Mary Shomon: In researching my book, Living Well With Hypothyroidism: What Your Doctors Don’t Tell You...That You Need to Know, from HarperCollins, I talked to Dr. Mike Fitzpatrick, an environmental scientist and phytoestrogen researcher who has conducted in-depth studies on soy, particularly the use of soy formulas. Dr. Fitzpatrick makes it clear that soy products can have a detrimental affect on both adults and infants. In particular, he firmly believe that soy formula manufacturers should remove the isoflavones (that part of the soy products that act as anti-thyroid agents) from their products.

Researchers have identified that the isoflavones act as potent anti-thyroid agents, and are capable of suppressing thyroid function, and causing or worsening hypothyroidism. Soy is a phytoestrogen, and therefore acts in the body much like a hormone, so it’s no surprise that it interacts with the delicate balance of the thyroid’s hormonal systems. High consumption of soy products is also proven to cause goiter. [2]

Isoflavones belong to the flavonoid or bioflavonoid family of chemicals, and are considered endocrine disrupters --- plants or other products that act as hormones, disrupting the endocrine system, and in some cases, this disruption involves acting as an anti-thyroid agent. (The grain millet, for example, contains high levels of flavonoids, and is commonly known as problematic for thyroid function). Flavonoids inhibit thyroid peroxidase (TPO), which disturbs proper thyroid function.

A feature on soy in the March 1999 issue of Natural Health magazine quoted Daniel R. Doerge, PhD, a researcher at the Food and Drug Administration’s National Center for Toxicological Research. Dr. Doerge has researched soy’s anti-thyroid properties, and has said

“ . . . I see substantial risks from taking soy supplements or eating huge amounts of soyfoods for their putative disease preventive value. There is definitely potential for interaction with the thyroid.”

One UK study of premenopausal women gave 60 grams of soy protein per day for one month. This was found to disrupt the menstrual cycle, with the effects of the isoflavones continuing for a full three months after stopping the soy in the diet. Isoflavones are also known to modify fertility and change sex hormone status. Isoflavones have been shown to have serious health effects -- including infertility, thyroid disease or liver disease --- on a number of mammals.

Mary Shomon: In researching my book, Living Well With Hypothyroidism: What Your Doctors Don’t Tell You...That You Need to Know, from HarperCollins, I talked to Dr. Mike Fitzpatrick, an environmental scientist and phytoestrogen researcher who has conducted in-depth studies on soy, particularly the use of soy formulas. Dr. Fitzpatrick makes it clear that soy products can have a detrimental affect on both adults and infants. In particular, he firmly believe that soy formula manufacturers should remove the isoflavones (that part of the soy products that act as anti-thyroid agents) from their products.

Researchers have identified that the isoflavones act as potent anti-thyroid agents, and are capable of suppressing thyroid function, and causing or worsening hypothyroidism. Soy is a phytoestrogen, and therefore acts in the body much like a hormone, so it’s no surprise that it interacts with the delicate balance of the thyroid’s hormonal systems. High consumption of soy products is also proven to cause goiter. [2]

Isoflavones belong to the flavonoid or bioflavonoid family of chemicals, and are considered endocrine disrupters --- plants or other products that act as hormones, disrupting the endocrine system, and in some cases, this disruption involves acting as an anti-thyroid agent. (The grain millet, for example, contains high levels of flavonoids, and is commonly known as problematic for thyroid function). Flavonoids inhibit thyroid peroxidase (TPO), which disturbs proper thyroid function.

A feature on soy in the March 1999 issue of Natural Health magazine quoted Daniel R. Doerge, PhD, a researcher at the Food and Drug Administration’s National Center for Toxicological Research. Dr. Doerge has researched soy’s anti-thyroid properties, and has said

“ . . . I see substantial risks from taking soy supplements or eating huge amounts of soyfoods for their putative disease preventive value. There is definitely potential for interaction with the thyroid.”

One UK study of premenopausal women gave 60 grams of soy protein per day for one month. This was found to disrupt the menstrual cycle, with the effects of the isoflavones continuing for a full three months after stopping the soy in the diet. Isoflavones are also known to modify fertility and change sex hormone status. Isoflavones have been shown to have serious health effects -- including infertility, thyroid disease or liver disease --- on a number of mammals.