Health Library Home>Natural & Alternative Treatments>Herbs & Supplements>Article


Supplement Forms/Alternate Names :



Kelp refers to many types of brown algae that grow in the ocean. It has been used to help promote weight loss and to lower blood pressure. Kelp has also been used help the body fight off illness. It can be taken as a pill or powder.


There are no advised doses for kelp.

What Research Shows

There is not enough data to support that kelp is helpful in treating health problems. We will review future studies as they are published.

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

Safety Notes

It may be safe to take kelp in small doses for a short time, but some kelp-containing supplements may contain arsenic and have large amounts of iodine which can damage the thyroid gland.1, 2 Women who are pregnant or breastfeeding should avoid kelp. Not enough studies have been done to say whether it is safe to take for a long period.


Talk to your doctor about any supplements or therapy you would like to use. Some can interfere with treatment or make conditions worse such as:

  • People with thyroid problems should talk to their doctors before taking kelp. It may interact with their medicine.


1. Amster E, Tiwary A, et al. Case report: potential arsenic toxicosis secondary to herbal kelp supplement. Environ Health Perspect. 2007 Apr;115(4):606-608.

2. Miyai K, Tokushige T, et al. Suppression of thyroid function during ingestion of seaweed "Kombu" (Laminaria japonoca) in normal Japanese adults. Endocr J. 2008 Dec;55(6):1103-1108.

Last reviewed February 2020 by EBSCO NAT Review Board Eric Hurwitz, DC  Last Updated: 5/27/2020