Can Watercress, Spinach, Brazil Nuts, And Lemon Water Help With Thyroid Issues Instead Of Taking Levothyroxine?

My son had melanoma cancer. The Dr cut it out of the top of his head 1st surgery. 2nd cut scalp and pulled it over the hole did not have enough skin had to take it from somewhere on his body. 3rd surgery had to cut from top of ear to clavicle and take out 300 lymph nodes. Then a month later did radiation on the side he had surgery. Also had a little over a year of immunotherapy. He went back to work but could only work a few mo. He started getting dehydrated and eventually could not walk, He got some better but over 6-8 mo. span same health issues dehydration and not being able to walk. Then started having thyroid issues bad. He does not want to take Levothyroxine is afraid too. Is watercress spinach-brazil nuts lemon water a helpful aid for thyroid?