In 2006, a large study on iodine supplementation and thyroid disease was unveiled in China and published in the New England Journal of Medicine, the world’s most prestigious medical journal. Excessive iodine intake increased the prevalence of subclinical hypothyroidism and thyroiditis by up to 10 times. And this year, a study in the journal Thyroid showed a significant decrease in TSH levels in people with subclinical hypothyroidism combined with high iodine intake after iodine intake restriction. Currently, iodine supplementation is universal. As an inland city, Chengdu has an average urinary iodine level of 184 mcg/day (urinary iodine is the main standard for evaluating dietary iodine intake, generally 100-150 mcg/day is sufficient, and greater than 300 mcg/day is not recommended), and the iodine in daily iodized salt is sufficient for the body’s needs. The iodine content of kelp is high and difficult to control, and ordinary vitamins such as Sun Cun contain 150 micrograms of iodine per tablet, which is more than what the body needs if supplemented with additional iodine. Therefore, for subclinical hypothyroidism with TSH <10mIU/L, a low iodine diet can be used for 3 months to 6 months before testing the thyroid function level.