Contents
Where does selenium accumulate?
Selenium in our body is present in small, trace amounts. It is most abundant in the liver, muscles, thyroid gland, kidneys and pituitary gland. In men, on the other hand, half of all selenium accumulated in the body is stored in the testes and sex glands. It is also found in the sperm they produce.
The effect of selenium on the body
Selenium affects the course of many biochemical and physiological processes that take place in our body. It is a component of about 20 enzymes, which makes it necessary for the proper functioning of enzyme systems. There is, among others in glutathione peroxidase. It is an antioxidant and protects cell membranes and red blood cells against the effects of harmful peroxides. Selenium is therefore a defense against free radicals.
Additionally, it affects the functioning of the immune system. It is assumed that an adequate supply of selenium may reduce the risk of developing some types of cancer, in particular prostate and bladder cancer. However, this applies only to situations in which the current supply of this component was too low and was supplemented over time. In other words, selenium deficiency can increase the risk of cancer. Additional supplementation in a situation where the selenium supply was adequate, does not play a protective role, and may act quite the opposite.
Selenium also plays a role in the proper functioning of the thyroid gland. It is essential for the proper synthesis, activation and metabolism of thyroid hormones. It also reduces the risk of a heart attack, increases the mobility of inflamed joints, improves sperm mobility, has antidepressant and antiviral properties. So it works in many directions and that is why it is called the element of life.
However, you have to be careful with selenium!
In the case of selenium, there is little difference between the recommended dose and the toxic dose. The relationship between its consumption and its effects on health is U-shaped. Both selenium deficiency and its excess can be harmful to the body. If we increase selenium intake from low values, our health will improve. However, if we exceed the recommended, safe dose, our condition may even worsen significantly.
Deficiency – what is it associated with?
The deficiency of this element results mainly from insufficient supply with the diet. They contribute to the weakening of immunity, increasing the risk of cancer, to the development of neurodegenerative diseases or ischemic heart disease. They also increase the risk of degeneration of many tissues and organs. Extreme deficiencies lead to Keshan disease, which is an endemic disease of the heart muscle) and Kashin-Bek disease (diseases of the osteoarticular system). Insufficient selenium supply may also be associated with hypothyroidism and goiter symptoms. In addition, it also increases the risk of depressive disorders.
Excess – just as harmful
Large doses of selenium, which exceed 400-600 μg / day, turn this element essential for life into one of the most toxic of all minerals. Symptoms of selenium poisoning include brittleness and loss of nails, hair loss, diarrhea, and kidney and liver damage. An excess of selenium may also contribute to the development of type 2 diabetes. It also increases the risk of cancer, as it happens in the case of a deficiency of this element.
However, you do not have to worry about an excess of selenium if you do not use additional supplementation. In such situations, even doses up to 800 µg per day did not appear to be toxic. The use of additional supplementation is primarily dangerous. It is difficult to find large doses of this mineral in food. Only Brazil nuts, which contain very large amounts of this element, can be dangerous. However, you would have to eat them in large amounts every day.
The content in the food
The selenium content of food varies greatly. It depends on the content of this element in water and soil. In acidic soils, it is scarce, while blackthorn and white-tailed eagles are quite rich in it. They occur in the form of selenates, which are quite well absorbed by plants. Unfortunately, Poland is considered to be selenium poor. Therefore, the average dietary selenium content is only about 40 μg / day, which is slightly too little. In countries where the soils are rich in selenium (e.g. in the USA), its consumption in the usual diet is much higher and amounts to about 100-220 μg.
Plants that are rich in selenium often contain higher sulfur content. Such plants include legumes and cruciferous vegetables, e.g. peas, Brussels sprouts, beans and broccoli. We can also find it in onions and garlic. A lot of selenium is also contained in foods that are rich in protein, because selenium is often found in organisms in conjunction with proteins. For this reason, we can find this element in meat, offal, seafood, fish and milk. In addition, selenium is found in grain products and eggs.
Absorbability
Selenium compounds are rather well absorbed from food. However, selenium in organic form is better absorbed than that of inorganic forms. Plants take up inorganic compounds from the soil and transform them into organic forms. On the other hand, in animal approach products, inorganic compounds may appear, e.g. metal sulfides or selenides. The bioavailability of this mineral is estimated at 55-65%. Absorption is facilitated by the presence of protein, vitamins E, C and A and other antioxidant compounds. However, with a large amount of heavy metals, the bioavailability decreases. Selenium obtained from yeast has the highest bioavailability.
It should also be remembered that heat treatment leads to the loss of this mineral. It is estimated that about 40% of this element is lost during such treatment. Frying and baking causes the greatest losses, and the least during cooking.
Who should supplement?
The selenium supplementation can benefit the inhabitants of areas poor in this mineral, smokers and people with impairment of the nutrient absorption function. However, it should be remembered that an excess of selenium can be extremely toxic, so before starting supplementation, the level of selenium in the body should be determined. This element can be found in blood, hair or urine. If it turns out that there are deficiencies in the body, supplementation can be started. However, it is better to always start with supplementing nutritional deficiencies. The more that it is enough to include 1 Brazil nut in the diet to ensure the proper supply of selenium.
Main photo: Photo credit: / Foter / CC BY
Photo from text: Photo credit: / Foter / CC BY