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This article by Dr. Enig is
in response to an article that was published in the Journal
of the American Medical Association, August 15, 2001 and widely
reported in the press as a vindication of soy
formula.
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 embarrassing questions,
cannot be used to draw any
meaningful conclusions," said Dr. Naomi Baumslag,
Professor of Pediatrics at Georgetown University. 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.
"The question we should be asking
is why are so many of our babies on soy?" said Dr. Baumslag.
"It can only be because of the advertising efforts of
the soy industry, because there is a great deal of 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."
Soy
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