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Oil derived from the livers of deep-water sharks shows some promise in fighting cancer and boosting the immune system. Until a decade ago, when a growing number of supplement manufacturers began to take an interest in this nutritional aid, most shark livers were routinely tossed overboard. Today, several companies harvest and process the oil from sharks caught off of Greenland, Norway, Sweden, and other coasts. The oil is available as a by-product of the commercial fishing industry; endangered sharks are not allowed to be killed solely for their oil.

In centuries past, Nordic fishermen used shark liver oil as a folk remedy to heal wounds and fight the flu. Japanese seamen called it samedawa, or "cure all." Interestingly, a new use emerged in the 1950s, when a Swedish doctor noted that children with leukemia who were fed calf bone marrow showed some protection against the adverse effects of radiation. Investigation revealed that the calf marrowâ€™s therapeutic actions were due to natural immune-boosting compounds called alkylglycerols, also present in notably high concentrations in shark liver oil.

Alkylglycerols are naturally found in much lower levels in the bone marrow, liver, spleen, and breast milk of mature cows as well as in humans. Much of the medical interest in shark liver oil--as a potential complement to standard cancer treatments and as a natural immune booster--has focused on these promising compounds.

Shark liver oil also contains squalamine, a substance which in animal studies has shown some ability to fight cancers of the breast, lung, brain, and skin (melanoma specifically) by choking off the tumor's blood supply; studies in people are under way. Shark liver oil capsules sometimes also contain generous amounts of squalene, an antioxidant and bacteria-fighter. Also present are omega-3 fatty acids (the heart-healthy oils found in other deep-water fish) and vitamin A.

There are several books about the health benefits of shark liver oil, all of which basically extol the virtues of the product. Even though these books are written by M.D.s and Ph.D.s, in actual fact, most of the information is based on either patients relating their successes or limited lab animal studies. This does not mean the product has no value, but rather that based on clinical trials in humans, thereâ€™s little hard evidence about the effectiveness of shark liver oil for any condition. As such, there are no formally established dosages for shark liver oil, and the WholeHealth MD recommendations below follow guidelines set forth in these books.

Health Benefits

Shark liver oil is sometimes added to lip balms to moisturize and prevent chapping, and one recent report indicated that it might even help heal canker sores. Other than occasional patient testimonials, however, evidence is weak that shark liver oil can cure serious diseases, such as AIDS, arthritis, chronic fatigue, fibromyalgia, and psoriasis.

Most of the promising studies with shark liver oil have focused on its possible benefits against cancer and infections. Unfortunately, many of the trials have been done in animals or have been very small and inconclusive. Many researchers contend that the supplement shows real promise, however, and new, more rigorous human studies are under way.

Specifically, shark liver oil may help to:

Augment traditional cancer treatments. In Europe, shark liver oil is widely used to complement traditional cancer treatments. Some preliminary research suggests that the alkylglyerols in shark liver oil may prime the immune system, causing cancer cells to come under attack and preventing spread of disease. The oil may also fortify healthy cells and ease the harsh side effects of cancer chemotherapy and radiation treatments. There are few sound studies, however, to confirm these possible cancer-fighting benefits in people.

Fight infections and inflammations and heal wounds. Enthusiasts claim that by boosting the immune system, shark liver oil may protect against as well as speed the healing of colds, flu, and various minor skin infections. These types of uses were certainly common in old fishing communities familiar with sharks. Alkylglycerol-rich bone marrow soup, for example, is an old-time home remedy used to ward off colds.

The liver oil also has been proposed as an immune-modulating remedy to ease asthma, arthritis, and the skin inflammations of psoriasis. Whether it is truly effective for any of these conditions remains to be proven, but for the minor ailments at least, it likely poses little risk and could possibly help.

Dosage Information

Special Tips
--Look for products standardized to contain "alkylglycerols," one of the key disease-fighting ingredients in shark liver oil. A 1,000 mg capsule should provide at least 200 mg of alkylglycerols. Squalamine and squalene are other potentially healing compounds found in the oil.

--In the case of shark liver oil, more is not better. Do not exceed recommended doses. Some products are high in vitamin A, which can be toxic if you take too much.

--If you take the product for longer than 30 days, see your doctor for follow-up. Your doctor may need to do a blood test and change your dosage because long-term use can alter blood consistency in unwanted ways.

As a complement to cancer treatments: 1 to 2 capsules (providing 100 mg alkylglycerols) 3 times a day with meals.

For fighting infections: 1 to 2 capsules a day with meals, for 7 days.

Guidelines for Use

Take shark liver supplements with meals. Food will enhance absorption of the active ingredients.

As with many supplements, shark liver oil has not been well studied in pregnant women. If you are pregnant or plan to become pregnant, let your doctor know.

General Interaction

There are no known drug or nutrient interactions associated with shark liver oil.

Possible Side Effects

Mild digestive upset, including nausea, diarrhea, and indigestion, may occur, especially when you first start taking shark liver oil. These reactions, however, are not common. There are no known serious side effects from taking shark liver oil at recommended doses.

Cautions

Buy capsules from a reputable manufacturer that you trust. It is important that supplement makers test and process the oil properly to remove potential toxins. A survey of some brands sold in Asia found some contained dangerously high levels of PCBs, cancer-causing pollutants that can accumulate in the bodies of sharks and other fish. Shark oil can also be high in mercury, a poisonous metallic element that can cause serious health problems when ingested at almost any dose.

Avoid ingesting high doses of pure squalene, one the ingredients in shark liver oil. Although it is a natural substance and is also found in vegetable oils, there have been isolated reports of pneumonia and immune-system cancers among fisherman and others exposed to high amounts of the substance. So while pure squalene is safely added to moisturizers and vaccines, and may have an array of beneficial effects, itâ€™s best to avoid high doses of the pure ingredient.