That depends on if it's in the grass that the cows eat. They first researched iodine in cows because there isn't much iodine in the grass around the great lake

That depends on if it's in the grass that the cows eat. They first researched iodine in cows because there isn't much iodine in the grass around the great lakes. This area was known as the "goiter belt". Adding iodine to the cow's food made them healthier and that's how they estimated the dose for humans (mcg / kg).