Disclaimer: Consult with a doctor before deciding on a treatment plan for cancer or any other disease.
Selenium deficiency has been earmarked as a possible causative agent behind the development of cancer by a number of studies. Adequate selenium levels have an inhibitory effect on cancer growth in part because selenium has the capacity to remove heavy metals from the body. It should be taken in tandem with vitamin E.
Selenium has been extensively researched in terms of its effects on cancer. Studies have shown time and again that adequate selenium levels inhibit cancer growth . Signs and symptoms of selenium deficiency include:
- Cardiomyopathy (Keshan disease – this disease occurs when individuals are exposed to the coxsackie virus when they are selenium deficient)
- Increased risk of mortality
- Poor immune function
- Cognitive decline
- Adverse mood states 
Selenium binds to heavy metals such as mercury and cadmium which are then excreted from the body. As such, selenium can help the body cope with heavy metals, but unfortunately, when the heavy metals are excreted from the body selenium is excreted along with it. Mercury and selenium bind in a 1:1 relationship. So for patients with high levels of heavy metals in the body, it may be hard to deliver selenium to the parts of the body that need it most . Heavy metal poisoning which can result from a variety of causes including from the gassing off of mercury amalgam dental fillings, can lead to a selenium deficiency which may then contribute to the development of cancer.
When the body has adequate selenium levels, the selenium is able to function in the following ways:
- Promotes a healthy immune system
- Helps in the production of active thyroid hormone
- Wards off viral infections in the body
- Promotes reproductive capacity and the production of normal sperm cells
- Scavenges for free-radicals and protects cells
- Inhibits cancer growth
- Supports healthy hair and nails
- Supports normal thyroid function
- Supports the production of glutathione peroxidase (an important enzyme with anti-oxidant properties) 
Selenium is an important component of a number of essential enzymes in the body but it is also an important component of the body’s structure .
The most important political debate about selenium over the past 20 years has primarily centered around whether or not the recommended daily allowance of selenium should be increased or kept the same. Despite compelling research showing that adequate levels of selenium can inhibit cancer growth, the lack of a known selenium deficiency disease has been used to argue against the need for an increase in the recommended daily allowance .
Over the past 25 years, the average daily selenium intake has been dramatically reduced as a result of lowered food quality. A quarter of a century ago, people consumed an average of 60 micrograms of selenium per day. Today, the average is 35 micrograms. Additionally, people are exposed to more toxicities in the environment which means that the minimum daily intake should be higher. The United Kingdom has elevated their recommended selenium intake to 75 micrograms per day to account for the increased toxicities and diminished food quality .
Out of 55 studies that were completed after 1949, 49 of them demonstrated that selenium inhibited cancer. Despite the substantial research supporting the role of selenium in preventing and inhibiting cancer growth, the FDA has decreed that the evidence is limited and inconclusive. .
Over the past 20 years, selenium research has been focused on the question of whether recommended daily allowances should be increased with some scientists arguing against others for increasing the daily allowance. Much of the dialectic regarding the recommended daily allowance of selenium focuses on its demonstrated value in preventing and inhibiting cancer as well as other diseases. Combs argues that if a nutrient such as selenium can reduce the risk of chronic disease, then it should be recommended for inclusion in adequate amounts in the diet, because such a nutrient is vital in maintaining good health . Other researchers have argued that the recommended daily allowance does not need to be amended even though, according to numerous studies, increasing the daily allowance of selenium could help prevent and treat cancer. Researchers arguing against the increased recommended allowance say that because there is no officially recognized deficiency syndrome associated with selenium deficiency, it’s recommended daily allowance should not be increased .
Safety and Effectiveness
Selenium is a trace mineral that should be taken in adequate quantities in tandem with vitamin E. It is not a supplement that should be taken in mega-doses however because it’s beneficial value is reduced if the body is inundated with too much selenium. Indeed, patients who take too much selenium can develop selenosis .
How Selenium Therapy Is Administered
Selenium may be taken by mouth or delivered by a health professional via blood infusion as sodium selenite .
Selenium Administration via Blood Infusion
When sodium selenite is delivered via infusion, it is given in high doses at 4,000 micrograms selenium on the first day and 1,000 micrograms on days 2 through 9.
Oral Selenium Administration
There are two forms of selenium available for oral supplementation:
- Selenomethionine – the body can convert selenomethionine to selenocysteine as needed.
- Selenocysteine 
Organic selenium supplements are more bio-available than inorganic supplements .
Possible Negative Effects
Abnormally low and abnormally high levels of selenium can both adversely affect health. Selenium is not a supplement to take in mega-doses! And supplementation with selenium may only confer benefits when the patient’s overall nutrient intake is adequate. People who already have adequate selenium intake who take selenium supplements could increase their risk of developing type II diabetes. Very high levels of selenium can cause selenosis which affects the liver, skin, hair, and nails. Selenosis can also cause neurological damage as well as alopecia .
Other Important Information
SelenoPrecise Selenium Supplements
SelenoPrecise is a brand recommended by Dr. Marc Sircus as one of the most bio-available selenium supplements on the market. These supplements can be purchased at:
 Sircus, M. (2014). Treatment Essentials: Practicing Natural Allopathic Medicine: Kindle Edition. IMVA Publications.
 Pharma Nord (n.d.). What Is SelenoPrecise? Retrieved May 29, 2018 from https://www.pharmanord.com/us-products/selenoprecise
 Willett, W. C. & Stampfer, M. J. (1988). Selenium and Cancer. Retrieved May 29, 2018 from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1834550/?page=1
 Dr. Axe (2018). Selenium Signs of Deficiency and Foods. Retrieved May 29, 2018 from https://draxe.com/selenium-benefits/
 Rayman, M. P. (2012). Selenium and Human Health. Retrieved May 29, 2018 from https://www.ncbi.nlm.nih.gov/pubmed/22381456
 Rayman, M. P. (2002). The argument for increasing selenium intake. Retrieved May 29, 2018 https://www.ncbi.nlm.nih.gov/pubmed/12133202
 Combs, G. F. Jr. (2001). Impact of selenium and cancer-prevention findings on the nutrition-health paradigm. Retrieved May 29, 2018 from https://www.ncbi.nlm.nih.gov/pubmed/11799925
 Burk, R. F. (2002). Selenium, an antioxidant nutrient. Retrieved May 29, 2018 from https://www.ncbi.nlm.nih.gov/pubmed/12134713
 Alexander, J. (2007). Selenium. Retrieved May 29, 2018 from https://www.ncbi.nlm.nih.gov/pubmed/17913229
 Tremblay, S. (2018). Results of Too Much Selenium. Retrieved May 29, 2018 from http://healthyeating.sfgate.com/results-much-selenium-6772.html
 Subramanian, S., Namasivayam, B., Rais, V., Ponniah, T. (2012). Paradise Nut Paradox: Alopecia Due to Selenosis from a Nutritional Therapy.Retrieved May 29, 2018 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3681114/