Selenium deficiency is a global problem that increases the risk of serious and common diseases

Lack of selenium, an essential trace element, may cause thyroid disorders, cardiovascular disease, virus infections, AIDS, infertility, neurological disturbances, and cancer. An estimated one billion people worldwide are selenium-deficient. This is mainly a result of nutrient-depleted soil, which is a real problem in places like Europe. For decades, scientists have been warning about this problem, and a lot suggests that we need more than the officially recommended intake to protect ourselves effectively against disease, according to a review article published in StatPearls.

Ever since selenium was first discovered in 1817, its importance for human health has been mapped out by scientists. It was first believed that selenium was simply a toxic metal, but researchers have discovered that it is actually an essential trace element, which we need in the right doses every day throughout life.
Selenium supports around 35 different selenium-dependent proteins that have different physiological functions. Selenium is also an element of the important GPX antioxidants that protect our cells, DNA and cardiovascular system. We need an adequate supply of selenium from food or from supplements in order to prevent a host of diseases and maintain proper health.

Why is selenium deficiency so common now?

Selenium, like all other minerals, is found in the soil. The amount of selenium in the soil determines how much selenium plants absorb, and that affects the entire food chain. Brazil nuts, seeds, grains, green vegetables, and shiitake mushrooms are good sources, provided that these foods have grown in selenium-rich soil. For that reason, American grain and American flour contain a lot more selenium than grain grown in Europe.
Likewise, egg yolk, offal, fish and shellfish are considered good selenium sources, but seafood (especially tuna and other types of fish from the top part of the food chain) also contain mercury, which makes these sources less useful. The reason is that selenium reacts with mercury and forms an inert compound called mercury selenide, which is harmless but sequesters selenium in the seafood that would normally be needed to support vital selenoproteins in the body. Exposure to toxic levels of mercury therefore increase the body’s need for selenium as a source of protection.
Selenium deficiencies typically occur in parts of the world where the soil is low in selenium. An estimated 500 million to one billion people worldwide get too little selenium from their diets. Severe selenium deficiencies have been documented in China, New Zealand, and Finland.
Health authorities in Denmark have not yet pointed to selenium deficiencies, but scientists such as the British professor, Margaret Rayman, have been warning about the problem for decades. According to Rayman, selenium deficiency contributes to a number of commonly occurring and serious diseases in our part of the world.

Cardiovascular disease and the need for selenium-enrichment of fertilizers

In the Keshan province of the northeast part of China, where the soil is critically low in selenium, scientists observed a lethal heart disease, which they named Keshan disease. The disease was caused by an otherwise harmless virus called the Coxsackie virus, which the immune defense is unable to defeat if it lacks selenium. Keshan disease leads to an enlargement of the heart and a risk of cardiac death. As far back as 1965, the Chinese population in that particular region started preventing and eradicating the disease with supplements of selenium. The soil in Finland also contains very little selenium, and blood samples have revealed extremely low selenium levels in the Finnish population. Because there used to be a high rate of cardiovascular disease in Finland, and because of the fear of conditions similar to those observed in the Keshan province, the Finnish government in 1984 introduced mandatory selenium-enrichment of all fertilizers. As a result of this, selenium levels in the soil and in the food chain increased markedly, and so did the selenium levels in the blood of the Finns.
Numerous studies conducted over the past decades have shown that selenium deficiency increases the risk of blood clots and cardiac death and that selenium supplements strengthen the heart and protect against atherosclerosis.
In the groundbreaking Swedish KiSel-10 study, where a group of older but healthy people took daily supplements of selenium yeast and Q10, the rate of cardiovascular death was reduced by over 50 percent compared with the control group that took a placebo (dummy pills). Follow-up studies after 10 and 12 years showed a continued positive effect among those, who took selenium and Q10.

Thyroid disorders

The thyroid gland produces two different thyroid hormones. There is T3 that contains three iodine atoms and is the active hormone, while T4 with four iodine atoms is the passive hormone. In order to activate the metabolism in the body’s different tissues, a group of selenoproteins called deiodinases remove an iodine atom from T4, whereby it is converted into active T3.
The selenium-dependent GPX antioxidants also protect the thyroid gland against inflammation caused by oxidative stress. An estimated 500,000 Danes suffer from Hashimoto’s disease that causes the metabolic rate to slow down. The disease is insidious and typically affects women.
Many people in T4 hormone therapy feel increasingly worse. A large Danish placebo-controlled study is currently looking into whether selenium supplementation of 500 patients for a 12-month period has a positive effect on their quality of life.
Earlier studies have shown that supplementation with 100-200 micrograms of selenium has a positive effect on the inflammation that occurs in Hashimoto’s disease and Graves’ disease (that causes hyperthyroidism).

The immune defense

Different selenoproteins can activate the immune defense and counteract undesirable inflammation. They are also able to prevent influenza, cold virus, herpes, HIV, and other types of RNA virus from mutating and deceiving the immune defense. As mentioned earlier, a selenium deficiency may cause normally harmless viruses to develop into life-threatening diseases like Keshan disease. Not surprisingly, new flu strains often originate from selenium-deprived parts of China where virus can more easily mutate in animals and humans and spread to the rest of the globe with infected carriers.
Being selenium-deficient is particularly critical if you have contracted HIV. Several studies of AIDS patients have shown a link between lack of selenium and lack of T helper cells.
Selenium supplementation can prevent HIV from turning into AIDS. Selenium is also vital for preventing patients with hepatitis B or C from getting worse.
The immune defense generally needs selenium to help it attack swiftly and effectively.

Cancer

GPXs are powerful antioxidants that protect cells and their DNA and mitochondria against free radicals and oxidative damage. Other selenium-containing proteins stimulate the immune defense, counteract inflammation, neutralize mercury and other environmental toxins, and help diseased cells to self-destruct (apoptosis).
These are all mechanisms that protect healthy cells against cancerous compounds and uncontrolled cell division.
In 1996, Professor Larry Clark, an American cancer researcher, documented in his NPC Study (Nutritional Prevention of Cancer) that supplementation with selenium yeast that contains a variety of organic selenium compounds could lower the risk of several common cancer forms by around 50 percent.
Later, in the so-called SELECT Trial, scientists tested supplements of selenomethionine and synthetic vitamin E but failed to demonstrate an effect. Because they used a single selenium compound (and not selenium yeast), it does not make sense to use this study as leverage for discouraging people from taking selenium. It would be much more prudent to recommend selenium yeast.
Cancer may take years to develop, and scientists have observed selenium deficiency in women several years before their cancer was diagnosed.
Supplementation with selenium yeast may therefore be relevant for long-term prevention of different cancer forms, especially in those parts of the world where the selenium content in the soil is low and deficiencies are common.

Neurological disorders

Studies have shown that selenium deficiency may lead to depression and other neurological disorders. Even if a person lacks selenium, the brain continues to receive relatively much selenium, which is a sign of how important the mineral is for brain health.
Lack of selenium may result in a deficiency of certain neurotransmitters. In patients with Alzheimer’s disease, for example, scientists have found selenium concentrations that were only 60% of the concentrations found in healthy controls.
A team of scientists from München has mapped out the specific mechanisms by which the selenium-containing GPX antioxidants protect neurons in the brain against cell death.

Male and female fertility

When a sperm cell wiggles ferociously to swim to the egg and fertilize it, the sperm cell needs specific selenoproteins in its tail piece for propulsion. These selenium-containing GPXs also serve as antioxidants that protect sperm cell DNA. Too little selenium leaves the sperm cells vulnerable to something called DNA fragmentation, which means that even if a sperm cell manages to fertilize the egg, the egg may not develop properly and ends up being rejected by the body.
Selenium stimulates the formation of sperm cells and protects the genetic coding. Selenium is also vital for a normal menstrual cycle and a normal pregnancy. Taking a daily supplement with 100 micrograms of selenium yeast from the first trimester until delivery may help lower by a third the risk of a ruptured fetal membrane. This was documented in a placebo-controlled study that is published in Journal of Obstetrics and Gynaecology.
The study also shows that pregnant women who take supplements of selenium yeast have a lower rate of preeclampsia, which is the leading cause of preterm delivery. Preeclampsia may also lead to life-threatening eclampsia.
There is a lot to suggest that selenium has a protective and supportive effect in pregnancy. Scientists point to circulatory effects in the placenta, the fact that selenium is a powerful antioxidant, and that selenium counteracts inflammation.

Muscle and skeletal diseases

In 1988, another serious selenium deficiency disease seen in combination with iodine deficiency was observed in China. It was named Kashin-Beck Disease and was seen to stunt growth in children and result in deformed joints and bones. The disease is also found in selenium-deprived areas of Tibet, Siberia, and North Korea. Moderate selenium deficiency may result in sarcopenia (loss of muscle mass and strength), according to an Italian study. Older people have a higher risk, as they already have a tendency to lose muscle mass with age.

Official recommendations and optimal intake levels

The recommended intake level (RI) for selenium in Europe is 50-70 micrograms daily, and most people fail to get that much from their diets. Several studies suggest that we need around 90-100 micrograms of selenium or more daily in order to saturate selenoprotein P, which is used ad a marker for the body’s selenium status.
In many studies that are conducted with e.g. patients with metabolic disorders and cancer, scientists have used doses of around 200 micrograms per day.
The European Food Safety Authority (EFSA) has set the upper safe limit for selenium at 300 micrograms daily, while WHO has set the limit at 400 micrograms daily.

References

Aparna Shreenath. Selenium Deficiency. StatPearls. May 6, 2019

Aparna P. Shreenath; Jennifer Dooley. Selenium, Deficiency. NCBI October 27, 2018

Nicolas V.C. Ralston, Laurs J. Raymund. Mercury’s neurotoxicity is characterized by its disruption of selenium biochemistry. Elsevier

Jones GD et al. Selenium deficiency risk predicted to increase under future climate change. Proceedings of the National Academy of Sciences 2017

Margaret P Rayman. Selenium and human health. The Lancet. 2012

Hashimoto’s thyroiditis – den oversete folkesygdom. OUH, Odense Univesitetshospital 2018

Alehagen U, et al. Cardiovascular mortality and N-Terminal-proBNP reduced after combined selenium and coenzyme Q10 supplementation. Int J Cardiol. 2012.

HERMHOLZ ZENTRUM MUNCHEN – GERMAN RESEARCH CENTER FOR ENVIROMENTAL HEALTH. Selenium protects a specific type of interneurons in the brain. EurekAlert 2017

Lasse Foghsgaard. Mysteriet om for tidlig fødsel er kommet nærmere en opklaring. Politiken 07- 09-2017
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Jefferys Amanda et al. Thyroid dysfunction and reproductive health. The Obstetrician & Gynaecologist. 2015

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Pernille Lund. Har du problemer med stofskiftet? Ny Videnskab 2015