Sally Fallon and Mary G. Enig
In order to produce estrogen and progesterone as required for the reproductive cycle, the body needs adequate amounts of cholesterol, because all the sex hormones are made from this vital substance. For this reason alone vegetarian diets for women are unwise as vegetarian diets will lower cholesterol.
… The thyroid gland is intimately involved in the female reproductive cycle … Dietary factors that contribute to healthy thyroid function include adequate protein and iodine (thyroid hormone is composed of iodine and tyrosine, a protein found in animal foods); trace elements such as iron, zinc and selenium (needed to prevent anemia and for key enzymes to make hormonal conversions); B vitamins, including B12; vitamin C; and, above all, adequate vitamin A from animal sources. Many substances in the modern diet depress thyroid function, including soy foods, fluoride and possibly even aspartame, the artifocial sweetener found in nutrasweet. Pesticides and other pollutants may also depress thyroid function.