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Age and time trends in fish consumption pattern of children and adolescents, and consequences for the intake of long-chain n-3 polyunsaturated fatty acids

Abstract

Background/Objectives:

There is a lack of detailed data on fish consumption in European children and adolescents. We therefore investigated fish consumption patterns, portion sizes and estimated intakes of long-chain n-3 polyunsaturated fatty acids (PUFA; eicosapentaenoic acid, docosahexaenoic acid).

Subjects/Methods:

From the Dortmund Nutritional and Anthropometric Longitudinally Designed study between 1985 and 2006, yearly 3-day weighed dietary records (N=7152) from 1024 subjects (2–18 years, 49% males) were evaluated.

Results:

On 14% of total recorded days fish consumption from 33 different species was documented. In the total sample (in the subgroup with fish intake), mean fish intake almost doubled from 5 to 14 g per day (from 15 to 37 g per day) within the age range. Mean portions of fish increased from 40 to 89 g per portion, predominantly from low-fat fish species. In the total sample mean long-chain (LC) n-3 PUFA intake increased with age from 42 to 141 mg per day (100–324 mg per day in the subgroup with fish intake). Without any fish consumption in the recording period, n-3 LC PUFA intake ranged below 20 mg per day. Within the 20-year time frame, the frequency of fish consumption increased significantly (P<0.0282) from 35% at the start in 1985 to 40% in 2005.

Conclusions:

Fish consumption—even with low intakes as observed here—improves LC n-3 PUFA considerably. Owing to the very low preference for high-fat fish in our sample, the potential of fish intake as an LC n-3 PUFA source was not considered.

Introduction

Salt water fish in general is a source of nutrients, for example, protein, retinol, vitamin D and E, iodine and selenium. In addition, high-fat salt water fish provides long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA): eicosapentaenoic acid (EPA; 20:5n-3), docosapentaenoic (DPA; 22:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). Evidence from different types of epidemiological studies indicates that the intake of LC n-3 PUFA may help to prevent cancers and cardiovascular diseases in adults (Welch et al., 2002; He et al., 2004; Whelton et al., 2004; Scientific Advisory Committee on Nutrition, 2004; Harris, 2007). In addition, LC n-3 PUFA, in particular DHA, is well known for positive influence on the cognitive and the visual development in infants. In the Food-Based Dietary Guidelines (FBDG) for children and adolescents in Germany, similar to population-based FBDG in adults, regular consumption of salt water fish including high-fat fish species is recommended up to 100 g per week depending on age (Kersting et al., 2005). Up to now, detailed data on how these recommendations were fulfilled in dietary practice were not available in our country and are also scarce elsewhere. An exception to this are recent comprehensive assessments of PUFA intake in Flemish children and adolescents including data on fish consumption (Sioen et al., 2007a, 2007b).

The Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study collects detailed data on food pattern and nutrient intake in German children and adolescents aged between 1 and 18 years, and started as early as 1985. Therefore, the objective of this investigation was (1) to assess fish consumption patterns in general and with respect to age and time trends (2) to estimate the LC n-3 PUFA regarding the role of fish and (3) to evaluate the findings in accordance with the FBDG for this population.

Methods

Study design

The DONALD Study is an observational (open) cohort study collecting detailed data on diet, metabolism, growth and development from healthy subjects between infancy and young adulthood: every 3 months in the first year of life, twice in the second year and once a year thereafter. The study started in 1985 with children and adolescents of all age groups from the district of Dortmund. Afterwards, around 40 infants aged 3 months were enrolled per study year. Details have been described elsewhere (Kersting et al., 1998; Kroke et al., 2004). The study was approved by the ethics committee of the University of Bonn, and all examinations were performed with parental consent.

Dietary assessment

Parents of the children or the adolescents themselves kept 3-day weighed diet records (consecutive days), that is, weighed and recorded all foods and fluids consumed as well as leftovers using electronic food scales (to the nearest 1 g). Product information from wrappers or product labels (for example, from frozen fish fingers) on ingredients and nutrients was kept by the participants. Semiquantitative recording (for example, numbers of fried fish fingers) was allowed if weighing was not possible. However, in 75% of the completed 3-day records more than 90% of the food items were weighed. Each individual assessment starts on a random day of a week (in total, about 27% of the days were weekend days). Here we report the results from the dietary records collected between 1985 and 2005 in study participants aged 2–18 years (mean number of repeated 3-day records: n=7).

Food and nutrient database

All food items ever reported in the DONALD study and their nutrient contents are stored in the in-house food and nutrient database LEBTAB (Sichert-Hellert et al., 2007). Data on LC n-3 PUFA of fish and non-fish foods (for example, eggs, meat) were taken from official and recently updated German (Lebensmittelchemie, 2000), US (USDA, 2006) and Danish databases (Møller et al., 2005). For commercial food products (for example, fish fingers) data were taken from product labels if available or otherwise estimated by simulated recipes from the ingredients (Sichert-Hellert et al., 2007). If product information was not available, the dieticians bought the food to weigh the portion and to identify the ingredients. Fish as an ingredient in recipes was calculated separately as the amount of pure fish. Even small fish amounts (for example, anchovy on pizza) were considered. Crustaceae and other seafood (for example, octopus, mollusk) were consumed only exceptionally and therefore not considered in the present evaluation. Also, fish-oil capsules as supplements had only been recorded in a few cases, and were not considered. No other food items fortified with LC n-3 PUFA were found in the records evaluated here.

Fish species were grouped according to their fat content into three categories: low-fat, <1%; medium-fat, 1–10% and high-fat fish >10% fat. Fish ‘consumers’ were defined as subjects reporting at least one meal occasion containing fish within the 3 recorded days, and ‘nonconsumers’ of fish as subjects not reporting any fish consumption in the 3 recorded days, respectively. The LC n-3 PUFA intake was calculated as the sum of EPA and DHA.

Statistical methods

SAS procedures (version 8.02; SAS Institute Inc. Cary, NC, USA) were used for data analysis. Descriptive statistics (that is, means, frequencies) were computed wherever appropriate. To analyze effects of age, sex and time, we used a mixed linear model (Proc Mixed). The following dependent variables were chosen: 3-day mean fish intake, 3-day mean energy intake from fish in percent of total energy, 3-day mean fat intake from fish in percent of total intake from fish and 3-day mean total LC n-3 PUFA intake in percent of total fat intake. An exponential structure of covariance was specified to consider correlation of repeated records dependent on the absolute time interval between measurements within the same subject. A possible time trend in the consumption frequencies of fish was analyzed with logistic regression (Proc Logistic). The statistical significance was set at P<0.05.

Results

Fish consumption pattern

Between 1985 and 2005, 7152 three-day records from 1024 subjects (49% males) between 2 and 18 years of age were collected. In 2717 (38%) of these 3-day records or on 3018 single days (14% of total recorded days) fish consumption was documented—mostly only as a single meal occasion per day (in total 3155 meals with fish) (Table 1).

Table 1 Mean intakes of energy, fish consumption, EPA+DHA, total fat and fat from fish in the total sample, in nonconsumers of fish, in consumers of fish and on days with fish consumption

A total of 33 different species of fish were consumed, with the highest variety among the medium- and high-fat species (n=5/16/12 with low/medium/high-fat content, respectively). In the low-fat group, the most consumed fish species was pollack (49% of total fish intake), in the medium-fat group tuna (13%) and in the high-fat group herring (8%), respectively.

In the total sample and in the subgroup with fish intake, mean fish intake almost doubled from the age of 2 until 18 years (Table 1). Mean portions of fish increased from 40 to 89 g per portion (Figure 1).

Figure 1
figure1

Mean fish portion sizes (g) in consumers of fish from the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study by age and gender. Values are means, medians and 10th, 25th, 75th, and 90th percentiles. References are German Food-Based Dietary Guidelines (Kersting et al., 2005).

LC n-3 PUFA intake

In the total sample mean LC n-3 PUFA intake increased with age from 42 to 102 mg per day in girls and from 49 to 141 mg per day in boys, and was more than twice as high in the subgroup with fish intake in the 3-day recording period and even about six times as high on days with fish intake only. In the subgroup without any fish consumption in the 3-day recording period, n-3 LC PUFA intake ranged below 20 mg per day (Table 1).

Based on the data in Table 1, mean LC n-3 PUFA intake in percent of total energy intake was quite constant irrespective of age and gender between 0.04 and 0.05% in the total sample, 0.09 and 0.1% in the subgroup of consumers of fish and between 0.2 and 0.3% on days with fish consumption. In the subgroup of nonconsumers of fish, mean LC n-3 PUFA did not exceed 0.01% of energy intake.

Time trends

Within the 20-year time frame (1985–2005), the frequency of 3-day records showing fish consumption increased significantly (P<0.0282) from 35% at the start in 1985 to 40% in 2005, independent of age (P<0.8854) and gender (P<0.0563).

Mean fish intake in the total sample increased by about 0.5 g per day and per year of age (P<0.0001), and in the subgroup of fish consumers by about 1.2 g per day and per year of age (P<0.0001). Boys in the total sample always had about 2 g per day (P<0.0001) higher mean intakes than girls, and about 3.7 g per day (P<0.0001) in the subgroup of fish consumers, respectively.

For the contribution of fish to total energy intake, however, there was neither a time trend in the total sample (time, P<0.7121; gender, P<0.3726), nor in the subgroup of fish consumers (time, P<0.0659; gender, P<0.5566).

With respect to changes in the fat content of fish consumed, there was neither a time trend in the total sample (time, P<0.1139; gender, P<0.5921), nor in the subgroup of fish consumers (time, P<0.2329; gender, P<0.4277). However, in the total sample, the fat content of fish increased significantly with age by about 0.05% per year of age (P<0.0001) and in consumers of fish by about 0.13% per year of age (P<0.0001).

In the total sample, LC n-3 PUFA intake (EPA+DHA) in percent of total fat intake increased slightly during the study period (0.0013% per year, P<0.0351), but was more pronounced with age (0.0025% per year, P<0.0005) independent of gender (P<0.7087). However, in consumers of fish, only a significant increase with age (0.0065% per year; P<0.0001; time, P<0.1237; gender, P<0.2614) was found.

Discussion

The present evaluation of fish consumption in a sample of German children and adolescents mainly found that (1) fish consumption frequency was rather low independent of age but increased with time, (2) fish consumption—even with low intakes as observed here—improves LC n-3 PUFA considerably and (3) fish portion sizes in children were closer to the FBDG than in adolescents. Our data supplement the rare information on fish consumption in children and adolescents in Europe and additionally provide time trend information for fish and LC PUFA intake in these age groups.

It is difficult to assess the habitual intake of foods that are rarely eaten in Germany, such as fish, by the use of prospective diet records over a few days. However, weighed dietary records are the most precise way to assess amounts consumed and portion sizes, and applied with sufficient number of cases (or days), habitual intake for population groups can be estimated with these data.

In the FBDG for children and adolescents in Germany (Kersting et al., 2005) portion sizes between 35 g (2 years of age) and 100 g (15–18 years of age) are recommended once a week. The mean recorded portion sizes in our sample were close to these recommendations: in the younger age groups of children but lower in older children and adolescents (Figure 1).

Fish consumption frequencies of around 40% in our total sample are similar to results from of an FFQ survey within the recent nationwide German Health Examination Study on 3- to 17-year-old children and adolescents where about 20% reported fish consumption at least once a week and about 60% 1–3 times per month (Mensink et al., 2007b). Thus both the nationwide and our local study show lower frequencies of fish than recommended. However, we could prove a small but significant increasing time trend that was independent of age and therefore seems to reflect general fish consumption pattern across age groups in children and adolescents.

In total, consumption frequencies of fish from Germany are similar to those of preschool children (3-day records: 31%; Sioen et al., 2007a) and lower than those of adolescents in Belgium (7-day records: 64; Sioen et al., 2007b).

Besides the assessment of food portion sizes, a further strength of weighed dietary records is the accessibility of detailed information on food selection. Because the contents of fat and n-3 LC PUFA of the various fish species vary (about 1–30 g fat and about 200 mg to 3.6 g n-3 LC PUFA per 100 g; Lebensmittelchemie, 2000), the identification of the fish species consumed is mandatory to estimate fat and fatty acid intake from fish.

In the children's age groups, mean fish intake with 8.6–11.0 g per day in our study was similar to 8–15 g per day from a recent nationwide survey using 3-day records in Germany in 6- to 11-year olds (Mensink et al., 2007a). In Belgium, mean fish intake with 8.6 g per day in the total sample (27.4 g per day in fish consumers) (Sioen et al., 2007a) was higher in children and lower in adolescents than reported for Germany.

Fish is a natural and important source for LC n-3 PUFA. However, due to the very low preference for high-fat fish in our sample, the potential of fish intake as an LC n-3 PUFA source was not considered. Low intakes of fatty fish were also found in pre-schoolchildren in Belgium (Sioen et al., 2007a), and the EPA and DHA intakes of 72 mg per day in children (Sioen et al., 2007a), and of 148 mg per day in adolescents (Sioen et al., 2007b), were only slightly higher than our results (Table 1).

At present, there are no German recommendations, and only a few recommendations for LC n-3 PUFA intake in children and adolescents from other countries, making the appraisal of our results difficult. References from the Netherlands recommend daily EPA and DHA intakes of 150–200 mg per day for children and adolescents (Health Council of the Netherlands, 2002), and Eurodiet population goals are 200 mg per day (Kafatos and Codrington, 2000). The estimated mean EPA and DHA intakes of about 40–140 mg per day in the total sample of our study are considerably lower than recommended but much higher in fish consumers. Changing preferences from low- to high-fat fish would further improve EPA and DHA intake. Taking into account the increase in fish consumption frequencies and amounts observed in our study, a further improvement might be expected. In addition, the use of n-3-rich vegetable oils could be a means of narrowing the n-6/n-3 ratio in the diet and enhance the metabolism pathways in preference for EPA and DHA (Valsta et al., 1996; Gerster, 1998). In conclusion, even the observed low fish intake in our sample is important under preventive aspects because studies in adults show a reduced stroke incidence even with low fish consumption (Keli et al., 1994; Streppel et al., 2008).

Conflicts of interest

The authors declare no conflict of interest.

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Acknowledgements

The DONALD study is supported by the Ministry of Innovation, Science, Research, and Technology North Rhine-Westphalia, Germany. The present evaluation was supported by a grant from Unilever Deutschland Holding GmbH, Dammtorwall 15, 20355 Hamburg.

We thank Christa Chahda and Ruth Schäfer for collecting and coding the dietary records in the DONALD study, and Diane Pavlitzek for proofreading.

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Correspondence to W Sichert-Hellert.

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Contributors: WSH analyzed the data and was primarily responsible for the preparation of the paper. MK initiated the evaluation and took part in the interpretation and the discussion of all results. MW prepared the data sets and tables.

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Sichert-Hellert, W., Wicher, M. & Kersting, M. Age and time trends in fish consumption pattern of children and adolescents, and consequences for the intake of long-chain n-3 polyunsaturated fatty acids. Eur J Clin Nutr 63, 1071–1075 (2009). https://doi.org/10.1038/ejcn.2009.40

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Keywords

  • dietary record
  • children
  • adolescents
  • fish consumption
  • long-chain n-3 polyunsaturated fatty acids
  • PUFA

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