Protein hydrolysates in hypo-allergenic infant formulas
Protein hydrolysates in hypo-allergenic infant formulas
FrieslandCampina Domo develops hydrolysates which are used in infant nutrition to manage existing cow’s milk allergy and reduce the risk for its development. This overview gives background information about cow’s milk allergy, as well as the causes of and risk factors for developing the allergy. In addition, a description is included about hydrolysates for infant nutrition in relation to their usefulness for cow’s milk allergy management and reduction of the risk to develop an allergy. These hydrolysates are classified into two focus areas:
CMA products, intended for use in formulas for infants with existing cow’s milk allergy, and
HA products intended for formulas to reduce the risk of the development of cow’s milk allergy.
Importance of cow’s milk in infant nutrition
Breast milk is best for newborn infants. When breast milk is limited or impossible, infant formulas are the only food products that satisfy the nutritional requirements of infants during the first months of life (EU2006/141). Unless the infant has a specific condition (congenital lactase deficiency or galactosaemia) milk protein is often the preferred source for infant formula, due to its high protein quality. Cow’s milk proteins are rich in all essential amino acids and they have a high nutritional quality in contrast to vegetable proteins*. The predominant milk proteins are casein and whey1. Although most infants grow up healthy with standard cow’s milk-based formulas, some infants are allergic to the intact cow’s milk proteins. For these infants, formulas have been developed based on hydrolysed cow’s milk proteins, which retain the high nutritional quality of the proteins, but have lower allergic potential.
What is cow’s milk allergy?
Cow’s milk allergy (CMA) is an immunologically-mediated disorder, in which the immune system is incorrectly programmed to react to bovine milk proteins. Most major milk and other proteins have been implicated in allergic responses, including casein and whey proteins2. A good example is the whey protein ß-lactoglobulin. The allergic reactions involve antibody-mediated, cell mediated mechanisms, or both. The symptoms associated with IgE-mediated CMA include one or more cutaneous (eczema, angioedema, urticaria), gastrointestinal (oral allergy syndrome, nausea, vomiting, diarrhoea) or respiratory manifestations (rhinoconjunctivitis, asthma)3.
Under normal conditions, antibodies react with detrimental agents such as viruses or bacteria. However, in the case of allergies, an immune response is triggered against harmless molecules (such as food proteins), which turn these molecules into so-called allergens. In cow’s milk allergies infants express IgE antibodies against epitopes on milk proteins. An epitope can be defined as a single antigenic site on a complex antigen and is determined by amino acid sequence and structural conformation. The binding of these IgE molecules to the epitopes trigger an immune response, such as the release of inflammatory mediators from various immune cells. This eventually leads to the allergic clinical symptoms4,5,6.
scheme of immunological reactions
Eczema in an infant with CMA
Incidence of CMA
CMA is most prevalent in infancy, when the immune system is relatively immature and susceptible to sensitization by environmental antigens7. The prevalence in early childhood has been reported to be between 2-6%8,9 and decreases into adulthood to an incidence of 0.1-0.5%10,11. The majority (80-90%) of affected infants acquires tolerance to cow’s milk by the age of five12. However, there remains a strong trend in infants who recover from CMA to develop atopic symptoms such as asthma, hay fever, or dermatitis to inhalant allergens later in life: the so-called “atopic career” or “atopic march” 12,13.
The allergic march
Risk factors for CMA
The risk of developing an allergy is determined by interactions between genetic and environmental factors14,15. Assessment of family history is key to identifying allergy-prone infants. The more family members who have a food allergy, the higher the risk of developing CMA (see table 1)16. Reducing the risk for allergy development should be targeted primarily at infants with a genetically determined susceptibility. However, since children without obvious risk factors for atopic disease may also develop a food allergy17, it has been suggested that a simpler strategy implemented in the general population would be preferred18. Risk reducing measures have included promoting breastfeeding and avoiding inhalant and potent food allergens and irritants.
Table 1: Genetic predisposition for developing CMA
* not only food-allergies, also eczema, asthma, hay-fever, etc. Source: Zeiger RS, Heller S. 199516
Infants more susceptible to developing CMA
The risk for sensitisation to food proteins is most critical during early infancy when the immune system and intestinal tract are still maturing. The first step of protein digestion occurs in the stomach, where proteins are hydrolysed into peptides and amino acids. The allergic potential of peptides is dependent on peptide size: smaller peptides are less allergenic. Also important is the level of exposure to the peptide.
The low pH in the stomach is important for the enzyme pepsin, which is effective in the pH range of 1.5 to 2.519. In adults, stomach pH is regulated at about 220. However, the pH of the gastric contents of infants is about 4.521, rising above 5 postprandially and remaining high for over one hour22. Such pH values are suboptimal for peptic activity and have been demonstrated to result in diminished hydrolysis of proteins23. Moreover, postprandial pepsin output is significantly lower in preterm infants than adults24. Therefore, gastric proteolysis is assumed to be low in infants24,25, which suggests that larger peptides or allergens survive digestion.
Allergens can cross the intestinal wall by different routes, including the enterocytes, the M-cells and via paracellular diffusion. In infants, there is more paracellular diffusion because the gut is not yet fully developed. This immature gut is also called “leaking wall” 26,27. It suggests that allergens which survive digestion have more chance of crossing the intestinal wall and contacting the immune system. Taken as a whole, the enhanced exposure to larger protein fragments and intact proteins is likely part of the reason why the risk for sensitisation to food proteins is highest during early infancy.
Strategic approach to CMA
In order to reduce the allergenicity of milk proteins and still retain their high nutritional quality, milk proteins are hydrolysed before being administered to the infant. Basically, the proteins are predigested. Predigestion or protein hydrolysis for infant nutrition can lower the allergenic potential by destroying the epitopes. Some proteins are broken down more easily than others because of structural differences. In general, it is considered that the higher the degree of hydrolysis, the smaller the peptides and the lower their allergenic potential. Depending on the degree of hydrolysis, proteins are referred to as partially hydrolysed or extensively hydrolysed proteins.
The antigenic potential decreases by protein breakdown.
Dietary management of cow’s milk allergy
CMA is managed by the avoidance of intact cow’s milk proteins on the part of individuals who are already sensitised to cow’s milk. In the development of infant formulas for cow’s milk allergy patients, allergenic epitopes are therefore destroyed through extensive hydrolysis of milk proteins to small peptides. These extensively hydrolysed cow’s milk proteins have been used in formulas for over 50 years for infants with CMA. These formulas have been subjected to extensive clinical testing and proven to be tolerated by the majority of allergic infants28,29,30,31,32.
Formulas based on partially hydrolysed cow’s milk proteins (1,000-100,000 times higher concentrations of intact cow’s milk proteins compared with extensively hydrolysed proteins) have provoked significant reactions in a high percentage of infants allergic to cow’s milk33,34 and are not intended for therapeutic use in existing CMA patients.
Professional guidelines summarizing the approach to allergy management have been presented by the American Academy of Pediatrics (AAP)35, the Section of Pediatrics of the European Academy of Allergy and Clinical Immunology (SP-EAACI, previously ESPACI) and the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN)36.
These organisations recommend complete exclusion of the causal protein for infants with confirmed CMA. Infants with CMA who are not breastfed should receive a dietary product with highly reduced allergenicity based on extensively hydrolysed protein or, in certain cases, on an amino acid mixture35,36. In infants with adverse reactions to food proteins and malabsorptive enteropathy, the use of an extensively hydrolysed formula without lactose and with medium-chain triglyceride might be useful until normal absorptive function of the mucosa is regained.
HA formulas – reduction of risk to develop allergy to cow’s milk protein
While infants with existing CMA require extensively hydrolysed formulas (eHF), human intervention studies have shown that partially hydrolysed formulas (pHF) reduce the incidence of atopic dermatitis in at-risk infants in the first two years compared to intact cow’s milk protein formulas37,38,39,40. Therefore, pHF could be used to reduce the risk of developing CMA in allergy-prone infants.
Moreover, it has been suggested that pHF are more effective than eHF in reducing the risk to develop CMA. While eHF remove allergenicity, the loss of immunogenicity could also retain the immune system from developing tolerance to milk proteins. Oral tolerance is the unresponsiveness of the immune system to dietary antigens and therefore permits exposure to foreign proteins, such as cow’s milk proteins, without developing hypersensitivity41. CMA is believed to result from the failure to develop these tolerogenic processes.
Partial hydrolysis of proteins can minimize the number of sensitising epitopes within milk proteins, while retaining peptides with sufficient size and immunogenicity to stimulate the induction of oral tolerance. However, despite animal studies indicating that pHF have an increased capacity to induce oral tolerance42,43,44, there is still no clear evidence from human studies that they are better than eHF in reducing the risk for developing CMA45,46.
Based on the available literature, the AAP, SP-EAACI and ESPGHAN formulated guidelines for the prevention of allergy. The SP-EAACI and ESPGHAN concluded that a dietary regimen is effective in reducing the risk of allergy to the avoided food in high-risk infants. This is particularly true in early infancy in the case of food allergy (cow’s milk allergy) and eczema (atopic or non-atopic)47. The most effective regimen is exclusive breastfeeding for at least 4-6 months. However, if this is not possible, formulas with documented reduced allergenicity may be considered for at least 4 months, combined with avoidance of solid food and cow’s milk during the same period47.
The American Academy of Pediatrics (AAP) states that in the case of infants at high risk of developing atopic disease, who are not breastfed exclusively for 4 to 6 months or who are formula-fed, there is evidence that atopic dermatitis may be delayed or have a reduced risk by the use of extensively or partially hydrolysed formulas – compared with cow’s milk formulas – in early childhood. Extensively hydrolysed formulas may be more effective than partially hydrolysed in the reducing the risk of atopic disease development48.
Partially hydrolysed protein based formula (HA) reduced the number of allergy diseases in at-risk infants in relation to cow’s milk based formula (CMF)37 (MM=mothers milk).
Legislation for claims on infant formulas Europe
In Europe, the Commission Directive 2006/141/EC of 22 December 2006 on infant formulas and follow-on formulas and amending Directive 1999/21/EC lays down the requirements for the composition and labelling of infant formulas and follow-on formulas. The annexes of the Directive give criteria for the composition (proteins, carbohydrates, fats, mineral substances, vitamins and certain other ingredients) of infant formulas and follow-on formulas including, where necessary, minimum and maximum levels.
The Directive distinguishes between two kinds of infant formulas with claims relating to the reduction of the risk of developing an allergy to milk protein:
infant formulas claiming reduced allergenicity, intended for nonallergic infants (we refer to these products as HA products), and
infant formulas claiming reduced allergenicity for infants with existing CMA (we refer to these products as CMA-products).
The following conditions apply to infant formulas included under I. (HA products):
Objective and scientifically verified data proving the claimed properties must be available.
The amount of immunoreactive protein measured using methods generally acceptable as appropriate shall be less than 1% of nitrogencontaining substances in the formula.
The label shall indicate that the product must not be consumed by infants allergic to the intact proteins from which it is manufactured.
The infant formula administered orally must not induce sensitization in animals to the intact proteins from which the infant formula is manufactured.
For Formulas intended for allergic infants (CMA formulas) the following applies:
Generally accepted clinical tests must provide proof of infant formula’s tolerance in more than 90% of infants (confidence interval 95%) hypersensitive to proteins from which the hydrolysate is manufactured.
The requirements for hypoallergenic claims laid down in Directive 2006/141/EC apply to infant formulas (up to 6 months of age) only. For these products, no claims other than those relating to reduced allergenic properties are allowed. For FOF, a claim relation to allergy risk reduction can only be made with an authorized art 14 health claim (Claims regulation 1924/2006).
In the United States, the HA segment does not exist and all formulas with reduced allergenicity are intended for infants with existing CMA. The requirements for claims related to these formulas are less clear than in Europe. The legal basis is Section 412 of the Federal Food, Drug and Cosmetic Act (FDA)49.
It stipulates rules on composition, good manufacturing practice and labelling. All infant food manufacturers must be registered and all new infant formulas have to be reported to the FDA at least 90 days before they are marketed. In these formulas, only substances that are GRAS for use in infant formulas or approved food additives may be used. Hydrosates are affirmed as GRAS by FDA as long as they have been prepared from casein, animal tissue, soy protein isolate, gelatin, defatted fatty tissue, egg albumin or lactalbumin (whey protein) with enzymes that are either considered GRAS or are regulated as food additives (FDA 21 CFR 184.1553).
Furthermore, the American Academy of Pediatrics has formulated criteria for the testing of hypoallergenic infant formulas. These tests should, at a minimum, ensure with 95% confidence that 90% of infants with documented cow’s milk allergy will not react with defined symptoms to the formula under double-blind, placebo-controlled conditions.
The information on this page is intended for industrial customers only and not intended for consumers. Potential consumer benefits are not to be considered as health claims. They should be considered as potential leads that might be developed into health claims complying with the local legal requirements.
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Hydrolysates and CMA
This video is adapted from the 2012 Lifestages webinar “It’s all about growth”. The presentation addresses the theory of cow’s milk allergy and how hydrolysates may contribute.