You don't see Cod Liver Oil ads all over the TV though.
My chiro/ kinesiologist is very clear that all supplements are not made equal either. He will tell me which brand makes the best whatever it is that he wants me to take... and it isn't always the same brand.

Keep in mind that mice get cancer very easily too. Also people take more of things than they need to 'cause they think it is good for them. Too much folate or iodine can be bad too. Don't go overboard and you should be OK.