Selenium is a trace mineral, an element on the periodic table close to sulphur. It was discovered 200 years ago by Swedish chemists refining industrial ore. It’s most important role is forming two key enzymes; one of which makes thyroid hormone functional, the other is a vital free-radical quenching enzyme. It was found to be essential for mammalian life in 1957.
Selenium has finally emerged from obscurity. It was not widely known or discussed as a supplement and often the only mention of it was as a caution against its likely toxicity. Except in some circles, where its benefit in managing cancer had generated some interest – although which form to use and safe dosages were uncertain.
Selenium is alkaline-forming and important for many reasons. This amazing mineral helps growth of centres in the brain that lead to its development. It has important mental and spiritual effects on human beings, along with silica it can displace heavier minerals from certain areas of the brain, assisting reasoning and more refined emotional expression including the higher emotions of compassion, peacefulness and joy.
Forms of Selenium
The mineral form of supplemental selenium is sodium selenite. The common organic supplemental form in Australia is selenomethionine. Both are safe and well absorbed.
Other organic forms of Selenium are found in food, they are called the selenoproteins and there is at least a dozen of them, for example selenodiglutathione, methylselenol, selenocysteine and methylselenocysteine.
The TGA (Therapeutic Goods Administration) controls the sale of selenium; most registered supplements contain selenomethione. It may be available at a pharmacy or healthfood shop; however natural health practitioners should be able to supply it, usually as liquid to be used in drop doses or as a tablet.
Because there are so many different selenium based enzymes with a such wide range of significant benefits it is no doubt best to supplement both the organic (food) and the mineral forms of selenium.
Global Distribution of Selenium
Is there enough in food?
Humans absorb selenium primarily through plant-based foodstuffs. But even in plants, the selenium content varies greatly according to where they grow.
The amount of selenium in food depends on the soil content of the mineral, this depends on the amount of organic material, the soil condition and the soil moisture. So soil selenium concentration is affected by rainfall, arid regions tend to have less.
In most parts of the USA, selenium levels in soil tend to be relatively high (northern Nebraska and the Dakotas have soil that is especially high in selenium). However, in other areas such as China, Russia, Australia, New Zealand and Europe, soil levels of selenium tend to be much lower, and if you eat food primarily grown in these areas, a high-quality selenium supplement may be beneficial.
If you live in one of these areas and focus your diet on locally grown foods, you may be low in selenium. You may also have low levels of selenium if you smoke cigarettes, drink alcohol, have had weight loss surgery or have Crohn’s disease or ulcerative colitis.
The best food source is Brazil nuts; each nut kernel contains about 90 µg selenium!
The unit of measure for selenium is the microgram. 1 gram has 1000 milligrams (mg); 1 milligram has 1000 micrograms (µg or mcg). So for example, 500 microgram is 1/2 a milligram
Any multivitamin containing selenium used to carry a TGA warning that daily doses above 50 µg from all sources were not to be exceeded; this has recently been revised upward to 150 µg.
The National Health and Medical Research Council (NH&MRC) published Nutrient Reference Values for selenium in 2006 which carried excellent guidelines for selenium use, however this extract is no longer available on their website. You may view and download this document below
The NH&MRC guidelines set the dose for an adult from 250 to 400 µg daily. The daily dose for a young child could be up to 50 µg, primary school ages up to 150 µg, adolescents could use adult doses.
Take it once daily with water, anytime.
Numerous trials showing benefit of selenium in cancer management have used doses of 200 and 250 µg. Many people have used doses of 1000 µg long term with no visible effects apart from vibrant health, although there is evidence that daily dosage of 5000 µg and more over some years may lead to hair loss and irreversible thickening of finger and toe nails.
It’s readily apparent that eating a handful of Brazil nuts would provide a very high dose, maybe one day they’ll carry a warning label or be involved in a health scare!
However, there’s nothing to gain from large doses, caution is advised. High amounts serve no useful purpose and the extra would only displace other needed minerals from the body. Acute overdose may be very dangerous. See “Selenium Toxicity” below.
The most important role of selenium is the body’s best antioxidant as part of glutathione peroxidase (GPx).
Glutathione peroxidases, also known as selenoproteins, are a family of antioxidant enzymes that speed up the reaction between glutathione and free radicals, particularly converting toxic hydrogen peroxide to harmless water. These enzymes maximize antioxidant protection both inside and outside the cells; particularly in the thyroid and the inner lining of the mitochondria.
In cases of selenium deficiency and with the resulting impaired function of glutathione peroxidases destructive hydrogen peroxide breaks down into even more dangerous hydroxyl radicals which damage cell membranes and cell DNA eventually leading to serious disease. Selenium is directly involved in preservation of cell membrane integrity and DNA integrity. It is this free radical quenching function which makes selenium such a potent anti-cancer mineral.
GPx prevents lipids and fats from being peroxidized (oxidized), which literally means that it prevents fats from going rancid (this can be seen on your skin as “age spots” or “liver spots”, autopsies show that skin “liver spots” are accompanied by similar spots of peroxidized fats in the liver.) Therefore selenium protects all of the cellular membranes, which are made up of fats, from peroxidation. Peroxidation of cellular membranes reduces the ability of the membrane to pass nutrients including minerals and vitamins, so selenium deficiency is the first step toward developing the many problems caused by nutrient deficiencies.
A selenium deficiency combined with high intake of vegetable oils (salad dressings, margarine, polyunsaturated cooking oils) may be a quick route to a heart attack and cancer. The body uses a lot of selenium trying to protect the fats from peroxidation.
Role in thyroid hormone
The thyroid is a master gland, controlling oxygen use and the basal metabolic rate, cellular metabolism and growth and development. Low thyroid function (hypothyroidism) is becoming an epidemic, principally due to a chronic deficiency of iodine exacerbated by chlorine and fluorine intake.
Selenium (along with iodine) is crucial to thyroid function in two ways. One is to quench the free radicals generated whilst producing thyroid hormone, the other is to provide the enzyme which controls the activation/inactivation of thyroid hormone.
Gross selenium deficiency is problematic for the thyroid because the metabolism of thyroid hormone creates the dangerous free radical hydrogen peroxide (H2O2) as a by-product, which can cause oxidative damage if a lack of selenium prevents GPx from being able to protect the cells (a possible cause of Hashimoto’s disease). Hydrogen peroxide is promptly neutralized if adequate GPx is available.
Selenium deficiency is one of the main reasons iodine supplementation has acquired a bad reputation.
However supplementing selenium if iodine is deficient causes another problem.
The selenium dependent enzyme which controls thyroid hormone is iodothyronine deiodinase. Supplementing selenium if iodine is deficient allows constant conversion/degradation of existing thyroid hormone to its active form causing depletion of thyroid hormone as well as the thyroid gland, leading to a worsening of hypothyroidism.
Immune function and retro-viruses
Selenium has a powerful ability to support immune function, especially with regard to viral and bacterial infection. It has been shown repeatedly that serum selenium levels are linked directly to immune system function, including CD4 T lymphocyte count.
Apart from its proven benefit in preventing and treating cancer, the most astonishing benefit of selenium is its ability to interfere with the replication of the HIV virus, thus preventing the progression to AIDS.
Many viruses have a long life inside the body, including the herpes simplex virus, cytomegalovirus, varicella zoster virus, and Epstein-Barr virus. These viruses do not usually cause progressive diseases that worsen over time, but are held in check by a protective immune response. However, disease outbreaks can occur when the immune system is depressed, which may be seen in intermittent herpes simplex infections and in the shingles suffered by the elderly who had chickenpox as children.
The decline in serum selenium levels that accompanies viral or bacterial infection results in some degree of immune system depression. However some pathogens, including certain retroviruses, effectively elude the immune system’s defence mechanisms and can continue to replicate indefinitely. Of particular significance are those viruses such as Coxsackievirus B3, Hepatitis C virus, and HIV-1 which encode glutathione peroxidase and, therefore, continue to deplete their hosts’ selenium.
This depletion of the selenium stores reduces the body’s ability to produce the CD4 T lymphocytes which require this compound, allowing opportunistic infections to thrive, further depressing serum selenium levels which allows high replication rates for HIV. Also depleted are the amino acids glutamine (vital for the health of the lining of the gut), tryptophan (building block for serotonin in the brain) and cysteine (the main component of glutathione).
Once this process has begun it accelerates; because AIDS defining infections increase selenium depletion, and because HIV itself encodes selenium and glutathione. A positive feedback loop that allows Kaposi’s sarcoma, tuberculosis, typhoid, syphilis, pneumonia, and various other AIDS-related diseases to flourish.
Adequate body selenium levels are shown to prevent the slide from HIV infection to AIDS. In fact, this link is so strong it was used as the method to determine soil selenium levels across the African continent. Senegal has been blessed by an ancient geographical history which has left the land selenium rich. Prostitution flourishes in the capital city Dakar, which attracts visitors from the Arab world, yet this nation has extremely low rates of AIDS, despite a liberal attitude to sex. It also has low rates of cancer.
A link between elevated mortality from AIDS and depressed environmental selenium has been confirmed in the continental United States. Selenium concentrations in US soils had been established on the basis of this element’s level in local alfalfa; it has been shown that an inverse relationship exists between local selenium levels and the death rates from AIDS. This relationship was particularly obvious amongst African Americans, apparently because they tended to be less mobile and more likely to eat locally grown foods.
So be sure to include the selenium rich foods such as Brazil nuts, tuna, mackerel, selenium yeast and crab in your diet; if the soil is rich enough, beef, lamb, eggs, poultry and garlic will have useful amounts.
And visit your natural health practitioner for a good selenium supplement!
Selenium poisoning is a rare event, usually inside a toxic industry or the result of agricultural/land-form runoff being concentrated in wetlands.
Overdosing selenium can be fatal and long term high dosing will cause serious health problems.
Fortunately an overdose of a nutritional supplement would have to be quite large to cause concerns; if for example a child was to consume the entire contents of a prescribed bottle of pills or liquid it would be unlikely to cause serious problems. However a call to the Poisons Information Centre in your state is advised; they have 24 hour hotlines.
Two examples of actual high doses give some perspective.
For a 70 kg adult to receive the same as a farmer uses to drench a sheep the amount would be 7,000 micrograms in a single dose.
A case of acute poisoning in the USA was reported in the February 8th, 2010 issue of the Archive of Internal Medicine, where a dietary supplement containing 200 times the concentration listed on the label affected over 200 persons across 10 states. The actual daily dose was 42,000 micrograms. Symptoms began to appear within two weeks; diarrhea (78%), fatigue (75%), hair loss (72%), joint pain (70%), nail discolouration or brittleness (61%) and nausea (58%). Symptoms persisting for 90 days or longer included fingernail discolouration and loss (52% of cases), fatigue (35%) and hair loss (29%). One person was hospitalized.
Nation Health & Medical Research Council (NH&MRC) – Selenium Dosage Recommendations