Kelp Drug Interactions

In our latest question and answer, the pharmacist discusses kelp and potential drug interactions.

Mar 26, 2018

Sharon asked

Hi there, I am currently taking Cod Liver Oil & Glucosamine Sulphate - 1 a day, 10mg Cetirizine Hydrochloride, Sertraline, 100mg Menopace. Can I also take Sea Kelp 150mg?

Answer

Sea kelp, also known as laminaria, brown seaweed or kombu, is rich in vitamins and minerals, especially iodine. It is rich source of:

  • Iodine
  • Potassium
  • Iron
  • Trace vitamins and minerals

There are no reported drug interactions between cod liver oil, Zyrtec (cetirizine), Zoloft (sertraline) and kelp.

While there is some concern that impure kelp supplements can contain arsenic, kelp is considered fairly safe to take if recommended by your doctor. However, it important to know that kelp supplements often contain a large amount of iodine, as much as 1,000 mcg serving. Ingesting large amounts of iodine has been known to cause hypothyroidism or  hyperthyroidism.

Uses of kelp include:

  • Bulk laxative: Kelp forms a viscous gel matrix when combined with water
  • Source of iodine and trace minerals
  • Anti-hypertensive effects
  • Loosening and thinning mucus

Kelp isn't thought to interact with many medications, but it must be kept in mind that kelp contains a large amount of iodine and other vitamins/minerals. Therefore, kelp could potentially interact with:

  • Thyroid medications (e.g. levothyroxine)
  • Anti-arrhythmics (e.g. digoxin due to the potassium content)
  • Blood pressure medication (due to the anti-hypertensive effects)

Summary

  • Kelp is thought to relatively safe but there are concerns due to the iodine content of supplements and possible arsenic contamination.
  • Kelp is used for a wide range of indications including constipation, excess mucus and for high blood pressure.

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