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February 2013 Newsletter Article


Children's Environmental Health Article Summary

by Mera Goodman MD submitted with Perry Sheffield, MD, MPH, Icahn School of Medicine at Mount Sinai, New York, NY

Review of: Ellwood P, Innes Asher M, García-Marcos L, Williams H, Keil U, Robertson C, Nagel G, and the ISAAC Phase III Study Group. Do fast foods cause asthma, rhinoconjunctivitis, and eczema? Global findings from the international study of asthma and allergies in childhood (ISAAC) phase three. Thorax (of BMJ), published online first on January 14, 2013.

Of the studies attempting to link dietary intake to increasing trends in asthma, rhinoconjunctivitis and eczema, one of the largest multicenter trials, or the ISAAC (International Study of Asthma and Allergies in Childhood) study, has recently released results from its multipart, global study examining possible associations. Part I of the study claimed to demonstrate strong association between increased caloric intake from rice, cereal, nuts and increased prevalence in all three symptoms of asthma, rhinoconjunctivitis, and eczema and potential protective effects of increased fruit consumption. Phase II of the study examined objective testing of atopy and claimed to show an association between frequent consumption of fruit, vegetables and fish with lower lifetime incidence of asthma; this was opposed to increased burger consumption which conversely had a higher association with asthma. Multiple similar studies were cited in both the recent phase III release as well as the phase I and phase II publications that are portrayed to support the hypothesis and findings. Whereas not to comment on the limitations of the approach, data analysis, and findings of the above studies, we will instead review the newest online publication: that of Phase III.

Phase III study looks at the dietary behaviors and symptoms of atopy of two age groups (13-14 year old "adolescents" and 6-7 year old "children") over the preceding year to again look at any dietary association with increased asthma, rhinoconjunctivitis, and eczema. A combination of standardized core questionnaire and optional environmental questionnaire looking at both dietary choices and scoring of symptoms were distributed to patients or parents in these age groups; in addition to showing a brief atopy video detailing symptoms for the purposes of gradating symptoms. The final analysis included over 350,000 adolescents and 220,000 children, across 122 centers in 54 countries and 75 centers in 32 countries, respectively. Prevalence and severity odds ratios were calculated, adjustments were made for possible confounders of gender, school design effects, region, per capita gross national income, and covariates (exercise, television watching, maternal smoking, maternal education, BMI) were examined. There are numerous tables of findings itemized by region, dietary item and symptom throughout the article; however, the general summary of the findings is as follows:

  • For adolescents: fruit, milk and vegetable consumed at least once per week were mildly protective for current wheeze, severe asthma, current/severe rhinoconjunctivitis, and severe eczema. Seafood, butter, "fast food", margarine and pasta consumed > 3 times per week showed strongest association with severe symptoms across all categories.
  • For children: eggs, fruit, meat, vegetables, and milk consumed more than three times per week were generally mildly protective across current and severe symptoms in all three symptom categories, whereas "fast food" consumed > 3 times per week was associated with increased current and severe symptoms across all three symptom categories.
  • Of note, the study was attempting to take a closer look at "fast food" but uses a variety of proxies for fast food given cultural differences from a multicenter approach, which may include a proxy of "red meat" or "hamburger". Further, associations with dietary intake were generally a predictor of disease severity not disease incidence. Odds ratios of statistical significance mostly indicated only a mild change in disease severity of 10% increase or decrease in incidence.

In conclusion, the ISAAC phase III study demonstrates only a mild change in disease severity as associated with dietary choices. Mechanisms for worsened disease severity may include increased intake of saturated fats, trans fatty acids, sodium, carbohydrates preservatives, and sugar or may reflect a general lifestyle and wellness influence (the latter not addressed in the article); whereas protective effects may be attributed to increased antioxidants and low inflammatory food consumption. Though the size and geographical breadth is a strong positive for the study, which allows for multiple sub-analyses and normalization by possible confounders given the large data set; the size may also be a limitation as we better understand local practices for food processing, complex reporting biases and genetic polymorphisms within subpopulations. Further, like most studies of this nature, there is the difficult question of causality that is left unanswered.

Submitted by
Perry Sheffield

perry.sheffield@mssm.edu

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