Children were warned yesterday against eating too much roasted seaweed.
Over-indulgence could cause a disease in the thyroid gland, the Consumer Council said.
The warning followed a test of 146 foods including meat, milk products, eggs and vegetables.
Six brands of roasted seaweed were found to have excessive iodine concentrations - up to 400 times higher than that of some vegetables. Over-consumption by children could lead to hyperthyroidism, which causes goitre, the council said.
Dr Gary Wong Wing-kin, of the Chinese University's department of paediatrics, said: 'Eating two grams or seven small slices would exceed the World Health Organisation's [WHO] recommended daily iodine intake.
'The body can adapt to high iodine content if consumed occasionally. But parents should be cautious with their children's eating habits with food of high iodine concentration.' WHO recommended a daily intake of 90mg to 120mg for children aged between two and 12.