Selenium supplementation

Selenium can be supplemented using inorganic forms such as sodium selenite, which has lower protein binding but greater safety in terms of long-term supplementation. Organic forms of selenium like L-selenomethionine or selenium-enriched yeast supply organic forms, which bioaccumulate more rapidly. Depending on the dose administered, plasma levels should be monitored.

Foods with selenium

Dietary selenium comes from nuts, grains, meat, fish, and eggs. Brazil nuts are the richest dietary source. In descending order by concentration, the highest levels are found in kidneys, tuna, and crab and lobster meat (Anonymous; Barclay, MacPherson et al).

Foods with trace elements

The foods that contain the most trace elements (zinc, selenium, chromium, copper, manganese, and molybdenum):

• Nuts (all types).
• Wholegrain cereals.

Dietary selenium comes from nuts, grains, meat, fish, and eggs. Brazil nuts are the richest dietary source. In descending order by concentration, the highest levels are found in kidneys, tuna, and crab and lobster meat (Anonymous; Barclay, MacPherson et al).

Foods with zinc. The highest concentrations of zinc are found in red meats, particularly beef and lamb, and in the livers of these animals.

Intake and deficiencies

• Selenium has an antioxidant effect and reduces chronic inflammation (Steinbrenner and Sies 2009).
• In asthma, heart disease, COPD, and frequent respiratory infections, selenium can help improve their control and prevent complications.
• Selenium needs the “team” of basic nutrients to achieve its maximum therapeutic potential in chronic diseases.
• Selenium has an excellent safety profile, with no side effects, in the recommended forms and doses.

Conclusions on its deficiency in the population are not possible, although it is known that levels depend on its soil content and that this is lower in Europe than in the United States. In Spain, according to the ENIDE Survey, average habitual intake of selenium is similar in men and women, 60–65 μg/day, with 1% to 4% of the population consuming too little (AESAN, 2011)

Intake. The selenium concentration depends on external inputs. A recent publication provided a panorama of the dietary habits of adolescents in Nordic countries. The studies reflect that, in general, vitamin and mineral intake is adequate for normal health and growth, while that of fiber, vitamin C, zinc, selenium and, in girls, iron is below national recommended levels. A decline in physical activity and a rise in sedentarism were also detected. Overweight and obesity, as a consequence and combination of dietary habits and the decline in physical activity is increasingly common in these countries, reaching levels even higher than in the United States (Samuelson 2000).

Deficiency. Selenium deficiency is rare in well nourished people, even in New Zealand and Finland, where selenium intake is around 30–50 μg/day, compared to 100–250 μg/day in the United States and Canada (Johnson, 2008). It can occur in patients with severely compromised intestinal function, those receiving parenteral nutrition or following gastrointestinal bypass surgery, and in very elderly people (over the age of 90) (Ravaglia, Forti et al. 2000).

However, establishing actual selenium intake and deficiency is difficult as its concentration in foods depends on its content in soils, which is highly variable. Soils deficient in selenium are much more common in Europe than in the United States.

Drugs. Corticosteroids can accentuate a marginal selenium deficiency.

Bibliography

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• Anonymous. “Selenium. Public Health Statement: Health Effects ” Retrieved 8 Feb, 2010, from http://www.atsdr.cdc.gov/toxprofiles/tp92-c3.pdf.
• Anonymous. (2009, 22 Jan 2009). “Selenium.” Retrieved 8 Feb 2010, 2010, from http://lpi.oregonstate.edu/infocenter/minerals/selenium/.
• Barbalace, K. “Periodic Table of Elements. Element Selenium – Se.” Retrieved 8 Feb, 2010, fromhttp://environmentalchemistry.com/yogi/periodic/Se.html.
• Barclay, M. N. I., A. MacPherson, et al. “Selenium Content of a Range of UK Foods.” J. Food Comp. Anal. 8(4): 307-318.
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• Douillet, C., A. Tabib, et al. (1996). “A selenium supplement associated or not with vitamin E delays early renal lesions in experimental diabetes in rats.” Proc Soc Exp Biol Med 211(4): 323-331.
• Duntas, L. H. (2009). “Selenium and inflammation: underlying anti-inflammatory mechanisms.” Horm Metab Res 41(6): 443-447.
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• Ravaglia, G., P. Forti, et al. (2000). “Effect of micronutrient status on natural killer cell immune function in healthy free-living subjects aged >/=90 y.” Am J Clin Nutr 71(2): 590-598.
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Reference values

NRV, PRI, UL for selenium

The NRV is 55 µg. The PRI is 55 µg for women and 70 µg for men.

The UL is 300 µg.

In the United States, the reference intake for adults is 55 µg/day. In Great Britain, 75 µg/day for adult men and 60 µg/day for women. The recommendation of 55 µg/day is based on complete expression of glutathione peroxidase. Selenoprotein P (Papp, Lu et al. 2007) is the best indicator of selenium nutritional status, and its complete expression may require more than 66 µg/day (Xia, Hill et al. 2005).

Although selenium is an essential trace element, it is toxic when consumed in excess. Exceeding the maximum tolerable intake of 400 µg/day can lead to selenosis (Anonymous). A 1992 study found a higher dose (800 µg/day) but maintained the recommendation of 400 µg/day. This was not only to avoid toxicity but also to avoid creating a dietary nutrient imbalance and to take into account data from other continents (Yang and Zhou 1994). A selenium dose of as little as 5 mg/day can be lethal for most humans (Barbalace).

NRV: Nutrient Reference Value. These are the daily amounts recommended for vitamins and minerals (micronutrients only) considered sufficient in the European Union to prevent a deficit in most healthy individuals in the population. They are the values used for labeling and claims.

PRI: Population Reference Intake. These are the reference values for a specific population group, defined as the amount of energy and/or nutrients (macronutrients and micronutrients) recommended to cover the nutritional needs of practically the entire population. They refer to healthy population groups. The values are expressed per person per day, as a 15-day average. To account for individual differences in digestive and metabolic processes, the PRI figure used for each nutrient is the average plus twice the standard deviation (except for energy, for which the average is used), thereby including almost all healthy individuals in the group (97.5%).

UL: Tolerable Upper Intake Level: the maximum level of total daily intake of a nutrient in a context of long-term or chronic consumption which does not pose a risk to health.