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Shark Liver Oil
Other common
name(s):
none
Scientific/medical name(s):
alkylglycerols, alkoxyglycerols, squalene,
squalamine
Description
Shark liver oil is promoted
as a complementary or alternative form of treatment for cancer and other
diseases. The oil is taken from the liver of cold-water sharks. Shark
liver oil is a rich source of alkylglycerols, chemicals that may have
anti-cancer properties. Alkylglycerols are also found in human bone
marrow and breast milk. Other chemicals in shark liver oil being studied
against cancer are squalamine and squalene.
Overview
Shark liver oil is widely
used along with conventional cancer treatment in northern Europe, and is
sold as a dietary supplement in the United States. Available scientific
evidence does not support claims that shark liver oil supplements are
effective against cancer in humans. Recent research has focused on
certain components of shark liver oil (alkylglycerols, squalamine, and
squalene). Early lab studies suggest that they may have anti-tumor
effects in animal models, but their effects in humans are not yet known.
Clinical trials are currently under way.
How is
it promoted for use?
Shark liver oil is promoted
as a dietary supplement used to boost the immune system, fight off
infections, heal wounds, and to treat cancer and lessen the side effects
of conventional cancer treatment.
Alkylglycerols, found in
shark liver oil, are thought to be helpful in several ways. It has been
suggested that they fight cancer by killing tumor cells indirectly.
Proponents claim they activate the immune system by stimulating
macrophages (immune system cells that consume invading germs and damaged
cells) and inhibiting protein kinase C (a key regulator of cell growth).
Proponents also claim that alkylglycerols reduce the side effects of
chemotherapy and radiation treatment. This activity is said to be due to
the ability of alkylglycerols to protect cell membranes.
Because of their supposed
immune boosting effect, alkylglycerols are also claimed to help against
colds, flu, chronic infections, asthma, psoriasis, arthritis, and AIDS.
Since macrophages are also important in wound healing, alkylglycerols
are said to have healing effects. These claims have not been studied in
controlled clinical trials.
Depending on the commercial
preparation, shark liver oil may also be rich in omega-3 fatty acids and
vitamin A (see
Omega-3 Fatty Acids and
Vitamin A).
Other compounds in shark
liver oil, such as squalamine and squalene, have also been promoted to
have anti-cancer effects. Because some early studies have shown that
squalamine can slow the growth of tumor blood vessels, proponents claim
it may help to treat cancer, either alone or when combined with
chemotherapy. It is also being studied for use against macular
degeneration, an eye condition that results in loss of vision. Squalene
has been promoted as having cell protective effects, which may reduce
the side effects of chemotherapy. These claims are currently being
studied.
What does it
involve?
Shark liver oil is
available as a dietary supplement in capsule and liquid forms. There are
no standardized dosages. These supplements are available at health food
stores and over the Internet.
What is the
history behind it?
Shark liver oil has been
used as a folk remedy by people on the coasts of Norway and Sweden for
hundreds of years. It was mainly used to promote wound healing and as a
general remedy for conditions of the respiratory tract and the digestive
system.
In the 1950s, a young
Swedish doctor suggested that extracts of bone marrow helped boost the
recovery of white blood cells in children getting radiation and
chemotherapy for leukemia. The active ingredient in the bone marrow
extract was identified as alkylglycerols. Shark liver oil was found to
be one of the richest sources of alkylglycerols. Around 1986, the first
commercially purified shark liver oil with a "standard dose" of
alkylglycerols was marketed. It is still widely used in many northern
European countries.
What is the
evidence?
Available scientific
evidence does not support claims that shark liver oil supplements are
effective against cancer in humans.
Most of the studies on
alkylglycerols against cancer have been done in the lab. A few studies
showed some benefit in women being treated for cervical cancer who were
also getting radiation therapy. These studies were published by a single
group of Scandinavian researchers in the 1970s and 1980s and have not
been confirmed by other research groups. There appears to be very little
recent research on the benefits of alkylglycerols in preventing or
treating cancer.
More recently, research has
focused on squalamine, a substance found in shark liver oil that stops
the growth of tumor blood vessels. Researchers found that squalamine
decreased the number of lung metastases found in lab animals. Early
studies in people with cancer have shown that the drug can safely be
combined with chemotherapy, but whether or not it helps shrink tumors or
prolongs survival is not clear. It is currently being studied along with
other treatments against lung and prostate cancers.
Squalene, a substance found
in olive oil and some types of shark liver oil, has been studied in the
lab. One study found that squalene seemed to protect normal bone marrow
cells in the test tube from the effects of certain chemotherapy drugs
while still allowing cancer cells to be affected by the drugs. It is not
yet clear if this protective effect will extend to animals and humans.
Are there any
possible problems or complications?
This product is sold as
a dietary supplement in the United States. Unlike drugs (which must be
tested before being allowed to be sold), the companies that make
supplements are not required to prove to the Food and Drug
Administration that their supplements are safe or effective, as long as
they don't claim the supplements can prevent, treat, or cure any
specific disease.
Some such products may
not contain the amount of the herb or substance that is written on the
label, and some may include other substances (contaminants). Actual
amounts per dose may vary between brands or even between different
batches of the same brand.
Most such supplements
have not been tested to find out if they interact with medicines, foods,
or other herbs and supplements. Even though some reports of interactions
and harmful effects may be published, full studies of interactions and
effects are not often available. Because of these limitations, any
information on ill effects and interactions below should be considered
incomplete.
Although many people have
taken shark liver oil, the issue of potential toxicity at the usual
doses has not been well studied. Some mild digestive problems such as
nausea, upset stomach, and diarrhea have been reported. Some animal
studies have found that shark liver oil and its components may raise
blood cholesterol levels. A Japanese study found some shark liver oil
supplements to be contaminated with polychlorinated biphenyls (PCBs) and
polybrominated diphenyl ethers (PBDEs). PCBs can have harmful effects in
humans, and may increase the risk of some types of cancer. People with
seafood allergies may also react to shark liver oil.
Relying on this type of
treatment alone, and avoiding or delaying conventional medical care, may
have serious health consequences.
Additional
Resources
More Information From
Your American Cancer Society
The following information
on complementary and alternative therapies may also be helpful to you.
These materials may be ordered from our toll-free number
(1-800-ACS-2345).
References
Akutsu K, Tanaka Y,
Hayakawa K. Occurrence of polybrominated diphenyl ethers and
polychlorinated biphenyls in shark liver oil supplements.
Food Addit Contam.
2006;23:1323-1339.
Bhargava P, Marshall JL,
Dahut W, Rizvi N, Trocky N, Williams JI, et al. A phase I and
pharmacokinetic study of squalamine, a novel antiangiogenic agent, in
patients with advanced cancers. Clin
Cancer Res. 2001;7:3912-3919.
Brohult A, Brohult J,
Brohult S, Joelsson I. Reduced mortality in cancer patients after
administration of alkoxyglycerols. Acta
Obstet Gynecol Scand. 1986;65:779-85.
Das B, Yeger H, Baruchel H,
Freedman MH, Koren G, Baruchel S. In vitro cytoprotective activity of
squalene on a bone marrow versus neuroblastoma model of cisplatin-induced
toxicity. Implications in cancer chemotherapy.
Eur J Cancer. 2003;39:2556-2565.
Hao D, Hammond LA, Eckhardt
SG, et al. A Phase I and pharmacokinetic study of squalamine, an
aminosterol angiogenesis inhibitor.
Clin Cancer Res. 2003;9:2465-2471.
Herbst RS, Hammond LA,
Carbone DP, et al. A phase I/IIA trial of continuous five-day infusion
of squalamine lactate (MSI-1256F) plus carboplatin and paclitaxel in
patients with advanced non-small cell lung cancer.
Clin Cancer Res.
2003;9:4108-4115.
PDRhealth. Alkoxyglycerols.
Available at:
www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/alk_0018.shtml.
Accessed July 11, 2007.
PDRhealth. Squalene.
Available at:
www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/squ_0240.shtml.
Accessed July 11, 2007.
Pugliese PT, Jordan K,
Cederberg H, Brohult J. Some biological actions of alkylglycerols from
shark liver oil. J Altern Complement
Med. 1998;4:87-99.
Sills AK Jr, Williams JI,
Tyler BM, et al. Squalamine inhibits angiogenesis and solid tumor growth
in vivo and perturbs embryonic vasculature.
Cancer Res. 1998;58:2784-2792.
Teicher BA, Williams JI,
Takeuchi H, Ara G, Herbst RS, Buxton D. Potential of the aminosterol,
squalamine in combination therapy in the rat 13,762 mammary carcinoma
and the murine Lewis lung carcinoma.
Anticancer Res. 1998;18:2567-2573.
U.S. Department of Health
and Human Services. Public Health Service, National Toxicology Program.
Report on Carcinogens, Eleventh Edition. 2005. Available at:
http://ntp.niehs.nih.gov/ntp/roc/toc11.html. Accessed January 30,
2006.
Note: This information may not cover all possible
claims, uses, actions, precautions, side effects or interactions. It is
not intended as medical advice, and should not be relied upon as a
substitute for consultation with your doctor, who is familiar with your
medical situation.
Revised: 07/20/2007 | 
