Experts Dispute Soy Formula Safety

WASHINGTON, DC, September 6, 2001 – Experts dispute the findings of a recent study on soy infant formula, published in the Journal of the American Medical Association, August 15, 2001 and widely reported in the press as a vindication of soy formula. The research team, headed by Dr. Brian L. Strom, called the results “reassuring” but other scientists disagree with this conclusion.

Dr. Mary Enig, President of the Maryland Nutritionists Association, points out that the researchers found higher rates of reproductive disorders, asthma and allergies in those who had received soy formula as infants. “This is in line with a number of reports in the scientific literature,” said Dr. Enig. “The research team glossed over negative findings and omitted them from the abstract and conclusions, noting only that women who had been fed soy formula reported slightly longer duration of menstrual bleeding and greater discomfort with menstruation.”

Other gynecological problems, which were omitted from the main body of the report, included higher rates of cervical cancer, polycystic ovarian syndrome, blocked fallopian tubes, pelvic inflammatory disease and hormonal disorders. In addition, although the study did not specifically determine thyroid function, soy-fed females reported higher rates of sedentary activity and use of weight-loss medicines, thus adding new evidence to numerous scientific reports of soy-induced thyroid problems.

Experts were also critical of the design of the study, in which researchers conducted telephone interviews with 282 adults fed soy formula and 563 adults fed milk formula during controlled feeding studies at the University of Iowa between 1965-1978. “Data derived from telephone interviews, particularly interviews that ask a lot of subjective questions, cannot be used to draw any meaningful conclusions,” said Dr. Naomi Baumslag, Clinical Professor of Pediatrics at Georgetown University and President of the Women’s International Public Health Network. She noted that the study provided no information on dose length or quantity, nor on the ages at which ingestion ended, all vital in a study on toxicity. “The amount of phytoestrogens in soy formula can vary as much as tenfold, depending on the way it is processed. And the soy used today is genetically engineered, which means that it has more isoflavones in it than the soy they were using twenty years ago.”

“The question we should be asking is why are so many of our babies on soy?” said Dr. Baumslag. “In the UK and New Zealand only 1% of babies get soy. In the US, at least 20% get soy. It can only be because of massive influence of the soy industry, because there is scientific evidence that soy formula can be damaging to newborns.” The soy formula study was funded by the National Institutes of Health and the International Formula Council and carried out under the auspices of the Fomon Infant Nutrition Unit at the University of Iowa. The Fomon Infant Nutrition Unit is supported by the major formula manufacturers Ross Products Division of Abbot Laboratories, Nestle, and Mead Johnson Nutritionals. Dr. Samuel Fomon played an important role in the development of soy infant formula. Early promotional efforts for soy formula described it as “better than breast milk.”

The questions were geared to assess reproductive disorders and age of maturation. The average age of maturation for both sexes was the same for both groups; however raw data that would show whether there was abnormal clustering for early or late maturation was not given. Women were not asked about the age of first appearance of breasts or pubic hair. Age of first wearing a bra was given as a proxy measure for age of breast development and education level attained as a proxy measure for intelligence. Trade school, college and post college were lumped together as one category. No questions were asked about digestive disorders.

Many of the negative findings for the soy-fed group were not “statistically significant.” But critics point out that the group of 282 soy-fed individuals was too small for statistical significance to be achieved. “With so many infants now receiving soy formula, the small differences noted in the study can affect thousands of individuals,” said Dr. Enig.

In the US, an estimated 750,000 infants per year receive soy formula. Consumer groups have voiced concern about adverse effects reported in the scientific literature, including thyroid disorders, asthma, digestive disorders, calcium deficiencies leading to rickets, high manganese levels leading to brain damage and endocrine disruption. A 1986 study in Puerto Rico found that use of soy formula was strongly correlated with premature maturation in girls. Anecdotal reports of other adverse effects include extreme emotional behavior, learning difficulties, immune system problems, irritable bowel syndrome, depression and disrupted sexual development in boys.

US scientists who have warned about potential dangers in the use of soy for infants include phytoestrogen researcher Dr. Kenneth Setchell, Professor of Pediatrics at the University of Cincinnati, and Dr. Daniel Sheehan, Director of the US Food and Drug Administration National Center for Toxicological Research. Setchell determined that babies on soy formula receive a daily exposure to isoflavones (plant-based estrogens) that is 6 to 11 times higher on a body weight basis than the dose that has undesirable hormonal effects in adults consuming soy foods. His research showed that serum isoflavone levels in soy-fed infants were 13,000 to 22,000 times higher than those of infants fed milk-based formula. According to Dr. Mike Fitzpatrick, a New Zealand toxicologist, babies fed exclusively on soy formula receive the estrogenic equivalent of at least five birth control pills per day.

Noting the adverse effects of similar high levels of isoflavones when given to young animals, Sheehan warned of key imprinting events affecting the development of many physical, physiological and behavioral characteristics in the human infant. Because of this evidence, both the British and New Zealand governments have issued warnings on the use of soy infant formula.

Lynn Goldman, MD, MPH, Professor of Environmental Health Science, Johns Hopkins University Bloomberg School of Public Health, also voiced concerns. In a letter to the Washington Post dated August 28, 2001, she was critical of press reports about the study and stated that “there are ample reasons to begin to question the safety of soy proteins in the diets of infants. There are several major limitations to this study.”

The study follows a June 1, 2001 report published in Cancer Research which found that genistein, one of the isoflavones in soy, was more carcinogenic (dose adjusted for estrogen potency) than the synthetic estrogen DES (routinely given to pregnant women to prevent miscarriage) when exposure occurred during “critical periods of differentiation,” such as during infancy. Medical professionals insisted that DES was safe for pregnant women until they discovered that many years later, women whose mothers took DES suffered from very high rates of cervical cancer. The authors of the Cancer Research study concluded that “. . . the use of soy-based infant formulas in the absence of medical necessity and the marketing of soy products designed to appeal to children should be closely examined.”

“Because the risks are so great, soy formula should only be used as a last resort,” said Dr. Enig. “There are many alternatives available for babies who have difficulties with ready-mixed milk-based formula.”

This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly magazine of the Weston A. Price Foundation, Fall 2001.

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