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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
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