Some basic side effects of consuming soy foods include constipation, bloating and nausea, according to WebMD. More serious side effects include itching and a rash. Soy milk not designed specifically for infants may lead to nutrition deficiencies in newborn babies. Using soy as a substitute for milk allergies may be unsafe in children since soy milk may also lead to the same allergic reactions.
Men's Health explains that consuming high amounts of soy milk leads to high levels of estrogen in men. One male patient drank 3 quarts of soy milk per day. Such a high consumption rate led to enlarged breasts, less body hair growth and reduced sex drive. The technical term for this condition is gynecomastia, a disease that causes breast enlargement in men. The Mayo Clinic explains that this disorder occurs when there is an imbalance of estrogen versus testosterone in men.
Television personality Dr. Oz reveals that soy may affect thyroid function in people who already have an existing thyroid problem or who take thyroid medication. The reason for this interference with thyroid medication is that soy reduces how the human body absorbs medication in the gastrointestinal tract. This reduces the effectiveness of thyroid medication. Dr. Oz recommends waiting a few hours between taking thyroid medication and consuming soy. The television personality also advises that soy should be eaten in moderation.