Soy Formulas Are Not Hypoallergenic
American
Journal of Clinical Nutrition 1990: 51: 705-6.
Dear Sir
In the
highly informative review, “Soy products and the human
diet,” by Erdman and Fordyce (1), I was surprised at the
authors’ conclusion that “….soy formulas contain a
less allergenic protein” than cow-milk-based formula (CMF).
Abundant literature on the antigenicity and allergenicity of soy
protein (SP) in infant feeding fail to support the authors’
conclusion. The SPs used in infant formulas appear to be equally and in
some cases, more antigenic than the heat-treated CMFs.
From an
immunological and biochemical standpoint, there is not a prior reason
to believe that SP possesses inherently hypoallergenic properties. May
et al. (2) noted the brisk antibody response in infants fed soy
formula, whereas Eastham et al. (3) concluded that SP is at least as
antigenic as cow-milk protein (CMP) and should be used with caution. In
animal models, investigators have been able to induce both anaphylaxis
and antibody production in guinea pigs, calves, rabbits and mice.
Protein
size and diversity are important predictors of allergic response. The
large molecular weights and multiple protein subclasses of SP rival the
20-30 antigenic fractions of bovine milk. One author found up to 24
fractions of SP potentially capable of antibody elicitation (4). Burks
et al. (5), using enzyme-linked immunoassays (ELISA) in infants with
atopic dermatitis (soy sensitised), demonstrated allergen-specific lgl:
antibodies to the 7S, IIS, and whey protein fractions of soy extract.
Other potentially allergenic or antinutritional substances found with
SP include lectins, soya saponins, trypsin inhibitors and
hemagglutinins. In addition, the molecular weights of SP fractions
range from 8,000 to 600,000 Da -certainly large enough to stimulate
antibody production and larger than most, if not all, of the
nutritional proteins found in cow milk (6).
Clinical
investigations with human infants validate the significance of SP
antigenicity. In the past 35 years, nine studies compared the efficacy
of SP – vs CMP-based formulas in the prevention of atopic
symptoms of food allergy (vomiting, colic, diarrhoea, eczema, rhinitis
and asthma) in infants at high risk of atophy. Eight of these studies
concluded that the incidence of atopic disease was not effected by the
exclusive feeding of soy formula. In the most recent clinical study
comparing CMF to soy-based formula, Miskelly et al. (7) concluded,
“…no evidence has so far emerged to support that soya milk
is better than cow’s milk in regards to the risk of allergic
disease.”
Finally,
the clinical literature is replete with numerous studies demonstrating
the deleterious effects of SP on multiple-organ systems. SP ingestion
or inhalation has been associated with asthma, diarrhoea, anaphylactic
shock, gastrointestinal injury and the classical symptoms of
atopy, i.e., eczema, rhinitis, vomiting, diarrhoea, otitis media,
etc. Cow-milk and SP allergy may also occur simultaneously or
as a consequence of soy feeding after gastronintestinal insult. Hill et
al. (8) found that >50% of the infants with CMP intolerance were
also reactive to soy formula and Lothe et al. (9) demonstrated that 35%
of the CMP-allergic infants were also allergic to soy.
With its
inherent antigenic properties, lack of efficacy in preventing, atopic
disease and frequency of simultaneous allergy in CMP-sensitised
infants, one must conclude that SP is not hypoallergenic compared with
CMF (10). The American Academy of Paediatrics Committee on
Nutrition (AAP/CON) recommends against the use of SP formulas in the
dietary management of documented clinical allergic reactions
to CMP or in the routine management of colic (11).
Although
soy-formula use is common in infants with suspected allergies (~24% of
the total formula market), its routine use as a hypoallergenic
substitute for CMP formulas is not supported by basic science or
clinical literature.
In Cancer
Research, Helferich compared soy protein isolates containing varying
levels of isoflavones. The researchers found that estrogen-dependent
tumor growth increased as the isoflavone content increased in the
soy-containing diet.
Stephen A
Witherly
Carnation
Company
Nutritional
Products Division
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