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Feb/Mar 2011 Issue
Research Roundup: Eating Eggs, Food Allergy & Asthma, Celiac Disease on the Rise
The latest medical news for people with allergies and food sensitivities
Parents concerned about egg allergy in infants may want to offer eggs sooner rather than later, say researchers in the Journal of Allergy and Clinical Immunology. Guidelines have traditionally advised parents to withhold eggs until 12 months of age or later. But in a study of more than 2,500 Australian infants recruited from the general population, researchers found that infants given eggs after 12 months of age were three times more likely to have challenge-proven egg allergy at 14 to 18 months than those introduced at 4 to 6 months of age. The increased risk held whether or not there was a personal history of eczema or family history of allergy. According to the study, introduction of cooked rather than baked egg products at 4 to 6 months carried the lowest risk for allergy. Duration of breast-feeding and age at introduction of solids were not associated with egg allergy.
Although further work is needed to confirm the study findings—and to see if they hold true with other allergens like cow’s milk and nuts—they support a recent American Academy of Pediatrics policy statement that there’s little evidence to suggest delaying the introduction of complementary foods beyond 4 to 6 months of age to lower risk of atopic dermatitis, asthma or food allergy.
Food Allergy Linked to Asthma
A new study validates that having a food allergy can raise the risk of asthma. The research was conducted by investigators at a number of institutions, including Johns Hopkins Children's Center, and appeared in the Journal of Allergy and Clinical Immunology.
In the study, researchers analyzed data on 8,203 people, ranging in age from 1 to 60, who completed a nationwide nutrition study. Unlike previous studies on food allergy prevalence, participants provided blood tests to establish the presence of four food allergies: peanut, milk, egg and shrimp.
Among those with food allergy (an estimated 2.5 percent of Americans), 1.3 percent were allergic to peanuts, 0.4 percent to milk, 0.2 percent to egg and 1 percent to shrimp. Many had allergies to more than one food. Children were at greater risk for food allergy than adults, with black male children at particular risk. (The odds of black male children having food allergies were more than four times higher than the general population.)
Those with food allergies were nearly four times more likely to have asthma than those without food allergies. Food allergy also appeared to be a marker for asthma severity. Participants with a food allergy were nearly seven times as likely to have visited the emergency room for an asthma attack in the previous 12 months as those without food allergies.
Just how food allergy and asthma are connected is not fully understood but the study helps substantiate a link that physicians have long suspected. In a press release, lead author Andrew Liu, MD, explained, “This study provides further credence that food allergies may be contributing to severe asthma episodes and suggests that people with a food allergy and asthma should closely monitor both conditions and be aware that they might be related.”
Celiac Disease on the Rise
To look at trends in celiac disease prevalence, a team led by the University of Maryland Center for Celiac Research tested blood samples from a group of 3,511 U.S. adults, followed since 1974. They found the number of people with markers for celiac disease increased steadily from one in 501 in 1974 to one in 219 in 1989. A widely cited 2003 study reported the number of people with celiac disease in the U.S. at one in 133. When looked at together, the studies suggest a five-fold increase over the past 30 years.
Researchers aren’t sure what’s responsible for the rise. But since the same group of 3,511 people was followed over time, the findings point to an environmental rather than genetic cause. Changes in intestinal bacteria, as well as changes in the amount and quality of gluten eaten today have been suggested. An unrelated Dutch study, recently published in Theoretical and Applied Genetics, found that compared to older wheat varieties, many modern wheat varieties contain higher concentrations of gluten proteins specifically thought to contribute to celiac disease.
Another key finding of the University of Maryland study was that you’re not necessarily born with celiac disease; several of the celiac cases were diagnosed in people in their 50s and 60s. Because people can live for decades before developing celiac disease, it suggests the disease may be preventable, say the researchers. For now, they urge physicians to consider screening elderly patients for celiac disease. The work was published in the Annals of Medicine.
In women, undiagnosed celiac disease has long been linked with infertility, recurrent miscarriages and fetal growth restriction but the underlying mechanisms weren’t understood until recently.
According to work published in the American Journal of Gastroenterology, anti-tissue transglutaminase (anti-tTG) antibodies may be to blame. Anti-tTG antibodies are the primary autoantibody found in untreated celiac disease.
Researchers exposed fetal cells called trophoblastic cells, isolated from full-term placenta, to anti-tTG antibodies collected from three women with untreated celiac disease. The anti-tTG antibodies bound to trophoblastic cells and inhibited their activity, providing a possible mechanism for compromised fertility and adverse pregnancy outcomes. Healthy trophoblast development is essential for a successful pregnancy.
Although the research sheds light on a possible mechanism, additional work is still needed. Researchers emphasize that the gluten-free diet appears to have a beneficial effect on fertility and pregnancy in women with celiac disease.
Root of the Problem
Alopecia areata causes spotty and, in some cases, disfiguring hair loss and is among the most prevalent autoimmune diseases, affecting 1 to 2 percent of the population. To better understand its genetic underpinnings, investigators recently undertook a rapid scanning of the DNA of two large groups of people to find genetic variations associated with the disease. Over 1,000 participant samples from the National Alopecia Areata Registry and 3,000 controls from other studies were tested. The work was published in Nature.
Among the findings, researchers noted a gene cluster called ULBP, which was strongly associated with alopecia areata. They speculate that ULBP is involved in the activation of T cells, which are likely responsible for, at least in part, the observed hair loss in alopecia areata. Researchers also found significant associations between certain gene clusters in alopecia areata patients and those with other autoimmune diseases, including rheumatoid arthritis, type I diabetes, celiac disease, systemic lupus erythematosus, multiple sclerosis and psoriasis.
The research helps validate the “common-cause” hypothesis of autoimmune disease—that a core set of genes predisposes a person to autoimmunity but the end organ is different in different diseases, raising the possibility of a coordinated search for novel therapies. LW