Natural history of soy allergy and/or intolerance in children, and clinical use of soy-protein formulas

Bile Acid Profile Influences Digestion Resistance and Antigenicity of Soybean 7S Protein

Soybean 7S storage protein (β-conglycinin) is the most important allergen, exhibits resistance in gastrointestinal (GI) digestion, and causes allergies in humans and animals. A previous study has demonstrated that 7S proteins contained innate amyloid aggregates, but the fate of these specific protein aggregates in intestinal digestion and correlation to allergenicity are unclear. In this study, via a modified INFOGEST static in vitro digestion and IgE binding test, we illustrate that the survived amyloid aggregates of soybean 7S protein in GI digestion might be dominant IgE epitopes of soybean protein in humans. The impact of conjugated primary bile acid salt (BS) profile on digestion resistance and immunogenicity of soybean protein is assessed, regarding the binding affinity of BS to protein aggregates with consideration of the BS composition and the physiologically relevant colloidal structure. The results show that chenodeoxycholate-containing colloidal structures exhibit high affinity and unfolding capacity to protein amyloid aggregates, promoting proteolysis by pancreatic enzymes and thus mitigating the antigenicity of soybean protein. This study presents a novel understanding of bile acid profile and colloidal structure influence on the digestibility and antigenicity of dietary proteins. It should be helpful to design in vitro digestion protocol and accurately replicate physiologically relevant digestion conditions.

Seeds

A wide variety of plant species provide edible seeds. Seeds are the dominant source of human calories and protein. The most important and popular seed food sources are cereals, followed by legumes and nuts. Their nutritional content of fiber, protein, and monounsaturated/polyunsaturated fats make them extremely nutritious. They are important additions to our daily food consumption. When consumed as part of a healthy diet, seeds can help reduce blood sugar, cholesterol, and blood pressure.

A comprehensive review of sensitization and allergy to soy-based products

Since 1943, cases of sensitization or allergy to soy-based formulas (SBFs) have been described without any consensus on their real prevalence. We identified the adjusted prevalence of IgE-mediated soy allergies in children and performed a secondary analysis of the impact of age (less than and more than 6 months). We performed a systematic review with meta-analysis of studies published from 1909 to 2013 in PubMed, Embase, LILACS, ARTEMISA, Cochrane, Bandolier, DARE and the GRADE system for grading quality. Results are presented in tables and graphs using a forest plot. The 40 studies identified established weighted prevalence of soy allergies of 0 to 0.5 % (0.27) for the general population, 0.4 to 3.1 % (1.9) for the referred population, and 0 to 12.9 % (2.7) for allergic children. Prevalence of sensitization after the use of SBFs is 8.7 and 8.8 %, depending on the method used. The prevalence of allergies to soy and IgE sensitization to the use of SBFs is less than reported. Not enough evidence exists to show a higher risk of allergy in infants younger than 6 months. The concern about soy allergy is no reason to postpone the use of SBFs in IgE-mediated cow's milk allergy infants until the age of 6 months.

Safety of soya-based infant formulas in children

Soya-based infant formulas (SIF) containing soya flour were introduced almost 100 years ago. Modern soya formulas are used in allergy/intolerance to cows' milk-based formulas (CMF), post-infectious diarrhoea, lactose intolerance and galactosaemia, as a vegan human milk (HM) substitute, etc. The safety of SIF is still debated. In the present study, we reviewed the safety of SIF in relation to anthropometric growth, bone health (bone mineral content), immunity, cognition, and reproductive and endocrine functions. The present review includes cross-sectional, case-control, cohort studies or clinical trials that were carried out in children fed SIF compared with those fed other types of infant formulas and that measured safety. The databases that were searched included PubMed (1909 to July 2013), Embase (1988 to May 2013), LILACS (1990 to May 2011), ARTEMISA (13th edition, December 2012), Cochrane controlled trials register, Bandolier and DARE using the Cochrane methodology. Wherever possible, a meta-analysis was carried out. We found that the anthropometric patterns of children fed SIF were similar to those of children fed CMF or HM. Despite the high levels of phytates and aluminium in SIF, Hb, serum protein, Zn and Ca concentrations and bone mineral content were found to be similar to those of children fed CMF or HM. We also found the levels of genistein and daidzein to be higher in children fed SIF; however, we did not find strong evidence of a negative effect on reproductive and endocrine functions. Immune measurements and neurocognitive parameters were similar in all the feeding groups. In conclusion, modern SIF are evidence-based safety options to feed children requiring them. The patterns of growth, bone health and metabolic, reproductive, endocrine, immune and neurological functions are similar to those observed in children fed CMF or HM.

Allergenicity of soybean: new developments in identification of allergenic proteins, cross-reactivities and hypoallergenization technologies

Soybean is considered one of the "big eight" foods that are believed to be responsible for 90% of all allergenic reactions. Soy allergy is of particular importance, because soybeans are widely used in processed foods and, therefore, represent a particularly insidious source of hidden allergens. Although significant advances have been made in the identification and characterization of soybean allergens, scientists are not completely certain about which proteins in soy cause allergic reactions. At least 16 allergens have been identified. Most of them, as with other plant food allergens, have a metabolic, storage, or protective function. These allergens belong to protein families which have conserved structural features in relation with their biological activity, which explains the wide immunochemical cross-recognition observed among members of the legume family. Detailed analysis of the structure-allergenicity relationships has been hampered by the complexity and heterogeneity of soybean proteins. A variety of technological approaches have been attempted to decrease soybean allergenicity. This paper provides a comprehensive review of the current body of knowledge on the identification and characterization of soybean allergens, as well as an update on current hypoallergenization techniques.

Role of dietary soy protein in obesity

Soy protein is an important component of soybeans and provides an abundant source of dietary protein. Among the dietary proteins, soy protein is considered a complete protein in that it contains ample amounts of all the essential amino acids plus several other macronutrients with a nutritional value roughly equivalent to that of animal protein of high biological value. Soy protein is unique among the plant-based proteins because it is associated with isoflavones, a group of compounds with a variety of biological properties that may potentially benefit human health. An increasing body of literature suggests that soy protein and its isoflavones may have a beneficial role in obesity. Several nutritional intervention studies in animals and humans indicate that consumption of soy protein reduces body weight and fat mass in addition to lowering plasma cholesterol and triglycerides. In animal models of obesity, soy protein ingestion limits or reduces body fat accumulation and improves insulin resistance, the hallmark of human obesity. In obese humans, dietary soy protein also reduces body weight and body fat mass in addition to reducing plasma lipids. Several potential mechanisms whereby soy protein may improve insulin resistance and lower body fat and blood lipids are discussed and include a wide spectrum of biochemical and molecular activities that favorably affect fatty acid metabolism and cholesterol homeostasis. The biologic actions of certain constituents of soy protein, particularly conglycinin, soyasaponins, phospholipids, and isoflavones, that relate to obesity are also discussed. In addition, the potential of soy protein in causing food allergy in humans is briefly discussed.

Soy formula for prevention of allergy and food intolerance in infants

BACKGROUND

Allergies and food reactions in infants and children are common and may be associated with a variety of foods including adapted cow's milk formula. Soy based formulas have been used to treat infants with allergy or food intolerance. However, it is unclear whether they can help prevent allergy and food intolerance in infants without clinical evidence of allergy or food intolerance.

OBJECTIVES

To determine the effect of feeding adapted soy formula compared to human milk, cow's milk formula or a hydrolysed protein formula on preventing allergy or food intolerance in infants without clinical evidence of allergy or food intolerance.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. Updated searches were performed of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2006), MEDLINE (1966-March 2006), EMBASE (1980-March 2006), CINAHL (1982-March 2006) and previous reviews including cross references.

SELECTION CRITERIA

Randomised and quasi-randomised trials that compare the use of an adapted soy formula to human milk, an adapted cow's milk or a hydrolysed protein formula for feeding infants without clinical allergy or food intolerance in the first six months of life. Only trials with > 80% follow up of participants and reported in group of assignment were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Eligibility of studies for inclusion, methodological quality and data extraction were assessed independently by each review author. Primary outcomes included clinical allergy, specific allergies and food intolerance. Where no heterogeneity of treatment effect was found, the fixed effect model was used for meta-analysis. Where significant or apparent heterogeneity was found, results were reported using the random effects model and potential causes of the heterogeneity were sought.

MAIN RESULTS

Three eligible studies enrolling high risk infants with a history of allergy in a first degree relative were included. No eligible study enrolled infants fed human milk. No study examined the effect of early, short term soy formula feeding. All compared prolonged soy formula to cow's milk formula feeding. One study was of adequate methodology and without unbalanced allergy preventing co-interventions in treatment groups. One study with unclear allocation concealment and 19.5% losses reported a significant reduction in infant allergy, asthma and allergic rhinitis. However, no other study reported any significant benefits from the use of a soy formula. Meta-analysis found no significant difference in childhood allergy incidence (2 studies; typical RR 0.73, 95% CI 0.37, 1.44). No significant difference was reported in one study in infant asthma (RR 1.10, 95% CI 0.86, 1.40), infant eczema (RR 1.20, 95% CI 0.95, 1.52), childhood eczema prevalence (RR 1.10, 95% CI 0.73, 1.68), infant rhinitis (RR 0.94, 95% CI 0.76, 1.16) or childhood rhinitis prevalence (RR 1.20, 95% CI 0.73, 2.00). Meta-analysis found no significant difference in childhood asthma incidence (3 studies, 728 infants; typical RR 0.71, 95% CI 0.26, 1.92), childhood eczema incidence (2 studies, 283 infants; typical RR 1.57, 95% CI 0.90, 2.75) or childhood rhinitis incidence (2 studies, 283 infants; typical RR 0.69, 95% CI 0.06, 8.00). One study reported no significant difference in infant CMPI (RR 1.09, 95% CI 0.45, 2.62), infant CMA (RR 1.09, 95% CI 0.24, 4.86), childhood soy protein allergy incidence (RR 3.26, 95% CI 0.36, 29.17) and urticaria. No study compared soy formula to hydrolysed protein formula.

AUTHORS' CONCLUSIONS

Feeding with a soy formula cannot be recommended for prevention of allergy or food intolerance in infants at high risk of allergy or food intolerance. Further research may be warranted to determine the role of soy formulas for prevention of allergy or food intolerance in infants unable to be breast fed with a strong family history of allergy or cow's milk protein intolerance.

Soy protein allergy: incidence and relative severity

Food allergy is a relatively rare and sometimes violent reaction of the immune system to food proteins. The first report characterizing soy allergy appeared in 1934. The Food and Agriculture Organization of the United Nations includes soy in its list of the 8 most significant food allergens. At least 16 potential soy protein allergens have been identified but their relative clinical significance is unknown. Conversely, soy has a long history of successful use in managing cow's milk allergies in infants. To better predict the utility of soy proteins for controlling food allergy, it is important to understand the relative allergenic reactivity of soy compared with other major food proteins. This can be studied using clinical data, animal models, and biochemical approaches; all show diminished reactivity for soy. Clinical studies using in vitro methods and blinded food challenges have generated substantial information. Study populations include high-risk asymptomatic infants and patients with atopic symptoms, positive food challenges, and specific milk allergies. Generally, these studies show lower allergic reactivity for soy proteins vs. other food allergens. Comparisons of food allergen dose-response relationships for triggering allergic symptoms also demonstrate a higher protein concentration threshold for soy (approximately 100 times), indicating lower allergenic reactivity. Extensive investigations of soy immunological reactivity have also been carried out using animal models. Consistent with clinical results, all of these data show substantially diminished immunological reactivity for soy proteins. Biochemical and immunochemical analyses indicate no striking differences between soy and other food proteins that would explain these unexpected differences in allergenic reactivity.

Genetic modification removes an immunodominant allergen from soybean

The increasing use of soybean (Glycine max) products in processed foods poses a potential threat to soybean-sensitive food-allergic individuals. In vitro assays on soybean seed proteins with sera from soybean-sensitive individuals have immunoglobulin E reactivity to abundant storage proteins and a few less-abundant seed proteins. One of these low abundance proteins, Gly m Bd 30 K, also referred to as P34, is in fact a major (i.e. immunodominant) soybean allergen. Although a member of the papain protease superfamily, Gly m Bd 30 K has a glycine in the conserved catalytic cysteine position found in all other cysteine proteases. Transgene-induced gene silencing was used to prevent the accumulation of Gly m Bd 30 K protein in soybean seeds. The Gly m Bd 30 K-silenced plants and their seeds lacked any compositional, developmental, structural, or ultrastructural phenotypic differences when compared with control plants. Proteomic analysis of extracts from transgenic seed detected the suppression of Gly m Bd 30 K-related peptides but no other significant changes in polypeptide pattern. The lack of a collateral alteration of any other seed protein in the Gly m Bd 30 K-silenced seeds supports the presumption that the protein does not have a role in seed protein processing and maturation. These data provide evidence for substantial equivalence of composition of transgenic and non-transgenic seed eliminating one of the dominant allergens of soybean seeds.

Soy formulas and nonbovine milk

BACKGROUND

Cow's milk allergy is frequently observed during the first year of life when nutritional requirements are critical. In those cases where breast-feeding is not available, a safe and adequate substitute to cow's milk should be offered.

OBJECTIVE

The primary aim of this review is to evaluate the clinical use of milk derived from vegetable proteins, such as soy, or from animals such as goat, mare, or donkey, or elemental diet in children with cow's milk allergy.

METHODS

MEDLINE searches were conducted with key words such as soy, goat's milk, donkey's milk, mare's milk, and elemental diet. Additional articles were identified from references in books or articles. Original research papers and review articles from peer-reviewed journals were chosen.

RESULTS

Soy formulas are nutritionally adequate and can be used in children with immunoglobulin E-mediated nongastrointestinal manifestations of cow's milk allergy. Goat's milk is as allergenic as cow's milk. Mare's milk and donkey's milk may be used in selected cases of cow's milk allergy after appropriate modification to make them suitable for human infants. Elemental diets are usually restricted to the most severe cases of cow's milk allergy (ie, sensitivity to extensively hydrolyzed protein formulas).

CONCLUSIONS

Vegetable formulas obtained from soy and milk derived from other mammals, such as mare or donkey, homemade preparations, and elemental diet may represent valid alternatives for children with cow's milk allergy. Extensive clinical trials are needed on the safety profile of any alternative mammal-derived milk. The choice of alternative milk should take into account the clinical profile of the child allergic to cow's milk, particularly as concerns age, severity of symptoms, degree of sensitivity to cow's milk proteins, and any multiple food allergies.

Severe oral allergy syndrome and anaphylactic reactions caused by a Bet v 1- related PR-10 protein in soybean, SAM22

BACKGROUND

Anaphylactic reactions to soy products have been attributed to stable class 1 food allergens.

OBJECTIVE

IgE- mediated reactions to a soy-containing dietary food product in patients allergic to birch pollen were investigated.

METHODS

Detailed case histories were taken from 20 patients. Their sera were analyzed for IgE (UniCAP) specific for birch, grass, mugwort, the recombinant birch allergens rBet v 1 and rBet v2, and soy protein. Extracts from birch pollen, soy isolate, rBet v 1, and the recombinant PR-10 soy protein rSAM22 were coupled to paper disks or nitrocellulose for IgE measurements (enzyme allergosorbent test) or Western blot analysis. Enzyme allergosorbent testing, Western blot inhibition, and histamine release studies were performed with the same allergens.

RESULTS

Most patients (17/20) experienced facial, oropharyngeal, and/or systemic allergic symptoms within 20 minutes after ingesting the soy product for the first time. Birch pollen allergy (16/20) was common, along with oral allergy syndrome to apple (12/20) or hazelnut (11/20). IgE levels to birch and Bet v 1 but not to other inhalants were high in 18 of 20 patients. Significant IgE binding to rSAM22 occurred in 17 of 20 patients. Blot experiments with the soy isolate revealed IgE-binding bands at 17 kd (15/20), 22 kd (1/20), and 35 to 38 kd (2/20); the former was inhibited by preincubation of the sera with rBet v 1 or rSAM22. Birch extract and soy isolate, rBet v 1, and rSAM22 induced dose-dependent histamine release in the nanomolar range.

CONCLUSION

Immediate-type allergic symptoms in patients with birch pollen allergy after ingestion of soy protein-containing food items can result from cross-reactivity of Bet v 1 -specific IgE to homologous pathogenesis-related proteins, particularly the PR-10 protein SAM22.

Allergy to soy formula and to extensively hydrolyzed whey formula in infants with cow's milk allergy: a prospective, randomized study with a follow-up to the age of 2 years

OBJECTIVES

We conducted a prospective, randomized study to evaluate the cumulative incidence of allergy or other adverse reactions to soy formula and to extensively hydrolyzed formula up to the age of 2 years in infants with confirmed cow's milk allergy.

STUDY DESIGN

Infants (n = 170) with documented cow's milk allergy were randomly assigned to receive either a soy formula or an extensively hydrolyzed formula. If it was suspected that the formula caused symptoms, a double-blind, placebo-controlled challenge (DBPCFC) with the formula was performed. The children were followed to the age of 2 years, and soy-specific immunoglobulin E antibodies were measured at the time of diagnosis and at the ages of 1 and 2 years.

RESULTS

An adverse reaction to the formula was confirmed by challenge in 8 patients (10%; 95% confidence interval, 4.4%-18.8%) randomly assigned to soy formula and in 2 patients (2.2%; 95% confidence interval, 0.3% to 7.8%) randomly assigned to extensively hydrolyzed formula. Adverse reactions to soy were similar in IgE-associated and non-IgE-associated cow's milk allergy (11% and 9%, respectively). IgE to soy was detected in only 2 infants with an adverse reaction to soy. Adverse reactions to soy formula were more common in younger (<6 months) than in older (6 to 12 months) infants (5 of 20 vs 3 of 60, respectively, P =.01).

CONCLUSIONS

Soy formula was well tolerated by most infants with IgE-associated and non-IgE-associated cow's milk allergy. Development of IgE-associated allergy to soy was rare. Soy formula can be recommended as a first-choice alternative for infants >or=6 months of age with cow's milk allergy.

Nutritional and health benefits of soy proteins

Soy protein is a major component of the diet of food-producing animals and is increasingly important in the human diet. However, soy protein is not an ideal protein because it is deficient in the essential amino acid methionine. Methionine supplementation benefits soy infant formulas, but apparently not food intended for adults with an adequate nitrogen intake. Soy protein content of another essential amino acid, lysine, although higher than that of wheat proteins, is still lower than that of the milk protein casein. Adverse nutritional and other effects following consumption of raw soybean meal have been attributed to the presence of endogenous inhibitors of digestive enzymes and lectins and to poor digestibility. To improve the nutritional quality of soy foods, inhibitors and lectins are generally inactivated by heat treatment or eliminated by fractionation during food processing. Although lectins are heat-labile, the inhibitors are more heat-stable than the lectins. Most commercially heated meals retain up to 20% of the Bowman-Birk (BBI) inhibitor of chymotrypsin and trypsin and the Kunitz inhibitor of trypsin (KTI). To enhance the value of soybeans in human nutrition and health, a better understanding is needed of the factors that impact the nutrition and health-promoting aspects of soy proteins. This paper discusses the composition in relation to properties of soy proteins. Also described are possible beneficial and adverse effects of soy-containing diets. The former include soy-induced lowering of cholesterol, anticarcinogenic effects of BBI, and protective effects against obesity, diabetes, irritants of the digestive tract, bone, and kidney diseases, whereas the latter include poor digestibility and allergy to soy proteins. Approaches to reduce the concentration of soybean inhibitors by rearrangement of protein disulfide bonds, immunoassays of inhibitors in processed soy foods and soybean germplasm, the roles of phytoestrogenic isoflavones and lectins, and research needs in all of these areas are also discussed. This integrated overview of the widely scattered literature emphasizes general concepts based on our own studies as well as recent studies by others. It is intended to stimulate interest in further research to optimize beneficial effects of soy proteins. The payoff will be healthier humans and improved animal feeds.

Mutational analysis of the IgE-binding epitopes of P34/Gly m Bd 30K

BACKGROUND

Peanuts and soybeans are 2 foods that have been shown to be responsible for many atopic disorders. Because of their nutritional benefit, soybean proteins are now being used increasingly in a number of food products. Previous studies have documented multiple allergens in soybean extracts, including glycinin, beta-conglycinin, and the P34/Gly m Bd 30K protein.

OBJECTIVE

Our overall goal was to identify soybean-specific allergens to begin to understand molecular and immunochemical characteristics of legume proteins. The specific aim of the current investigation was to identify the essential amino acid residues necessary for IgE binding in the 5 distinct immunodominant epitopes of P34/Gly m Bd 30K.

METHODS

Serum IgE from 6 clinically sensitive soybean-allergic individuals was used to identify P34/Gly m Bd 30K in the native and single amino acid substituted peptides with use of the SPOTS peptide synthesis technique to determine critical amino acids required for IgE binding.

RESULTS

The intensity of IgE binding and epitope recognition by serum IgE from the individuals varied substantially. With use of serum from 6 clinically soybean-sensitive individuals, 2 of the 5 immunodominant epitopes could be mutagenized to non-IgE binding peptides.

CONCLUSIONS

Single-site amino acid substitution of the 5 immunodominant epitopes of Gly m Bd 30K with alanine revealed that IgE binding could be reduced or eliminated in epitopes 6 and 16 in the serum obtained from 6 soybean-sensitive patients.

Dietary aspects of food allergy prevention in infants and children

Food allergy occurs in approximately 4% to 6% of children, has increased in prevalence during the past decade, and thus represents a major burden to our young. The natural history of food allergy documents that allergies to cow's milk, egg, and soy frequently remit whereas allergies to peanut, nuts, and fish typically persist to adulthood, although exceptions exist. Food allergen avoidance subsequent to sensitization and manifestation of symptoms appears to hasten tolerance; however, the immunologic mechanism responsible for tolerance to one food group and not another is poorly understood. Identification and characterization of allergens and determination of B- and T-cell epitopes has provided an opportunity to better define these mechanisms. Identifying and developing effective strategies to prevent food and other allergic diseases represents a high priority for medicine at this time because of the unbridled increase in the prevalence and morbidity attributed to them. Immunologic engineering holds the greatest promise for allergy prevention in the not too distant future, but environmental strategies that promote food avoidance provide an avenue for prevention at present. Such efforts rely actively on reducing the food allergenic load and exposure of atopy-prone infants and children.

Soy allergy in infants and children with IgE-associated cow's milk allergy

OBJECTIVES

To determine the prevalence of soy allergy in IgE-associated cow's milk allergy (CMA).

STUDY DESIGN

Children <3.5 years with documented IgE-associated CMA (n = 93) were evaluated for soy allergy by double-blind, placebo-controlled food challenge, open challenge, or convincing previous history of an anaphylactic reaction to soy. Children tolerant to soy at entry received soy formula and were followed up for 1 year.

RESULTS

Of this IgE-associated CMA cohort (ages 3 to 41 months), 14% (95% CI = 7. 7%-22.7%) were determined to have soy allergy, 12 definitely at entry and 1 possibly after 1 year of soy ingestion. The latter child experienced severe failure to thrive at enrollment and exhibited improved growth while receiving soy during follow-up but was diagnosed with eosinophilic esophagitis at study completion. Improved growth (P <.05) occurred in the non-soy-allergic cohort ingesting soy formula (579 31 mL/d) during the year of follow-up.

CONCLUSIONS

Soy allergy occurs in only a small minority of young children with IgE-associated CMA. As such, soy formula may provide a safe and growth-promoting alternative for the majority of children with IgE-associated CMA shown to be soy tolerant at the time of introduction of soy formula.