INTRODUCTION

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Currently, the potential influence of altered consumption of polyunsaturated fatty acids on the increasing prevalence of atopic diseases is under investigation (1). It has been proposed that the formation of arachidonic acid-derived eicosanoids from -6 fatty acids leads to enhanced production of IgE, thus promoting allergic sensitization. Several studies failed to find any biochemical evidence for a delta-6-desaturation defect as potential cause of the altered composition of polyunsaturated fatty acids in atopic individuals (5, 6).

Epidemiologic studies based on an ecological study design (7, 8) supported the hypothesis that dietary fat consumption might play a role in atopy. On the basis of qualitative data on temporal changes in household consumption, a cross-sectional study in East Germany (9) reported an association of increased margarine consumption with hay fever in children, but no relation with atopic sensitization as assessed by skin prick test.

Using data of a cross-sectional health survey which comprises information on the individual use of different types of fat as spread (butter, margarine) during the past year, our aim was to assess whether the consumption of margarine in contrast to butter is associated with allergic sensitization and diseases in children.

	METHODS

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Study Subjects and Study Design

In 1998-1999 the third survey of a repeated cross-sectional study was conducted in the state of Sachsen-Anhalt, Germany. The study design, population sampling, and methods are described in detail elsewhere (10). In total, 2,348 children (47% girls) age 5 to 14 yr took part in the study (76% response rate). Questionnaire information on fat consumption was obtained from 2,228 children (47% girls). Blood analysis was performed in 1,940 children (47% girls). The study protocol was approved by the responsible ethics committee, and informed consent was obtained from the parents.

Procedures

Data on sociodemographic factors, living conditions, and children's health were gathered by a self-administered questionnaire. Parents were asked to report rhinitis symptoms during the past 12 mo (frequent sneezing, runny or blocked nose without concurrent infection, itchy eyes), ever physician's diagnosis of hay fever or asthma/asthmalike bronchitis, and whether their children ate exclusively butter, margarine, or both types of fat as spread during the past 12 mo. Data on other dietary factors were not collected. Allergic sensitization to common aeroallergens (house dust mite Dermatophagoides pteronyssinus, Cladosporium, cat, mixed grasses, and birch pollen) was assessed by specific serum IgE concentrations, using the RAST-FEIA-CAP system (Pharmacia, Freiburg, Germany). A child with at least one specific IgE  0.35 kU/L (RAST 1) was considered to be sensitized. In addition, children were categorized according to the degree of sensitization, suspecting higher specificity and clinically relevant manifestation of allergic sensitization in children with high specific IgE serum levels.

Statistical Analysis

Differences between boys and girls were determined by ² test of independence. Adjusted odds ratios (OR) for the association of allergic sensitization or diseases with the type of fat consumed (margarine only or margarine and butter versus butter only as reference group) were calculated by logistic regression. OR were adjusted for sex, age group, place of residence, parental education, parental atopy, presence of siblings, and body mass index. The software package SAS version 6.12 (SAS Institute, Cary, NC) was used for all calculations.

	RESULTS

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Most of the children used exclusively margarine as spread (n = 1,000, 45%), 636 children (29%) ate exclusively butter, 492 (22%) both types of fat, and 100 (5%) did not use butter or margarine at all. The analysis was refined to those 2,128 children who consumed butter or margarine, or both.

Prevalence of atopic diseases (asthma, hay fever), rhinitis symptoms, and allergic sensitization was higher in boys compared with girls (Table 1). Moreover, boys had higher total IgE serum concentrations than girls: geometric mean 67.8 kU/L (95% confidence interval [CI]: 62.1 to 74.1) versus 48.8 kU/L (44.6 to 53.5). No sex differences were observed in type of fat consumed and in sociodemographic characteristics known to be related to atopy development such as parental education and atopy, breast feeding, or age at entry into nursery (data not shown).

Allergic sensitization was significantly associated with the exclusive consumption of margarine in all children compared with butter-eating children as reference group (OR 1.30, 95% CI 1.01 to 1.67, Table 2). When children were categorized according to the degree of sensitization, the OR for the association with exclusive margarine consumption increased with increasing levels of specific serum IgE antibodies, i.e., higher RAST classes. The highest OR was observed in the group of children with IgE concentrations of RAST class 5 or 6 (OR 2.32, 95% CI 1.38 to 3.90).

On the other hand, the consumption of both types of fat was neither significantly associated with allergic sensitization at all (RAST class  1: OR 1.30, 95% CI 0.97 to 1.75) nor with very high specific IgE concentrations (RAST class  5: OR 1.29, 95% CI 0.68 to 2.46).

The sex-stratified analysis demonstrated that the association of margarine consumption with allergic sensitization (RAST class  1) existed only in boys, but not in girls (Table 2). In children with high specific IgE levels (RAST class  5), however, the OR for exclusive margarine consumption were increased in boys and girls, but reached statistical significance in boys only.

In accordance with these results, symptoms of allergic rhinitis during the past 12 mo were associated with exclusive margarine usage in all study subjects compared with butter consumption (Table 3). Again, sex-stratified analysis gave a stronger association in boys and no association in girls. Additional adjustment for allergic sensitization lowered the OR for rhinitis symptoms (margarine only, all children: 1.32 [0.93 to 1.87], boys: 1.50 [0.92 to 2.44]). The OR for physician-diagnosed hay fever showed a similar tendency with a significant association in case of margarine and butter consumption in boys but not in girls. Furthermore, no statistically significant relation between the type of fat consumed and ever physician-diagnosed asthma was found for the total population nor for a single sex stratum.

	DISCUSSION

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It is well-known that boys before puberty have higher serum IgE levels than girls (11, 12), suffer more often from atopic diseases than girls (12), and seem to be more vulnerable in general during childhood (13). Concerning the higher atopy prevalence of boys, this holds in our study population, too. Moreover, we found a sex-specific association of margarine consumption with allergic sensitization assessed by specific IgE serum levels and with symptoms of allergic rhinitis given as parents' report.

Clearly, our results have to be interpreted with great caution owing to the cross-sectional study design and the crude assessment of fat consumption. Parents' reporting of type of fat consumed is unlikely to differ between boys and girls. However, we do not know whether the amount of fat consumed differed between boys and girls. Moreover, additional data on total energy intake and on other dietary factors probably influencing atopy development were not available. Therefore, we adjusted OR for children's body mass index as a measure of body size in multivariate analyses. Body size is, besides metabolic efficiency and physical activity, one of the factors influencing energy intake and may be used as a crude indirect measure (14).

Margarine consumption might be a proxy for health awareness. With respect to environmental and sociodemographic factors studied in our health survey, we neither observed major differences between boys and girls nor differences between margarine or butter-eating children in our study group. Results of von Mutius and coworkers (9) also suggested an impact of margarine consumption on hay fever in children, but the investigators did not describe sex-stratified results.

It is tempting to speculate whether in boys, having higher total IgE levels than girls, the intake of certain polyunsaturated fatty acids amplifies the IgE production and subsequently enhances the probability to develop an atopic disease. Therefore, it seems worthwhile to study sex differences in dietary habits and fatty acid metabolism in the context of allergy-related immune functions and atopy development.