Rising childhood obesity levels may also be driving the increases in food allergies, suggests new research from the US.
Data from over 4,000 children indicated that increases observed in allergic disease in children, particularly food allergy, may be due to obesity, with inflammation also linked to allergy development.
“The associations were stronger for the obese weight category than the overweight category, providing evidence of a dose response for weight,” wrote the researchers, led by Cynthia Visness from University of North Carolina at Chapel Hill, in the Journal of Allergy and Clinical Immunology.
“The analysis of continuous BMI with total IgE levels supports the concept that increased weight is associated with increased allergic predisposition,” they added. Immunoglobulin E (IgE) is the predominant antibody associated with an allergic response.
The research was called ‘tantalising’ by John Collard, clinical director at British charity Allergy UK. “This piece of research […] seems to show a relationship between obesity and allergy, which has been the subject of debate before,” Collard told FoodNavigator.com.
Obesity and allergies rise in tandem
According to background information from the authors, only 5 per cent of American children between 6 and 11 were overweight before 1980, but 25 years later this number had risen to 19 per cent. Similar increases have been reported in Europe, with the International Association for the Study of Obesity estimating in 2006 that the number of obese school age children in Europe increased by almost 50 per cents since the late 1990s.
At the same time, the number of allergic disease has also been rising, with an estimated eight per cent of children in the EU suffering from food allergies, according to the European Federation of Allergy and Airways Diseases Patients' Associations.
The most common food allergen ingredients and their derivatives are cereals containing gluten, fish, crustaceans, egg, peanut, soybeans, milk and dairy products including lactose, nuts, celery, mustard, sesame seed, and sulphites.
Visness and her co-workers analysed data from the National Health and Nutrition Examination Survey (NHANES) data from 2005-2006, including data on IgE, and the prevalence of allergy.
IgE levels were significantly higher amongst obese and overweight children than normal-weight children, said the researchers. Furthermore, obesity was linked to a 26 per cent increase in atopy, “driven largely by allergic sensitisation to foods”, and a 59 per cent increase in food sensitisation.
C-reactive protein (CRP), a marker of inflammation, was also linked to IgE levels, atopy, and food sensitisation, they said.
“NHANES 2005-2006 is the largest dataset of serum IgE levels that has ever been collected, and it comes from a sample that is generalizable to the population of the United States,” wrote the researchers.
“Our analysis, using an objective assessment of atopy, shows that overweight status in children is associated with allergic predisposition, especially to food.
“Childhood obesity might be the most important health issue facing US children today. Although an increase in allergy might not be the most consequential health risk faced by overweight children, it does provide additional motivation for undertaking the difficult challenge to reduce childhood obesity,” they concluded.
Commenting independently on the study, Allergy UK’s Collard said: “The suggestion that both might be related to generalised inflammation, as measured by CRP levels, is interesting. However there are a lot of unanswered questions,” he added.
“Obesity is shown to be related to an increased level of sensitization to foods, but not to actual allergy symptoms, which were rather less in the obese group. The risk of sensitization in the obese seems greater for some foods, like peanut and shrimp, but is actually less for others, like milk,” said Collard.
“Other research has suggested that the underweight are at greater risk of allergy, so although there is clearly some relationship between body mass, the tendency to make IgE, and the expression of allergic disease, it is far from clear what that relationship is,” he said.
Source: Journal of Allergy and Clinical Immunology May 2009, Volume 123, Issue 5, Pages 1163-1169.e4“Association of obesity with IgE levels and allergy symptoms in children and adolescents: Results from the National Health and Nutrition Examination Survey 2005-2006” Authors: C.M. Visness, S.J. London, J.L. Daniels, J.S. Kaufman, K.B. Yeatts, A.-M. Siega-Riz, A.H. Liu, A. Calatroni, D.C. Zeldin