A WORD OF CAUTION

BABIES AND SOY:

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 formula.

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 he 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.