food diversity in young kids and subsequent allergy

as perhaps a complementary article to the recent mouse one i sent out on soluble fiber, changes in the microbiome, and asthma, this article also just came out finding that increased variety of foods introduced in the first year of life led to decreased asthma, food allergy and food sensitization, as well as several biological markers of allergy (see allergy and food diversity in kids j allerg clin immunol 2014 in dropbox, or doi.org/10.1016/j.jaci.2013.12.1044). this was a birth cohort study of 856 children from rural Europe with parents reporting monthly food diaries during the first year of life (which should decrease likelihood of reverse causality). they also assessed environmental factors and the development of allergic diseases up til the kids were 6 years old. results:

    --51.5% of kids grew up on farms, 53.6% had at least one allergic parent (note: this may affect generalizability of results)

    --dose-response effect: each additional food item introduced into the diet was associated with 26% decreased likelihood of developing asthma, with similar effect on food allergy and food sensitization.

    --this inverse relation between increased complementary foods and asthma did not change after if parents avoided food because of presumed allergy. the relation between numbers of foods and allergies was independent of whether the kids grew up on farms or had allergic parent(s)

    --in terms of specific foods, strong negative association with milk products (eg yogurt and butter) or with in the first year of life and subsequent allergies

    --also increased expression of marker for regulatory Tcells in those on diverse diets

    --this same research group previously reported similar findings with atopic dermatitis

one link with the last study is that the infant gut develops its microbiome early which may be affected by different foods ingested. studies have found an inverse relation between bacterial diversity of the gut microbiota in the first month of life and later development of eczema. prior pediatric feeding guidelines have recommended food allergy avoidance/delayed introduction of foods to prevent allergic diseases, but no clear benefit has been evident and there has been a clear increase in allergic diseases -- hence newer guidelines have changed (eg, see infant feeding guidelines j pedi gastro nutr 2008 in dropbox, or DOI:10.1097/MPG.0b013e3181615cf2, or see below). as in the previous blog on asthma and the microbiome, the current study again challenges our model of health and disease. had we been "protecting" our kids too much by overly regulating/constraining what they eat? (perhaps similar to the studies finding that kids in "cleaner environments" at an early age are more allergic later on).  have the recommendations by various societies (pediatrics, nutrition), which seem to be based on logic (better to have kids in clean surroundings, or old guidelines to avoid potentially allergy-inducing foods...) been myopic/ looking only short-term? we have certainly been through a prolonged strong recommendation by the am heart assn and various nutrition societies that low fat/high carb diets were good for the heart (and perhaps the resulting dramatic increase in obesity/diabetes)... the issue, as always, is to develop our models of disease with our best understanding of physiology, etc, but then to continually test and challenge them.

here is prior blog on nutrition recs for kids from 3/5/2013:

There were recent recommendations from the American Academy of of Allergy, Asthma, and Immunology regarding the primary prevention of allergic disease in infants through nutritional interventions (see  allergy and nutrition recs kids. 2013 in dropbox).  These recommendations were specifically for prevention of allergy and not for kids who already have allergic disorders.  In brief, through their literature review which is current as of August 2012, they suggest the following:

-- maternal avoidance during pregnancy of essential foods such as milk and eggs is notrecommended.  The data are mixed and inconclusive for peanut ingestion during pregnancy and the subsequent development of peanut allergy in children, so no recommendation is made. (Given the severity of peanut allergy and data suggesting that maternal ingestion of peanuts more than a few times a week may be associated with peanut sensitization in infants, it still might be prudent to minimize peanut ingestion to less than twice a week.  My suggestion.)

-- maternal avoidance of highly allergenic foods during lactation is not recommended at this time.

-- they recommend exclusive breast-feeding for at least 4 months and up to 6 months of age,which may possibly reduce the subsequent development of atopic dermatitis in kids younger than the age of two years and to reduce early-onset wheezing before age 4 years, as well as to reduce the incidence of cow's milk allergy but not food allergy in general for the first two years of life. the data are however not conclusive

-- for infants that have increased risk of allergic disease (eg lots of fam members with allergic diseases, though this definition varies considerably from one study to another) and cannot be exclusively breast fed for the first 4 to 6 months of life, hydrolyzed formula appears to offer advantages to prevent allergic disease and cow's milk allergy.  An extensive casein or whey hydrolysate formula may be slightly more beneficial than the partial whey hydrolysate formula. There does not seem to be any advantage to soy based formulas.

-- as I mentioned in my e-mail on celiac disease, there has been a major rethinking of introduction of complementary foods in infants.  The gist of these studies, which are observational, is that delayed introduction of  cereal grains, cow's milk, eggs, and even peanut butter may lead to more allergic problems.  The report details these observational studies, which are quite impressive, and notes that there need to be interventional studies done.  But they do state that the studies support the general notion that highly allergenic foods may be introduced earlier in the diet as complementary foods.  They do note that it is important to start solid foods by 6 months of age to support growth, though different societies very a bit on this recommendation. (the celiac dz article i sent out suggested more specifically that gluten-containing foods be added after 6 months of age in small quantities at first and while breastfeeding at the same time)

-- guidelines on food introduction have basically not changed, with the introduction of a single ingredient foods between 4 to 6 months of age at a rate not faster than one new food every 3 to 5 days.  Complementary foods are typically rice or oat cereal, yellow/orange vegetables, fruits, green vegetables, and then age-appropriate staged foods with meats.  They do not recommend delaying the introduction of acidic fruits, though they can cause localized perioral reactions on contact with the skin.  These do not usually result in systemic reactions and therefore should not be delayed.  Highly allergenic food should not be the first complementary food introduced, however once a few typical complementary foods are tolerated, highly allergenic foods may be introduced.  Whole cow's milk as the infant's main drink or other cow's milk-based products such as cheese and yogurt are safe before the age 1, but should be minimized because of increased solute load and low iron content.

-- children who have one underlying food allergy are at risk for other food allergies.  Referral to an allergist is recommended.  Children with siblings with peanut allergy have a 7% risk of peanut allergy themselves.  They feel that these children can have peanuts at home, in the form of peanut butter to avoid choking. they suggested the first introduction to peanuts be at home as opposed to in daycare.  Parents should be told that the initial reaction to such foods as peanuts typically happen after the initial ingestion but that fatal reactions have not been reported on a first exposure.