Exposure to Soy-Based Formula in Infancy

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Exposure to Soy-Based Formula in Infancy

JAMA / volume:286 (page: 2402)

Lynn R. Goldman, MD, MPH; Retha Newbold; Shanna H. Swan, PhD L. Strom,

MD, MPH; Rita Schinnar, MPA; Kurt T. Barnhart, MD, MSCE; D. Sammel, ScD;

A. Macones, MD, MSCE; Virginia A. Stallings, MD

November 21, 2001  

<A HREF= " http:// " >http://jama.ama-assn.org/issues/v286n19/ffull/jlt1121-3.html

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To the Editor: Dr Strom and colleagues1 found no differences in later

pubertal maturation or growth between infants who had been fed soy-based vs

milk-based formula. However, this does not prove that soy-based formulas are

safe. In fact, the authors found that infants who had been given soy-based

formula later used more asthma and allergy medications (P = .047 and .08 for

female and male subjects, respectively). This important observation was not

mentioned in the abstract, which stated that " [n]o statistically significant

differences were observed . . . for more than 30 outcomes. " 1

This conclusion contradicts the findings of both human and animal studies. A

retrospective epidemiological study by Fort et al2 found that children with

autoimmune disease were significantly more likely to have received soy

formula as infants than were healthy siblings or control subjects. A recent

study from the National Toxicology Program found that rats receiving dietary

genistein (an isoflavone found in soybeans) had increased T-cell immune

responses.3 These findings suggest that soy consumption could adversely

affect the course of autoimmune disease in children by modulating immune

function. Since asthma is a potentiated immune response to an antigen, this

finding of Strom et al should not be ignored; clearly, additional studies are

warranted before confidence in the safety of soy formula is complete.

Strom et al also found that women who had been fed soy formula as infants had

a small average increase in the duration of their menstrual cycles (0.37

days) and greater discomfort with menstruation. The authors suggested these

effects were small and could be disregarded. Both findings, however, might

reflect endometriosis or uterine fibroids, which could theoretically result

from early life exposure to estrogens. In fact, these conditions were among

several reproductive problems that the authors controlled in their analyses,

suggesting that their distribution may have differed in the 2 exposure

groups. However, the number of cases in exposed and unexposed subjects was

not stated. In addition, the authors reported a 4-fold increase of multiple

births in women who had received soy formula. Although the absolute numbers

were small, a recent study found an excess of multioocyte follicles in the

ovaries of genistein-fed mice.4

There are several other limitations to this study. First, fertility was

assessed by using total numbers of live births and whether subjects reported

" attempting pregnancy without success. " In this young population, only 74

soy-fed women had ever tried to become pregnant. Although fewer of these

women succeeded in becoming pregnant than women fed cows' milk as infants,

the numbers are too small to draw any conclusions about infertility. The

number of men with fertility difficulty was not stated. In addition, the

authors did not assess time to pregnancy, which is a more sensitive measure

of reproductive impairment, nor did they ask whether women used fertility

technologies in order to become pregnant. Second, there was no discussion of

male reproduction except pubertal onset, and there was no indication of

possible impact of exposure on fertility or semen quality. Third, most of the

outcome measures were subjective, such as whether menstrual pain was

nonexistent, mild, or severe. Fourth, the authors did not assess the cancer

risks that might have resulted from soy-based formulas. However, a recent

animal study5 raises this concern. Finally, this study did not address the

actual exposures to estrogenic compounds in the various soy-based formulas.

Strom et al state that " [e]ven if the adverse outcomes under consideration

here were relatively uncommon, the potential for a major public health impact

is large. Conversely, insupportable allegations of adverse effects can affect

a large proportion of the population, denying them access to a useful type of

infant feeding product. " We agree that the potential public health impacts

should be taken seriously and that alarmist positions should be avoided.

However, there is now ample reason to question the safety of soy proteins in

the diets of infants. Just as scientists should avoid insupportable

allegations, they should also avoid absolute declarations of safety in areas

whose risks have yet to be assessed.

 

Lynn R. Goldman, MD, MPH

Environmental Health Sciences

Bloomberg School of Public Health

s Hopkins University

Baltimore, Md

Retha Newbold

National Institute of Environmental Health Sciences

Research Triangle Park, NC

Shanna H. Swan, PhD

Department of Family and Community Medicine

University of Missouri

Columbia

 

 

1. Strom BL, Schinnar R, Ziegler EE, et al. Exposure to soy-based formula in

infancy and endocrinological and reproductive outcomes in young adulthood.

JAMA. 2001;286:807-814. ABSTRACT  |  FULL TEXT  |  PDF  |  MEDLINE

2. Fort P, Moses N, Fasano M, Goldberg T, Lifshitz F. Breast and soy-formula

feedings in early infancy and the prevalence of autoimmune thyroid disease in

children. J Am Coll Nutr. 1990;9:164-167. MEDLINE

3. National Institutes of Health. Immunotoxicity of Genistein. Research

Triangle Park, NC: National Toxicology Program; 1998.

4. Jefferson WN, Newbold RR. Potential endocrine-modulating effects of

various phytoestrogens in the diet. Nutrition. 2000;16:658-662. MEDLINE

5. Newbold RR, Banks EP, Bullock B, Jefferson WN. Uterine adenocarcinoma in

mice treated neonatally with genistein. Cancer Res. 2001;61:4325-4328. MEDLINE

NOTE: Of course I wouldn't use either dairy or soy