Lecithin is a complicated mixture of molecules that are especially concentrated in egg yolks, soybeans, and wheat germ. Three components are especially plentiful in lecithin. These components are phosphatidylcholines, phosphatidylethanolamines, and phosphatidylinositols. Lecithin is found in the cell membranes of all cells, including human cells.
Soybeans are sometimes referred to as "goitrogenic" because they contain substances that can interfere with production of thyroid hormones under certain circumstances. These substances are called isoflavones and are naturally occurring substances found in numerous foods that are known to have a variety of health-supportive properties. Especially in the case of women's health surrounding the stage of menopause, isoflavones have been shown to provide risk-lowering benefits in the areas of cardiovascular disease and certain types of cancer.
With respect to potential interference with thyroid function, I want to emphasize the words "under certain circumstances" when it comes to soy foods. Several research studies have repeatedly shown that it only during times of measurable iodine deficiency that soy isoflavones have an unwanted impact on thyroid function. In other words, for individuals who have normal amounts of iodine in their body, the risk posed by soybean consumption appears to be extremely low.
When it comes to soy lecithin, the risk posed is even lower, since lecithin does not contain isoflavones. Those substances are left behind in the unused part of the soybeans when lecithin is extracted from them. For all of the reasons I've described above, I do not have concerns about the use of soy lecithin in processed foods from the standpoint of thyroid function. However, I always prefer whole, natural, organically grown foods (like the soybeans themselves) as a source of nourishment in comparison to processed components like soy lecithin.
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