USDA or Phenol-Explorer, retention factors were applied. The retention factors reported in various foods were between 42 and 74 % for catechins and 0 and 95 % for tannins(38). Therefore, to simplify and homogenise the calculations, we used the same retention factors for all flavonoids, as in our previous studies(23, 39, 40). They were 70, 35 and 25 % after frying, cooking in a microwave oven and boiling, respectively(41). The final FCDB created contained a total of 1877 food items. The unknown composition values, without any analytical or estimated data, were calculated as a zero by default and ranged from 2 % (theaflavin gallates) to 16 % (epicatechin-3-gallates). Finally, the 24-HDR food items were linked with the expanded flavonoid FCDB using an ad hoc SQL (Structured Query Language) application.

Statistical methods

General linear modelling was used for the calculation of the adjusted daily mean (least squared) intake and standard error using SPSS (version 17.0.0, SPSS, Inc.) for total flavan-3-ols, their individual compounds and subgroups. The mean intake was adjusted for age, weighted by season and day of 24-HDR and stratified by EPIC centre and age. Flavan-3-ol monomers as aglycones included: catechin, epigallocatechin, epicatechin, epicatechin-3-gallate, epigallocatechin-3-gallate, gallocatechin and catechin-3-gallate. PA were divided into the following subgroups: dimers, trimers, 4–6mers, 7–10mers and >10mers (polymers). Theaflavins included compounds: theaflavin, theaflavin-3,3′-digallate, theaflavin-3′-gallate and theaflavin-3-gallate. Although present in the USDA database, due to the extensive limitations in analytical methods currently employed to identify and quantify thearubigins, we did not include them in our analysis of total flavan-3-ols(1, 41). Epigallocatechin, epicatechin-3-gallate, epigallocatechin-3-gallate, gallocatechin and catechin-3-gallate were later combined into a single group called ‘(epi)gallocatechins’ due to the resemblance among the chemical structures. Flavan-3-ol monomer, PA and theaflavin intakes are calculated as the sum of the individual compounds or subgroups and expressed in mg/100 g of fresh weight. During the analysis of the related factors and of the main food sources, EPIC centres were combined by geographical regions into a Mediterranean (MED) region (Greece, Italy, Spain and South of France) and non-MED (non-MED) region (France other than the South centre, Germany, The Netherlands, Norway, Denmark and Sweden). The UK General population cohort and the Health-conscious cohort presented similar intakes for flavan-3-ols and their food sources but markedly different from all others; therefore, in the socio-demographic analysis they were kept as a separate UK region. The contribution of each food and food group to the total and individual intake of flavan-3-ols was calculated as a percentage. The general linear modelling was also used in the comparison of the mean intakes by socio-demographic, anthropometric and lifestyle factors, adjusting for age, region, energy intake and BMI, and weighted for season and day of 24-HDR. P values < 0·05 indicated significance.

Results

A south-to-north gradient in the daily mean intake of total and monomers of flavan-3-ols and of theaflavins was observed among EPIC centres in both men and women (Table 1). The highest total flavan-3-ol intake was observed in the UK Health-conscious men (453·6 mg/d) and in women of the UK General population cohort (377·6 mg/d). The lowest total intake was observed in Greek men (160·5 mg/d) and women (124·8 mg/d). Flavan-3-ol monomer intake was the highest in the UK General population (213·5 mg/d in men, 178·6 mg/d in women) and the lowest in Greece (26·6 mg/d in men, 20·7 mg/d in women). Theaflavin intake was the highest in the UK General population for both men (29·3 mg/d) and women (25·3 mg/d). Daily theaflavin intake was close to 0 mg in Greece and in Spanish and southern Italian centres (Ragusa, Naples and Florence). In contrast, daily intake of total PA was the highest in Spanish centres (455·2 mg in men from Asturias and 237·9 mg in women from San Sebastian), followed by men in Turin (Italy) and women in Asturias (Spain), respectively. However, PA intake was the lowest in Greece (134·6 mg/d in men and 101·0 mg/d in women). Intake amounts of the individual flavan-3-ols, theaflavins and of PA subgroups are presented in Annexes 1 and 2. PA subclass, particularly the group of polymers (>10mers), was the highest contributor to the total flavan-3-ol intake (Table 2). Flavan-3-ol monomers were the second highest contributors to the total intake, providing contribution of between 18·6 % in the MED region and 44·9 % in the UK. Catechins and epicatechins, equally, were the main single-compound contributors in the MED region, while in the non-MED and UK regions it was the epigallocatechin-3-gallate monomers. Theaflavins were the lowest contributors to the total flavan-3-ol intake. The four theaflavin compounds contributed almost equally to the total theaflavins in all three regions.

Table 1 Adjusted* daily mean intakes (mg/d) of total and subgroups of flavan-3-ols in men and women by European Prospective Investigation into Cancer and Nutrition centre ordered from south to north

(Mean values with their standard errors)

PA, proanthocyanidins.

* Adjusted for age and weighted by season and day of recall.

Sum of catechin, epicatechin and epicatechin 3-gallate, epigallocatechin 3-gallate, gallocatechin and catechin-3-gallate.

Sum of theaflavin, theaflavin-3′-gallate, theaflavin-3 gallate and theaflavin-3,3′-digallate.

Table 2 Percentage contribution* of individual and subclasses of flavan-3-ols to subclass and total intake in the European Prospective Investigation into Cancer and Nutrition cohort by European region

MED, Mediterranean; Non-MED, non-Mediterranean; PA, proanthocyanidins.

* Values are percentages derived from models adjusted for sex, age and weighted by season and day of recall.

Non-citrus fruit, particularly apples/pears, was the most important food source of total flavan-3-ols in the MED (56·2 %) and non-MED (34·1 %) regions (Table 3). Wine and then tea were the other two major sources of flavan-3-ols in these two regions. On the other hand, tea (51·3 %) was the most prominent source of total flavan-3-ols in the UK, followed by non-citrus fruit (19·9 %) and wine (6·1 %). The major food sources of catechins and epicatechins in all three regions were tea, non-citrus fruits and wine; however, chocolate candy/bars were also noteworthy dietary contributors. Tea was the lone source of theaflavins and a major source of (epi)gallocatechins in all three regions (77·7 % in the MED, 90·5 % in the non-MED and 95·1 % in the UK region). The principal dietary source of total PA in the MED region was non-citrus fruit (62·3 %) followed by wine (17·3 %) and chocolate candy/bars (4·6 %). Non-citrus fruits were also the main source of PA in the non-MED and UK regions, but their contributions were smaller (48·0 and 37·2 %, respectively). In the non-MED region, wine was the second most important source (12·6 %), followed by chocolate/candy (6·6 %) and tea (5·0 %). Whereas in the UK region, the secondary sources of PA were tea (15·0 %), wine (10·0 %), cakes/pies/pastries/puddings (7·6 %) and pulses (7·1 %).

Table 3 Major food sources of dietary flavan-3-ols, their monomers, proanthocyanidins (PA) and theaflavins in the Mediterranean (MED), non-Mediterranean (non-MED) and UK regions*

EGC, (epi)gallocatechins.

* Values are percentages derived from models adjusted for centre, age and sex, and weighted by season and day of recall.

Sum of epigallocatechin, epicatechin 3-gallate, epigallocatechin 3-gallate, gallocatechin and catechin-3-gallate.

Sum of theaflavin, theaflavin-3′-gallate, theaflavin-3 gallate and theaflavin-3,3′-digallate.

Sex-stratified analysis of the related factors showed similar results; therefore the data are presented for men and women combined (Table 4). Total flavan-3-ol intake and also the intake stratified by monomers, PA and theaflavins were shown to significantly vary between the geographical regions. The intake of flavan-3-ol monomers and theaflavins in the UK region was almost 4-fold and over 16-fold that of the MED region, respectively. Conversely, PA intake was significantly higher in the MED region (217·2 mg/d) compared to the non-MED (177·9 mg/d) and the UK (198·4 mg/d) regions. After adjusting for BMI and energy, women had significantly higher intakes of total flavan-3-ols and their subclasses. The intake of total flavan-3-ols and their subclasses was significantly different between the age groups, being the highest in the 55- to 64-year-olds. It also increased with the level of education completed and the level of physical activity. On the other hand, current smokers and obese participants (BMI ≥ 30 kg/m2) had the lowest intakes of total flavan-3-ols and their subclasses.

Table 4 Socio-demographic, lifestyle and anthropometric determinants of intake (mg/d) of total flavan-3-ols and their subgroups*

(Mean values with their standard errors)

* General linear model adjusted for age, sex, region, BMI (whenever not stratified for the respective variables) and energy intake, and weighted by season and day of recall.

Sum of catechins, epicatechins and (epi)gallocatechins.

Sum of theaflavin, theaflavin-3′-gallate, theaflavin-3 gallate and theaflavin-3,3′-digallate.

§ P values are for overall differences in mean consumption by general linear model among the socio-demographic, lifestyle and anthropometric subgroups.

Discussion

To our knowledge, this is the only study thus far assessing the intake of total and flavan-3-ol monomers, PA and flavan-3-ol-derived compounds as well as their food sources and associated factors in all twenty-seven EPIC centres of ten European countries using a common expanded flavonoid FCDB and dietary assessment method (24-HDR). Our results show a wide range of total flavan-3-ol intakes following a south-to-north geographical gradient. When stratified by regions, total flavan-3-ol intake in the UK was about 2-fold that of the MED region. This relatively steep gradient in flavan-3-ol intake was mainly due to higher intakes of theaflavins and epigallocatechins in northern EPIC cohorts; indeed the main source of these subclasses of flavan-3-ols was found to be tea. On the other hand, PA intake was found to be statistically higher in the MED region, although large differences were also noted among centres within the same region. The main source of PA in the MED region was non-citrus fruit, chiefly apples and pears, followed by wine, similar to what was previously reported for the EPIC Spanish cohort(23). Furthermore, the almost-nil intake of theaflavins in Greece, Spain and southern Italy indicates minimal consumption of tea in these countries. Even so, the major sources identified for the total and individual flavanols, PA and theaflavins were quite similar except in the UK where pulses also formed a considerable food source of PA.

A well-established inverse geographical gradient of CVD mortality exists(42), which may seem paradoxical with the north-to-south gradient for flavan-3-ol intake and the observed beneficial effects of these compounds and flavonoid-rich foods against CVD(13, 15, 16). Though far-fetched at this point to imply that flavan-3-ols have a significant role in CVD, a few factors could be considered to help elucidate this. Despite their higher observed antioxidant activity in vitro (43, 44), galloylated flavan-3-ol monomers (mainly found in fermented/black teas) have lower bioavailability than non-galloylated monomers(3, 44) (found more commonly in non-citrus fruit, green tea and cocoa). However, it is more likely that other risk factors of CVD may be more prevalent in the northern countries, such as high intake of SFA(45), low intake of MUFA(46), low intake of fruits and vegetables(47), low wine consumption(48), sedentary lifestyle(49, 50) and social class influences(51).

The present study also demonstrated that statistical differences exist in flavan-3-ol intakes among groups with different socio-demographic, anthropometric and lifestyle characteristics. Consumption of total flavan-3-ols, monomers and PA increased with age up to about 64 years of age and then it fell slightly. Similar results were seen in Spanish-EPIC(23), US(8, 22) and Australian(52) studies in adults. The intakes were significantly higher in former and never smokers. Since the major sources were tea and fruits, respectively, this suggests possible interaction between the consumption of these food sources and smoking habits(53, 54). Additionally, two case–control studies suggested that a flavonoid-rich diet may protect against pancreatic and lung cancer in smokers only(55, 56). Total flavan-3-ol intakes have been shown to be significantly associated with a slower increase of BMI in women in The Netherlands Cohort Study after adjusting for confounders including dieting, and some healthy habits such as fruit and vegetable intake(57). Our study showed that the intakes of total and subclasses of flavan-3-ols were lower in obese subjects and, in addition, higher in physically active subjects. Further investigation explaining the association between all these factors and their role in obesity is needed. In our study, intakes of PA increased with higher level of education, and were found to be considerably low in the group without formal schooling. In line with our findings, consumption of fruits, fruit juice, wine and tea has been previously associated with higher socio-economic status(58). These factors should be taken into consideration when looking at disease prevention, planning of healthy diets within a specific population and may also be instrumental when establishing ‘lifespan essential’ dietary reference intakes for flavan-3-ols, PA and theaflavins in different populations, and in subgroups with unfavourable lifestyle factors(59).

Major differences in total flavan-3-ol intake can be observed between our study and other descriptive studies (Table 5). Our estimates of total flavan-3-ol intake were much higher than those reported in other countries and the main reason being that some individual compounds or subclasses of flavan-3-ols were not included in the total estimation of flavan-3-ols in those studies. Comparison of the subclasses (monomers, PA and theaflavins) may therefore be preferable. Even then, the intakes may vary because of other important factors involved in the estimation, such as different methodologies used to assess dietary intake of cohorts (FFQ, 24-HDR, diet history, etc); compositional data of the compounds may come from different sources or from older versions of the USDA database(23, 60), or the median intake reported rather than the mean. The latter is particularly the case in the Greek EPIC study(61). Finally, cohort characteristics, especially those that are associated with flavan-3-ol consumption (e.g. age and sex) may vary considerably. All these are to be kept in mind when making comparisons. Flavan-3-ol monomer intake reported recently for the UK and Ireland by Beking & Vieira(62) and based on food balance sheets was about one-third that of our reported intake for the UK region. The monomer intake reported in an elderly Dutch cohort(63) as closer but still slightly lower than our estimates for the Dutch cohorts of Bilthoven and Utrecht even though, in our study, intakes were found to be higher in older age groups. Monomer intakes reported recently in Italy(21) and for Spanish(23) and Greek(61) EPIC cohorts were within our ranges for those countries. As for other countries known to have a tea culture, Otaki et al. (60) have estimated monomer intake in Japanese women to be around 380 mg/d, more than double the value we reported for the UK region. This is probably because of higher consumption of non-fermented tea, such as green tea, in Japan. Green tea is a rich source of flavan-3-ol monomers but not a source of theaflavins, which was found exclusively in black tea, the tea more commonly consumed in the UK. In contrast, monomer intake (188 mg/d) reported in Australia was comparable to our value in the UK region. PA intake for Spain in our study is slightly higher than previously reported for the EPIC Spain cohort; however, the previous study used dietary history questionnaires and only the USDA food composition values in their estimation of flavan-3-ols(23). A recent Italian case–control study assessed the mean PA intake to be around 290 mg/d which is within the range of the Italian values in our study(21). However, most PA estimations have been done in case–control studies, which assess small groups of controls and not always all the subgroups of PA were included(20, 21, 64). Surprisingly, Greece being a MED country had the lowest intake of PA of all EPIC centres. Among the other previously mentioned factors for this difference, this finding is also supported by the lower consumption of fruit in Greece compared to Italy and Spain reported previously in EPIC studies(47). Perez-Jimenez et al. (65) reported intakes of flavan-3-ol monomers (114 mg/d), PA (191 mg/d) and theaflavins (16 mg/d) in French women that are within the range of our values for the French EPIC centres. A limited number of descriptive studies is available on PA to facilitate a comparison with non-EPIC countries. Using their own composition database, Ovaskainen et al. (66) reported lower PA intakes for a Finnish population compared to the northern EPIC countries such as Sweden and Norway. The sources of PA in northern EPIC countries were found to be similar to those in Finland, with the exception of berries, which were not singled out in our study but were an important source of PA in Finland. These differences in intake and food sources compared to our study are most probably due to the varying study variables already exposed earlier. Finally, Wang et al. (67) recently estimated PA intake for the US population to be about 95 mg/d. This is still slightly lower than the lowest intakes found in our study (Greek cohorts). Clearly, more consistent methods of intake estimation between and within countries are needed. Parallel to that, improved methods for identification and quantification of some flavan-3-ol compounds, such as thearubigins, are needed to allow for more exhaustive flavonoid composition databases.

Table 5 Previously estimated daily flavan-3-ol intakes (mg) in adults in several countries*

C, catechins; EC, epicatechins; EGC, (epi)gallocatechins; PA, proanthocyanidins; ns, not specified; –, value not provided by the original study; DR, dietary recall; USDA, US Department of Agriculture.

* Where applicable and when not provided by the study, total flavan-3-ols were calculated as the sum of the subgroups.

Median values given instead of the mean.

Total flavan-3-ols were calculated as the sum of the values in Rossi et al. (21) for C, EC, theaflavins and thearubigins combined and in Wang et al. (67) for PA.

The use of a common expanded flavonoid database provided us with greater coverage of foods representative of the EPIC countries while allowing for comparisons of results across the countries. Despite the fact that we applied retention factors to foods prepared by cooking, we estimated higher intakes than in the previous studies. Moreover, our values are likely to be underreported due to spices and herbs often not accounted for during diet assessment and because a small proportion (2–16 %) of flavan-3-ol analytical values in our study was still missing. The underestimation of intakes is also probably due to the omission of dietetic supplements in this analysis. However, few consumers of herb/plant supplements participated in this study (the highest was 5 % reported in Denmark)(68).

To our knowledge, this is the largest study to date describing flavan-3-ol and PA intake across several European countries. Since not all the EPIC cohorts are representative of the population, the observed level of intake cannot be extrapolated to the general population of each region.

In summary, this study provides total and individual flavan-3-ol, PA and theaflavin intakes for ten EPIC countries by sex and EPIC centre. The major dietary contributors of these flavonoid subclasses are described by the MED, non-MED and UK regions. In addition, we show that socio-demographic, anthropometric and lifestyle factors associated with differential consumption of flavan-3-ols, PA and theaflavins exist. Combined with more elucidated information on the bioavailability of these compounds, these descriptive data will be valuable in future evaluations of total and individual flavan-3-ols and their role in health and disease in the European population.

Acknowledgements

The present work was carried out with the financial support of the European Commission: Public Health and Consumer Protection Directorate 1993–2004; Research Directorate-General 2005; Ligue contre le Cancer, Institut Gustave Roussy, Mutuelle Générale de l'Education Nationale, Institut National de la Santé et de la Recherche Médicale (INSERM, France); German Cancer Aid; German Cancer Research Centre; German Federal Ministry of Education and Research; Danish Cancer Society: Health Research Fund (FIS) of the Spanish Ministry of Health (RTICC (DR06/0020); the participating regional governments and institutions of Spain; Cancer Research UK; Medical Research Council, UK; the Stroke Association, UK; British Heart Foundation; Department of Health, UK; Food Standards Agency, UK; the Wellcome Trust, UK; Hellenic Ministry of Health; the Stavros Niarchos Foundation and the Hellenic Health Foundation; Italian Association for Research on Cancer; Compagnia San Paolo, Italy; Dutch Ministry of Public Health, Welfare and Sports; Dutch Ministry of Health; Dutch Prevention Funds; LK Research Funds; Dutch ZON (Zorg Onderzoek Nederland); World Cancer Research Fund (WCRF); Swedish Cancer Society; Swedish Scientific Council; Regional Government of Skane, Sweden; Nordforsk – Centre of Excellence programme. Some authors are partners of ECNIS, a network of excellence of the 6FP of the EC. R Z.-R. is thankful for a postdoctoral programme Fondo de Investigación Sanitaria (FIS; no. CD09/00133) from the Spanish Ministry of Science and Innovation. The authors thank Raul M. García for developing an application to link the FCDB and the 24-HDR. The authors declare that there are no conflicts of interest. The authors' contributions are as follows: R. Z.-R. and C. A. G. designed the research; V. K. and R. Z.-R. conducted the research; V. K. and L. L.-B. performed the statistical analysis; V. K. and R. Z.-R. wrote the manuscript. V. K., R. Z.-R., L. L.-B., I. R., A. S., N. S., E. R., C. T. M. v. R., H. B. B.-d. M., A. T., V. D., K. T., G. S., D. E., J. R. Q., E. M., J. M. H., F. C., E. W., U. E., P. H. M. P, R. K., B. T., G. J., I. J., R. T., H. B., D. D., P. A., A. M., K.-T. K., R. L., V. Kr., E. A., C. S., S. S., K. O., A. T., A. O., M.-C. B.-R., G. F., F. P. and C. A. G. read, critically reviewed and approved the final manuscript.

Annex 1 Adjusted* mean daily intakes (mg/d) of flavan-3-ol monomer compounds by European Prospective Investigation into Cancer and Nutrition centre ordered from south to north (Mean values with their standard errors)

* Adjusted for sex and age, and weighted by season and day of recall.

Annex 2 Adjusted* mean daily intakes (mg/d) of proanthocyanidin (PA) and theaflavin subgroups by European Prospective Investigation into Cancer and Nutrition centre ordered from south to north (Mean values with their standard errors)

* Adjusted for sex and age, and weighted by season and day of recall.

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