Both hyperthyroidism and hypothyroidism have been linked to too much kelp intake. This is due to its high amount of iodine. Abnormal thyroid function has also been linked directly to too much use of kelp supplements.
Kelp may contain harmful metals. These include cadmium, lead, aluminum, and other heavy metals. This is more likely if you eat a lot of kelp from areas of contaminated ocean water.
People who are pregnant or breastfeeding shouldn't use kelp supplements.
If you're being treated for thyroid issues, you shouldn't take kelp. You also shouldn't use it if you take certain heart medicines.
If you need an X-ray with a contrast media, talk to your doctor. You may have to stop taking kelp one month before your X-ray. You may not be allowed to take it again until the contrast medium leaves your body.