Algue Brune, Brown Algae, Brown Seaweed, Hai Dai, Kelp, Kombu, Kun Bu, Laminaire, Laminaire Digitée, Laminaire Japonaise, Laminaria digitata, Laminaria japonica, Laminariae stipites, Limu, Makombu Thallus, Sea Girdles, Seagirdle Thallus, Thallus Laminariae.
Laminaria is a type of seaweed that is native to Japan. Laminaria contains iodine, an element that the body needs to make thyroid hormones. It is also a rich source of iron and potassium. Despite serious safety concerns about laminaria, some people use laminaria as medicine.
Sometimes healthcare providers use laminaria to expand the cervix, the mouth of the uterus, before certain medical procedures. They place a layer of laminaria directly inside the cervix, the “neck” of the uterus. This layer of laminaria is sometimes called a “tent.” The purpose of the tent is to enlarge the cervix before “D&C,” also known as dilation and curettage (scraping of the uterus); removal of a medical device that is in the uterus; diagnostic procedures; placement of radium for cancer treatment; and other gynecological procedures. Laminaria tents are also used in pregnant women to “ripen” (expand) the cervix to make labor and delivery easier, and also to cause abortions during the first three months of pregnancy.
How does it work?
Laminaria seems to be able to form a thick, sticky gel when it comes into contact with water. This allows laminaria to work as a bulk laxative. It also allows laminaria “tents” that have been placed inside the cervix to expand the cervix for procedures or to “ripen” the cervix and speed up the onset of labor. These laminaria tents absorb water, gradually swelling to a diameter of 1/2 inch over 4-6 hours. This swelling causes the cervix to expand, and that can bring on labor.
Possibly Ineffective for...
- Preparation ("ripening") of the cervix in women, such as during childbirth or procedures. Although laminaria might speed up childbirth, it doesn't seem to reduce the number of women who need Cesarean sections to deliver. Laminaria also increases the chance of infection in both mother and infant.
Insufficient Evidence to Rate Effectiveness for...
- Weight loss.
- High blood pressure.
- Cancer prevention.
- Other conditions.
Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).
Laminaria is POSSIBLY UNSAFE when taken by mouth. It contains iodine in amounts that are high enough to harm the thyroid, the gland that uses iodine to make hormones. The average laminaria-based supplement might contain as much as 1000 mcg of iodine. Taking in more than 150 mcg of iodine per day can cause a normal thyroid to become overactive or underactive, or make an overactive thyroid worse. Some laminaria products also contain significant amounts of arsenic, a chemical element that is poisonous.
Taking laminaria by mouth during breast-feeding is LIKELY UNSAFE because laminaria might contain some poisonous chemicals.
If you are pregnant or breast-feeding, it's best to avoid laminaria.
Kidney problems: Laminaria might cause dangerously high potassium and iodine levels. Don't take laminaria if you have kidney problems.
Thyroid problems: Laminaria contains significant amounts of iodine, which might make thyroid problems worse.
Digoxin (Lanoxin)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Laminaria contains large amounts of potassium. Large amounts of potassium can increase the effects and side effects of digoxin (Lanoxin). Do not take laminaria if you are taking digoxin (Lanoxin).
Medications for high blood pressure (ACE inhibitors)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Laminaria contains large amounts of potassium. Some medications for high blood pressure can increase potassium levels in the blood. Taking laminaria along with some medications for high blood pressure might cause too much potassium in the blood.
Potassium supplementsInteraction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Laminaria contains large amounts of potassium. Taking potassium supplements along with laminaria might cause too much potassium to be in the body. Do not take laminaria if you are taking potassium supplements.
Thyroid hormoneInteraction Rating: Moderate Be cautious with this combination.Talk with your health provider.
The body naturally produces thyroid hormones. Laminaria might increase how much thyroid hormone the body produces. Taking laminaria along with thyroid hormone pills might increase the effects and side effects of thyroid hormones.
Water pills (Potassium-sparing diuretics)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.
Laminaria contains large amounts of potassium. Some "water pills" can also increase potassium levels in the body. Taking some "water pills" along with laminaria might cause too much potassium to be in the body.
The appropriate dose of laminaria depends on several factors such as the user's age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for laminaria. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Amster E, Tiwary A, Schenker MB. Case report: potential arsenic toxicosis secondary to herbal kelp supplement. Environ Health Perspect 2007;115:606-8. View abstract.
Covington TR, et al. Handbook of Nonprescription Drugs. 11th ed. Washington, DC: American Pharmaceutical Association, 1996.
Eliason BC. Transient hyperthyroidism in a patient taking dietary supplements containing kelp. J Am Board Fam Pract 1998;11:478-80.
Fetrow CW, Avila JR. Professional's Handbook of Complementary & Alternative Medicines. 1st ed. Springhouse, PA: Springhouse Corp., 1999.
Foster S, Tyler VE. Tyler's Honest Herbal, 4th ed., Binghamton, NY: Haworth Herbal Press, 1999.
Harrell BL, Rudolph AH. Letter: Kelp diet: A cause of acneform eruption. Arch Dermatol 1976;112:560.
Kathan RH. Kelp extracts as antiviral subatances. Ann N Y Acad Sci 1965;130:390-7.
Kazzi GM, Bottoms SF, Rosen MG. Efficacy and safety of Laminaria digitata for preinduction ripening of the cervix. Obstet Gynecol 1982;60:440-3.. View abstract.
Norman JA, Pickford CJ, Sanders TW, Waller M. Human intake of arsenic and iodine from seaweed-based food supplements and health foods available in the UK. Food Addit Contam 1988;5:103-9.. View abstract.
Pye KG, Kelsey SM, House IM, et al. Severe dyserythropoeisis and autoimmune thrombocytopenia associated with ingestion of kelp supplement. Lancet 1992;339:1540. View abstract.
US Department of Health and Human Services, Public Health Service. Agency for Toxic Substances and Disease Registry. Toxicological profile for strontium. April 2004. Available at: www.atsdr.cdc.gov/toxprofiles/tp159.pdf. (Accessed 8 August 2006).