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Soy based Infant Formulas

Soy protein based formula is a substitute that can be used as an alternative to cow milk in infant feeding. It contains soy protein isolates, derived from soy flour, and a mixture of carbohydrates in the form of sucrose and corn syrup.

Soy protein has a lower biological value than cow milk protein; the total protein content is lower for soy protein isolates than for cow milk protein. The amino acid pattern is different (soy protein contains lower amounts of methionine and higher quantities of aspartate, glycine, arginine, and cystine than cow milk protein).

The amino acids used to supplement soy formulas, as approved by government legislation are:

• L-methionine, an amino acid that ensures adequate growth, nitrogen balance, and plasma albumin concentrations.
• L-carnitine, an amino acid deficient in foods of plant origin and required for the optimal mitochondrial oxidation of long-chain fatty acids.
• taurine, an amino acid abundant in human milk, an antioxidant and along with glycine, maximises fat absorption.

There are concerns about specific compounds found in soy formulas. Some of these are as follows:

• phytates are phosphorous based compounds which complex with calcium, iron and zinc making them unavailable for absorption into the body;
• nucleotides are the elements of nucleic acids that in soy formulas are four or five times higher than in human milk or in cow milk infant formulas. Until now, there is not adequate scientific data to conclude that higher concentrations of nucleotides would provide additional benefits;
• aluminium is found in higher concentrations in soy formulas compared to cow milk formulas as soy beans contain naturally occurring aluminium. Although long-term consequences of higher levels of aluminium are unknown, continued efforts should be made by manufacturers to reduce the aluminium content of soy protein formula;
• phytoestrogens, in particular isoflavones, a broad group of plant derived compounds that are present in beans in general and soybeans in particular and that have weak estrogen activity. There is good evidence that these compounds are absorbed and metabolised by infants but little evidence to date shows, unequivocally, that compounds are pharmacologically active at the levels found in infants.
  Infant formulas based on soy protein isolates contain relatively high concentrations of isoflavones. There is no data to suggest that phytoestrogens produce clinical effects in humans but phytoestrogens given in high doses have been demonstrated to affect development and neuroendocrine function in different animal species. For this the European Society for Paediatric Gastroenterology Hepatology and Nutrition Committee recommends that the content of phytoestrogens in soy protein formulas be reduced because of uncertainties regarding safety in infants and young children.

The use of soy protein based formula in Cow Milk Allergy and intolerance

Bottle-fed infants may be unable to tolerate standard cow milk based formulas because they are allergic to the cow milk protein and/or intolerant to the lactose present. For this reason, soy formulas have a long history of use, not just for Cow Milk Allergy, but also for lactose intolerance, galactokinase deficiency and galactosaemia. Before the availability of therapeutic formulas based on cow milk protein hydrolysates and amino acids, soy formula was the only dietetic product available for feeding infants with cow milk protein allergy.

A joint statement of the European Society for Paediatric Gastroenterology Hepatology (ESPGHAN) and Nutrition Committee on Nutrition and the European Society for Pediatric Allergology and Clinical Immunology (ESPACI) suggest that:

• in general, soy based formulas are not recommended for the initial treatment of food allergy in infants;
• soy protein formulas should not be used in infants with food allergy during the first 6 months of life;
• after the age of 6 months soy protein formulas can be used as an alternative nutrient due its low cost and better acceptance. Tolerance to soy protein should first be established by a healthcare professional.
• commercial soy milk may be useful as part of a varied diet for children from the age of 1 year with Cow Milk Allergy who are tolerant to soy.

European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) Recommendations

1. cow milk-based formulas should be preferred as the first choice for feeding healthy infants that are not fully breast fed.
2. Soy based formulas should only be used in specified circumstances because they may have nutritional disadvantages and contain high concentrations of phytate, aluminium, and phytoestrogens, the long term effects of which are unknown.
3. Indications for soy formulas include severe persistent lactose intolerance, galactosemia, religious, ethical, or other considerations that stipulate the avoidance of cow milk based formulas and treatment of some cases of cow milk protein allergy.
4. The Committee recommends that the use of therapeutic formulas based on extensively hydrolyzed proteins (or amino acid preparations if hydrolysates are not tolerated) should be preferred to that of soy protein formula in the treatment of cow milk protein allergy. Soy protein formula should not be used in infants with food allergy during the first 6 months of life. If soy protein formulas are considered for therapeutic use after the age of 6 months because of their lower cost and better acceptance, tolerance to soy protein should first be established.
5. Soy protein formulas have no role in the prevention of allergic diseases.
6. There is no evidence supporting the use of soy protein formulas for the prevention or management of infantile colic, regurgitation, or prolonged crying.
7. Manufacturers should aim to reduce the concentrations of trypsin inhibitors, lectins, goitrogenic substances, phytate, aluminium, and phytoestrogens in soy protein formulas.