Plant Foods Hum Nutr (2007) 62:93–98 DOI 10.1007/s11130-007-0047-7
ORIGINAL PAPER
Estimation of Daily Human Intake of Food Flavonoids P. Mullie & P. Clarys & P. Deriemaeker & M. Hebbelinck
Published online: 28 June 2007 # Springer Science + Business Media, LLC 2007
Abstract The daily intake of food flavonoids was determined using a semiquantitative food frequency questionnaire (FFQ) and a four day non consecutive food diary (4DFR) in a group of 45 female Flemish dietitians. The subjects were asked to report their food intake three times: day 1 using the FFQ (FFQ1); between day 2 and 13 using a four day non consecutive food diary (4DFR); and again the FFQ on day 14 (FFQ2). The total flavonoid intake in mg/day as estimated with the different methods were respectively (mean and SD) for FFQ1 166.0±146.6 mg/day; for 4DFR 203.0±243.2 mg/day; and for FFQ2 158.3±151.8 mg/day. There was a significant different estimate for the amount of flavan-3-ols, flavanones and flavones when comparing the two FFQs with the 4DFR. The two research methods classified 88% of the 45 dietitians in the same or in an adjacent quartile for total flavonoid intake. The findings of this study indicate that the developed FFQ seems to be a simple and reliable method to assign subjects in quartiles of flavonoid intake. Keywords Epidemiology . Flavonoid . Food frequency questionnaire . Food records . Human intake Abbreviations FFQ1 first semiquantitative food frequency FFQ2 second semiquantitative food frequency 4DFR four day non consecutive food diary FFQ semiquantitative food frequency P. Mullie (*) : P. Clarys : P. Deriemaeker : M. Hebbelinck Faculty of Physical Education and Physiotherapy, Department of Human Biometry and Biomechanics, Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium e-mail:
[email protected]
Introduction Flavonoids are the largest subclass of polyphenols [1]. Flavonoids receive increasing attention as research suggested their potential role in supporting health, particularly cardiovascular health. In numerous in vitro and in vivo studies, anti-allergic, anti-inflammatory, antiviral or antioxidant properties were attributed to selected flavonoids [1–3]. Although flavonoids are widely distributed in nature and in foods, they lack uniform distribution throughout the plant kingdom. Many commonly consumed fruits, vegetables and beverages contain various classes of flavonoids in varying quantities. High concentrations of flavonoids are found mainly in foods characterized by a high skin-volume ratio such as grape and cherry tomatoes [4]. The accumulation of plant flavonoids is positively related with the amount of received sunlight. Flavonoid intake estimates in humans vary by nearly 50-fold, from 20 to 1,000 mg/day [5]. This high variation can be attributed to widely differing intake levels of specific food sources of flavonoids, as well as the use of food composition tables which are often incomplete with respect to the flavonoid content of the food items. The purpose of the current study was to establish a valid method by determining subclasses of flavonoids, using a semiquantitative food frequency questionnaire (FFQ) and a four day non consecutive food diary (4DFR).
Methods and Materials After approval of the study by the institutional board, 300 female subjects were randomly selected from the membership database of the Flemish Dietetic Association. Between February and May 2004 they were invited by mail to participate in this validation study. The inclusion criteria
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were: not pregnant, no health problems, and willing to participate in the study without receiving any financial support. The subjects were asked to report their own food intake three times using two different recording methods. The first time using a semiquantitative food frequency questionnaire (FFQ1), the second time (between day 2 and 13) using a four day non consecutive food diary (4DFR) and the third time (day 14) using a semiquantitative food frequency again (FFQ2). A FFQ specifically designed to collect data on the consumption of flavonoids and subgroups of flavonoids was developed. The main and only objective of this FFQ was to estimate the daily intake of the most important flavonoids during the last month. A list of 86 of flavonoidcontaining foods was included in the FFQ. The subjects recorded their consumption in a frequency table. An experienced dietitian analysed the FFQ. The consumption frequencies as described by Willett were used: more than six a day, four to six a day, two to three a day, once a day, five to six a week, two to four a week, once a week, one to three a month, almost never [6]. The consumption frequencies were transformed to obtain mean consumption a day. Mean flavonoid intake was calculated using Microsoft Office Excel 2003. For the assessment of overall energy, nutrient and flavonoid intake, a 4DFR method was used. A structured food diary was designed. For each food item consumed, the subjects were asked to give as much information as possible about the amount and type of food. The recorded food items were converted into quantities, and analysed for nutrient and flavonoid composition. Daily intake was estimated by averaging. This work was carried out by an experienced research dietitian in order to limit observer differences. Macronutrient analysis (total energy, proteins, carbohydrates and fat-types) was performed using the Unilever Nutritional Software (Becel Institute Nutritional Software BINS; Humaniteitslaan, 292 B-1190, Brussel). The used database for flavonoid content of different food items was created through a collaborative effort between (1) the USA Department of Agriculture and the Epidemiology Group, Jean Mayer USDA Human Nutrition Research Center on Aging, Frances Stern Nutrition Center, Tufts University School of Nutrition Science & Policy, and (2) Tufts New England Medical Center, Boston, MA; the Bell Institute of Health and Nutrition, General Mills, Minneapolis, MN; and (3) Unilever Bestfoods, North America, Englewood Cliffs, NJ [7]. For practical purposes, we limited our flavonoid validation study to the most important flavonoids: flavonols (quercetin, kaempferol, myricetin, isorhamnetin), flavones (luteolin, apigenin), flavanones (hesperetin, naringenin, eriodictyol) flavan-3-ols [(+)-catechin, (+)-gallocatechin, (−)-epicatechin, (−)-epigallocatechin, theaflavin, thearubigins)] and anthocyanidins (cyanidin, delphinidin, malvidin, pelargonidin, peonidin, petunidin).
Plant Foods Hum Nutr (2007) 62:93–98
Daily nutrient and flavonoid intake was described using the median, the mean and the standard deviation. The normality of flavonoid intake was visually tested with histograms and with the Kolmogorov–Smirnov goodness-of-fit test. Because of the non-normal distribution (Kolmogorov–Smirnov p
