Australian Pediatric Soy Protein Formula Policy
Policy Statement of Royal College of Australian Physicians
The lack of a suitable diagnostic test for food intolerance has allowed for an exaggeration of the incidence and a tendency for over-diagnosis. The true incidence of milk intolerance in our community is difficult to ascertain but a reasonable working figure would be 2.0% (1).
The number of infants on soy formula outweighs this figure as soy formula accounts for approximately 10% of formula sales in Australia.
There is no evidence that soy formulas are nutritionally better than cow's milk formula for normal infants. The assumption that symptomatic infants who improve on soy formula are therefore intolerant of milk protein is addressed in this statement (2).
There are several well-characterized disorders caused by cow's milk protein intolerance (CMPI), including cow's milk allergy, cow's milk enteropathy and cow's milk colitis. There is also a range of vague signs and symptoms ascribed to CMPI, which includes excessive crying, vomiting, wind, colic, vague ill health, and tension-fatigue syndrome (3).
With the latter symptoms, there is usually no evidence of associated chronic diarrhea or growth failure. Of concern, is that many of these latter symptoms may be the result of parent-child relationship problems, which are inappropriate to treat with soy formula. Controlled trials of cow's milk and soy formulae in colicky infants have not demonstrated a benefit from soy formula (4).
The rationale for the use of soy formula is the assumption that soy protein is less antigenic than cow's milk protein and thus should be used in the treatment of CMPI, or prophylactically in patients at high risk for developing CMPI.
Soy protein can cause intolerance reactions with gastrointestinal symptoms as well as acute anaphylaxis and up to 40% of infants intolerant of cow's milk also develop soy protein intolerance (6).
Studies show that feeding soy formulae from birth in infants at increased risk of developing allergy, does not have a beneficial effect (7-9). Eastham et al, in a prospective feeding trial, showed soy protein to be at least as antigenic as cow's milk protein (8).
Miskelly et al, in a randomized clinical trial of cow's milk vs soy protein formulae in children with family histories of atopic disease, demonstrated a similar incidence of wheezing and eczema between the groups and an increased incidence of napkin rash, diarrhea and oral thrush in the group fed soy formula (9).
Thus, it seems that soy formula is inappropriate even in cases of proven CMPI, because of its ability to cause reactions. In cases of true gastrointestinal CMPI, the use of protein which has been hydrolyzed to the point that it is no longer antigenic, is preferred.
Soy protein contains only one-third of available nitrogen as essential or semi-essential amino acids (10) and therefore has a lower biological value than milk protein.
Soy may cause loss from the gut of vitamins, minerals and trace elements and it has been suggested that 10% more calories are needed in soy preparations in order to promote equivalent growth to infants breastfed or fed a milk formula (11). Low levels of chloride have been reported and may result in serious hypochloraemic alkalosis in infants fed soy formula (12).
Manufacturers currently attempt to compensate for these potential problems by adding extra protein, trace elements and chloride to soy formulae. Growth of infants fed soy formulae is similar to that of infants fed formulae based on cow's milk protein but there is concern about poorer bone mineralization in infants fed soy formulae (13).
The carbohydrate content of soy formula differs in each of the three commonly available preparations (Isomil: sucrose 36%, corn syrup solids 64%; Prosobee: maltodextrins 100%; Infasoy: sucrose 25%, corn syrup solids 75%). Sucrose is not the preferred carbohydrate in infancy because of its potential effect on teeth and development of inappropriate eating habits.
High aluminum content has also been documented in soy formula (14).
Soy is also a rich source of phytoestrogens (nonsteroidal estrogens of the isoflavone class). It is unclear whether these are beneficial (protect against breast and prostate cancer) or harmful (result in infertility and liver disease) (15).
It is also possible that soy formula impairs immunity. Infants fed soy formula had lower levels of antibodies in response to routine immunizations and more infections than those fed human milk or cow's milk formula (16).
http://www.racp.edu.au/index.cfm?obj...46135DBF3DBE77 (has been updated in PDF form)