Selenium, Fertility, Immune Health and so much more...
Selenium is an essential nutrient that carries fundamental importance to the human biology . Being a trace element, it functions as a preventive agent on the detoxification of reactive oxygen species (ROS) through the activation of several endogenous systems [2-4]. For instance, in a fundamental cellular process such as DNA synthesis, the presence of selenium within the catalytic site of thioredoxin reductases (TrxR) is required [4,5]. The importance of selenium in the human physiological processes has been shown through the available previous study reports. For example, the increased risk of cancer, infections and male infertility have been associated with mild selenium deficiency. Besides, the decrease in the immune defense system as well as in the thyroid and several neurological functions also have been linked to the conditions of insufficient selenium [1,4].
History of Selenium
The history of selenium discovery goes back, way back to the earlier centuries. Based on the available information, it is believed that selenium was first observed in around the year 1300 by Arnold of Villanova, who was a chemist (~ year 1235 – 1310). He wrote in a book entitled Rosarium Philosophorum on the description of red sulfur (or red rebeum) which had been left behind in an oven after the native sulfur had been vaporized. It was suggested to be one of the selenium’s red colored allotropes [6-8]. Unfortunately, the discovery of selenium was set into silence for about 500 years.
The attention on selenium was re-emerged after 500 years of the initial discovery, following the report by Jöns J. Berzelius, who was an eminent Swedish chemist on a red deposit left behind after sulfur had been burned in sulfuric acid factory . The factory was his partly owned with his friend Johann Gahn, who was also a chemist . He wrote about the red deposit in September 1817, and also informed a friend, Dr. Marcet that the deposit contained the element tellurium, which by then was an already known element. However, in February 1818, Berzelius changed his mind and again told Dr. Marcet about his discovery of a new element. According to an available study report, the discovery of selenium was cited as the following:
“…what Mr. Gahn and I took for tellurium is a new substance, endowed with interesting properties. This substance has the properties of a metal, combined with that of sulfur to such a degree that one would say it is a new kind of sulfur. The similarity to tellurium has given me occasion to name the new substance selenium.”.
How much do we need per day? How much is too much?
The need of selenium in the body are mainly to support the developmental and growth. This mineral is normally required in small amounts. The Food and Nutrition Board, Institute of Medicine, suggested a recommended dietary allowance (RDA) of selenium for both men and women of 55 micrograms per day for adults . Besides, for pregnant and lactating women they may have a slightly higher need for selenium at 60 and 70 micrograms per day, respectively.
It seems that the body only needs small amounts of the mineral selenium, however failing to consume this amount of selenium over a period of time can lead to a deficiency that increases the risk of heart disease, hypothyroidism and a weakened immune system. In addition, consuming higher amounts of selenium, which is defined as a concentration of more than 100 micrograms over a long period of time, can lead to selenium toxicity, a condition called selenosis.
Foods that contain selenium?
There are a number of foods that were reported to contain selenium and the amount of selenium in grains and grain-based foods greatly depends on soil content . Among these are:
- Brazil nuts, 1 ounce: 543 micrograms
- Halibut, baked, 1 fillet: 148 micrograms
- Tuna, canned, 3 ounces: 68 micrograms
- Oysters, raw, 3 ounces: 56 micrograms
- Rice, white, long grain, 1 cup: 44 micrograms
- Lobster, 3 ounces: 36 micrograms
- Sunflower seeds, ¼ cup: 25 micrograms
- Egg, 1 large: 16 micrograms
- Bread, whole wheat, 1 slice: 10 micrograms.
In contrast, most fruits and vegetables are reported to be low in selenium.
What is selenium used for in the body and its health benefits?
The beneficial effects of selenium intake have been previously reported. In general, it were reported that higher selenium status or selenium supplements exerted the antiviral effects . It was also essential for successful male and female reproduction and helped to reduce the risk of autoimmune thyroid disease . Besides, an earlier study report by Kiremidjian-Schumacher et al. (2000) showed that treatment with sodium selenite (the clinical form of selenium) significantly enhanced the cell-mediated immune responsiveness in head and neck cancer patients . This finding was also supported by another study on the effects of selenium supplementation for 6 months in oral cancer patients . In this study, it was found that the supplementation helped to increase the enzymatic (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), Glutathione reductase (GRx), Glucose-6-phosphate dehydrogenase (G6PDH)) and non-enzymatic (glutathione (GSH), vitamin E, vitamin C, vitamin A and ceruloplasmin) defense systems. In addition, the mechanism of the increase in the activity of the enzymatic defense system was reported to be due to increased GPx synthesis as a result of the enhanced de novo synthesis of this enzyme in the erythroid precursors of red blood cells .
Selenium is a trace element that is required in normal body functions. Selenium can be found in a number of food sources, and its intake should be within the allowed rate. Over consumption of selenium may lead to a health problem known as selenosis. The beneficial effects of selenium include the antioxidant and anti-sterility effects as well as role in the immune system and others.
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