Nodular goiter is by far the most common condition seen in thyroid surgery. Many patients ask why they get this disease. How can it be prevented? Nodular goiter is also known as big neck disease. It is usually said to be caused by iodine deficiency. But the salt sold in the market contains iodine, so why do you still have this disease? The reason is that this disease was common in the past when there was no iodized salt, but since the introduction of iodized salt, it has decreased significantly. However, there are still some patients who, even if they take enough iodine, still suffer from iodine deficiency in their bodies and develop thyroid nodules because their bodies cannot absorb or use it. In spite of this, we recommend that it is best to consume some seaweed or nori-type seafood on a regular basis to supplement iodine, which may slow down the development of nodular goiter.