Part of an occasional series on new health information.
Mrs. J. is the mother of a one-year-old girl and a three-year-old boy. There is no allergic history in the family. She was counseled by her pediatrician to avoid exposing the children to peanut products, shellfish and cow’s milk for the first year of their lives.
They enjoyed family outings to a Chinese buffet restaurant, but when her daughter was 9 or 10 months old and insisted on eating what everyone else was eating, she temporarily halted outings to the buffet because of the possibility of exposure to peanut oil used in the cooking.
Mrs. K had so many conversations at the playground about delaying the introduction of certain foods that she can’t remember which restrictions came from her pediatrician and which from other sources. She recalls hearing about delaying cow’s milk, other dairy products, eggs, peanut butter, nuts and citrus fruits.
The N’s, parents of two, ages 1 and almost 3, use a pair of pediatricians and received different recommendations for their two children. With the first, they were advised to avoid cow’s milk, soy, nuts, peanuts, berries, wheat, tomatoes, egg white, fish and citrus for the first year. Since the family is vegetarian, this posed something of a challenge. With their second child, the other pediatrician in the practice advised avoiding a shorter list of foods which didn’t include soy and made it easier on the family’s meal planning. Both lists came without regard for a family history of allergy and seemed to be simply routine practice.
ADVICE ABOUT introducing foods to infants comes from primary healthcare providers, baby care books and magazines and from conversations with other parents. Delayed introduction of certain foods may be recommended because of the possibility of inadequate nutrition, food allergy, diaper rash, infection and choking, for example. New parents, in particular, seem to be anxious about this and employ various measures to reduce or avoid exposure of their infants and young children to undesirable foodstuffs.
Food allergy in young children seems to be a growing problem in industrialized countries, affecting about 4-8 percent of infants and young children. Percentages are higher in allergic families. Foods that are most likely to induce specific allergy in the U. S. are eggs, dairy products, peanuts, fish, nuts, wheat and soy.
The serious nature of certain allergic reactions to foods raises anxiety as well as interest in prevention. Because allergy appears to result from a combination of genetic predisposition together with opportunity through exposure, the best available avenue for prevention at present seems to be avoidance of exposure.
I began wondering about the nature of the evidence behind the recommendations directed at prevention. One benefit might be preventing a child from ever developing a particular allergy.
IS THERE EVIDENCE that delaying exposure to certain foods makes a difference in the eventual development of allergy to that food? Does delaying exposure to peanuts or peanut products reduce the incidence of peanut allergy in later life?
Another possibility is that even if a particular food allergy is not prevented, it is delayed so that the infant or young child is spared the symptoms of allergy until later in life when the consequences may be more tolerable.
Just what are the possible benefits of delaying the introduction of foods considered to be allergenic and what should a parent know? First of all, other than a recommendation for exclusive breastfeeding for the first 4-6 months, there is little guidance for parents with children of average risk because most of the evidence is from studies of high-risk children.
The recommendations made by the American Academy of Pediatrics (AAP) Committee on Nutrition and by the two European pediatric nutrition committees are only for high-risk children, not for average-risk children. The AAP committee identifies high-risk infants by a "strong (biparental; parent and sibling) family history of allergy…" while the European committees require only one allergic parent or sibling.
Secondly, good, consistent evidence is lacking. The chapter on Food Sensitivity in the 2004 edition of the Academy’s Nutrition Handbook acknowledges, "Conclusive studies are not yet available to permit definitive recommendations."
In the face of incomplete evidence and based instead on consensus, the American Academy of Pediatrics states, "…recommending the following guidelines for high-risk infants seems reasonable:…(2) exclusive breast feeding for the first 4-6 months of life or use of a hypoallergenic formula if breastfeeding is not possible or supplementation is required (mothers should eliminate all peanut and tree nuts from their diet, and, if highly motivated, consider eliminating eggs and milk; dietary counseling to achieve the recommended allowances of minerals and other nutrients is important with these highly restricted diets); (3) delay introduction of solid foods until after 6 months of age; and (4) delay introduction of cow milk until 1 year of age; eggs until two years; and peanuts, nuts, fish and shellfish until 3 years of age."
In making similar recommendations in August of 2000, the Academy’s Committee on Nutrition stated, "The recommendations in this statement do not indicate an exclusive course of treatment or serve as a standard of medical care." It seems that the Academy regards these measures as reasonable precautions to take in the absence of conclusive evidence that such measures make a difference.
While the Europeans agree with the American Academy of Pediatrics that exclusive breastfeeding is the first line of defense, they recommend four to six months instead of six. When it comes to solid food introduction, however, because of the lack of adequate scientific data, the European committees do not make specific recommendations about delaying certain foods, recommending only that "supplementary foods should not be introduced before the 5th month of life." One European review of the evidence in 2002 states, "…there is no evidence of an allergy preventive diet after the age of six months."
THE POINT IS that there is considerable uncertainty about measures to prevent food allergies. There is controversy about the effects of breastfeeding on the development of allergic disease in children. Good, consistent evidence about the effectiveness of delaying the introduction of certain foods in reducing the development food allergy is lacking.
Furthermore, even if delayed exposure prevents food allergy early in life, it may not prevent the eventual development of allergies later. For example, there is no published study at this time that documents that delayed introduction of peanuts or peanut products reduces overall occurrence of sensitivity to peanuts later in childhood, says Robert Zeiger, M.D., Clinical Professor of Pediatrics at the University of California, San Diego and Director of Allergy Research at the San Diego Kaiser Permanente Medical Center.
According to Dr. Zeiger, "Uncertainty still remains with respect to the degree of benefit attainable by food allergen avoidance in primary allergy prevention." Therefore, the AAP and European recommendations "should be considered provisional, should be directed only at high-risk offspring, and should be expected to be updated as new information becomes available."
Concerns about food allergy should not get all of the attention. Dr. Ronald Kleinman, Professor of Pediatrics at Harvard Medical School, Chief of Pediatric Gastroenterology and Nutrition at Massachusetts General Hospital, Boston, and editor of the fourth and fifth editions of the AAP Nutrition Handbook, is concerned about choking and recommends that parents delay introducing small, hard particulate foods such as carrots, celery, raisins, nuts, grapes until about age three.
Mark H. Zweig, M.D., previously a staff physician at NIH, has more than 35 years of experience in medical research and 25 years in patient care. He can be reached at firstname.lastname@example.org