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Soy Protein Intolerance

  • Author: Stefano Guandalini, MD; Chief Editor: Carmen Cuffari, MD  more...
Updated: Nov 19, 2015


Soy-based formulas were introduced in infant nutrition 100 years ago, when their use was recommended for the treatment of summer diarrhea. Eighty years ago, the use of soy-based formulas was extended to the treatment of cow's milk intolerance. In the 1970s, use of soy-based formulas became common; in the 1970s and 1980s, US consumption of soy-based formulas was around 25% of that of cow's milk–based formulas.

In the last few years, interest in soybeans and soybean components has markedly increased, mainly because of the potential influence of soy on the development of heart disease, cancer, kidney disease, osteoporosis, and menopause symptoms. Unfortunately, soy protein formulas (SPFs) can cause allergies and other intolerance reactions. For many years after the first description by Duke in 1934, soy was considered a weak sensitizing protein based on animal study findings. In the 1960s, several other authors confirmed the potential allergenicity of soy protein formulas.

A higher prevalence of soy intolerance has generally been reported in non–immunoglobulin E (IgE)-associated enterocolitis and enteropathy syndromes. Authorities have failed to reach consensus on the risk of feeding allergic or nonallergic infants with soy protein milks.[1, 2] This divisive clash of opinion is also reflected in the mutually antagonistic stances adopted by 2 important scientific societies, the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) and the European Society of Pediatric Allergy and Clinical Immunology (ESPACI).

However, the general agreement is that a significant number of children with cow's milk protein intolerance develop soy protein intolerance when soy milk is used in dietary management. For this reason, the American Academy of Pediatrics (AAP) and ESPGHAN recommend the use of extensively hydrolyzed or free amino acid-based formulae in the treatment of cow's milk protein allergy.[3] According to ESPGHAN, soy protein formula should particularly not be used in infants with food allergy during the first 6 months of life.[4]

However, the AAP states that infants with IgE-associated symptoms of cow's milk allergy may benefit from a soy formula because the risk of cross-reactivity does not appear to be very high.[3] A Cochrane systematic review confirms that soy formula cannot be recommended for prevention of allergy or food intolerance in infants.[5]



Two heat-stable globulins constitute 90% of the pulp-derived proteins: beta-conglycinin, which has a molecular weight (MW) of 180,000, and glycinin, which has an MW of 320,000. Immunoblotting and competitive enzyme-linked immunosorbent assays have identified a 30-kD glycinin from soybeans that cross-reacts with cow's milk caseins and is composed of 2 polypeptides (A5 and B3) linked by a disulphide bond. The protein's capacity to bind to the different antibodies relies on the B3 polypeptide.

However, other soy proteins can act as allergens in humans. At least 9 proteins with MW ranging from 14,875-54,500 were found to react with human IgE in patients with asthma. Moreover, after enteric digestion, numerous potential antigens are generated at the mucosal surface.

According to some animal study findings, soy proteins appear to be less sensitizing than cow's milk proteins; however, infants with a previous history of cow's milk protein intolerance have a greater risk of developing soy protein intolerance. The intestinal mucosa damaged by cow's milk proteins may allow increased uptake of the potentially allergenic soy proteins.

Antigenicity of soy-based products is strongly influenced by methods of preparation; therefore, clinical manifestations can be elicited by some soy-based products and not others.


All soybean proteins and foods currently available for human consumption contain significant amounts of the isoflavones daidzein and genistein, either in the unconjugate form or as different types of glycoside conjugates.

The isoflavones have structural homology to steroidal estrogens; therefore, they are considered to be phytoestrogens, but little is known about their biological activity. Unquestionably, isoflavone ingestion can elicit biological effects; however, isoflavones and their metabolites have biological properties that are quite separate from classic estrogen action.

Genistein is a potent inhibitor of tyrosine kinases and can interfere with signal transduction pathways. The threshold intake of dietary estrogens necessary to achieve a biological effect in healthy adults appears to be 30-50 mg/d.

In soy flours and concentrates, isoflavone concentrations are relatively high (0.5-3 mg/g). In soy milk and soy-based infant formulas, the concentration of isoflavones is lower (0.3-0.5 mg/g) but is 10,000-fold higher than the concentration found in breast milk. Moreover, the volume intake of these products is sufficient to account for a significantly high dietary intake of isoflavones. Infants fed soy-based formulas have plasma concentrations of isoflavones that are 3000- to 22,000-fold higher than plasma concentrations of estradiol.

Even if these substances have a weak estrogenic activity compared with estradiol, they could have adverse effects; however, the concerns about the adverse role of phytoestrogens in the first months of life are exclusively theoretical. At this time, the very limited available evidence from adult and infant populations indicates that dietary isoflavones in soy-based infant formulas do not adversely affect human growth, development, or reproduction.

The results of a study that enrolled 48 children (mean age, 37 mo; range, 7-96 mo) suggest that long-term feeding with soy protein formulas in early life does not produce estrogenlike hormonal effects.[6] No developmental problems were observed in a cohort of 129 soy protein–based formula–fed infants.[7] However, according to the Center for the Evaluation of Risks to Human Reproduction (CERHR), the possibility that adverse effects might occur cannot be dismissed. Without conclusive findings in humans, ESPGHAN recommends reducing the content of phytoestrogens in soy protein formulas because of uncertainties regarding safety in infants and young children.[4]




United States

In a national survey of pediatric allergists, the prevalence rate of soy protein allergy was reported to be 1.1%, compared with a 3.4% prevalence rate of cow's milk protein allergy.[8]


In a prospective study of healthy infants fed soy-based formula, allergic responses to soy were documented in 0.5% of infants.[9]

In a group of 243 children who were born to atopic parents and who received soy protein formula for the first 6 months of life to prevent cow's milk allergy, 14 (6%) of the children had positive skin test prick reactions to soy.[10] Only 1 of these 14 children reacted to the double-blind placebo-controlled oral food challenge to soy.

The prevalence of food allergy in patients with atopic dermatitis varies with age and the severity of atopic dermatitis. Different prevalence rates have been reported; however, in most series, 30-40% of the patients received a diagnosis of food allergy. In a study from Italy, a positive radioallergosorbent assay test (RAST) result to soy was found in 25% of children with atopic dermatitis, but a positive challenge test result to soy was elicited in only 3% of the patients.[6] Two other studies documented soy positivity in 5% of 204 patients[11] and in 4% of 143 children.[6] See the image below.

Typical atopic dermatitis on the face of an infant Typical atopic dermatitis on the face of an infant.

In a group of 93 children with documented IgE-associated cow's milk allergy who received soy formula, 14% developed soy allergy.[12] Among 35 children with food-protein enterocolitis syndrome diagnosed in a single center of Australia during a 16-year period, 34% had soy protein intolerance.[13]

In 1990, one of the authors reviewed the evidence obtained from 2108 Italian children with proven cow's milk protein intolerance and non–IgE-associated enterocolitis and enteropathy syndrome.[14] Forty-seven percent of the patients had to discontinue soy formulas because of intolerance. A higher prevalence was noted in infants younger than 3 months (53%). Thirty-five percent of children older than 1 year developed soy intolerance.

A soy-based formula is often substituted for cow's milk in infants recovering from acute gastroenteritis; however, in a previous study that recruited 18 infants with acute gastroenteritis, 3 (16%) of the children developed a clinical reaction to soy challenge, and 7 (38%) of the children developed histologic and enzymologic changes after soy challenge.[15]


Anaphylactic reactions to soy proteins are extremely rare; however, a population study in Sweden from 1993-1996 reported 4 deaths caused by soy.[16]


The risk of developing soy protein intolerance decreases with age. Among children with cow's milk protein intolerance, infants younger than 3 months are at higher risk for developing soy protein intolerance (53%) compared with children older than 1 year (35%).

Contributor Information and Disclosures

Stefano Guandalini, MD Founder and Medical Director, Celiac Disease Center, Chief, Section of Pediatric Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, University of Chicago Medical Center; Professor, Department of Pediatrics, Section of Gastroenterology, Hepatology and Nutrition, University of Chicago Division of the Biological Sciences, The Pritzker School of Medicine

Stefano Guandalini, MD is a member of the following medical societies: American Gastroenterological Association, North American Society for Pediatric Gastroenterology, Hepatology and Nutrition, European Society for Paediatric Gastroenterology, Hepatology & Nutrition, North American Society for the Study of Celiac Disease

Disclosure: Received consulting fee from AbbVie for consulting.


Agostino Nocerino, MD, PhD Chief of Pediatric Oncology, Department of Pediatrics, University of Udine, Italy

Agostino Nocerino, MD, PhD is a member of the following medical societies: American Society of Pediatric Hematology/Oncology, Italian Society of Pediatric Hematology and Oncology, Italian Society of Pediatric Emergency and Urgent Care Medicine, Italian Society of Pediatrics

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

David A Piccoli, MD Chief of Pediatric Gastroenterology, Hepatology and Nutrition, The Children's Hospital of Philadelphia; Professor, University of Pennsylvania School of Medicine

David A Piccoli, MD is a member of the following medical societies: American Association for the Study of Liver Diseases, American Gastroenterological Association, North American Society for Pediatric Gastroenterology, Hepatology and Nutrition

Disclosure: Nothing to disclose.

Chief Editor

Carmen Cuffari, MD Associate Professor, Department of Pediatrics, Division of Gastroenterology/Nutrition, Johns Hopkins University School of Medicine

Carmen Cuffari, MD is a member of the following medical societies: American College of Gastroenterology, American Gastroenterological Association, North American Society for Pediatric Gastroenterology, Hepatology and Nutrition, Royal College of Physicians and Surgeons of Canada

Disclosure: Received honoraria from Prometheus Laboratories for speaking and teaching; Received honoraria from Abbott Nutritionals for speaking and teaching.

Additional Contributors

Jorge H Vargas, MD Professor of Pediatrics and Clinical Professor of Pediatric Gastroenterology, University of California, Los Angeles, David Geffen School of Medicine; Consulting Physician, Department of Pediatrics, University of California at Los Angeles Health System

Jorge H Vargas, MD is a member of the following medical societies: American Liver Foundation, Latin American Society of Pediatric Gastroenterology, Hepatology & Nutrition, American Society for Gastrointestinal Endoscopy, American Society for Parenteral and Enteral Nutrition, North American Society for Pediatric Gastroenterology, Hepatology and Nutrition

Disclosure: Nothing to disclose.

  1. Vandenplas Y, Castrellon PG, Rivas R, Gutiérrez CJ, Garcia LD, Jimenez JE, et al. Safety of soya-based infant formulas in children. Br J Nutr. 2014 Apr 28. 111 (8):1340-60. [Medline].

  2. Mäkinen OE, Wanhalinna V, Zannini E, Arendt EK. Foods for Special Dietary Needs: Non-Dairy Plant Based Milk Substitutes and Fermented Dairy Type Products. Crit Rev Food Sci Nutr. 2015 Jan 9. [Medline].

  3. [Guideline] American Academy of Pediatrics Committee on Nutrition. Soy protein-based formulas: recommendations for use in infant feeding. Pediatrics. 1998 Jan. 101(1 Pt 1):148-53. [Medline].

  4. ESPGHAN Committee on Nutrition. Soy Protein Infant Formulae and Follow-On Formulae: A Commentary by the ESPGHAN Committee on Nutrition. J. Ped. Gastroenterol. Nutr. Apr 2006. 42 (4):352-361. [Medline]. [Full Text].

  5. Osborn DA, Sinn J. Soy formula for prevention of allergy and food intolerance in infants. Cochrane Database Syst Rev. 2006. (4):CD003741. [Medline].

  6. Giampietro PG, Ragno V, Daniele S. Soy hypersensitivity in children with food allergy. Ann Allergy. 1992 Aug. 69(2):143-6. [Medline].

  7. Andres A, Cleves MA, Bellando JB, Pivik RT, Casey PH, Badger TM. Developmental status of 1-year-old infants fed breast milk, cow's milk formula, or soy formula. Pediatrics. 2012 Jun. 129(6):1134-40. [Medline].

  8. Johnstone DE, Roghmann KJ. Recommendations for soy infant formula: a review of the literature and a survey of pediatric allergists. Pediatr Asthma Allergy Immunol. 1993. 7:77-88.

  9. Halpern SR, Sellars WA, Johnson RB, Anderson RB, Saperstein S, Reisch JS. Development of childhood allergy in infants fed breast, soy, or cow milk. Allergy Clin Immunol. 1973. 51:139-151.

  10. Bruno G, Giampietro PG, Del Guercio MJ. Soy allergy is not common in atopic children: a multicenter study. Pediatr Allergy Immunol. 1997 Nov. 8(4):190-3. [Medline].

  11. Sampson HA. Jerome Glaser lectureship. The role of food allergy and mediator release in atopic dermatitis. J Allergy Clin Immunol. 1988 Apr. 81(4):635-45. [Medline].

  12. Zeiger RS, Sampson HA, Bock SA, et al. Soy allergy in infants and children with IgE-associated cow's milk allergy. J Pediatr. 1999 May. 134(5):614-22. [Medline].

  13. Mehr S, Kakakios A, Frith K, Kemp AS. Food protein-induced enterocolitis syndrome: 16-year experience. Pediatrics. 2009 Mar. 123(3):e459-64. [Medline].

  14. Zoppi G, Guandalini S. The story of soy formula feeding in infants: a road paved with good intentions. J Pediatr Gastroenterol Nutr. 1999 May. 28(5):541-3. [Medline].

  15. Iyngkaran N, Yadav M, Looi LM. Effect of soy protein on the small bowel mucosa of young infants recovering from acute gastroenteritis. J Pediatr Gastroenterol Nutr. 1988 Jan-Feb. 7(1):68-75. [Medline].

  16. Foucard T, Malmheden Yman I. A study on severe food reactions in Sweden--is soy protein an underestimated cause of food anaphylaxis?. Allergy. 1999 Mar. 54(3):261-5. [Medline].

  17. Ballmer-Weber BK, Holzhauser T, Scibilia J et al. Clinical characteristics of soybean Clinical characteristics of soybean allergy in Europe: A double-blind, placebo-controlled food challenge study. J Allergy Clin Immunol. Jun 2007. 119 (6):1489-96. [Medline]. [Full Text].

  18. Katz Y, Goldberg MR, Rajuan N, Cohen A, Leshno M. The prevalence and natural course of food protein-induced enterocolitis syndrome to cow's milk: a large-scale, prospective population-based study. J Allergy Clin Immunol. 2011 Mar. 127(3):647-53.e1-3. [Medline].

  19. Lucarelli S, Di Nardo G, Lastrucci G, D'Alfonso Y, Marcheggiano A, Federici T, et al. Allergic proctocolitis refractory to maternal hypoallergenic diet in exclusively breast-fed infants: a clinical observation. BMC Gastroenterol. 2011 Jul 16. 11(1):82. [Medline].

  20. Masilamani K, Jolles S, Huddart S, Tuthill DP. Successful dietary treatment of recurrent intussusception. Arch Dis Child. 2009 Mar. 94(3):248-9. [Medline].

  21. Syrigou EI, Pitsios C, Panagiotou I, Chouliaras G, Kitsiou S, Kanariou M, et al. Food allergy-related paediatric constipation: the usefulness of atopy patch test. Eur J Pediatr. 2011 Feb 25. [Medline].

  22. Duenas-Laita A, Pineda F, Armentia A. Hypersensitivity to generic drugs with soybean oil. N Engl J Med. 2009 Sep 24. 361(13):1317-8. [Medline].

  23. Savage JH, Kaeding AJ, Matsui EC, Wood RA. The natural history of soy allergy. J Allergy Clin Immunol. 2010 Mar. 125(3):683-6. [Medline].

  24. Nowak-Wegrzyn A, Sampson HA. Future therapies for food allergies. J Allergy Clin Immunol. 2011 Mar. 127(3):558-73; quiz 574-5. [Medline]. [Full Text].

  25. Aggett PJ, Haschke F, Heine W. Comment on antigen-reduced infant formulae. ESPGAN Committee on Nutrition. Acta Paediatr. 1993 Mar. 82(3):314-9. [Medline].

  26. American Academy of Pediatrics: Committee on Nutrition. Hypoallergenic infant formulas. Pediatrics. Aug 2000. 106 (2 Pt1):346-9. [Medline]. [Full Text].

  27. Businco L, Bruno G, Giampietro PG. Soy protein for the prevention and treatment of children with cow-milk allergy. Am J Clin Nutr. 1998 Dec. 68(6 Suppl):1447S-1452S. [Medline].

  28. Businco L, Dreborg S, Einarsson R, et al. Hydrolysed cow's milk formulae. Allergenicity and use in treatment and prevention. An ESPACI position paper. European Society of Pediatric Allergy and Clinical Immunology. Pediatr Allergy Immunol. 1993 Aug. 4(3):101-11. [Medline].

  29. Eastham EJ, Lichauco T, Pang K, Walker WA. Antigenicity of infant formulas and the induction of systemic immunological tolerance by oral feeding: cow's milk versus soy milk. J Pediatr Gastroenterol Nutr. 1982. 1(1):23-8. [Medline].

  30. Franck P, Moneret Vautrin DA, Dousset B, et al. The allergenicity of soybean-based products is modified by food technologies. Int Arch Allergy Immunol. 2002 Jul. 128(3):212-9. [Medline].

  31. Halpin TC, Byrne WJ, Ament ME. Colitis, persistent diarrhea, and soy protein intolerance. J Pediatr. 1977 Sep. 91(3):404-7. [Medline].

  32. Herian AM, Bush RK, Taylor SL. Protein and allergen content of commercial skin test extracts for soybeans. Clin Exp Allergy. 1992 Apr. 22(4):461-8. [Medline].

  33. Perkkio M, Savilahti E, Kuitunen P. Morphometric and immunohistochemical study of jejunal biopsies from children with intestinal soy allergy. Eur J Pediatr. 1981 Sep. 137(1):63-9. [Medline].

  34. Poley JR, Klein AW. Scanning electron microscopy of soy protein-induced damage of small bowel mucosa in infants. J Pediatr Gastroenterol Nutr. 1983 May. 2(2):271-87. [Medline].

  35. Setchell KD. Phytoestrogens: the biochemistry, physiology, and implications for human health of soy isoflavones. Am J Clin Nutr. 1998 Dec. 68(6 Suppl):1333S-1346S. [Medline].

  36. Setchell KD, Zimmer-Nechemias L, Cai J. Exposure of infants to phyto-oestrogens from soy-based infant formula. Lancet. 1997 Jul 5. 350(9070):23-7. [Medline].

Typical atopic dermatitis on the face of an infant.
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