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Article Excerpt
Byline: Daniel Venarske, MD, Xinqing Deng, MD, MPH, Terryl Hartman, PhD, RD, and Tina V. Hartert, MD, MPH
Abstract: Dietary factors, such as intake of fatty acids, vitamins, minerals, and probiotics, appear to influence the development of asthma and other allergic disease. The results of recent studies indicate that a higher maternal intake of vitamin D during pregnancy is associated with a lower risk of childhood asthma. However, vitamin D intake among children does not appear to reduce the risk of wheezing in early childhood. Maternal intake of probiotics during pregnancy also appears to have a protective effect against some allergies. For example, supplementation with Lactobacillus rhamnosus GG is associated with a reduced risk of atopic eczema in children. There is no current evidence that probiotic supplementation prevents asthma.
(J Respir Dis. 2007;28(11):500-508)
Key Words: Diet, Nutrition, Asthma, Atopy, Pregnancy, Probiotics
A number of dietary factors have been identified as having a protective effect against certain allergic diseases. For example, there is evidence that consumption of antioxidants, such as vitamins C and E, may protect against asthma. In the October 2007 issue of The Journal of Respiratory Diseases, we reviewed the role of fatty acids and antioxidants and the impact of maternal dietary intake during pregnancy on respiratory outcomes in children. In this article, we address the effects of vitamin D and probiotics.
VITAMIN D
As both a nutrient and a hormone, vitamin D is important not only for normal mineral homeostasis but also for the differentiation and function of various cells. The presence of the vitamin D receptor in monocytes, macrophages, and activated T and B cells suggests that vitamin D acts as an immunoregulatory hormone.1,2 Vitamin D also has been considered in the treatment of several of T helper (TH)1-mediated diseases, such as multiple sclerosis, type 1 diabetes mellitus, rheumatoid arthritis, and inflammatory bowel disease.3-7
Molecular mechanisms
Vitamin D has an immunoregulatory effect once it is converted to 1,25-dihydroxyvitamin D3. This metabolite of vitamin D has been shown to inhibit mitogen-induced T-lymphocyte proliferation; decrease the synthesis of TH1 type cytokines, such as interleukin (IL)-2, IL-12, and interferon-g in blood mononuclear cells; and increase the TH2 type cytokine IL-4. It also decreases B cell immunoglobulin production of IgE in vitro.8,9
These findings suggest that vitamin D inhibits the TH1-mediated immune response and may therefore promote a TH2 response. However, Pichler and colleagues10 have reported that in human cord blood T cells, vitamin D3 not only inhibited the secretion of TH1 cytokines but also suppressed the expression of TH2 cytokines. Cord blood cells contain mainly naive T cells expressing CD45RA+ phenotype. Thus, vitamin D may regulate naive T cells and mature cells differently.
Study findings
-Animal studies: Vitamin D may modulate rat fetal lung maturation by stimulating surfactant synthesis and secretion in type II pneumocytes and by decreasing their glycogen content.11 In a murine model of pulmonary eosinophilic inflammation, early treatment with vitamin D led to increased allergen-induced T-cell proliferation and high levels of IL-4 and IL-13 (by splenocytes) and serum IgE, while the pulmonary inflammation was suppressed with impaired recruitment of eosinophils and reduced levels of IL-5 in the airways.12
-Observational studies: Recently, the results...
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