In recent years there has been much interest in selenium and its role in nutrition. As Europe has seen a sharp decline in selenium intakes [1], there is strong concern that marginal deficiencies may increase the risk of chronic diseases such as cancer and heart disease.

The powerful antioxidant trace element selenium, prevents and helps to treat a variety of serious conditions such as depression, anxiety, thyroid dysfunctions, deficiencies and problems of the immune system, asthma, psoriasis, rheumatoid arthritis, cataracts, polycystic ovaries, liver damage, heart disease, cancer, AIDS.

What is Selenium

Selenium is a trace element essential for health but necessary only in small amounts. Selenium is incorporated into proteins called selenoproteins, which are important antioxidant enzymes.

The antioxidant properties of these proteins help prevent the destruction of cells by free radicals.

Radicals are natural by-products of oxygen metabolism that can contribute to chronic diseases such as cancer and heart disease.

These proteins also help regulate thyroid function and play an important role in the immune system. Its antioxidant action is enhanced when combined with vitamin E.

– Bohr model of selenium: Source: Signal Garden

Selenium Sources

Selenium is found in the soil, concentrated in plants and, in this way, passes through the food chain and is found in most foods.

Very good sources of selenium are

nuts (especially Brazil nuts),
fish (sardines),
seafood,
offal (kidneys and liver)
meat
Whole grains
sunflower seeds
brown rice
onions Cereals

European soil is relatively poor in selenium compared to other regions such as America, Canada and China.

Recommended Daily Intake

Recommended daily intakes for selenium (μg/day)

Despite the small amount of selenium needed by the human body, it is estimated that half to one billion people in the world are selenium deficient. [2]

A pack of canned sardines — – Sardines are a very good source of Selenium

According to UK’s NHS, the minimum recommended intake for adults through diet is 75 micrograms (μg) for men and 65 μg for women. [3]

On the other hand, overloading the body with selenium (of 400 micrograms per day) has been linked to an increased risk of diabetes. [4]

However, it is practically impossible to meet this amount through diet, especially for those who consume mainly processed foods, since selenium is destroyed during food processing.

Recommended daily intakes for selenium (mg/day)

Age	(μg/day)
0-3 months	10
4-6 months	10
7-9 months	15
10-12 months	15
1-3 years	20
4-6 years	20
7-10 years	30
Men
11-14 years	40
15-18 years	50
19-50+ years	75
Women
11-14 years	45
15-18 years	50
19-50+ years	60
Pregnancy	65
Breastfeeding	75

Selenium levels in the body can be determined by means of a blood test or urine analysis.

Selenium Health Benefits

Selenium, offers a range of benefits, from boosting your immune system to improving your cognitive function. Here are some of the most important health benefits of selenium.

Acts as a powerful antioxidant – If we lead an “intense” lifestyle, including late nights, smoking, alcohol, and increased stress, then the number of free radicals in our body increases.

The older we get, the more difficult it is to “deal” with free radicals, which cause oxidative stress, which has been linked at times to many chronic diseases (diabetes, cardiovascular disease, nervous system diseases, etc.) and premature ageing.

Selenium, as a powerful antioxidant, neutralizes excess free radicals and protects cells from potential damage due to oxidative stress.

Strengthens our immune system – There is evidence that selenium supports the proper functioning of our immune system. In fact, it seems that higher levels of selenium can strengthen the immune system of people suffering from some chronic diseases, as well as more “simple” ones, such as the flu. [5]

Helps prevent mental deterioration – Oxidative stress has been linked to both the onset and progression of neurological diseases such as Parkinson’s and Alzheimer’s. Some studies even suggest that antioxidant intake, either through diet or supplementation, improves memory in Alzheimer’s patients.

Protects against heart disease – A selenium-rich diet promotes heart health by counteracting oxidative stress and inflammation in the body, which, in turn, are associated with cardiovascular disease. [6]

It is important for thyroid health – The thyroid gland secretes very small amounts of the biologically active hormone triiodothyronine or T3 and large amounts of an inactive form of the hormone thyroxine or T4 into the circulation.

Most of the biologically active T3 in the circulation and inside cells is created by the removal of an iodine atom from T4 in a reaction catalyzed by the selenium-dependent enzymes, iodothyronine deiodinases.

Through their actions on T3, T4, and other thyroid hormone metabolites, three different selenium-dependent iodothyronine deiodinases (types I, II, and III) can both activate and inactivate thyroid hormone, making selenium an essential element for normal growth, development, and metabolism through the regulation of thyroid hormones.

May help prevent serious diseases – In a review of related studies, a high level of selenium in the blood was associated with a lower risk of certain types of cancer, including breast, lung, colon and prostate cancers. [7]

Helps reduce asthma symptoms – Asthma is a chronic disease that affects the ducts that carry air in and out of the lungs, with symptoms such as wheezing, shortness of breath, chest tightness and coughing. Asthma has been linked to increased levels of oxidative stress and inflammation in the body. Selenium, as a powerful antioxidant, benefits asthma sufferers by helping to reduce the symptoms of the condition. [8]

Male fertility – Selenium is associated with successful reproduction, as its deficiency has been associated with premature miscarriages. It is also essential for male fertility required for testosterone biosynthesis, formation and normal spermatozoa development. [9]

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Selenium Deficiency?

The most common symptoms of selenium deficiency are brittle nails and thinning hair. Other symptoms include gastrointestinal upset, skin rashes, fatigue, irritability and nervous system disorders.

Some of the most important include:

Psychological stress – Inadequate selenium intake results in reduced glutathione peroxidase activity. Even very high selenium deficiency usually does not result in obvious clinical conditions. However, individuals who are selenium deficient are more vulnerable to additional psychological stress. [9]

Hypothyroidism and weakened immune system – Selenium deficiency in humans is most evident in China, where the soil selenium concentration is very low. There is evidence to suggest that selenium deficiency may contribute to a type of heart disease, hypothyroidism and weakened immune system. There is also evidence that selenium deficiency alone cannot cause disease. It can make the body more vulnerable to diseases caused by other nutritional, biochemical or infectious causes.

Carcinogenesis – Low levels of selenium intake are associated with carcinogenesis. [10] Patients with cancer have low levels of selenium. The exact mechanism of action has not yet been clarified but it is believed that its deficiency impedes the action of glutathione peroxidase in fighting free radicals.

Problems in the synthesis of thyroid hormones – Selenium deficiency can exacerbate the effects of iodine deficiency. Iodine is essential for the synthesis of thyroid hormones, but selenium enzymes are also necessary for the conversion of thyroxine (T4) to the biologically active thyroid hormone triiodothyronine (T3).

Selenium Absorption

What affects the absorption of selenium?

Selenium is absorbed in the small intestine and its absorption increases in deficiency states. Vitamin C, Vitamin A and Vitamin E increase selenium absorption while heavy metals such as mercury and phytic acids decrease its absorption.

As an integral part of glutathione peroxidase and thyroxine reductase, selenium probably reacts with any nutrient that affects the antioxidant balance of the cell.

Other minerals that are essential components of antioxidant enzymes include copper, zinc, dismutase peroxide, iron (as catalase).

Selenium and Vitamin E

Selenium as a glutathione peroxidase also appears to help the action of vitamin E (alpha-tocopherol) by limiting lipid oxidation.

Animal studies show that selenium and vitamin E tend to substitute for each other and that selenium may prevent some of the damage caused by vitamin E deficiency in cases of oxidative stress.

Thyroxine also maintains the antioxidant function of vitamin C by catalyzing its regeneration.

Final Take

Selenium is an important trace mineral that is difficult to become deficient in. It has many health benefits, including boosting the immune system and helping to prevent cancer. Selenium is absorbed in the small intestine, and Vitamin C, Vitamin A and Vitamin E increase selenium absorption.

Make sure you get adequate selenium from your diet by eating foods rich in this nutrient.

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Selenium (Se): Health Benefits, Sources, Deficiency, RDA