> They usually have a lower dosage of everything than do single thing supplements. For example the iodine supplements I've seen are in the 225 mcg to 325 mcg ra

> They usually have a lower dosage of everything than do single thing supplements. For example the iodine supplements I've seen are in the 225 mcg to 325 mcg range. The RDA for iodine is 150 mcg, so 325 should normally draw concern. However, the average iodine intake in Japan is well over 1000 mcg, to no ill effect. Too much iodine is definitely bad, but the dosage that is firmly established as causing problems (oddly, a similar effect as too little iodine) is at least another order of magnitude beyond the Japanese intake. (There may be weird interactions between iodine and fluoride, but that recent data is still very tentative and suspect, and even at 325 mcg/day isn't concerning.) Supplements are made from kelp, so there's potential issues with heavy metals. But, again, the average Japanese intake of the types of heavy metals kelp accumulates is multiples of the US RDA limit, to no known ill effect. However, there are no USP or similar reputably certified iodine supplements, only certified multivitamins with iodine. That's more concerning to me than anything else. Nonetheless, FWIW I give my kids an iodine supplement once or twice a week. I also cook with iodized salt, but we eat out or consume prepared food enough times in a week that I figured a supplement was worthwhile, all things considered. RDAs are typically computed by measuring urine excretion, so it's possible "topping up" iodine that way might not be very effective--just quickly excreted. I dunno. Cows milk can be a good source of iodine, but my kids don't consume milk regularly, and only one drinks cows milk. Fortunately, they do like anchovies, so I try to add those into the mix.