Kelp supplement benefit and side effects, laminarins in laminaria
March 22 2017 by
Ray Sahelian, M.D.


Kelp are large seaweeds. Kelps vary widely in size and form. One type of kelp, called giant kelp, may have hundreds of branches, each of which has hundreds of leaves. Giant kelp may reach over 200 feet in length and will create entire forests of kelp. Despite their appearance sea kelp are not grouped with the normal aquatic or land plants (kingdom Plantae), but instead are included in either kingdom Protista or Chromista. Kelp grows in underwater forests ( kelp forests ) in clear, shallow, oceans, requiring nutrient rich water below about 20C, Sea kelp offer protection to some sea creatures, or food for others. Kelp is known for its high growth rate.  Kelp is a popular food in some cultures, such as the Japanese. Kelp has been promoted as a weight loss supplement, but, in my opinion, it is not effective.



Kelp is a sea vegetable and a good source of minerals, including iodine, potassium, magnesium, calcium, and iron. The health benefit of kelp may occur in individuals who have an underactive thyroid gland due to iodine deficiency. However, iodine deficiency is not common in Western countries.


Adv Food Nutrition Research. 2011. Physical, chemical, and biological properties of wonder kelp. Laminaria is a kelp that finds its place in the brown algae family. It has been an area of study for past many years, and its wonderful biological properties have always attracted medical professionals and researchers to explore more and more from this wonder kelp. The constituents of Laminaria include iodine, potassium, magnesium, calcium and iron. Iodine compounds, TEA-hydroiodide in particular, are great lipolytic agents as they stimulate lipase activity. Laminarins on the other hand are used as a tumor angiogenic blocker. This genus of the kelps is also rich in algin, a high molecular weight polysaccharide that forms viscous colloidal solutions or gels in water leading to the use of kelp derivatives as bulk laxatives. It has great applications in cosmeceutical science, as well as some antibacterial properties have also been assigned to Laminaria. A deeper insight into the physical, biological, and chemical properties of this wonder kelp would lead to further exploitation of Laminaria for medicinal and cosmeceutical purpose.

Kelp supplement - who needs it?
Kelp is a healthy sea vegetable to include in one's diet, but as with any other food, moderation is suggested. A kelp supplement may be used occasionally, but I prefer alternating different supplements rather than taking one supplement in a high dose on a continual basis. Some types of sea kelp, such as bladderwrack, laminaria, and rockweed, are harvested and developed into dietary supplements. If you do plan to take a kelp supplement, take only one or two tablets a day, and take 2 days off a week and a week off each month.

Kelp Meal is brown seaweed harvested from the cold waters of the north Atlantic Ocean.

Kelp powder

Soluble Kelp Powder is a dehydrated liquid extract from the kelp Ascophyllum nodosom, which is harvested on the Maine coast.

Kelp thyroid gland

Sea kelp as a source of iodine assists in making thyroid hormones, which are necessary for maintaining normal metabolism in all cells of the body. Since the introduction of iodized salt, additional sources of iodine, such as kelp, are not necessary for most people.


Risk, side effects, danger, safety
I've read that iodine supplementation can trigger off autoimmune disease potentially (Reference: Patrick L (June 2008). "Iodine: deficiency and therapeutic considerations" Altern Med Rev 13 (2): 11627). I'm concerned about this because a member of my family attributes her autoimmune disease onset to a course of iodine supplements she was given. I was wondering if there is a similar risk with kelp supplementation, as it is rich in iodine. I would like to give this to a family member showing signs of hypothyroidism, but as he has a family history of autoimmune disease, I am concerned about the risk of setting something terrible off with kelp or even with a multi containing iodine. Thanks in advance for your help, and thank you so much again for your wonderful website.
    I am aware of one report from 1992 that potentially associates use of kelp to autoimmune thrombocytopenia but it does not appear any reports have been mentioned since then.

Lancet. 1992; Severe dyserythropoiesis and autoimmune thrombocytopenia associated with ingestion of kelp supplements.

Kelp Research

Effects of kelp supplementation on thyroid function in euthyroid subjects.
Endocr Pract. 2003. Clark CD, Bassett B, Burge MR. Department of Internal Medicine, Division of Endocrinology and Metabolism, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
To study the effects of ingestion of two different doses of supplemental kelp on the thyroid function of healthy euthyroid subjects. We conducted a double-blind prospective clinical trial involving 36 healthy euthyroid subjects, who were randomly assigned to receive placebo (4 alfalfa capsules per day), low-dose kelp (2 kelp capsules and 2 alfalfa capsules per day), or high-dose kelp (4 kelp capsules per day) for 4 weeks. Thyrotropin (thyroid-stimulating hormone or TSH), free thyroxine, and total triiodothyronine were assessed at weeks 0, 4, and 6. TSH concentrations did not differ significantly between week 0 and week 4 in the placebo group but increased significantly in both the low-dose kelp and high-dose kelp groups. Free thyroxine concentrations decreased slightly but significantly after 4 weeks of placebo but were unchanged in the low-dose and the high-dose kelp groups. In contrast, total triiodothyronine levels did not differ significantly after 4 weeks of placebo or low-dose kelp therapy but were significantly decreased after high-dose kelp therapy. Similarly, the thyrotropin-releasing hormone stimulation test showed no significant change in poststimulation TSH after 4 weeks in the placebo or low-dose kelp groups but revealed a significantly increased response after high-dose kelp therapy. The 24-hour urinary iodine excretion showed dose-dependent increases in the two kelp study groups. Basal metabolic rate did not change significantly in any study group during the 4-week study period. All thyroid laboratory values returned to baseline 2 weeks after cessation of kelp supplementation, except for TSH in the high-dose kelp group, which was significantly decreased. Short-term dietary supplementation with kelp significantly increases both basal and poststimulation TSH. These findings corroborate previous studies on the effects of supplemental iodide given to euthyroid subjects for a similar period. Further studies are needed to determine whether long-term kelp supplementation would cause clinically significant thyroid disease.



Q. I was looking for information on kelp benefit and came across a website that was claiming this: "The electrolytic magnetic action of the sea plants releases excess body fluids from congested cells and dissolves fatty wastes through the skin, replacing them with depleted minerals, particularly potassium and iodine. Sea Vegetables (Spirulina - Kelp - Chlorella) have been acknowledged as a detoxifyer, a balanced nourishment and a miraculous healing plant."
   A. The person who wrote this obviously does not have a medical background and does not seem to have a good understanding of molecular biochemistry. When you see people using the word "detoxify" be on alert.


Q. Part two of my question is a claim I came across another site. "The immediate benefit obtained from kelp can be attributed to the release of auxins, cytokinins and gibberellins. These plant growth hormones, required in small quantities, are essential for cell division and cell elongation, basic functions of plant growth."
   A. Since no long term human studies have been done to determine benefit of kelp, it is premature to make such a kelp benefit claim.


Q. Is Norwegian kelp supplement healthier than sea kelp from other areas?
   A. I have not seen any studies that indicate Norwegian kelp is any better than kelp from other oceans.


Have been taking Kelp for the Breast Cysts and Low Thyroid for about 3 months.
The one I take is Natures Way. I take two 660mg Capsules every morning.
They contain each: Iron 390mcg, 400mcg Iodine, Sodium 20mg, Kelp 660mg

I have had breasts filled with fluid filled painful cysts for about 7 years. I am a 50 year old woman. No menopause symptoms yet. I have noticed a change in my breasts the last couple of months. Softer, with fewer cysts and less pain. I think it's helping the cysts go away. I also think that I am a little Hypothyroid. TSH 3.8. I think that the kelp will help the thyroid function also. I also take a B100, Vit C 1000 mg a MultiVitamin, vitamin E 800 IU. What other supplements do you think I should take? How much of this Kelp should I be taking? or what do you think is a safe dosage?
   Taking too much kelp may cause excess intake of iodine. Different people need different amounts so it is not possible for me to say how much any one person needs or can tolerate.  The nutritional treatment of breast cysts has not been studied that well, there are no easy answers at this time.