“The recommended daily intake of iodine is 150 micrograms a day for the average person, but these seaweed and sea-based capsules can sometimes contain 1,000 times the recommended daily allowance. So, if you already have thyroid issues, you have to read those labels, and you have to be very careful,” says Dr. Moyad. It's just as — or more — crucial to be mindful of this if you're pregnant or breast-feeding.