Soy Infant Formula

By Cat, April 2007

The following essay the third segment condensed “Newest Research On Why You Should Avoid Soy:  Cinderella’s Dark Side” (1), by Sally Fallon & Mary G. Enig, Ph.D. (1). While there is a fair amount of political content in the original article, I only focus on the health content.  Those who are interested in the political content can read the entire article. 

Cat’s disclaimer:

It is true that soy contains beneficial nutrients as well as the antinutrients described in the Fallon/Enig essay.  The food industry is very quick to laud the good, and ignore or downplay the bad.  But the truth is that the bad in soy outweighs the good, especially when fed to infants who are most vulnerable, developmentally, to the bad side of soy.

Soy-Based Infant Formula

Birth Control For Babies

Many American families feed their babies a soy based formula, accounting for approximately 25% of bottle-fed children — a much higher percentage than in other parts of the Western world. A 1998 report cites that the daily exposure of infants to isoflavones in soy formula is 6 to 11 times higher (on a body-weight basis) than the dose that has hormonal effects in adults.  Indeed, an infant exclusively fed soy formula receives the estrogenic equivalent of at least 5 birth control pills per day (based on body weight).  The concentration of isoflavones in the blood of these infants were 13,000 to 22,000 times higher than plasma estradiol concentrations in infants fed cow’s milk formula.

By contrast, almost no phytoestrogens have been detected in dairy-based infant formula or in human milk, even when the mother consumes soy products.

But, what effect does soy formula have on the babies, male and female?

Thyroid Problems

It is well documented that soy-based formula can cause thyroid problems in babies.  This is because goitrogens, known toxins in soy, depress thyroid activity.

Male Development

Normally, male infants undergo a “testosterone surge” during the first few months of life, when testosterone levels may be as high as those of an adult male.  This surge programs the infant to express male characteristics after puberty.  Exposure to the phytoestrogens (isoflavones) in soy formula interferes with this programming.

Deficiency of male hormones impair the development of:

  • spatial perception;
  • learning ability;
  • visual discrimination tasks (such as required for reading).

Learning disabilities have reached epidemic proportions (especially in male children); soy infant feeding cannot be ignored as a probably cause for these tragic developments.

Male children exposed during gestation to DES (diethylstibestrol, a synthetic estrogen that has effects similar to those of the phytoestrogens from soy) have smaller than normal testes on maturation.  While soy’s estrogenic effect is less than that of DES, the dose is likely to be higher because it’s consumed as a food, not taken as a drug.

Sexual orientation may also be influenced by early hormonal environment.

Early Puberty in Girls

An alarming number of girl children are entering puberty much earlier than normal.  1% of all girls now show signs of puberty, such as breast development or pubic hair before the age of 3.  14.7% of white girls, and almost 50% of African American girls have one or both of these characteristics.  Does soy infant formula play a role in these statistics?

The 1986 Puerto Rico Premature Thelarche study revealed the most significant dietary association with premature sexual development was soy infant formula (and not chicken, as reported in the press).

New data indicate that environmental estrogens (such as PCBs and breakdown products of DDT) may cause early sexual development in girls.

Daughters of women who took DES (diethylstibestrol, a synthetic estrogen that has effects similar to those of the phytoestrogens from soy) during pregnancy suffered from infertility and cancer when they reached their twenties.  While soy’s estrogenic effect is less than that of DES, the dose is likely to be higher because it’s consumed as a food, not taken as a drug

Early maturation is frequently a harbinger for problems with the reproductive system later in life, including:

  • failure to menstruate;
  • infertility;
  • breast cancer.

Young girls with mature bodies must cope with feelings and urges that most children are not well-equipped to handle.

Other Reported Problems for Both Sexes

Children fed soy-based formula exhibit:

  • extreme emotional behavior
  • asthma
  • immune system problems
  • pituitary insufficiency
  • thyroid disorders
  • irritable bowel syndrome

Parrots on soy

Parrots fed a soy-based feed experienced similar endocrine and digestive havoc. Administration of a soy-based feed to these tropical birds in the early 1990s caused striking and deadly effects. Male birds developed colored plumage months earlier than normal, which was considered an asset.

But in the ensuing years, more problems were noted in both males and females:

  • Decreased fertility;
  • Precocious maturation;
  • Deformed, stunted and stillborn babies;
  • Premature deaths, especially among females.
  • Beak and bone deformities,
  • Goiter (overactive thyroid),
  • Immune system disorders, and
  • Pathological aggressive behavior.

Autopsy revealed digestive organs in a state of disintegration.  And all of these problems could be traced back to genistein, an isoflavone present in soy.


  1. and following pages: page 2:, and page 3 (includes the author’s sources):
  2. The Dark Side of Soy by Mary Vance Terrain in Utne Reader, July/August 2007:

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