Health Care Professional Information
Common Name
Selenocysteine, selenomethionine, selenate, selenite
Clinical Summary
Selenium, an essential dietary trace mineral, is an important component of antioxidant systems such as glutathione peroxidase (1) that neutralize and protect against damage caused by free radicals and reactive oxygen species. It also plays an important role in thyroid function. Selenium can be obtained from the diet by consuming whole grains, meats, seafood, poultry and nuts. It is also marketed as a supplement to boost immune function and for prevention of cardiovascular, rheumatic diseases, and cancer.
Several studies have been conducted to determine the role of selenium in reducing the risk of cardiovascular disease but data are inconclusive (23) (28).
Selenium supplementation was found to reduce the viral load in individuals infected with human immunodeficiency virus (HIV) (19). Studies also indicate that selenium may improve glucose metabolism but it was not useful in preventing type 2 diabetes and in some cases may increase the risk (20) (21) (30).
The importance of selenium in cancer prevention has been documented in epidemiological studies and clinical intervention trials. Data suggest its benefits in preventing gastrointestinal (16), lung (17) and bladder cancers (26). Selenium supplementation resulted in significant reduction of side effects including hair loss, abdominal pain, and loss of appetite in ovarian cancer patients undergoing chemotherapy (15). It was also effective in reducing head and neck lymphedema (12) (14) and diarrhea associated with radiation therapy (24).
However, the large prevention study SELECT (Selenium and Vitamin E Cancer Prevention Trial) (8), based on previous data indicating that selenium and vitamin E reduced the incidence of prostate cancer, did not find evidence of protective effects of selenium. The trial was suspended in January 2009, when initial data analysis showed no reduction in the risk of prostate cancer with selenium alone or with vitamin E (21). Another study showed selenium, when used together with soy and Vitamin E, did not prevent prostate cancer progression (27). Moreover, results from a cross-sectional analysis of men with prostate cancer indicate that selenium levels may influence the risk of aggressive prostate cancer (22). Further, a review of randomized controlled trials did not find any evidence of selenium's cancer preventive potential (29).
A chemoprevention trial of selenium in patients with NSCLC (non small-cell lung cancer) was also halted after interim analysis as data did not show any benefit of selenium supplementation; there was an increase in secondary lung cancers in selenium users, although it was statistically insignificant (25).
Long-term use of selenium may also increase the risk of certain types of skin cancer (13).
Purported Uses
- Cancer prevention
- Cancer treatment
- Cardiovascular disease
- Immunostimulation
- Rheumatoid arthritis
Mechanism of Action
Selenium is an essential structural element of the antioxidant enzyme glutathione-peroxidase that converts aggressive oxidation products and intracellular free radicals into less reactive or neutral components (3). Other biological functions of selenium include regulation of thyroid hormone action and regulation of the reduction status of vitamin C (2).
Pharmacokinetics
Absorption:
Absorption of selenium is efficient and not regulated. More than 90 percent of selenomethionine, the major dietary form of the element, is absorbed by the same mechanism as methionine itself. Selenocysteine appears to be absorbed well also. Of the inorganic forms, selenate is almost completely absorbed, but with a significant fraction lost in the urine before incorporation into tissue. Selenite has a more variable absorption probably related to interactions with substances in the gut lumen, but it is better retained, once absorbed, than selenate. Absorption of selenite is generally greater than 50 percent. Selenate and selenite are not major dietary constituents, but are commonly used to fortify foods and as selenium supplements.
Distribution:
Selenomethionine enters the methionine pool in the body and shares the fate of methionine until catabolized by the transsulfuration pathway ultimately leading to the reduced form.
Metabolism / Excretion:
Ingested selenocysteine, selenate, and selenite are all apparently metabolized by methylation to selenide. The selenide can be metabolized to selenophosphate, the precursor of selenocysteine in selenoproteins. The mechanism that regulates production of excretory metabolites has yet to be elucidated. The excretory metabolites appear in the urine primarily.
(2)
Adverse Reactions
Case Report: Oral consumption of 10 g of sodium selenite supplement for treatment of prostate cancer resulted in the death of a 75-year-old man (18).
Chronic selenosis (doses greater than 1000 mcg/day): Muscle weakness, fatigue, peripheral neuropathy, dermatitis, nail and hair changes/loss, garlic breath/body odor, irritability, growth retardation, hepatic necrosis
Toxicity: Acute toxicity via selenium poisoning has occurred with either accidental or suicidal ingestion of gun bluing solution or sheep drench. Consumption of gram quantities of selenium can cause severe gastrointestinal disturbance, neurological disturbance, acute respiratory distress syndrome, myocardial infarction, and renal failure.
(2) (5)
Herb-Drug Interactions
Supplement Interactions: High doses of selenium may decrease vitamin C absorption.
(5)
Literature Summary and Critique
Dosage (Inside MSKCC Only)
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References
- Whitney EN, et al. Understanding Normal & Clinical Nutrition, 4th ed. Belmont (CA): West Publishing; 1994.
- Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington (DC): National Academy Press; 2000.
- Suadicani P, Hein HO, Gyntelberg F. Serum selenium concentration and risk of ischaemic heart disease in a prospective cohort study of 3000 males. Atherosclerosis 1992;96:33-42.
- Feifer AH, Fleshner NE, Klotz L. Analytical accuracy and reliability of commonly used nutritional supplements in prostate disease. J Urol 2002;168:150-4.
- Pronsky ZM. Power's and Moore's Food-Medication Interactions, 11th ed. Pottstown (PA): Food Medication Interactions; 2000.
- Ip C. Lessons from basic research in selenium and cancer prevention (Review). J Nutr 1998;128:1845-54.
- El-Bayoumy K. The protective role of selenium on genetic damage and on cancer (Review). Mutat Res 2001;475:123-39.
- Klein EA, et al. SELECT: the selenium and vitamin E cancer prevention trial: rationale and design. Prostate Cancer Prostatic Dis 2000;3:145-51.
- Duffield-Lillico AJ, et al. Baseline characteristics and the effect of selenium supplementation on cancer incidence in a randomized clinical trial: a summary report of the Nutritional Prevention of Cancer Trial. Cancer Epidemiol Biomarker Prev 2002;11:630-9.
- Clark LC, et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. JAMA 1996;276:1957-63.
- Klein EA, et al. SELECT: the selenium and vitamin E cancer prevention trial. Urol Oncol. 2003 Jan;21(1):59-65.
- Micke O, et al. Selenium in the treatment of radiation-associated secondary lymphedema. Int J Radiat Oncol Biol Phys . 2003 May 1;56(1):40-9.
- Duffield-Lillico AJ, et al. Selenium supplementation and secondary prevention of nonmelanoma skin cancer in a randomized trial. J Natl Cancer Inst. 2003 Oct 1;95(19):1477-81.
- Bruns F, et al. Selenium in the treatment of head and neck lymphedema. Med. Princ Pract. 2004;13(4):185-90.
- Sieja K and Talerczyk M. Selenium as an element in the treatment of ovarian cancer in women receiving chemotherapy. Gynecol Oncol. 2004;93:320-327.
- Bjelakovic G, et al. Antioxidant supplements for prevention of gastrointestinal cancers: a systematic review and meta-analysis. Lancet 2004;364:1219-28.
- Zhuo H, Smith AH, and Steinmaus C. Selenium and lung cancer: A quantitative analysis of heterogeneity in the current epidemiological literature. Cancer Epidemiol Biomarkers Prev 2004;13(5):771-778.
- See KA, Lavercombe PS, Dillon J, Ginsberg R. Accidental death from acute selenium poisoning. MJA 2006; 185(7):388-389.
- Hurwitz BE, Klaus JR, LLabre MM, et al. Suppression of Human Immunodeficiency Virus Type I Viral Load With Selenium Supplementation. Arch Intern Med 2007: 167:148-154.
- Stranges S, Marshall JR, Natarajan R, et al. Effects of Long-Term Selenium Supplementation on the Incidence of Type 2 Diabetes: A Randomized Trial. Ann Intern Med. 2007.
- Lippman SM, Klein EA, Goodman PJ, et al. Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2009 Jan 7;301(1):39-51.
- Chan JM, Oh WK, Xie W, et al. Plasma Selenium, Manganese Superoxide Dismutase, and Intermediate- or High-Risk Prostate Cancer. J Clin Oncol. 2009 Jun 15 [Epub ahead of print].
- Mozaffarian D. Fish, mercury, selenium and cardiovascular risk: current evidence and unanswered questions. Int. J. Environ. Res. Public Health. 2009;6:1894-1916.
- Muecke R, Schomburg L, Glatzel M, et al. Multicenter, Phase 3 Trial Comparing Selenium Supplementation With Observation in Gynecologic Radiation Oncology. Int J Radiat Oncol Biol Phys. 2010 Feb 2. [Epub ahead of print]
- Karp DD, Lee SJ, Shaw Right GL, et al. A phase III, intergroup, randomized, double-blind, chemoprevention trial of selenium (Se) supplementation in resected stage I non-small cell lung cancer (NSCLC). J Clin Oncol 28:7s, 2010 (suppl; abstr CRA7004).
- Amaral AFS, Cantor KP, Silverman DT, and Malats N. Selenium and Bladder Cancer Risk: a Meta-analysis. Cancer Epidemiol Biomarkers Prev. 2010;19(9):2407-15.
- Fleshner NE, Kapusta L, Donnelly B, et al. Progression From High-Grade Prostatic Intraepithelial Neoplasia to Cancer: A Randomized Trial of Combination Vitamin-E, Soy, and Selenium. J Clin Oncol. 2011 May 2.
- Rayman MP, Stranges S, Griffin BA, Pastor-Barriuso R, Guallar E. Effect of supplementation with high-selenium yeast on plasma lipids: a randomized trial. Ann Intern Med. 2011 May 17;154(10):656-65.
- Dennert G, Zwahlen M, Brinkman M, et al. Selenium for preventing cancer. Cochrane Database Syst Rev. 2011 May 11;5:CD005195.
- Rayman MP. Selenium and human health. Lancet. 2012 Feb 29. doi:10.1016/S0140-6736(11)61452-9.
Consumer Information
How It Works
Bottom Line: Selenium has not been shown to treat cancer or heart disease.
Selenium is an element obtained in the diet from Brazil nuts, seafood, meats, cereals and grains. It is an essential part of the antioxidant enzyme glutathione-peroxidase, which protects cells from damage and DNA from mutations. For this reason, it has been studied for the prevention of diseases that are caused by or aggravated by this type of cellular damage, including cancer, heart disease, and rheumatoid arthritis. Selenium is also necessary for proper function of the immune system, but it is not known whether higher-than-normal levels of selenium can stimulate the immune system. Long-term use of selenium may increase the risk of certain types of cancer.
Purported Uses
- To prevent and treat cancer
Clinical trials show that selenium may not help prevent cancer; it may actually increase the risk of aggressive and secondary cancers.
- To reduce secondary lymphedema (swelling due to the accumulation of lymph)
A clinical trial suggests that selenium supplementation can reduce the swelling that occurs in patients who have undergone extensive surgery or radiation therapy.
- To prevent heart disease
Although low blood selenium levels have been associated with heart disease, studies in the general population have not supported the use of selenium to protect against heart disease. This use remains controversial.
- To stimulate the immune system
Selenium is essential for proper functioning of the immune system, and a few studies have shown an enhanced immune response in people taking selenium supplements.
- To treat rheumatoid arthritis
Low blood levels of selenium have been found in patients with rheumatoid arthritis. However, treatment of rheumatoid arthritis with selenium has not shown benefit in a few clinical trials.
Do Not Take If
- You are taking vitamin C supplements (selenium can reduce their absorption into the bloodstream).
Side Effects
- Chronic selenosis can develop with doses greater than 1000 micrograms per day and results in muscle weakness, fatigue, peripheral neuropathy, dermatitis (redness and irritation of the skin), nail and hair changes/loss, garlic breath/body odor, irritability, growth retardation, and liver damage.
- Selenium poisoning has occurred with either accidental or suicidal ingestion of gun bluing solution or sheep drench. This usually involves ingestion of grams of selenium and can cause severe gastrointestinal and neurological disturbance, acute respiratory distress syndrome, myocardial infarction (heart attack), and kidney failure.
Special Point
- The tolerable uptake level (TUL) of selenium is 400 micrograms per day. Dosages higher than this can cause toxicity.
- The daily recommended intake is 55 micrograms, which is usually provided by seafood, meat, and fortified grain products.
Last updated: September 29, 2012
abdominal (ab-DAH-mih-nul)
Having to do with the abdomen, which is the part of the body between the chest and the hips that contains the pancreas, stomach, intestines, liver, gallbladder, and other organs.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)absorption (ub-SORP-shun)
The process of taking nutrients from the digestive system into the blood so they can be used in the body.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)acute (uh-KYOOT)
Symptoms or signs that begin and worsen quickly; not chronic.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)aggressive (uh-GREH-siv)
In medicine, describes a tumor or disease that forms, grows, or spreads quickly. It may also describe treatment that is more severe or intense than usual.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)analysis (uh-NA-lih-sis)
A process in which anything complex is separated into simple or less complex parts.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)antioxidant (AN-tee-OK-sih-dent)
A substance that protects cells from the damage caused by free radicals (unstable molecules made by the process of oxidation during normal metabolism). Free radicals may play a part in cancer, heart disease, stroke, and other diseases of aging. Antioxidants include beta-carotene, lycopene, vitamins A, C, and E, and other natural and manufactured substances.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)appetite (A-peh-tite)
A desire to satisfy a physical or mental need, such as for food, sex, or adventure.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)arthritis (ar-THRY-tis)
A disease that causes inflammation and pain in the joints.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)baseline (BAYS-line)
An initial measurement that is taken at an early time point to represent a beginning condition, and is used for comparison over time to look for changes. For example, the size of a tumor will be measured before treatment (baseline) and then afterwards to see if the treatment had an effect.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)biological (BY-oh-LAH-jih-kul)
Pertaining to biology or to life and living things. In medicine, refers to a substance made from a living organism or its products. Biologicals may be used to prevent, diagnose, treat or relieve of symptoms of a disease. For example, antibodies, interleukins, and vaccines are biologicals. Biological also refers to parents and children who are related by blood.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)bladder (BLA-der)
The organ that stores urine.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)bladder cancer (BLA-der KAN-ser)
Cancer that forms in tissues of the bladder (the organ that stores urine). Most bladder cancers are transitional cell carcinomas (cancer that begins in cells that normally make up the inner lining of the bladder). Other types include squamous cell carcinoma (cancer that begins in thin, flat cells) and adenocarcinoma (cancer that begins in cells that make and release mucus and other fluids). The cells that form squamous cell carcinoma and adenocarcinoma develop in the inner lining of the bladder as a result of chronic irritation and inflammation.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)blood (blud)
A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)cancer (KAN-ser)
A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is a cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord. Also called malignancy.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)carcinoma (KAR-sih-NOH-muh)
Cancer that begins in the skin or in tissues that line or cover internal organs.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)cardiovascular (KAR-dee-oh-VAS-kyoo-ler)
Having to do with the heart and blood vessels.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)cell (sel)
The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)chemoprevention (KEE-moh-pree-VEN-shun)
The use of drugs, vitamins, or other agents to try to reduce the risk of, or delay the development or recurrence of, cancer.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)chemotherapy (KEE-moh-THAYR-uh-pee)
Treatment with drugs that kill cancer cells.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)clinical (KLIH-nih-kul)
Having to do with the examination and treatment of patients.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)clinical trial (KLIH-nih-kul TRY-ul)
A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called clinical study.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)dermatitis (DER-muh-TY-tis)
Inflammation of the skin.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)diabetes (dy-uh-BEE-teez)
Any of several diseases in which the kidneys make a large amount of urine. Diabetes usually refers to diabetes mellitus in which there is also a high level of glucose (a type of sugar) in the blood because the body does not make enough insulin or use it the way it should.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)diarrhea (dy-uh-REE-uh)
Frequent and watery bowel movements.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)diet (DY-et)
The things a person eats and drinks.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)distress (dih-STRESS)
Extreme mental or physical pain or suffering.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)DNA
The molecules inside cells that carry genetic information and pass it from one generation to the next. Also called deoxyribonucleic acid.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)element (EH-leh-ment)
A basic part of a whole. In chemistry, refers to a simple substance that cannot be broken down into smaller parts or changed into another substance. The basic part of an element is an atom, which contains protons, neutrons, and electrons. All atoms of an element have the same number of protons. Examples of elements are hydrogen, carbon, oxygen, nitrogen, and calcium.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)enzyme (EN-zime)
A protein that speeds up chemical reactions in the body.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)fatigue (fuh-TEEG)
A condition marked by extreme tiredness and inability to function due lack of energy. Fatigue may be acute or chronic.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)follow-up (FAH-loh-up)
Monitoring a person's health over time after treatment. This includes keeping track of the health of people who participate in a clinical study or clinical trial for a period of time, both during the study and after the study ends.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)garlic (GAR-lik)
A European plant that has a bulb used to flavor food. It has also been used in some cultures to treat certain medical conditions including high cholesterol, high blood pressure, infections, and cancer. The scientific name is .
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)gastrointestinal (GAS-troh-in-TES-tih-nul)
Refers to the stomach and intestines. Also called GI.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)glucose (GLOO-kose)
A type of sugar; the chief source of energy for living organisms.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)gram (gram)
A unit of weight in the metric system. One gram is equal to one thousandth of a kilogram and is approximately 30-times less than an ounce.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)hepatic (heh-PA-tik)
Refers to the liver.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)hormone (HOR-mone)
One of many chemicals made by glands in the body. Hormones circulate in the bloodstream and control the actions of certain cells or organs. Some hormones can also be made in the laboratory.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)human immunodeficiency virus (HYOO-mun IH-myoo-noh-dih-FIH-shun-see VY-rus)
The cause of acquired immunodeficiency syndrome (AIDS). Also called HIV.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)immune function (ih-MYOON FUNK-shun)
Production and action of cells that fight disease or infection.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)immune response (ih-MYOON reh-SPONTS)
The activity of the immune system against foreign substances (antigens).
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)immune system (ih-MYOON SIS-tem)
The complex group of organs and cells that defends the body against infections and other diseases.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)immunodeficiency (IH-myoo-noh-dih-FIH-shun-see)
The decreased ability of the body to fight infections and other diseases.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)incidence (IN-sih-dents)
The number of new cases of a disease diagnosed each year.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)inconclusive (IN-kun-KLOO-siv)
A negative test result in an individual where a clearly deleterious mutation has not been found in any family members. The genetic risk status of such an individual must be interpreted in the context of his or her personal and family history. Also called indeterminate and uninformative.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)ingestion (in-JES-chun)
Taking into the body by mouth.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)intervention (IN-ter-VEN-shun)
In medicine, a treatment or action taken to prevent or treat disease, or improve health in other ways.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)kidney (KID-nee)
One of a pair of organs in the abdomen. Kidneys remove waste from the blood (as urine), produce erythropoietin (a substance that stimulates red blood cell production), and play a role in blood pressure regulation.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)liver (LIH-ver)
A large organ located in the upper abdomen. The liver cleanses the blood and aids in digestion by secreting bile.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)lumen (LOO-men)
The cavity or channel within a tube or tubular organ such as a blood vessel or the intestine.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)lung (lung)
One of a pair of organs in the chest that supplies the body with oxygen, and removes carbon dioxide from the body.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)lymphedema (LIM-fuh-DEE-muh)
A condition in which extra lymph fluid builds up in tissues and causes swelling. It may occur in an arm or leg if lymph vessels are blocked, damaged, or removed by surgery.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)melanoma (MEH-luh-NOH-muh)
A form of cancer that begins in melanocytes (cells that make the pigment melanin). It may begin in a mole (skin melanoma), but can also begin in other pigmented tissues, such as in the eye or in the intestines.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)meta-analysis (meh-tuh-uh-NA-lih-sis)
A process that analyzes data from different studies done about the same subject. The results of a meta-analysis are usually stronger than the results of any study by itself.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)metabolism (meh-TA-buh-lih-zum)
The chemical changes that take place in a cell or an organism. These changes make energy and the materials cells and organisms need to grow, reproduce, and stay healthy. Metabolism also helps get rid of toxic substances.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)methylation (MEH-thuh-LAY-shun)
A chemical reaction in which a small molecule called a methyl group is added to other molecules. Methylation of proteins or nucleic acids may affect how they act in the body.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)neuropathy (noor-AH-puh-thee)
A nerve problem that causes pain, numbness, tingling, swelling, or muscle weakness in different parts of the body. It usually begins in the hands or feet and gets worse over time. Neuropathy may be caused by physical injury, infection, toxic substances, disease (such as cancer, diabetes, kidney failure, or malnutrition), or drugs, including anticancer drugs. Also called peripheral neuropathy.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)nutrition (noo-TRIH-shun)
The taking in and use of food and other nourishing material by the body. Nutrition is a 3-part process. First, food or drink is consumed. Second, the body breaks down the food or drink into nutrients. Third, the nutrients travel through the bloodstream to different parts of the body where they are used as "fuel" and for many other purposes. To give the body proper nutrition, a person has to eat and drink enough of the foods that contain key nutrients.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)odor (OH-der)
A smell.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)ovarian (oh-VAYR-ee-un)
Having to do with the ovaries, the female reproductive glands in which the ova (eggs) are formed. The ovaries are located in the pelvis, one on each side of the uterus.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)oxygen (OK-sih-jen)
A colorless, odorless gas. It is needed for animal and plant life. Oxygen that is breathed in enters the blood from the lungs and travels to the tissues.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)peripheral neuropathy (peh-RIH-feh-rul noor-AH-puh-thee)
A nerve problem that causes pain, numbness, tingling, swelling, or muscle weakness in different parts of the body. It usually begins in the hands or feet and gets worse over time. Peripheral neuropathy may be caused by physical injury, infection, toxic substances, disease (such as cancer, diabetes, kidney failure, or malnutrition), or drugs, including anticancer drugs. Also called neuropathy.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)plasma (PLAZ-muh)
The clear, yellowish, fluid part of the blood that carries the blood cells. The proteins that form blood clots are in plasma.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)prevention (pree-VEN-shun)
In medicine, action taken to decrease the chance of getting a disease or condition. For example, cancer prevention includes avoiding risk factors (such as smoking, obesity, lack of exercise, and radiation exposure) and increasing protective factors (such as getting regular physical activity, staying at a healthy weight, and having a healthy diet).
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)preventive (pree-VEN-tiv)
Used to prevent disease.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)progression (pruh-GREH-shun)
In medicine, the course of a disease, such as cancer, as it becomes worse or spreads in the body.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)prostate (PROS-tayt)
A gland in the male reproductive system. The prostate surrounds the part of the urethra (the tube that empties the bladder) just below the bladder, and produces a fluid that forms part of the semen.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)prostate cancer (PROS-tayt KAN-ser)
Cancer that forms in tissues of the prostate (a gland in the male reproductive system found below the bladder and in front of the rectum). Prostate cancer usually occurs in older men.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)radiation (RAY-dee-AY-shun)
Energy released in the form of particle or electromagnetic waves. Common sources of radiation include radon gas, cosmic rays from outer space, medical x-rays, and energy given off by a radioisotope (unstable form of a chemical element that releases radiation as it breaks down and becomes more stable).
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)radiation therapy (RAY-dee-AY-shun THAYR-uh-pee)
The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. Also called irradiation and radiotherapy.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)randomized
Describes an experiment or clinical trial in which animal or human subjects are assigned by chance to separate groups that compare different treatments.
(http://www.cancer.gov/dictionary)reduction (ree-DUK-shun)
A chemical reaction that takes place when a substance comes into contact with hydrogen or another reducing substance.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)renal failure (REE-nul FAYL-yer)
A condition in which the kidneys stop working and are not able to remove waste and extra water from the blood or keep body chemicals in balance. Acute or severe renal failure happens suddenly (for example, after an injury) and may be treated and cured. Chronic renal failure develops over many years, may be caused by conditions like high blood pressure or diabetes, and cannot be cured. Chronic renal failure may lead to total and long-lasting renal failure, called end-stage renal disease (ESRD). A person in ESRD needs dialysis (the process of cleaning the blood by passing it through a membrane or filter) or a kidney transplant. Also called kidney failure.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)rheumatoid arthritis (ROO-muh-TOYD ar-THRY-tis)
An autoimmune disease that causes pain, swelling, and stiffness in the joints, and may cause severe joint damage, loss of function, and disability. The disease may last from months to a lifetime, and symptoms may improve and worsen over time.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)selenium (seh-LEE-nee-um)
A mineral that is needed by the body to stay healthy. It is being studied in the prevention and treatment of some types of cancer. Selenium is a type of antioxidant.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)significant (sig-NIH-fih-kunt)
In statistics, describes a mathematical measure of difference between groups. The difference is said to be significant if it is greater than what might be expected to happen by chance alone. Also called statistically significant.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)skin cancer (skin KAN-ser)
Cancer that forms in the tissues of the skin. There are several types of skin cancer. Skin cancer that forms in melanocytes (skin cells that make pigment) is called melanoma. Skin cancer that forms in the lower part of the epidermis (the outer layer of the skin) is called basal cell carcinoma. Skin cancer that forms in squamous cells (flat cells that form the surface of the skin) is called squamous cell carcinoma. Skin cancer that forms in neuroendocrine cells (cells that release hormones in response to signals from the nervous system) is called neuroendocrine carcinoma of the skin. Most skin cancers form in older people on parts of the body exposed to the sun or in people who have weakened immune systems.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)soy (soy)
A product from a plant of Asian origin that produces beans used in many food products. Soy contains isoflavones (estrogen-like substances) that are being studied for the prevention of cancer, hot flashes that occur with menopause, and osteoporosis (loss of bone density). Soy in the diet may lower cholesterol levels and reduce the risk of heart disease. Also called Glycine max, soya, and soybean.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)stage (stayj)
The extent of a cancer in the body. Staging is usually based on the size of the tumor, whether lymph nodes contain cancer, and whether the cancer has spread from the original site to other parts of the body.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)supplementation (SUH-pleh-men-TAY-shun)
Adding nutrients to the diet.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)surgery (SER-juh-ree)
A procedure to remove or repair a part of the body or to find out whether disease is present. An operation.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)syndrome (SIN-drome)
A set of symptoms or conditions that occur together and suggest the presence of a certain disease or an increased chance of developing the disease.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)therapy (THAYR-uh-pee)
Treatment.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)thyroid (THY-royd)
A gland located beneath the larynx (voice box) that makes thyroid hormone and calcitonin. The thyroid helps regulate growth and metabolism. Also called thyroid gland.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)tissue (TIH-shoo)
A group or layer of cells that work together to perform a specific function.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)toxicity (tok-SIH-sih-tee)
The extent to which something is poisonous or harmful.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)urine (YOOR-in)
Fluid containing water and waste products. Urine is made by the kidneys, stored in the bladder, and leaves the body through the urethra.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)viral (VY-rul)
Having to do with a virus.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)vitamin (VY-tuh-min)
A nutrient that the body needs in small amounts to function and stay healthy. Sources of vitamins are plant and animal food products and dietary supplements. Some vitamins are made in the human body from food products. Vitamins are either fat-soluble (can dissolve in fats and oils) or water-soluble (can dissolve in water). Excess fat-soluble vitamins are stored in the body’s fatty tissue, but excess water-soluble vitamins are removed in the urine. Examples are vitamin A, vitamin C, and vitamin E.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)vitamin C (VY-tuh-min…)
A nutrient that the body needs in small amounts to function and stay healthy. Vitamin C helps fight infections, heal wounds, and keep tissues healthy. It is an antioxidant that helps prevent cell damage caused by free radicals (highly reactive chemicals). Vitamin C is found in all fruits and vegetables, especially citrus fruits, strawberries, cantaloupe, green peppers, tomatoes, broccoli, leafy greens, and potatoes. It is water-soluble (can dissolve in water) and must be taken in every day. Vitamin C is being studied in the prevention and treatment of some types of cancer. Also called ascorbic acid.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)vitamin E (VY-tuh-min ...)
A nutrient that the body needs in small amounts to stay healthy and work the way it should. It is fat-soluble (can dissolve in fats and oils) and is found in seeds, nuts, leafy green vegetables, and vegetable oils. Vitamin E boosts the immune system and helps keep blood clots from forming. It also helps prevent cell damage caused by free radicals (highly reactive chemicals). Vitamin E is being studied in the prevention and treatment of some types of cancer. It is a type of antioxidant. Also called alpha-tocopherol.
Source: The National Cancer Institute's Dictionary of Cancer Terms
(http://www.cancer.gov/dictionary)
