How would someone go about shrinking a somewhat-enlarged thyroid (with several nodules) via diet, supplements, or similar?

Why enlarged?: It is important to know why the gland is enlarged and treatment needs to be directed at the cause. It is not a do-it-yourself issue. Please see a doctor for an evaluation and proper treatment. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.

Won't work: No supplement or set of food choices will outperform placebo for multinodular goiter. Your physician can shrink it if you wish using hormonal manipulations.