Eating more fruits and vegetables may not protect children from developing allergies, according to a large Swedish study that questions earlier hints of benefit. Fruits and vegetables are rich in antioxidants, which are thought to reduce airway inflammation. So recent studies reporting less asthma, wheezing and hay fever among children who consumed more produce appeared to make sense.
But not all research has found that link, and the studies that did may have had a surprising flaw, said Helen Rosenlund of Karolinska Institutet in Stockholm, who led the new study. She said some proteins in fruits like apples and pears resemble the pollen parts that trigger hay fever, meaning that kids might react to both. In other words, existing allergies may have caused them to eat around the produce, rather than the other way around. “This could confuse research findings,” explained Rosenlund, “falsely suggesting that diets with fewer fruits and vegetables result in more allergic disease.”
To find out if this was the case, Rosenlund and her colleagues looked at data on nearly 2,500 eight-year-olds who had participated since birth in a larger Swedish study. Based on blood tests and questionnaires filled out by parents, the researchers found that seven percent of the children had asthma. The rates of hay fever and skin rashes were more than twice as high. The average child ate between one and two servings of fruit, and between two and three servings of vegetables each day.
At first glance, some produce did seem helpful: Kids with the biggest appetite for fruit had less than two-thirds the odds of developing hay fever than those who ate the least amount. Apples, pears and carrots appeared to be particularly helpful, the researchers report in the Journal of Allergy and Clinical Immunology, but there was no such link for vegetables overall. However, it turned out that half the children with hay fever were sensitive to birch tree pollen, one of the pollens known to resemble the proteins in apples and carrots. And sure enough, after the team repeated their analysis excluding the 122 kids with food-related allergy symptoms, the hay fever link disappeared as well. “Fruits do not seem to offer protection against allergic if diet modifications are considered,” say Rosenlund.
The researchers say more studies are needed, particularly in other parts of the world that may have a different variety of allergy triggers, or allergens. And they advise those studies should not forget to look at how allergies might influence what participants eat. “Studying diet it is not so easy when it comes to the relation with allergic disease,” Rosenlund said, “because it is such a complex disease pattern.”
SOURCE: bit.ly/g3DpI7 The Journal of Allergy and Clinical Immunology, online January 10, 2011.
Consumption of Vitamin B during pregnancy does not increase the risk of allergy in the infants, says a new study from Japan that challenges previous findings. Maternal consumption of folate and vitamins B2, B6, and B12 during pregnancy was not associated with the risk of the infant developing asthma or eczema, according to findings from 763 infants published in Pediatric Allergy and Immunology.
The link between folate and folic acid, the synthetic form of the vitamin, and respiratory health is not clear cut, with contradictory results reported in the literature. A study from Johns Hopkins Children’s Center found that higher levels of folate were associated with a 16 per cent reduction of asthma in (Journal of Allergy & Clinical Immunology, June 2009, Vol. 123, pp. 1253-1259.e2). However, a Norwegian study reported that folic acid supplements during the first trimester were associated with a 6 per cent increase in wheezing, a 9 per cent increase in infections of the lower respiratory tract, and a 24 per cent increase in hospitalisations for such infections, (Archives of Diseases in Childhood, doi:10.1136/adc.2008.142448). In addition, researchers from the University of Adelaide in Australia reported that folic acid supplements in late pregnancy may increase the risk of asthma by about 25 per cent in children aged between 3 and 5 years (American Journal of Epidemiology, 2010, doi:10.1093/aje/kwp315).
Illumination from the Land of the Rising Sun?
The new study, performed by researchers from Fukuoka University, the University of Tokyo, and Osaka City University, goes beyond folate and folic acid, and reports no link between Vitamin B intake and the risk of asthma or eczema in children. “To the best of our knowledge, there has been no birth cohort study on the relationship between maternal consumption of Vitamin B during pregnancy and the risk of allergic disorders in the offspring,” wrote the researchers. The findings were based on data from 763 pairs of Japanese mother and child. A diet history questionnaire was used to assess maternal intakes of the various B vitamins during pregnancy, and the infants were followed until the age of 16 to 24 months. Japan has no mandatory fortification of flour with folic acid.
Results showed that, according to criteria from the International Study of Asthma and Allergies in Childhood, 22 and 19 percent of the children had symptoms of wheeze and eczema, respectively, but there was no association between these children and the dietary intakes of the various B vitamins by their mothers. “Our results suggest that maternal intake of folate, vitamin B12, vitamin B6, and vitamin B2 during pregnancy was not measurably associated with the risk of wheeze or eczema in the offspring,” said the researchers. “Further investigation is warranted to draw conclusions as to the question of whether maternal Vitamin B intake during pregnancy is related to the risk of childhood allergic,” they concluded.
According to the European Federation of Allergy and Airway Diseases Patients Association (EFA), over 30m Europeans suffer from asthma, costing Europe €17.7bn every year. The cost due to lost productivity is estimated to be around €9.8bn. The condition is on the rise in the Western world and the most common long-term condition in the UK today. According to the American Lung Association, almost 20m Americans suffer from asthma. The condition is reported to be responsible for over 14m lost school days in children, while the annual economic cost of asthma is said to be over $16.1bn.
Source: Pediatric Allergy and Immunology. Volume 22, Issue 1-Part-I, February 2011, Pages: 69–74 DOI: 10.1111/j.1399-3038.2010.01081.x
“Maternal B vitamin intake during pregnancy and wheeze and eczema in Japanese infants aged 16–24 months: The Osaka Maternal and Child Health Study”. Authors: Y. Miyake, S. Sasaki, K. Tanaka, Y. Hirota