Sugar’s likely role in allergy development

EXPECTANT mothers may want to cut back on sugary foods and drinks lest their children develop maddening, and sometimes fatal, allergy. An association between sugar intake during pregnancy and allergy and asthma in children was recently discovered by a study led by Queen Mary University of London (QMUL), which was published early this month in the

According to the researchers, high consumption of sugar-sweetened beverages and fruit juices has been linked to asthma, and, in particular, its most common form, atopic asthma.

One study from 2015 found that high consumption of 100% fruit juice and total sugar-containing beverages is associated with increased asthma risk in children, but that the consumption of other types of beverages and fruits is not. But the team behind the current study claim that the relation between total maternal consumption of free sugar during pregnancy and respiratory and atopic outcomes in the offspring has not been studied.

The American Academy of Allergy, Asthma & Immunology defines atopy as a genetic tendency to develop allergic diseases like asthma, and is associated with heightened immune responses to common allergens. Asthma is a respiratory condition in which the airways, or bronchial tubes, are inflamed, causing the afflicted to cough, wheeze, and feel a shortness of breath, among others. The World Health Organization refers to all monosaccharides and disaccharides added to foods by a manufacturer, cook or consumer, plus the sugars that are naturally present in honey, syrups and fruit juices as free sugars.

The QMUL-led study used data from a birth cohort study, the Avon Longitudinal of Parents and Children. The cohort recruited more than 14,000 pregnant women in the early 1990s and has been following up their offspring since then. Through a food frequency questionnaire, the intake of free sugars by these women was estimated.

Although evidence for the link between free sugar intake in pregnancy and asthma overall was weak, the investigation yielded strong positive associations between free sugar and allergy and allergic asthma. An increased risk of 38% for allergy in the offspring and 101% for allergic asthma was found when the 20% of mothers with the highest sugar intake were compared with the 20% of mothers with the lowest sugar intake.

“In this population-based birth cohort study, we found that a higher maternal intake of free sugar during pregnancy was associated with an increased risk of atopy and atopic asthma in the offspring, independently of sugar intake in early childhood,” the researchers said. “To the best of our knowledge, these are novel findings.”

The team, which controlled for numerous potential confounders in their analysis, like the nutrients and foods that have been previously linked to childhood asthma and atopy, think that the strong associations may be explained by high maternal fructose consumption. Fructose, the team noted, causes the production of uric acid, which may be an essential initiator and amplifier of T-helper cell type 2 (Th2) immunity and allergic inflammation. This simple sugar might also be influencing atopic immune responses by conditioning the microbiome in the gut.

“We therefore propose that one explanation for our main findings is that high fetal exposure to fructose may cause persistence of Th2 immune responses post-natally and allergic inflammation in the developing lung,” researchers said.

It is important to stress that the study, which is observational, establishes an associative, and not a causal, link between maternal sugar intake and allergies or asthma. Sief Shaheen, the study’s lead researcher from QMUL, said, “We cannot say on the basis of these observations that a high intake of sugar by mothers in pregnancy is definitely causing allergy and allergic asthma in their offspring.”

He noted that they will investigate the hypothesis further. “The first step is to see whether we can replicate these findings in a different cohort of mothers and children. If we can, then we will design a trial to test whether we can prevent childhood allergy and allergic asthma by reducing the consumption of sugar by mothers during pregnancy,” he said.

“In the meantime,” Mr. Shaheen said, “we would recommend that pregnant women follow current guidelines and avoid excessive sugar consumption.”