Early-life folate levels are associated with incident allergic sensitization
Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wis.The Journal of allergy and clinical immunology (Impact Factor: 11.48). 10/2012; 131(1). DOI: 10.1016/j.jaci.2012.08.015
Article: Mucosal Immunology of Food Allergy[Show abstract] [Hide abstract]
ABSTRACT: Food allergies are increasing in prevalence at a higher rate than can be explained by genetic factors, suggesting a role for as yet unidentified environmental factors. In this review, we summarize the state of knowledge about the healthy immune response to antigens in the diet and the basis of immune deviation that results in immunoglobulin E (IgE) sensitization and allergic reactivity to foods. The intestinal epithelium forms the interface between the external environment and the mucosal immune system, and emerging data suggest that the interaction between intestinal epithelial cells and mucosal dendritic cells is of particular importance in determining the outcome of immune responses to dietary antigens. Exposure to food allergens through non-oral routes, in particular through the skin, is increasingly recognized as a potentially important factor in the increasing rate of food allergy. There are many open questions on the role of environmental factors, such as dietary factors and microbiota, in the development of food allergy, but data suggest that both have an important modulatory effect on the mucosal immune system. Finally, we discuss recent developments in our understanding of immune mechanisms of clinical manifestations of food allergy. New experimental tools, particularly in the field of genomics and the microbiome, are likely to shed light on factors responsible for the growing clinical problem of food allergy.
Article: Folate and Asthma[Show abstract] [Hide abstract]
ABSTRACT: Findings from experimental studies and animal models led to the hypothesis that folic acid supplementation during pregnancy confers an increased risk of asthma. This review provides a critical examination of current experimental and epidemiologic evidence of a causal association between folate status and asthma. In industrialized nations, the prevalence of asthma was rising before widespread fortification of foodstuff with folic acid or folate supplementation before or during pregnancy, thus suggesting that changes in folate status are an unlikely explanation for "the asthma epidemic". Consistent with this ecologic observation, evidence from human studies does not support moderate or strong effects of folate status on asthma. Given known protective effects against neural tube and cardiac defects, there is no reason to alter current recommendations for folic acid supplementation during conception or pregnancy based on findings for folate and asthma. While we believe that there are inadequate data to exclude a weak effect of maternal folate status on asthma or asthma symptoms, such effect could be examined within the context of very large (and ongoing) birth cohort studies. At this time, there is no justification for funding new studies of folate and asthma.
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ABSTRACT: Although both folic acid intake and vitamin D levels are hypothesized to be contributors to the increased incidence of allergic diseases, prospective studies of these relationships have not been done in adults. We sought to determine whether serum folate or vitamin D levels are associated with incident mouse sensitization among new workers at a mouse facility. Subjects started employment at the Jackson Laboratory between June 2004 and July 2007. Skin testing to mouse and other allergens and collection of questionnaire data were performed at baseline and every 6 months. Serum folate and vitamin D levels were assessed on baseline samples stored at -80°C. Folate was categorized into tertiles (2.5-10.5, 10.5-16.2, and 16.2-78.4 ng/mL, respectively). Vitamin D was categorized as less than 20 ng/mL, 20 to 29 ng/mL, or 30 ng/mL or greater. This was a nested case-control study in which 5 control subjects were matched to each case on baseline atopy and type of employment. Multivariate analyses controlled for age, sex, education, smoking, season, personal mouse exposure, and serum folate and vitamin D levels. Thirty-five cases and 47 control subjects were included. The odds of incident mouse sensitization were higher in the intermediate and highest tertiles of serum folate compared with the lowest tertile of serum folate (odds ratio of 10.5 [95% CI, 1.8-61.5; P = .009] and odds ratio of 5.6 [95% CI, 1.8-31.3; P = .049], respectively, in the multivariate model). Serum vitamin D levels were not associated with incident mouse sensitization. These findings support a role for higher serum folate levels in increased risk of incident allergic disease, even during adulthood.
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