{"id":3453,"date":"2024-06-30T13:47:18","date_gmt":"2024-06-30T13:47:18","guid":{"rendered":"https:\/\/seleniumfacts.com\/?p=3453"},"modified":"2024-12-16T15:21:32","modified_gmt":"2024-12-16T15:21:32","slug":"selenium-intake-and-status-are-important-for-the-formation-of-selenoproteins","status":"publish","type":"post","link":"https:\/\/seleniumfacts.com\/index.php\/selenium-intake-and-status-are-important-for-the-formation-of-selenoproteins","title":{"rendered":"Selenium: An Essential Trace Element"},"content":{"rendered":"

We humans need an adequate dietary supply of selenium. Like iron and iodine, our bodies need this essential trace element in sufficient amounts from food for normal physiological functioning.<\/strong><\/p>\n

\"Prof
Guest author Prof. Jan Alexander, MD PhD, specialist in occupational medicine, professor and former specialist director at the Norwegian Institute of Public Health, Oslo, Norway.<\/strong><\/figcaption><\/figure>\n

The content of selenium in food varies according to the selenium content of the soil in any particular region [Stoffaneller & Morse 2015]. Unfortunately, in most areas of the Nordic and Baltic countries, the soil is poor in selenium. Accordingly, the local crops and fruits tend to have low selenium content. An exception is Finland, which enriches soil fertilizers with selenium. Import of wheat from regions with high contents of selenium in the soil has earlier been an important source of selenium in Norway [Alexander & Olsen 2023].
\n<\/strong><\/p>\n

Note: It is not possible for all selenium-poor regions of the world to adopt the Finnish model of selenium fertilization. Industrial demands for selenium are so great that not enough is available to allow for widespread fertilization with selenium<\/a>. Supplementation seems to be the more economical alternative [Haug 2007].<\/p>\n

Selenium for the Bio-Synthesis of Selenoproteins<\/h5>\n

We need adequate intakes of selenium for the synthesis and maintenance of 25 known selenoproteins. We absorb the selenium in food and supplements at a rate of approximately 70-80%. The absorbed selenium does not circulate in its elemental form; instead, it is incorporated into proteins as selenocysteine, the 21st amino acid. The selenium in the selenium-dependent selenoproteins<\/a> exists in the form of selenocysteine [Alexander & Olsen 2023].<\/p>\n

Several of these selenoproteins have important antioxidant properties. Some purpose-specific selenoproteins are also involved in the regulation of the thyroid hormones [Alexander & Olsen 2023].<\/p>\n

Importance of Selenoprotein P<\/h5>\n

The selenoprotein known as Selenoprotein P<\/a> (SELENOP) is the main transporter of selenium in the blood circulation. It plays a central role in the transport of selenium to extrahepatic tissues. SELENOP is synthesized primarily in the liver. It seems to control whole-body selenium homeostasis [Alexander & Olsen 2023].<\/p>\n

Selenium supplementation studies show that SELENOP concentrations increase in plasma until the plasma SELENOP concentration plateaus. Thereafter, even if the selenium intake and the selenium status in plasma increase, the SELENOP level in plasma stays constant. That is to say, additional selenium intake in selenium-replete individuals does not result in an increase in SELENOP concentrations [Alexander & Olsen 2023].<\/p>\n

Several factors affect the amount of time required for SELENOP to reach a saturation level. Among these factors are the individual\u2019s baseline selenium status and the selenium species and dose used in the supplement. In studies, the amount of time needed to reach a saturation level of SELENOP has varied from four weeks to 30\u201340 weeks [Alexander & Olsen 2023].<\/p>\n

The maximal expression of SELENOP occurs when the plasma or serum selenium concentration of selenium reaches about 110 mcg\/L. Plasma and serum selenium values are equivalent [Alexander & Olsen 2023].<\/p>\n

Thus, it can be seen that the SELENOP concentration in plasma is the most appropriate biomarker of the selenium status of the body\u2019s regulated selenium pool. Measurements of selenium concentrations in plasma or serum are an indicator of dietary selenium intake. SELENOP status in the blood gives the best picture of overall selenium status [Alexander & Olsen 2023].<\/p>\n

Importance of Other Selenoproteins<\/h5>\n

There is insufficient space here to enumerate the biological functions of all the selenoproteins. For a more detailed discussion, please see the review article Selenium \u2013 a scoping review for the Nordic Nutrition Recommendations 2023<\/em> by Jan Alexander and Ann-Karin Olsen.<\/p>\n

Glutathione peroxidases<\/h6>\n

Some of the most important selenoproteins are enzymes that neutralize peroxides and protect against oxidative damage. These antioxidant seleno-enzymes include five glutathione peroxidases (GPXs) that convert hydroperoxides and lipoperoxides to water or alcohols in various body compartments [Alexander & Olsen 2023].<\/p>\n

Thioredoxin reductases<\/h6>\n

Three thioredoxin reductases (TXNRDs) play key roles in cellular redox regulation, again in various body compartments [Alexander & Olsen 2023].<\/p>\n

Iodothyronine deiodinases<\/h6>\n

Three deiodinase enzymes regulate thyroid hormone activity. The iodothyronine deiodinases (DIO1, DIO2, DIO3) control the central and
\nperipheral activation and inactivation of thyroid hormones [Alexander & Olsen 2023]. Proper thyroid activity<\/a> is important for the regulation of our body\u2019s metabolism: how efficiently we convert food into energy, how fast or slowly our heart beats, how much we gain or lose weight, and so on.<\/p>\n

Selenium Intake Levels<\/h5>\n

Whenever supplementation is used to increase selenium intakes, the form of the selenium compound \u2013 whether inorganic or organic, whether pure selenomethionine or a selenium-enriched yeast formation \u2013 will influence the extent of the rise in plasma selenium concentration. In Finland, an estimated daily selenium intake of 88 mcg for men and 68 mcg for women has yielded plasma selenium concentrations of approximately 110 mcg\/L on average [Alexander & Olsen 2023].<\/p>\n

Note that, whereas the serum selenium concentrations in US citizens are estimated to be about 120 mcg\/L on average, the mean concentrations in many northern European countries are below 90 mcg\/L [Alehagen 2020].<\/p>\n

Data from a 2022 report show the following daily adult intakes of selenium in Nordic countries<\/a> [Lemming & Pitsi 2022].<\/p>\n