TG and neuropathy: Notably, iron malabsorption effects, neuropathy, genotoxic effects, a decrease in the levels of thyroid hormones in plasma, and a reduction in the bioavailability of some synthetic drugs have been reported upon the administration of extremely high concentrations of polyphenols, indicating that a careful evaluation of polyphenol use regarding their purity, concentration, bioavailability, and doses is required [229].