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Nutritional Epidemiology

Vitamin Intakes from Supplements and Fortified Food in German Children and Adolescents: Results from the DONALD Study¹

Research Institute of Child Nutrition (FKE), Dortmund and Rheinische Friedrich–Wilhelms–Universität, Bonn, Germany

² To whom correspondence should be addressed. E-mail: sichert{at}fke-do.de.

	ABSTRACT

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Frequent consumption of supplements is a common behavior in adults, as well as children and adolescents. We report on vitamin intake from consuming supplements, taking into account the vitamin intake from fortified and usual foods. A total of 5990 3-d weighed dietary records from 931 German subjects (452 males, 479 females, 2–18 y of age) between 1986 and 2003 from the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study were evaluated. We identified 133 different vitamin-containing supplements in 451 records (7.5%). Slightly more males (8.0%) than females (7.1%) consumed supplements, with highest frequencies found between ages 15 and 18 y. For the majority (10 of 13) of vitamins (vitamin A, vitamin E, vitamin K, thiamin, riboflavin, vitamin B-6, vitamin B-12, niacin, biotin, and vitamin C), intake from usual and fortified food already reached or exceeded 80% of the recommended dietary allowances in all age groups. In the case of folate and pantothenic acid, intake from supplements was necessary to achieve at least 80% of recommended dietary allowances for half of the age groups, especially in females. Supplements with vitamin D considerably helped increase vitamin intake but failed to achieve 80% of references in almost all age groups. Intakes of vitamin A and folic acid exceeded the tolerable upper level most frequently in many age groups and were most pronounced in up to 32% and 13% of children aged 2–3 y. Intake of vitamin D, vitamin E, and vitamin C exceeded the tolerable upper level in single age groups only (<7% of subjects). For the other vitamins, no exceeded limits were identified. The ubiquitous availability of supplements might indicate that even healthy children and adolescents profit by taking them. However, it is difficult to evaluate whether consumers receive more benefits or risks from the unrestricted consumption of supplements as they are marketed today.

KEY WORDS: • dietary • supplements • vitamin intake • children • adolescents • dietary reference intakes • tolerable upper intake level

The German market for dietary supplements is extremely buoyant, with rising sales and a volume of over 1 billion Euros per annum (1–3). The consumption of dietary supplements may contribute to micronutrient intake considerably. Therefore, dietary evaluations and nutrient intake assessments in countries like Germany are likely to be misleading if dietary supplement consumption is not quantified. However, surveys on supplement use focus mostly on adults, and little is known about the consumption of supplements by children and adolescents. In the USA, 55% of children receive some sort of vitamin and mineral supplements (4,5). A study of a Netherlands population during 1987–1988 showed that dietary supplement consumption decreased with age, from 63% in ages 1–3 y (mainly fluorine) to 9% in ages 16–18 y (6).

In Germany, dietary supplements are ubiquitously available in food stores and pharmacies. A recent market survey on supplements intended for children and adolescents identified 110 different products from 37 producers. These products contained a total of 31 different nutrients, with vitamins more frequently indicated than minerals (7). In actual dietary practice as well, supplements containing vitamins are consumed more often than supplements containing minerals (8). We therefore analyzed the dietary records of the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study to examine consumer vitamin intake in the age range of 2–18 y, as well as consumption time trends during 1986–2003. In particular, we focused on the different sources of vitamin intake, such as usual food, fortified food, fortified instant beverages, and supplements.

	SUBJECTS AND METHODS

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
    Subjects. The DONALD Study is an ongoing longitudinal open cohort study that started in Germany 1985 in the city of Dortmund with the collection of detailed data on the diets, growth, development, and metabolism of healthy subjects between infancy and adulthood. Approximately 40 infants per year are recruited and examined, first at the age of 3 mo, and then followed to the age of 20 y (girls) and 23 y (boys). Compared with the general population, parents of DONALD Study participants are characterized as having a higher educational and socio-economic status (9). Parents of the children, or the older subjects themselves, kept 3-d weighed dietary records once per year, i.e., they weighed and recorded all foods and fluids consumed over the course of 3 d, including leftovers, using electronic food scales (±1 g). Approximately 20% of males and 30% of females aged 13–14 y, and 70% males and 90% females aged 15–18 y, kept records self-dependently. Product information from containers, wrappers, cartons, etc., including any type of preparation (e.g., medicines or supplements) were kept and evaluated along with the dietary records kept by our dieticians. Our study reports on subjects with at least 1 supplement intake in a 3-d dietary record.

    Supplements. According to the U.S. FDA, dietary supplements are defined, in part, as products "intended to supplement the diet that bears or contains one or more of the following dietary ingredients: a) a vitamin, b) a mineral, c) an herb or other botanical, d) an amino acid, d) a dietary substance for use by man to supplement the diet by increasing the total dietary intake, or f) a concentrate, metabolite, constituent, extract, or a combination of any ingredient described [above]" (10; online). This definition is in accordance with the German regulations. In our study, only supplements containing vitamins were considered. Supplements available only through prescription, or supplements with vitamin D combined with fluorine for infants only, were excluded.

Supplements were subdivided into 3 groups: 1) combination products that contained 1 vitamin and 1 mineral, 2) vitamin-only products that contained 1 vitamin and no minerals, and 3) special products for special purposes, e.g., sports and energy drinks.

Vitamin A and niacin were calculated as equivalents and folic acid in supplements and fortified foods (instant and others) as folate (i.e., dietary folate equivalents). To identify subjects with intakes above the tolerable upper intake level (UL) only preformed vitamin A and folic acid contents were used (11).

    Statistics. Between 1986 and 2003, a total of 5990 3-d weighed dietary records from 931 German subjects (452 males and 479 females) between the ages of 2 and 18 y were collected. Subjects under the age of 2 y were excluded, because food intake patterns differ markedly from older children as shown by previous evaluations of the DONALD Study (12).

SAS system for Windows (release 8.02) was used for data analysis. Only consumers of vitamin supplements were considered, i.e., those who reported at least 1 such supplement within a 3-d record. Subjects who reported using different supplements during the 3-d recording period were defined as multiple consumers. Mean intakes reported in individual 3-d records were calculated. Results are expressed as means (vitamin intake), or as means, medians, and percentiles (of vitamin content in supplements). The level of significance was set at P < 0.05. Differences of frequencies between subgroups were analyzed using chi-square test. For trend analysis PROC GENMOD (dist = bin, link = logit) was used to estimate the probability of supplement consumption in the sample and controlled for age, gender, season, year of the study, and repeated measurements of subjects or families.

To compare the contribution of supplements with the contribution of other dietary sources of vitamin intake, we distinguish between usual food (nonfortified), fortified commercial instant beverages (marketed and consumed similarly to dietary supplements), and other fortified commercial products. Nutrient intake was calculated as a percentage of German US FDA reference values (13) to achieve comparable data for different age groups. Mean intakes of at least 80% of US FDA reference values (i.e., estimated average requirements) were considered as sufficient. To evaluate supplement dosages, the US FDA reference values for nutrition labeling were used (10). Vitamin loss due to food preparation was taken into account but not for fortified instant beverages, other fortified food, and dietary supplements.

The DONALD Study is exclusively observational, noninterventional, and noninvasive as approved by the International Scientific Committee of the Research Institute for Child Nutrition.

	RESULTS

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
    Type of supplements. Overall, 133 different vitamin-containing supplements (59% combinations, 41% vitamins only) were consumed. The most frequently added was vitamin C (90% of products), followed by thiamin, riboflavin, vitamin E, vitamin B-6, and niacin (60–70%), whereas vitamin D and vitamin K were used less frequently (20 and 9%, respectively). Labeled dosages in vitamin-only supplements tended to be higher than in combinations. Medians varied greatly from 10 to 120% of US FDA reference values (Fig. 1). Particular supplements with vitamin C, riboflavin, vitamin B-6, vitamin B-12, and folic acid had broad ranges for dosages.

View larger version (17K): [in this window] [in a new window]   FIGURE 1  Distribution of vitamin content in supplements expressed as a percentage of US FDA reference values for nutrition labeling (10). The number of supplements containing the vitamin is given in brackets. Boxplots are percentiles (P10, P25, P75, P90), medians, and means.

    Vitamin intake. In almost all age groups, total vitamin intake exceeded 120% of US FDA reference values except for vitamin D and folate (Fig. 2A). Mean intake over 200% of the US FDA reference values were identified in many age groups, especially for vitamin K (data not shown), riboflavin, niacin (Fig. 2B), vitamin B-6, vitamin B-12, vitamin C, and biotin (Fig. 2C).

View larger version (25K): [in this window] [in a new window]   FIGURE 2  Intake of vitamins in consumers of supplements (mean values are expressed as percentages of German US FDA reference values) from different sources (usual and fortified food, fortified instant beverages, and supplements) from the DONALD Study. Vitamin D, folate, pantothenic acid, and vitamin A (A). Vitamin E, thiamin, niacin, and riboflavin (B). Vitamin C, vitamin B-12, vitamin B-6, and biotin (C).

Overall, we identified 3 vitamin-intake scenarios. 1) No benefit at all: For the majority (10 of 13) of vitamins studied (vitamin A, vitamin E, vitamin K, thiamin, riboflavin, B-6, vitamin B-12, niacin, biotin, and vitamin C), the intake from usual plus fortified food reached or exceeded 80% of the US FDA reference values in all age groups (Figs. 2A, C). 2) Benefit to single age groups: For some age groups, in the case of folate and pantothenic acid, intake from supplements was necessary to achieve at least 80% of the US FDA reference values, especially in females (Fig. 2A). 3) Benefit to almost all age groups: In the case of vitamin D, supplements considerably increased vitamin intake, but failed to achieve 80% of the US FDA reference values in almost all age groups (Fig. 2A).

    UL. Consumer intake of folic acid and preformed vitamin A exceeded the UL most frequently and was most pronounced in 13 to 32% of consumers, respectively. The frequency of intake above the UL for both vitamins decreased with age. Vitamin D, vitamin E, and vitamin C intakes above the UL were found only in single-age groups. For all other vitamins examined intakes fell below the UL.

	DISCUSSION

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
This report is an analysis of vitamin intake in consumers of supplements and takes into account the vitamin intake from fortified instant beverages, other fortified food, and usual food. The main findings from our analysis of the DONALD Study are the following: 1) despite supplement intake, the mean total intake of vitamin D remains mostly inadequate, and folate and pantothenic acid supplements are necessary for raising intake levels above 80% of the US FDA reference values in some age groups; 2) for most of the vitamins (vitamin E, vitamin K, vitamin C, thiamin, riboflavin, vitamin B-6, niacin, vitamin B-12, and biotin) intake from food, including fortified food, was at least adequate, and for vitamin C, vitamin K, thiamin, vitamin B-6, vitamin B-12, and biotin, intake was abundant; and 3) for vitamin A and folic acid, intakes exceeded the UL in a considerable number of individuals, indicating a potential risk for high intake due to supplement consumption.

In many countries, including Germany, the frequent consumption of supplements is common behavior, not only in adults but also in children and adolescents. However, differences in study design, assessment method, sample selection, and definition of supplement type or use make comparisons among studies difficult. We report actual supplement consumption in 3-d dietary records and may therefore underestimate this habit, whereas data in the literature (4,5,14,15) that has been collected through household interviews investigate supplement consumption over a longer period of time.

The types of supplements, however, are less affected by the method of assessment. Hence our data of supplement types consumed accords with data from other studies from various countries, including Germany, all confirming the predominant use of vitamin supplements over mineral supplements. In the National Health and Nutrition Examination Survey III (1988–1994), 30% of all products recorded were vitamin-mineral combinations, 37% were vitamin supplements, and 15.7% were mineral supplements (4), similar to frequencies of product types reported in our study (8).

A recent report (16) of German children and adolescents indicates that time trends in supplement consumption show a pattern similar to those of nutrient intakes from fortified food. We also found a uniform increase until 1994, and a decrease thereafter, in 6 of 8 fortified vitamins studied. A comparison of the data of change in supplement consumption in a U.S. population of 18–24 y olds between 1987 and 1992, showed a 1% increase (up to 14.2%) (17). During the same period in our sample, supplement consumption increased by 2% but only to 7% in 1992. In contrast, the National Health and Nutrition Examination Survey indicates that U.S. children's consumption of supplements has decreased since 1980 and is stable in adults (18).

The mean frequency of supplement consumers throughout the study period was about one-half as high as in another regional study in Germany, with 23% in 4–16 y olds assessed using a 7-d record (19), but was similar to data obtained from a German-adolescent food-habit questionnaire (20) and to children and adolescents in other European countries (6,14,21,22). During the periods studied, supplement consumption in U.S. populations, according to age, was higher than reported here (23) and, in many cases, considerably higher (5,24–26). Also, the consumption of more than one supplement at a time is more common in U.S. populations than in our study population (5,17,27), whereas findings from the U.K. are similar to ours (14).

Our finding, that males consume supplements more often than females, has also been shown in other studies (20,21). In addition, our result of seasonal effects on consumption habits, with higher frequencies in winter compared with summer, is supported by the literature (6,22).

Studies reporting the contribution of supplemented vitamins to total vitamin intake in children and adolescents are rare. Results are inconsistent with our data. However, in the U.S., and similar to our study, supplements contributed between 30 and 60% of the total vitamin intake for 2 y olds (24). But, in contrast to our data, and especially in the case of vitamin E and vitamin B-12, as much as 80–90% of vitamin intake came from supplements in 12–14 y olds (28). In summary, we were unable to establish whether age has a consistent effect on total vitamin intake after consuming supplements.

A few studies have focused on whether supplements benefit the vitamin intake of children or adolescents. In a study of 2 y old U.S. children, a majority of nonsupplement users received adequate levels of nutrients from food (except vitamin E, vitamin A, and folate), and between 92 and 100% of supplement users exceeded the US FDA reference values of vitamin intake (24). In adolescents, the mean intake of vitamins from food sources alone exceeded US FDA reference values (except vitamin A and vitamin E), while the intake (for all vitamins studied) from food and supplements, taken together, far exceeded the US FDA reference values (28). These results agree with other findings where individuals who were already consuming enough vitamin C to meet US FDA reference values were more likely to supplement their diet (6,26).

The present report demonstrates that, in the case of vitamin D, pantothenic acid, and folate, female consumers especially benefit from supplementation. However, vitamin D is obtained also through sunlight exposure, making oral intake alone nonessential in principal. At present, Germany is proposing that production of commercial food products with folic acid should be stopped, if basic foods, such as flour, will be fortified with folic acid. Our data supports this idea after identifying a considerable number of individuals with intakes of folic acid above the UL among supplement users, especially in the children's age groups.

The use of nutritional supplements, together with the wider consumption of fortified food, has led to a focus on the possible risks of excessive vitamin intake. Excessive consumption of vitamin A, vitamin E, vitamin D, niacin, vitamin B-6, and folic acid may be harmful (29–32). Nutrients that play a vital role in immune function may often affect, or be affected by, other nutrients. For example, an antagonistic effect has been noted from vitamins E and vitamin A (33) as well as for vitamin C, when taken in combination with more complex multivitamin supplements (34). We found that total intakes above the UL are especially frequent in the case of folic acid and vitamin A, and, in some individuals, for vitamin D, vitamin E, and vitamin C. Similarly, in Korean adolescents, intakes of vitamins A, vitamin C, niacin, and folic acid in supplement consumers exceeded UL levels (35–37). In Korean adults this was the case for vitamin A, vitamin B-6, folic acid, and especially niacin (38,39). In the U.S., 27% of adolescents, 12–14 y old, consumed supplements exceeding the age-appropriate UL for niacin (28).

At present there is no agreement in the scientific community as to whether to fortify food, educate people, or use supplements. But it is agreed that priority should be given to a balanced food choice, combined with nutrition education, especially in children and adolescents. The ubiquitous availability of supplements in Germany might lead parents of children (or the adolescents themselves) to believe that even healthy children and adolescents profit by taking supplements. However, at present, not even experts can evaluate whether children and adolescents receive more benefit or risk from the unrestricted use of supplements as they are marketed today.

	ACKNOWLEDGMENTS

 
We are grateful to Christa Chahda, and Ruth Schäfer for collecting and coding dietary records in the DONALD Study.

	FOOTNOTES

 
¹ The DONALD Study is supported by the Ministry of Innovation, Science, Research, and Technology of Nordrhein-Westfalen, Germany.

Manuscript received 11 October 2005. Initial review completed 22 November 2005. Revision accepted 25 January 2006.

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