Kelp supplements are promoted as a natural source of iodine, an important mineral for healthy thyroid function. But are they a good alternative to regular iodine supplements? To find out, ConsumerLab.com, White Plains, NY, recently selected six popular kelp supplements sold in the U.S. and Canada and tested their quality. ConsumerLab found that half contained approximately twice the amount of iodine listed on their labels, and one of these products was also contaminated with arsenic, a toxic heavy metal. 

High doses of iodine can cause thyroid dysfunction and have other negative effects. To be safe, the FDA states that a kelp supplement should not provide more than 225 mcg of iodine per daily serving. ConsumerLab found 530 mcg to 960 mcg per daily serving in the three products which failed its testing. 

“While a quality kelp supplement can be a good, natural source of iodine, our tests show that consumers must choose very carefully to ensure they are not getting more iodine than expected, or unnecessary exposure to arsenic” said ConsumerLab.com President Tod Cooperman, MD. 

Most people get enough iodine through their diet, from dairy foods, bread, seafood and iodized salt. However, people who maintain a low-salt diet (or who regularly use specialty salts, which typically are not iodized), or who have other dietary restrictions, may be at risk for deficiency. Women who are pregnant or nursing who need iodine are advised to supplement with potassium iodide, the form of iodine commonly found in other iodine supplements as well as many multivitamins. Clinical research suggests that iodine from kelp may be absorbed only half as well as that from a potassium iodide supplement. 

ConsumerLab.com’s findings are available online in its  Kelp Supplements Review. Included in the report is information to help consumers understand the pros and cons of using kelp supplements, dosage, and the potential side-effects and drug interactions of kelp supplements.