Herbs & Supplements

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Uses

Brown seaweed has been promoted for treating numerous conditions ranging from obesity to cancer. Generally, studies using laboratory animals have been inconclusive and large well controlled human studies have not been done for most of its possible uses.

In western countries, brown seaweed is included in some weight loss supplements--usually along with other natural ingredients such as chromium, guarana, lecithin, or vinegar, that are also promoted for weight loss. Because brown seaweed contains iodine, it may help to increase metabolism (the conversion of food to energy within the body) for individuals with low thyroid function. If excessive weight is due to low thyroid activity, brown seaweed might help slightly to enhance weight loss. Thyroid problems caused by iodine deficiencies are rare in North America, so the effects of brown seaweed on weight are not usually very great. Brown seaweed is eaten as a low-calorie vegetable in many countries. Where it is consumed regularly as food, it may replace higher calorie foods and help control weight for individuals who eat it instead of higher calorie foods.

Another common use of brown seaweed is as a laxative. Brown seaweed contains several types of fibers, including some that break down in the stomach and intestines (soluble fiber) and some the body does not digest (insoluble fiber). When exposed to water, soluble brown seaweed fibers become a thick, syrupy liquid. Insoluble brown seaweed fibers form a large soft mass, which moves quickly through the intestines and also triggers intestinal muscle contractions. Both actions help to relieve constipation.

Brown seaweed may help prevent or delay heart disease in at least three ways. First, soluble fiber in brown seaweed may play a role in reducing cholesterol because it sticks to fats from food in the gastrointestinal (GI) tract. As a result, more cholesterol may be eliminated and less cholesterol may be absorbed by the body. In addition, chemicals in brown seaweed reduce blood levels of an enzyme known as trans-sialidase, which is thought to be involved in atherosclerosis (hardening of the arteries). By blocking cholesterol absorption and trans-sialidase activity, brown seaweed may keep some cholesterol from depositing on artery walls. Thirdly, brown seaweed also contains small amounts of chemicals known as fucoidans (also fucans or sulfated fucans), which help keep blood from becoming thick and gummy. Therefore, the possibility of forming blood clots and arterial plaques may be reduced. Plaques are accumulations of blood cells, fats, and other substances that may build up in blood vessels, possibly reducing or blocking blood flow and potentially leading to a heart attack or stroke.

Fucoidans have shown antiviral effects in laboratory and animal studies. They kept viruses from attaching to host cells and may also have kept individual virus particles from combining to form giant superparticles. Fucoidans also appear to interrupt the action of enzymes needed by several viruses, including human immunodeficiency virus (HIV), to survive. HIV is the virus that causes AIDS. Very little research has been done in humans, however, and much more study is needed to determine the potential for fucoidans in treating viral illnesses.

Brown seaweed may have some anticancer activity. Laboratory studies of fucoidans from some types of brown seaweed show that they interfere with a substance known as epidermal growth factor (EGF). A small protein, EGF is made by the body to regulate cell growth and promote wound healing. Some types of cancer cells have extra receptors for EGF, so blocking it may prevent or limit the growth of some cancer cells. Fucoidans may also stop cancer cells from sticking to normal body cells, such as blood platelets. Both effects help to keep cancer cells from spreading. Fucoidans may also promote the disintegration (apoptosis) of rapidly changing cells. Since cancer cells generally grow much faster than normal cells, fucoidans could have a more disruptive effect on cancer cells than on normal cells.

In addition, brown seaweed may enhance immune function through several possible pathways. They may increase the production of immune cells from bone marrow. Specifically, fucoidans and possibly other chemicals in brown seaweed are thought to increase blood levels of interleukin-12 (IL-12), which is one of several natural substances that strengthen the body's response to infections and diseases. They also seem to play a role in directing leukocytes (white blood cells) to areas of inflammation. Possible immune enhancing effects of brown seaweed may increase its potential antiviral and anticancer activity.

Orally, brown seaweed may have several other effects, but none has been proven:

In laboratory studies, a chemical obtained from brown seaweed has kept calcium oxalate in solution and prevented it from forming clumps when the solution cannot dissolve any more calcium oxalate. If a similar effect occurs within the human body, brown seaweed may help to prevent the formation of calcium oxalate stones in the bladder and kidneys.

In a study of laboratory animals with artificially caused diabetes, brown seaweed helped to normalize blood sugar levels--possibly by affecting enzymes in the blood.

Some research with laboratory animals shows that brown seaweed fibers may attract and trap potentially harmful substances, such as bacteria, in the gastrointestinal (GI) tract. Causing possibly harmful substances to be eliminated from the body may help to prevent diarrhea and diseases caused by intestinal parasites.

Historically, fresh brown seaweed--particularly bladderwrack--has been applied to the skin to relieve irritation and injuries. The wet, slimy texture of fresh seaweed protects skin wounds and keeps them from drying. Recently, fucoidans have been shown in laboratory studies to affect the action of a body chemical known as transforming growth factor beta (TGF-b). As a result, the production of new skin cells and collagen is increased, helping wounds heal and possibly reducing scar formation. Alginte, a second chemical in brown seaweed, has shown antibacterial effects, which may help prevent infection. Chemicals from brown seaweed are now included in commercially available burn and wound dressings. Additionally, results from a small human study seem to show that skin thickness and softness improved when a preparation containing brown seaweed was applied to facial skin twice daily for five weeks.

When exposed to fluids, dried kelp (Laminaria) expands because it attracts and holds water from surrounding areas. Especially in Asia, it has been used to "ripen" or relax the cervix, the narrow muscular opening between the vagina and the uterus. When kelp is folded or rolled and inserted as a cervical "tent", it expands and gradually makes the cervix soften and dilate (widen)--usually after 12 hours to 24 hours. Diagnostic or medical procedures are easier and more comfortable and the risk of cervical injury from stretching is reduced. Kelp tents have also been used to help ease labor and birth. In some parts of the world, they are used to cause abortions.