Mediterranean Diet as a Protective Factor for Wheezing in Preschool Children
Article Outline
Objective
To test the hypothesis that the Mediterranean diet can be a protective factor for current wheezing in preschoolers.
Study design
Questionnaires were completed by parents of 1784 preschoolers (mean age, 4.08 ± 0.8 years). Children were stratified according to whether they experienced wheezing (20.0%) or not in the previous year. A Mediterranean diet score was built according to the intake frequency of several foods.
Results
Age, birth by cesarean section, low birth weight, exposure to livestock during pregnancy, antibiotic use in the first year of life, acetaminophen consumption in the previous 12 months, rhinoconjunctivitis, eczema, parental asthma and tobacco consumption, maternal educational level, maternal age, physical activity, cat at home, and Mediterranean diet were associated with current wheezing but not with obesity. In the multivariate analysis, eczema, rhinoconjunctivitis, paternal asthma, and acetaminophen consumption remained risk factors for current wheezing (adjusted odds ratio [aOR] = 2.35 [95% confidence interval (CI) = 1.2 to 4.8], 2.78 [95% CI =1.3 to 6.1], 3.89 [95% CI = 1.4 to 10.7], and 2.38 [95% CI = 1.2 to 4.6], respectively). Conversely, Mediterranean diet and older age remained protective factors (aOR = 0.54 [95% CI = 0.3 to 0.9] and 0.67 [95% CI = 0.5 to 0.9], respectively).
Conclusions
The Mediterranean diet is an independent protective factor for current wheezing in preschoolers, irrespective of obesity and physical activity.
Abbreviations: aOR, Adjusted odds ratio, BMI, Body mass index, CI, Confidence interval, ISAAC, International Study of Asthma and Allergies in Childhood, OR, Odds ratio, PUFA, Polyunsaturated fatty acid
Changes in diet could be potentially responsible for the parallel increase in asthma and obesity observed in recent decades. Although the causal relationship between obesity and asthma is subject to debate,1, 2 it is possible that diets that favor obesity are associated with asthma if in fact obesity is a risk factor for this disease. Furthermore, it has been hypothesized that the effect of diet on asthma pathogenesis could be directly related to both immunomodulatory and antioxidant mechanisms.3 Decreasing intake of antioxidants (in fruits and vegetables) and n-3 polyunsaturated fatty acid (PUFA) (in oily fish) and increasing intake n-6 PUFA (in margarine or vegetable oil) may have contributed to the recent increase in asthma and atopic diseases.3 Epidemiologic studies in adults and schoolchildren have reported an association of dietary antioxidants, such as vitamin C4, 5 and lipids (fish and fish products),6, 7, 8, 9, 10, 11 with a lower prevalence of asthma and atopic diseases. Conversely, fast food has been associated with increased asthma prevalence.12
See editorial, p 749
Dietary lipids exert numerous complex effects on proinflammatory and immunologic pathways; for example, omega-3 fatty acids can inhibit both arachidonic acid synthesis and cycloxygenase and 5-lipoxygenase action, leading to an overall reduction in inflammatory mediators, such as prostaglandins and leukotrienes.13 The spatial structure of fatty acids also appears to be important; trans fatty acids (the main source of industrially hydrogenated vegetable fats, used widely in fast food) were related to an increase in asthma prevalence in a European ecological study.14 It is known that the intake of trans fatty acids drops from higher levels in northern Europe to lower levels in the south (ie, Mediterranean countries).15 Curiously, according to the International Study of Asthma and Allergies in Childhood (ISAAC), asthma prevalence is lower in the Mediterranean countries.16 One common factor in those Mediterranean countries, besides the climate, is the “Mediterranean diet.” There are several variants of the Mediterranean diet, but common components include high monounsaturated/saturated fat ratio; high consumption of vegetables, fruit, legumes, and grains; and moderate consumption of milk and dairy products.17 Recently, our group in Spain18 and Chatzi et al19 in Crete reported that in school-age children, the Mediterranean diet is a protective factor for clinically significant asthma and allergic rhinoconjunctivitis, respectively. The role of diet in fetal (programming) and early life (preschool age) thus is an important area for future research.3
In the present study, we tested the hypothesis that the Mediterranean diet can be a protective factor for current wheezing in Spanish preschool-age children.
Methods
The study population comprised preschool-age children from the 3 major cities—Murcia, Cartagena, and Lorcain—in the province of Murcia in southeastern Spain. Because most preschool-age children attend school/kindergarten, all parents of children in a random sample of all primary schools (having preschool education) in each city were invited to participate. The number of schools included in the sample was that which allowed a sampling frame of 1000 children per city. All classes of the 2 grades (age 3 and 4 years) within those schools were included in the survey. Questionnaires were given to the parents by the children's teachers (either directly or through the children) and were returned within 1 week, at which point they were collected by a field worker.
The questionnaire used was based on the ISAAC phase III core and environmental questionnaires (see http://isaac.auckland.ac.nz) and included questions on asthma, rhinoconjunctivitis, and eczema, along with questions to elicit other demographic and environmental data. Demographic data obtained included age, sex, race, birth weight, type of delivery, current height and weight, number of younger and older siblings, maternal age, and maternal education level. Environmental data included breast-feeding, exposure to livestock during pregnancy and during the first year of the child's life, antibiotic consumption during the first year of the child's life, acetaminophen consumption during that period as well as during the previous 12 months, father's and mother's tobacco consumption (currently and during pregnancy), dogs and cats at home during the first year of the child's life as well as during the previous 12 months, truck traffic in front of the house, type of fuel used in heating and cooking systems, frequency of vigorous physical activity of sufficient duration to make the child breathe hard, and hours spent watching television per day.
For the purpose of the present study, current wheezing was defined as a positive answer to the question: “Has your child had wheezing or whistling in the chest during the last 12 months?” Current rhinoconjunctivitis was defined as a positive answer to the question: “Has your child had a problem with sneezing or a runny or blocked nose when he/she did not have a cold or the flu accompanied by itchy, watery eyes during the last 12 months?” Current eczema was defined as a positive answer to the following 3 questions: (1) “Has your child ever had an itchy rash that came and went for at least 6 months?”; (2) “Has your child had this itchy rash at any time in the past 12 months?”; and (3) “Has this itchy rash at any time affected any of the following places: the folds of the elbows, behind the knees, in front of the ankles, under the buttocks, or around the neck, ears, or eyes?”
From the parent-informed current height and weight of the child, body mass index (BMI; in kg/m2) was calculated. Obesity was defined according to the cutoff points of BMI reported by Cole et al20 for each age group and sex.
The environmental questionnaire also included questions on the consumption of certain foods in the past 12 months (never or occasionally, 1 or 2 times per week, and 3 or more times per week). The Mediterranean diet score used in this study was previously developed by our group18 and is based on the scoring system of Psaltopoulou et al.15 Fruit, fish, vegetables, legumes, cereals, pasta, rice, and potatoes are considered “pro- Mediterranean” foods and rated according the frequency of intake (0 points = never or occasionally; 1 point = 1 or 2 times/week; 2 points = ≥3 times/week). Meat, milk, and fast food are considered “anti-Mediterranean” foods and rated inversely (0 points = ≥3 times/week; 1 point = 1 or 2 times/week; 2 points = never or occasionally). Candies, industrial pastry, precooked pizzas, and fried food, along with hamburgers taken in fast food restaurants, are classified generically as fast food (Table I; available at www.jpeds.com). Quartiles of Mediterranean diet were calculated to compare the highest quartile against the lowest quartile.
Table I. Mediterranean diet score⁎
| Food | Never or occasionally, points | 1 or 2 times per week, points | ≥3 times per week, points |
|---|---|---|---|
| Fruit | 0 | 1 | 2 |
| Fish | 0 | 1 | 2 |
| Vegetables | 0 | 1 | 2 |
| Legumes | 0 | 1 | 2 |
| Cereals | 0 | 1 | 2 |
| Pasta | 0 | 1 | 2 |
| Rice | 0 | 1 | 2 |
| Potatoes | 0 | 1 | 2 |
| Meat | 2 | 1 | 0 |
| Milk | 2 | 1 | 0 |
| Fast food† | 2 | 1 | 0 |
⁎After summarizing all of the points, higher scores mean greater adhesion to the Mediterranean diet, and lower scores mean less adhesion. |
†Candies, industrial pastry, precooked pizzas, and fried food, together with hamburgers taken in fast-food restaurants, were considered generically as “fast food.” |
The Ethics Committee of the University of Murcia approved this study. Full informed and signed consent was obtained from a parent of each subject.
Statistical Analysis
Statistical analyses of the differences between the current wheezing and non–current wheezing groups were performed using the χ2 test for categorical variables, Student's t-test for continuous variables, and the Mann-Whitney U-test for ordinal variables. Odds ratios (ORs) and 95% confidence intervals (CIs) also were calculated. A multivariate logistic regression model was built using the presence of current wheezing as the dependent variable and those factors that were statistically significant (P < .05) in the univariate analysis as independent variables. Then a second model was built using those factors that attained near statistical significance (P ≤ .1) in the univariate analysis. When the same factor was measured in 2 different ways (ie, during the first year of the child's life and during the previous 12 months), the more significant value of the 2 was incorporated in the analysis. Adjusted ORs (aORs) and 95% CIs were calculated from the logistic regression model. All analyses were performed using Stata 7.0 statistical software (Stata Corp, College Station, TX).
Results
Of the 2922 children invited to participate in the study, 1784 children completed the questionnaire (a 61% participation rate), and 1757 children (mean age, 4.08 ± 0.8 years; 48.8% male) answered the question regarding current wheezing status. In this group, the prevalence of current wheezing was 20.0% (n = 351). There were no significant sex differences between wheezing and nonwheezing children; however, there were slightly more Caucasians among the nonwheezing children. Children in the current wheezing group were significantly younger than those in the current nonwheezing group; the proportion of older and younger siblings was similar in both groups (Table II; available at www.jpeds.com).
Table II. Demographic characteristics in the children of the current wheezing and nonwheezing groups
| Current wheezing (n = 351) | Current nonwheezing (n = 1406) | OR (95% CI) | P | |
|---|---|---|---|---|
| Male | 53.3 | 51.1 | 1.1 (0.8to1.4) | .51 |
| Age, years | 3.87±0.8 | 4.13±0.8 | <.0001 | |
| Caucasian | 91.5 | 94.3 | 0.7(0.4to1.1) | .06 |
| Birth weight, kg | 3.976±0.82 | 4.085±0.79 | .025 | |
| Delivery by cesarean section | 29.5 | 23.5 | 1.4(1.0to1.8) | .02 |
| Breastfeeding ≥6 months | 39.9 | 45.1 | 1.2(0.9to1.6) | .08 |
| Livestock during pregnancy | 12.6 | 8.8 | 1.5(1.0to2.2) | .027 |
| Livestock during the first year of life | 14.0 | 12.7 | 1.1(0.8to1.6) | .5 |
| Antibiotic consumption the first year | 68.2 | 57.4 | 1.5(1.2to2.1) | <.0001 |
| Acetaminophen consumption the first year | 38.8 | 27.0 | 1.7(1.3to2.2) | <.001 |
| Acetaminophen consumption in the previous 12 months | ||||
| Never | 24.2 | 30.5 | ||
| Less than once per month | 45.9 | 54.5 | <.0001 for trend | |
| At least once per month | 29.9 | 15.1 | ||
| Current rhinoconjunctivitis | 21.8 | 6.0 | 4.4(3.1to6.1) | <.0001 |
| Current dermatitis | 10.9 | 7.0 | 1.6(1.7to2.5) | .016 |
| Paternal asthma | 6.3 | 3.1 | 2.1(1.2to3.7) | .004 |
| Maternal asthma | 8.0 | 4.0 | 2.1(1.3to3.4) | .002 |
| Maternal age, years | 33.5±5.3 | 34.3±5.3 | .014 | |
| Number of older siblings | ||||
| 0 | 47.8 | 51.0 | .30 for trend | |
| 1 | 36.7 | 36.4 | ||
| ≥2 | 15.5 | 12.6 | ||
| Number of younger siblings | ||||
| 0 | 73.8 | 67.7 | .096 for trend | |
| 1 | 24.5 | 29.8 | ||
| ≥2 | 1.8 | 2.5 | ||
| Maternal education | ||||
| No education | 6.9 | 4.3 | .045 for trend | |
| Elementary | 41.7 | 41.7 | ||
| High school | 33.3 | 33.3 | ||
| University | 18.2 | 23.7 | ||
| Truck traffic near the child's house | ||||
| Never | 26.3 | 23.5 | .11 for trend | |
| Rarely | 41.04 | 47.1 | ||
| Frequently during the day | 23.7 | 23.0 | ||
| Almost all day and night | 8.9 | 6.4 | ||
| Current paternal smoking | 51.9 | 44.5 | 1.3(1.1to1.7) | .014 |
| Current maternal smoking | 48.7 | 39.6 | 1.4(1.1to1.8) | .002 |
| Maternal smoking during pregnancy | 40.2 | 35.1 | 1.2(0.9to1.6) | .075 |
| Dog in the first year | 17.9 | 14.0 | 1.3(0.9to1.8) | .06 |
| Dog in the previous 12 months | 15.7 | 14.5 | 1.1(0.8to1.5) | .6 |
| Cat in the first year | 7.9 | 4.6 | 1.8(1.1to2.8) | .017 |
| Cat in the previous 12 months | 9.5 | 4.7 | 2.5(1.4to3.6) | <.0001 |
| Highest quartile of Mediterranean diet | 42.9 | 53.2 | 0.7(0.4to0.9) | .037 |
| BMI | 16.59±2.74 | 16.54±2.5 | .765 | |
| Obesity | 12.6 | 11.4 | 1.1(0.7to1.7) | .56 |
| Vigorous physical activity | ||||
| Never or occasionally | 54.5 | 46.9 | .027 for trend | |
| 1 to 2 times per week | 22.0 | 28.3 | ||
| 3+ times per week | 23.5 | 24.8 | ||
| Time watching TV per day | ||||
| <1 hour | 28.2 | 23.5 | .054 for trend | |
| >1 hour ≤3 hours | 54.1 | 62.0 | ||
| >3 hours ≤5 hours | 14.8 | 11.7 | ||
| >5 hours | 2.9 | 2.8 |
More children from the current wheezing group were born by cesarean section, and birth weight was significantly lower in this group. The current wheezing group also had a slightly lower proportion of children who had been breast-fed for 6 months or longer. The proportion of mothers who had contact with livestock (at least once per week) during pregnancy was significantly higher in the current wheezing group; however, the proportion of children who had contact with livestock during their first year of life was similar in both groups (Table II).
Children in the current wheezing group had significantly higher antibiotic and acetaminophen consumption during the first year of life. Consistent with this finding, the proportion of children who used acetaminophen in the previous 12 months was significantly higher in the current wheezing group (Table II).
There were significantly more current eczema and rhinoconjunctivitis symptoms, as well as significantly higher prevalence of parental asthma, in the current wheezing group. Mothers were significantly younger in the current wheezing group, and maternal educational level was significantly higher in the nonwheezing group (Table II).
Parental current smoking was significantly higher in the current wheezing group, and maternal smoking during pregnancy was also higher in this group (although the difference between the 2 groups did not reach statistical significance). Truck traffic in front of the child's house tended to be heavier in the current wheezing group (Table II). There were no differences in the type of fuel heating and cooking systems used at home between the 2 groups (data not shown).
The proportion of families owning a cat in the first year of the child's life and in the previous 12 months was significantly higher in the current wheezing group, and the proportion of children owning a dog during the first year of life was marginally higher in this group (Table II). The current wheezing group had a lower rate of vigorous physical activity. Sex was found to modify the effect of physical activity on wheezing. In boys, the prevalence of current wheezing in children engaging in the various levels of vigorous physical activity was 23.8% in those reporting never or occasionally, 15.1% for those reporting 1 to 2 times per week, and 19.3% for those reporting 3 or more times per week (P = .029 for trend). In girls, the corresponding prevalences were 20.6%, 17.0%, and 18.3%, respectively (P = .5 for trend). In addition, the number of hours per day spent watching television was marginally higher in the current wheezing group (Table II).
BMI and obesity were similar in the 2 groups. For the entire study group, the Mediterranean diet score ranged from 14 to 36. We divided this range into quartiles; the prevalence of current wheezing in these quartiles, from lowest to highest, was 21.0%, 19.8%, 22.0%, and 16.4%, respectively. Comparing the lowest quartile with the highest quartile, those children with greater adherence to the Mediterranean diet (highest quartile) had a significantly lower risk of having current wheezing (OR = 0.6; 95% CI = 0.4 to 0.9; P = .037) (Table II). When grouped by sex or obesity, the proportion of children in the highest quartile of Mediterranean diet consumption was similar in the 2 groups (data not shown). Neither sex nor age modified the effect of Mediterranean diet on wheezing (data not shown).
The frequency of intake of vegetables, cereals, margarine, and candies over the previous 12 months differed significantly (P for trend <.1) between the 2 groups (Table III). The types of oil used for cooking (ie, olive oil, margarine/butter, other) were similar in the 2 groups (85%, 0.3%, and 12.9%, respectively, in current wheezing group vs 85.2%, 0.3%, and 13.7% in the nonwheezing group; P for trend = .24).
Table III. Prevalence (%) of the intake of different foods among children with current wheezing and current nonwheezing
| Current wheezing(n=351) | Current nonwheezing(n=1406) | P for trend | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Never or occasionally | 1 or 2 times per week | ≥3 times per week | NA | Never or occasionally | 1 or 2 times per week | ≥3 times per week | NA | ||
| Meat | 2.7 | 36.1 | 61.0 | 0.2 | 2.2 | 37.4 | 60.1 | 0.3 | .67 |
| Seafood | 16.0 | 72.4 | 11.3 | 0.3 | 13.4 | 74.4 | 11.8 | 0.4 | .67 |
| Fruit | 10.7 | 20.5 | 68.5 | 0.3 | 9.4 | 20.9 | 69.3 | 1.7 | .86 |
| Vegetables | 48.7 | 19.6 | 29.7 | 2.0 | 45.1 | 25.8 | 28.7 | 0.4 | .001 |
| Legumes | 6.8 | 52.5 | 40.7 | 0 | 7.3 | 56.5 | 36.0 | 0.2 | .49 |
| Cereals | 2.7 | 15.7 | 80.8 | 0.8 | 3.1 | 18.7 | 78.0 | 0.2 | .04 |
| Pasta | 10.2 | 68.2 | 21.6 | 0 | 8.5 | 71.0 | 20.3 | 0.2 | .71 |
| Rice | 10.7 | 73.4 | 15.9 | 0 | 7.8 | 77.5 | 14.6 | 0.1 | .27 |
| Butter | 73.3 | 15.8 | 9.1 | 1.8 | 74.8 | 17.7 | 6.0 | 1.5 | .18 |
| Margarine | 78.1 | 10.8 | 9.6 | 1.5 | 77.2 | 16.5 | 5.0 | 1.3 | .003 |
| Nuts | 59.4 | 31.6 | 8.1 | 0.9 | 55.9 | 35.8 | 7.6 | 0.7 | .53 |
| Potatoes | 7.6 | 41.1 | 51.3 | 0 | 8.9 | 46.7 | 44.2 | 0.2 | .19 |
| Milk | 2.0 | 3.2 | 92.8 | 2.0 | 2.9 | 4.9 | 90.4 | 1.8 | .56 |
| Yogurt | 5.2 | 13.1 | 80.2 | 1.5 | 4.1 | 14.2 | 80.3 | 1.4 | .90 |
| Eggs | 8.2 | 77.4 | 13.2 | 1.2 | 8.5 | 76.5 | 14.3 | 0.7 | .94 |
| Candies | 47.2 | 34.0 | 17.9 | 0.9 | 49.8 | 36.9 | 13.1 | 0.2 | .095 |
| Industrial pastry | 53.8 | 34.1 | 10.9 | 1.2 | 55.3 | 32.4 | 11.8 | 0.5 | .33 |
| Precooked pizzas | 70.3 | 26.9 | 1.2 | 1.6 | 72.3 | 25.9 | 0.8 | 1.0 | .31 |
| Hamburgers | 87.7 | 9.5 | 1.0 | 1.8 | 91.1 | 6.9 | 0.7 | 1.3 | .14 |
| Precooked fried food | 44.7 | 47.2 | 6.3 | 1.8 | 45.6 | 48.2 | 5.4 | 0.8 | .46 |
In multiple logistic regression analysis, after controlling for variables found to be significantly (P < .05) related to current wheezing in the univariate analysis, only older age and being in the highest quartile of Mediterranean diet consumption remained protective factors for current wheezing. Conversely, rhinoconjunctivitis and eczema, along with acetaminophen consumption at least monthly in the previous 12 months and paternal asthma, remained risk factors for current wheezing (Table IV). In the second multiple logistic regression model, in which variables with marginal significance (P ≤ .1) in the univariate analysis also were introduced, no significant changes were seen (data not shown).
Table IV. Multivariate analysis for factors related to current wheezing
| aOR (95% CI)⁎ | P | |
|---|---|---|
| Age, years† | 0.67(0.48to0.93) | .018 |
| Birth weight, kg† | 0.78(0.58to1.05) | .102 |
| Livestock during pregnancy | 0.99(0.41to2.43) | 1.00 |
| Delivery by cesarean | 1.03(0.59to1.81) | .91 |
| Antibiotic consumption during the first year | 1.55(0.94to2.57) | .09 |
| Acetaminophen consumption during the previous 12 months | ||
| None | 1 | — |
| At least once per year | 1.08(0.60to1.94) | .79 |
| At least once per month | 2.38(1.22to4.64) | .011 |
| Rhinoconjunctivitis | 2.78(1.27to6.12) | .011 |
| Dermatitis | 2.35(1.15to4.81) | .019 |
| Paternal asthma | 3.89(1.41to10.69) | .008 |
| Maternal asthma | 1.86(0.45to7.70) | .39 |
| Maternal age | 1.01(0.96to1.06) | .61 |
| Maternal educational level | ||
| No studies | 1 | — |
| Elementary | 1.30(0.30to5.75) | .72 |
| High school | 1.88(0.43to8.25) | .40 |
| University | 1.49(0.32to6.90) | .61 |
| Current paternal smoking | 0.95(0.57to1.59) | .83 |
| Current maternal smoking | 1.47(0.87to2.48) | .15 |
| Vigorous physical activity | ||
| Never or occasionally | 1 | — |
| 1 to 2 times per week | 0.96(0.54to1.71) | .89 |
| 3+ times per week | 0.91(0.51to1.63) | .75 |
| Cats in the last 12 months | 1.84(0.73to4.60) | .20 |
| Highest quartile of Mediterranean diet | 0.54(0.33to0.88) | .014 |
⁎OR adjusted for all of the variables in the table. |
†Per unit increment. |
Discussion
The present cross-sectional study suggests that the Mediterranean diet may be a protective factor for current wheezing in preschool-age children, independent of obesity and physical activity. This finding is in agreement with a recent study reported by our group in which Mediterranean diet was found to be a protective factor, and obesity a risk factor, for clinically significant asthma in 6- to 7-year-old Spanish females.18 In the present study, current wheezing was not associated with obesity or sex, and no interaction of obesity or sex with Mediterranean diet was found. Possible explanations for the differences in the 2 studies include that the populations of the 2 studies were dissimilar in terms of age (6 to 7 years in the previous study vs 3 to 4 years in the current study) and geographical distribution (several areas of the country in the previous study vs only a Mediterranean population in the current study). Second, the ranges of the Mediterranean diet score were quite different: 4 to 20 (4 to 20 for boys and 4 to 19 for girls) in the previous study versus 14 to 36 (14 to 35 for boys and 15 to 36 for girls) in the present study. This difference is likely due to 2 reasons: The food questionnaire was slightly expanded to offer a better explanation of certain foods (eg, various fast foods besides hamburgers), and it was addressed to children in different geographic settings. Finally, in the previous study, it was possible to stratify asthma in 2 levels of severity (because the number of children was large), but this could not be done in the current study.
When considering the complex relationship between obesity and asthma, it is important to mention that many cross-sectional and longitudinal studies21 have reported that obesity is indeed a risk factor for asthma—but only in schoolchildren, with the effect greatest in prepubertal girls with early menarche,22 suggesting a possibly important effect of sex hormones. Few studies have been conducted in children under age 5 years. Von Kries et al23 reported an association of overweight/obesity and asthma in girls age 5 to 6 years, and Guilliland et al2 demonstrated an association between BMI and asthma in nonallergic children age 4 to 11 years. The children in the present study are younger than those in these 2 studies, a possibly important factor in the discrepancy.
The Mediterranean diet is rich in both antioxidants and cis-monounsaturated fatty acids. A European ecological study found a trend toward lower prevalence of sensitization with higher intake of fruit and vitamins A and C,24 and a worldwide ecological ISAAC study reported an inverse relationship between vegetable consumption and asthma.7 Moreover, 2 cross-sectional studies in Italian schoolchildren (age 6 to 7 years) using the ISAAC questionnaire found inverse associations between consumption of citrus/kiwi fruit in winter and asthma25 and between consumption of cooked vegetables and current wheezing.26 Very recently, our group, using the ISAAC questionnaire in Spanish schoolchildren (age 6 to 7 years), found an inverse association between fruit intake and rhinoconjuntivitis and a certain trend between vegetable intake and asthma.18 Pastorino et al27 reported that intake of cooked vegetables was a protective factor for asthma in Brazilian adolescents.
In the present study, the nonwheezing group had higher vegetable and cereal intake and lower margarine and candy intake compared with the current wheezing group. Wickens et al12 reported fast food as a risk factor for asthma in New Zealand schoolchildren age 10 to 12.5 years. Nonetheless, a recent interventional study in preschool children failed to show any protective effect on asthma, wheezing, or atopy from a diet high in omega-3 long-chain PUFA and low in omega-6 acids; however, the ratio of omega-6 to omega-3 acids in plasma was lower in the diet group.28 A potential explanation for these controversial results is that the protective effect may not be related to one particular food—rather, the entire diet is important. In the present study, as in our previous study,18 the Mediterranean diet seemed to offer protection from wheezing, likely due to a positive balance effect of eating “protective” foods and avoiding “risky” foods rather than only eating specific foods; however, our findings cannot be used to devise recommendations on the quantities of Mediterranean foods necessary to exert a protective effect, because our data are based on the frequency of food consumption in the previous 12 months. In a recent study of schoolchildren age 7 to 18 years in rural Crete, Chazti et al20 found that good adherence to the Mediterranean diet was protective for allergic rhinoconjunctivitis and uncovered a more modest protection for wheezing and atopy (skin test). These authors suggested a beneficial effect of commonly consumed fruits (especially grapes), vegetables, and nuts. Grapes and nuts are rich in the potent antioxidant substances phenolics and vitamin E, respectively.20 In contrast, and similar to the present study, they found that intake of margarine had a harmful effect on asthma.
Recently, physical activity or exercise has been posited as a potential factor in the relationship between obesity and asthma in children.29 Our previous study18 found that physical activity was a protective factor for occasional asthma but not for clinically significant asthma; however, an earlier longitudinal study22 and other cross-sectional studies30, 31 have found no clear association between low physical activity and asthma in children or adults.32 In the present study, preschool-age children (mainly boys) who engaged in less physical activity had a higher prevalence of current wheezing; but this association did not remain significant after adjustment for other variables in the multivariate analysis. It is important to note that although diet and BMI are relatively simple to measure and follow, objectively quantifying physical activity is more challenging over long periods, especially in children.29 The other factors that remained significantly associated with current wheezing (eg, rhinoconjunctivitis, eczema, and paternal asthma) are well-known and well-accepted risk factors.33, 34, 35
The present study has some potential limitations. First, an information bias on food intake could be present. However, it has been shown that parents generally are reliable when reporting the children's food intake, especially with fruit and vegetables.36 In addition, our food questionnaire unfortunately did not allow for correction of energy intake; nevertheless, most other studies on diet and asthma in children also did not correct for this variable.37 Second, a bias on reported height and weight also could be present; however, a previous study conducted in the same area as ours found that parental reports of children's height and weight are reliable data for epidemiologic studies.38 Finally, as in all cross-sectional studies, the findings of the current study cannot establish a causal relationship. Consequently, prospective studies on the relationship between asthma and diet are needed, especially during fetal and early life,3, 37 to provide insight into the potential of various foods in preventing asthma and atopy.
The authors thank Anthony Carlson for his editorial assistance.
References
- . Obesity and asthma: evidence for and against a causal relation. J Asthma. 2003;40:1–16
- Obesity and the risk of newly diagnosed asthma in school-age children. Am J Epidemiol. 2003;158:406–415
- . Diet as a risk factor for atopy and asthma. J Allergy Clin Immunol. 2005;115:1109–1117
- . Increase in asthma: a more toxic environment or a more susceptible population?. Thorax. 1994;49:171–174
- . Relationship of serum antioxidants to asthma prevalence in youth. Am J Respir Crit Care Med. 2004;169:393–398
- Nutrition and respiratory health in children in six Central and Eastern European countries. Thorax. 2003;58:231–236
- . Diet and asthma, allergic rhinoconjunctivitis and atopic eczema symptom prevalence: an ecological analysis of the International Study of Asthma and Allergies in Childhood (ISAAC) data (ISAAC Phase One Study Group). Eur Respir J. 2001;17:436–443
- . Diet, serum fatty acids, and atopic diseases in childhood. Allergy. 2001;56:425–428
- . Consumption of oily fish and childhood asthma risk. Med J Aust. 1996;164:137–140
- . Factors associated with bronchial hyperresponsiveness in Australian adults and children. Eur Respir J. 1992;5:921–929
- . Asthma and allergic rhinoconjunctivitis at 4 years of age in relation to fish consumption in infancy. J Asthma. 2003;40:343–348
- . Fast foods: are they a risk factor for asthma?. Allergy. 2005;60:1537–1541
- . Effect of dietary enrichment with eicosapentaenoic and docosahexaenoic acids on in vitro neutrophil and monocyte leukotriene generation and neutrophil function. N Engl J Med. 1985;312:1217–1224
- . Intake of trans fatty acids and prevalence of childhood asthma and allergies in Europe (ISAAC Steering Committee). Lancet. 1999;353:2040–2041
- . Olive oil, the Mediterranean diet, and arterial blood pressure (The Greek European Prospective Investigation Into Cancer and Nutrition (EPIC) study). Am J Clin Nutr. 2004;80:1012–1018
- Worldwide variations in the prevalence of asthma symptoms: The International Study of Asthma and Allergies in Childhood (ISAAC). Eur Respir J. 1998;12:315–335
- . Healthy traditional Mediterranean diet: an expression of culture, history, and lifestyle. Nutr Rev. 1997;55:383–389
- The relationship of asthma and rhinoconjunctivitis with obesity, exercise and Mediterranean diet in Spanish schoolchildren 6-7 years old. Thorax. 2007;62:503–508
- Protective effect of fruits, vegetables and the Mediterranean diet on asthma and allergies among children in Crete. Thorax. 2007;62:677–683
- . Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ. 2000;320:1240–1243
- . Obesity and asthma: what are the links?. Curr Opin Allergy Clin Immunol. 2005;5:185–193
- . Increased incidence of asthma-like symptoms in girls who become overweight or obese during the school years. Am J Respir Crit Care Med. 2001;163:1344–1349
- . Is obesity a risk factor for childhood asthma?. Allergy. 2001;56:318–322
- . Allergic sensitization and diet: ecological analysis in selected European cities. Eur Respir J. 2001;17:395–402
- . Consumption of fresh fruit rich in vitamin C and wheezing symptoms in children (SIDRIA Collaborative Group, Italy (Italian Studies on Respiratory Disorders in Children and the Environment)). Thorax. 2000;55:283–288
- . Dietary factors associated with wheezing and allergic rhinoconjunctivitis in children. Eur Respir J. 2003;22:772–780
- . Risk factors for asthma in adolescents in a large urban region of Brazil. J Asthma. 2006;43:695–700
- Prevention of asthma during the first 5 years of life: a randomized controlled trial. J Allergy Clin Immunol. 2006;118:53–61
- . Paediatric asthma and obesity. Paediatr Respir Rev. 2006;7:233–238
- . Asthma and maternal body mass index are related to pediatric body mass index and obesity: results from the Third National Health and Nutrition Examination Survey. Obes Res. 2000;8:575–581
- . Decreased physical activity among Head Start children with a history of wheezing: use of an accelerometer to measure activity. Pediatr Pulmonol. 2005;40:57–63
- . Asthma is associated with weight gain in females but not males, independent of physical activity. Am J Respir Crit Care Med. 2001;164:2045–2050
- . The Melbourne Asthma Study: 1964-1999. J Allergy Clin Immunol. 2002;109:189–194
- . Tucson Children's Respiratory Study: 1980 to present. J Allergy Clin Immunol. 2003;111:661–675
- . A clinical index to define risk of asthma in young children with recurrent wheezing. Am J Respir Crit Care Med. 2000;162:1403–1406
- The accuracy of parental reports of their children's intake of fruits and vegetables: validation of a food frequency questionnaire with serum levels of carotenoids and vitamins C, A, and E. Epidemiology. 1993;4:350–355
- . Diet and asthma. Am J Respir Crit Care Med. 2004;170:725–729
- Validity of parent-reported height and weight for defining obesity among asthmatic and nonasthmatic schoolchildren. Int Arch Allergy Immunol. 2006;139:139–145
Supported by the Environmental Department, Cartagena District Health Authority, Cartagena, Spain.
PII: S0022-3476(08)00004-8
doi:10.1016/j.jpeds.2008.01.003
© 2008 Mosby, Inc. All rights reserved.
Refers to article:
- A Tough Nut to Crack
