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Other common
name(s): none
Scientific/medical
name(s): none
Description
Fasting involves eating no food and drinking only water or
juice for a period of one to five days or longer. Tea or broth may
sometimes be part of the fasting process. Fasting is often promoted as
part of a "detoxification" process in some types of metabolic therapies
for cancer or other conditions.
Overview
Available scientific evidence does not support claims that
fasting is effective for preventing or treating cancer. Even a
short-term fast can have negative health effects, while fasting for a
longer time could cause serious health problems.
How is it promoted for use?
Practitioners of a type of alternative therapy called
metabolic therapy (see Metabolic Therapy)
believe the body contains environmental toxins and other harmful
substances that can be removed by fasting or detoxifying the body. They
claim that fasting allows the body to focus energy on cleansing and
healing itself. According to these practitioners, fasting helps the
immune system work more efficiently, allows more oxygen and white blood
cells to flow through the body, helps the body to burn more fat, helps
increase energy, and allows other healing functions to improve. Some
supporters claim that fasting by a person who has cancer can "starve" a
tumor, leading to cell death.
Other illnesses and conditions proponents claim can be treated
by fasting include acne, allergies, arthritis, asthma, non-cancerous
tumors, digestive disorders, fever, glaucoma, headaches, heart disease,
high blood pressure, inflammatory diseases, pain, polyps, and ulcers.
Fasting is also promoted to rejuvenate the body, help maintain normal
body weight, increase longevity and sex drive, and to improve mental
clarity, self-awareness, and self-esteem. It is also said to be helpful
in quitting or cutting back on use of tobacco, alcohol, caffeine, or
non-prescription drugs. Some practitioners claim it can heighten
spiritual awareness.
What does it involve?
Short fasts, lasting from 1 to 5 days, are often done at home.
Other than drinking only water or juice, fasting involves a lot of
rest. Sometimes other methods of detoxification, such as liver flushes
or enemas, are recommended as part of the regimen (see also Juicing, Liver Flush,
Colon Therapy).
Longer fasts require professional supervision and often take place at a
spa, resort, or similar facility.
What is the history behind it?
Ancient cultures believed fasting could purify the soul. The
belief that fasting can also purify or cleanse the body is a fairly
modern idea, gaining popularity in the second half of the 20th century.
What is the evidence?
Available scientific evidence does not support fasting as a
treatment for cancer. Some studies in animals have suggested that
long-term calorie restriction -- that is, consuming less than one's
normal amount of calories each day -- may slow the growth of certain
tumors, but this is not the same as fasting. In fact, some animal
studies have found that actual fasting in which no food is eaten
several days could actually promote the growth of some tumors. No human
studies on the effects of fasting on cancer have been published in the
available medical literature.
A brief fast (usually 8 to 12 hours) is often advised by
medical professionals in preparation for certain diagnostic tests. In
this case, the fast helps to produce more accurate test results.
Fasting may also be advised for a period of time before and after
surgery, especially if digestive system organs are involved. This is
mainly to ensure the stomach and bowels are empty during surgery. This
is important in order to avoid getting stomach contents into the lungs,
since anesthesia disables the usual protections, such as swallowing and
coughing, that keep a person from inhaling foreign matter into the
lungs when he or she is awake. It also allows the intestines time to
recover from anesthesia before reintroducing food.
As for reaching and maintaining proper weight, most experts
recommend a combination of limiting portion sizes, choosing healthful
foods, and being physically active instead of fasting.
Some research has suggested that short-term fasts may briefly
improve the symptoms of rheumatoid arthritis. However, the benefits do
not last longer than 10 days, and fasting is not a recommended
component of arthritis care.
Are there any possible problems or
complications?
Fasting can have short-term side effects such as headaches,
dizziness, fatigue, abnormal heart rhythms, and a fruity taste in the
mouth. It can also raise the risk of an attack in people with gout.
Longer-term fasting can interfere with the immune system and vital
bodily functions and can damage the liver, kidneys, and other organs.
Fasting can be especially dangerous in people who are already
malnourished, such as those with some forms of advanced cancer. Women
who are pregnant or breast-feeding should not fast.
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
Caderni G, Perrelli MG, Cecchini F, Tessitore L. Enhanced
growth of colorectal aberrant crypt foci in fasted/refed rats involves
changes in TGFbeta1 and p21CIP expressions. Carcinogenesis.
2002;23:323-327.
Cassileth B. The
Alternative Medicine Handbook. New York: W. W. Norton
& Co; 1998.
Hikita H, Nuwaysir EF, Vaughan J, et al. The effect of
short-term fasting, phenobarbital and refeeding on apoptotic loss, cell
replication and gene expression in rat liver during the promotion
stage. Carcinogenesis.
1998;19:1417-1425.
Hikita H, Vaughan J, Pitot HC. The effect of two periods of
short-term fasting during the promotion stage of hepatocarcinogenesis
in rats: the role of apoptosis and cell proliferation. Carcinogenesis.
1997;18:159-166.
Legro RS, Finegood D, Dunaif A. A fasting glucose to insulin
ratio is a useful measure of insulin sensitivity in women with
polycystic ovary syndrome. J
Clin Endocrinol Metab. 1998;83:2694-2698.
PDRhealth. Detoxification therapy. 2004. Accessed at:
www.pdrhealth.com/content/natural_medicine/chapters/201160.shtml on
August 4, 2005. Content no longer available.
PDRhealth. Fasting. 2004. Accessed at:
www.pdrhealth.com/content/natural_medicine/chapters/201200.shtml on
August 4, 2005. Content no longer available.
Sesca E, Premoselli F, Binasco V, Bollito E, Tessitore L.
Fasting-refeeding stimulates the development of mammary tumors induced
by 7,12-dimethylbenz[a]anthracene. Nutr
Cancer. 1998;30:L25-30.
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
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