Take Caution When Using Baby Soy Formula

Health problems may occur from using baby soy formula as the your baby’s main nutrition.

A Word of Caution When Using Baby Soy Formula

Considering all of soy’s health benefits, it is tempting
for new and expectant mothers to see soy-based infant
formula as a “miracle food” and to stock their pantries
sky-high with the stuff. Well, hold on there, mama: That
most vulnerable member of the population, an infant unable
to breastfeed, stands at great risk of developing a serious
thyroid disorder due to a diet based entirely on soy

That disorder is hypothyroidism, or an underactive thyroid,
and it is a common cause of fatigue, depression, obesity,
constipation, extreme sensitivity to cold and a number of
other symptoms, most so common that the disorder can go
undiagnosed for years. Since hormones from the thyroid
gland regulate all other glands in the body (and thereby
all human growth and development), altered thyroid hormone
levels in infants may lead to disorders of the central
nervous system and abnormal psycho-motor development, as
well as slowed sexual development later in life.

Most soy foods, excluding soy oil and soy sauce, contain
estrogenic compounds, known as isoflavones. These compounds
are commonly thought to be protective against heart
disease, stroke, diabetes and osteoporosis, while reducing
the risk of breast, prostate and uterine cancers. You may
find it ironic, then, that isoflavones can also be
responsible for bringing on a hypothyroid condition.

Recent research by Japan’s Ishizuki Thyroid Clinic and New
Zealand’s Ministry of Health (MOH) has helped determine the
degree of danger soy’s isoflavones pose. MOH research from
1998 shows that infants fed solely a soy-formula diet are
exposed to 16 times more isofilavones than the amount
necessary to cause goiter (enlargement of the thyroid due
to poor functions in adults. The danger is especially great
if soy formula is given to infants for longer than three
months. Because this danger has long been known, many
manufacturers add iodine, which is necessary for thyroid
function, to their formulas. This does tend to prevent the
onset of goiter, but in many cases does not prevent the
underlying hypothyroid condition indicated by the goiter.

Because of their many documented benefits, isoflavone
supplements have become a common part of adult preventative
medicine regimens. But the Ishizuki study showed that
isoflavone intake by healthy adults could also have a
thyroid-suppressing effect. The study concluded that 33 mg
of soy isoflavones per day was sufficient to cause goiter
in adults. Yet some popular supplements provide from 40 to
120 mg of soy isoflavones daily.

Hypothyroidism can be detected by your doctor through blood
tests and can be treated, though not reversed. If your
child was raised on soy formula and exhibits developmental
problems, depression, obesity or especially low energy, it
may be a good idea to have your pediatrician conduct the
necessary checks. Through preventative measures, you could
keep your child from suffering future effects of

For more information on the connection between soy foods
and hypothyroidism, see Mary Shomon’s book: Living Well
With Hypothyroidism: What Your Doctor Doesn’t Tell You That
You Need to Know
(Wholecare, 2000).

— Katie Mehrer