|
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 in breast milk.
Other chemicals in shark liver oil being studied against cancer are
squalamine and squalene.
Overview
Shark liver oil is widely used alongside 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 laboratory
studies suggest that they may have anti-tumor effects in animals, 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, one of the components 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 in two ways: by stimulating
immune system cells called macrophages, which consume invading germs
and damaged cells; and by inhibiting protein kinase C, which is a key
regulator of cell growth. Proponents also claim that alkylglycerols
reduce the side effects of chemotherapy and radiation treatment,
supposedly because of their ability to protect cell membranes.
Because of their supposed immune-boosting effects,
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.
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 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-protecting
abilities, which may reduce the side effects of chemotherapy.
These claims are currently being studied. Depending on the
commercial preparation, shark liver oil may also be rich in omega-3
fatty acids and vitamin A. Shark liver oil has also been used in some
moisturizing skin creams and lotions, although several cosmetics
companies have recently removed this ingredient because of concern
regarding the decline of some shark species.
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 undergoing radiation therapy 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 and cancer have been done in the
laboratory. A few studies showed some benefit in women with cervical
cancer who were also undergoing 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—tumors that spread to the lung from a primary
cancer elsewhere in the body—found in laboratory animals.
Early studies in people with cancer have shown that squalamine can
safely be combined with chemotherapy, but whether it helps shrink
tumors or prolongs survival is not clear. It is currently being studied
with other treatments for lung and prostate cancer.
Squalene, a substance found in olive oil and some types of
shark liver oil, has been studied in the laboratory. One laboratory
study found that squalene seemed to protect normal bone marrow cells
from the effects of some chemotherapy drugs while still allowing the
drugs to affect cancer cells. It is not yet clear whether 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 companies that produce
drugs (which must provide the FDA with results of detailed testing
showing their product is safe and effective before the drug is approved
for sale), the companies that make supplements do not have to show
evidence of safety or health benefits to the FDA before selling their
products. Supplement products without any reliable scientific evidence
of health benefits may still be sold as long as the companies selling
them do not 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).
Though the FDA has written
new rules to improve the quality of manufacturing processes for dietary
supplements and the accurate listing of supplement ingredients, these
rules do not take full effect until 2010. And, the new rules do not
address the safety of supplement ingredients or their effects on health
when proper manufacturing techniques are used.
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 for cancer 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 found on
our Web site (www.cancer.org)
or ordered from our toll-free number (1-800-ACS-2345).
References
AAkutsu 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. Accessed at:
www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/alk_0018.shtml
on July 11, 2007.
PDRhealth. Squalene. Accessed at:
www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/squ_0240.shtml
on June 11, 2008.
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. Accessed at: http://ntp.niehs.nih.gov/ntp/roc/toc11.html
on June 11, 2008.
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.
Last Medical Review: 11/01/2008
Last Revised: 11/01/2008
|
