Evidence-Based Nutrient Recommendations

Selenium

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Summary

Selenium is an essential mineral that’s needed in trace amounts. Selenium is involved in protection from oxidative damage, reproduction, DNA synthesis, and thyroid hormone metabolism. Selenium levels have been positively associated with great bone mineral density (Hoeg, 2012). The selenium content of plant foods depends on the selenium content of the soil where the foods were grown (Rayman, 2012).

Vegans in the U.S. appear to have adequate intakes of selenium (Mangels, 2011). Low intakes and lower blood concentrations have been reported in vegans and vegetarians in other areas of the world where soil selenium is low (Mangels, 2011; Judd, 1997; Kristensen, 2015; Sobiecki, 2017).

Dietary Reference Intakes for Selenium

The Recommended Dietary Allowance (RDA) for selenium is 55 micrograms per day for adolescents and adults, 60 micrograms per day during pregnancy, and 70 micrograms per day when breastfeeding (Institute of Medicine, 2000). Most Americans get more than the RDA and over 99% of participants in a large survey of people in the U.S. had serum selenium in the normal range (Institute of Medicine, 2000).

Selenium Content of Plant Foods

The selenium content of plant foods depends on the amount of selenium in the soil the plants were grown in as well as on other factors including soil pH and fertilizer use (Rayman, 2012). The amount of selenium in soil varies by geographic location.

The lowest selenium intakes in the world are in some parts of China where soil selenium is very low (2), while other regions of China have a very high soil selenium and high selenium intakes (Rayman, 2012). Areas of Europe also have low soil selenium (Rayman, 2012) although not as low as in China. New Zealand soil is low in selenium but selenium intakes are adequate because of the use of imported high-selenium wheat (Mangels, 2011).

In the U.S and Canada, selenium intakes, even in areas with lower soil selenium, are generally adequate (Niskar, 2003; Kafai, 2003; Thompson, 1975). This is, at least in part, due to the food distribution system which usually makes it possible for even those living in areas with lower soil selenium to get enough selenium.

Selenium values in food composition tables may or may not reflect the actual selenium content of foods eaten by an individual. For example, the USDA Food Composition Database reports that Brazil nuts have 544 micrograms of selenium per ounce but other sources report values ranging from 45 to 566 micrograms/ounce (Thomson, 2008; Parekh, 2008; USDA, 2018).

A 2017 study analyzed the selenium content of Brazil nuts and soil from the Amazon and found selenium concentrations varied widely in the nuts and soil (Silva Junior, 2017). Selenium concentrations in the nuts were greater when the nuts were grown in soils with higher selenium content, and lower when the soil was acidic. For example, some Brazil nuts grown in selenium-poor soils still took up a good amount of selenium due to the soil pH. Whereas nuts grown in acidic, selenium-poor soils had lower selenium concentrations.

In addition to Brazil nuts, foods that are relatively high in selenium include whole grains (whole-wheat bread and pasta, oatmeal, barley), brown rice, soy products, and beans. The table below shows the selenium content of selected plant foods from the USDA’s nutrient database (USDA, 2018). Note that selenium content will vary depending on soil selenium.

Selenium in Plant Foods in the United States
Food Serving Size Selenium
(micrograms)
Brazil nuts 1 ounce (about 6 nuts) 544
Couscous, cooked 1 cup 43
Whole-wheat pasta, cooked 1 cup 42
Sunflower seed butter 2 tablespoons 33
Wheat bagel 1 bagel 28
Sunflower seeds, dry roasted 1 ounce 23
Wheat germ, toasted 1 ounce 18
Chia seeds 1 ounce 16
Whole-wheat tortilla 1 tortilla 15
Barley, pearled, cooked 1 cup 13.5
Soybeans, cooked 1 cup 13
Oatmeal, cooked 1 cup 13
Firm tofu ½ cup 12.5
Brown rice, cooked 1 cup 12
Soymilk 1 cup 12
Pinto beans, cooked 1 cup 11
Tahini 2 tablespoons 10
Lima beans, cooked 1 cup 8.5
Whole-wheat bread 1 slice 8
Great northern beans 1 cup 7

Selenium Intakes and Status of Vegans

Vegans in the U.S. appear to have adequate intakes of selenium (Mangels, 2011).

Depending on food choices, vegans in Europe may have lower intakes of selenium. Lower soil selenium in European countries affects the selenium content of locally-grown grains, fruits, and vegetables.

In Denmark, both vegans and the general population had median selenium intakes that were lower than recommendations; the vegans had significantly lower selenium intakes than the general population (Kristensen, 2015).

One report found lower selenium status among UK vegans than among UK non-vegetarians (Judd, 1997). A more recent study in the U.K. found lower mean selenium intakes in lacto-ovo and lacto vegetarians compared to meat or fish eaters. Vegans’ mean selenium intakes were lower than those of meat and fish eaters but higher than lacto-ovo/lacto-vegetarians (Sobiecki, 2016). Almost half of vegan women and one-third of vegan men in the U.K. had selenium intakes below recommendations (Sobiecki, 2016).

In Finland, vegans had lower selenium intakes and lower blood selenium compared to non-vegetarians (Elorinne, 2016). Both groups, however, had selenium intakes that met or exceeded recommendations and serum selenium was in an acceptable range (Elorinne, 2016). Finland is unique in that it adds selenium to fertilizers (Alfthan, 2015).

A cross-sectional study from Germany comparing 36 sex and age-matched omnivores and vegans found no significant difference between median plasma selenium levels: 77 µg/l vs. 68 µg/l, respectively (Weikert, 2020). However, there was a significant difference in selenoprotein P levels which are more indicative of selenium status (omnivores: 5.0 mg/l; vegans: 3.3 mg/l). In comparing the vegans in Weikert et al. to the quintiles of women with higher fracture rates in Hoag et al., the vegans would have had low selenium plasma levels but adequate selenoprotein P levels. No reference range was provided and selenium intakes weren’t measured.

Recommendations

Vegans in the U.S. and other areas with adequate selenium content in the soil, who eat a variety of foods including whole grains and beans, are likely to get enough selenium. Vegans in low selenium areas should eat Brazil nuts regularly and/or use a supplement supplying a moderate amount of selenium.

The tolerable upper intake level (UL) for selenium is 400 micrograms/day for adolescents and adults and includes both selenium obtained from food and selenium from supplements (Institute of Medicine, 2000). Long-term use of high amounts of selenium can cause health problems including hair and nail loss or brittleness, nausea, diarrhea, fatigue, and neurologic disorders (NIH, 2018).

References

Last updated January 2019

Alfthan G, Eurola M, Ekholm P, et al. Effects of nationwide addition of selenium to fertilizers on foods, and animal and human health in Finland: From deficiency to optimal selenium status of the population. J Trace Elem Med Biol. 2015;31:142-7.

Elorinne AL, Alfthan G, Erlund I, et al. Food and nutrient intake and nutritional status of Finnish vegans and non-vegetarians. PLoS One. 2016 Feb 3;11(2):e0148235.

Hoeg A, Gogakos A, Murphy E, Mueller S, Köhrle J, Reid DM, Glüer CC, Felsenberg D, Roux C, Eastell R, Schomburg L, Williams GR. Bone turnover and bone mineral density are independently related to selenium status in healthy euthyroid postmenopausal women. J Clin Endocrinol Metab. 2012 Nov;97(11):4061-70.

Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academy Press, Washington, DC, 2000.

Judd PA, Long A, Butcher M, Caygill CP, Diplock AT. Vegetarians and vegans may be most at risk from low selenium intakes. BMJ. 1997 Jun 21;314(7097):1834.

Kafai MR, Ganji V. Sex, age, geographical location, smoking, and alcohol consumption influence serum selenium concentrations in the USA: third National Health and Nutrition Examination Survey, 1988-1994. J Trace Elem Med Biol 2003;17:13-8.

Kristensen NB, Madsen ML, Hansen TH, et al. Intake of macro- and micronutrients in Danish vegans. Nutr J. 2015 Oct 30;14:115.

Mangels R, Messina V, Messina M. The Dietitian’s Guide to Vegetarian Diets, 3rd ed. Sudbury, MA: Jones & Bartlett Learning, 2011.

NIH Office of Dietary Supplements. Selenium – Fact Sheet for Health Professionals. Updated September 26, 2018.

Niskar AS, Paschal DC, Kieszak SM, et al. Serum selenium levels in the US population: Third National Health and Nutrition Examination Survey, 1988-1994. Biol Trace Elem Res 2003;91:1-10.

Parekh PP, Khan AR, Torres MA, Kitto ME. Concentrations of selenium, barium, and radium in Brazil nuts. J Food Comp Anal 2008; 21:332-335.

Rayman MP. Selenium and human health. Lancet 2012;379:1256-68.

Silva Junior EC, Wadt LHO, Silva KE, Lima RMB, Batista KD, Guedes MC, Carvalho GS, Carvalho TS, Reis AR, Lopes G, Guilherme LRG. Natural variation of selenium in Brazil nuts and soils from the Amazon region. Chemosphere. 2017 Dec;188:650-658.

Sobiecki JG, Appleby PN, Bradbury KE, Key TJ. High compliance with dietary recommendations in a cohort of meat eaters, fish eaters, vegetarians, and vegans: results from the European Prospective Investigation into Cancer and Nutrition-Oxford study. Nutr Res. 2016 May;36(5):464-77.

Sobiecki JG. Vegetarianism and colorectal cancer risk in a low-selenium environment: effect modification by selenium status? A possible factor contributing to the null results in British vegetarians. Eur J Nutr. 2017 Aug;56(5):1819-1832.

Thompson JN, Erdody P, Smith DC. Selenium content of food consumed by Canadians. J Nutr. 1975 Mar;105(3):274-7.

Thomson CD, Chisholm A, McLachlan SK, Campbell JM. Brazil nuts: an effective way to improve selenium status. Am J Clin Nutr. 2008 Feb;87(2):379-84.

US Department of Agriculture (USDA), Agricultural Research Service, Nutrient Data Laboratory. USDA National Nutrient Database for Standard Reference, Legacy. Version Current: April 2018.

Weikert C, Trefflich I, Menzel J, Obeid R, Longree A, Dierkes J, Meyer K, Herter-Aeberli I, Mai K, Stangl GI, Müller SM, Schwerdtle T, Lampen A, Abraham K. Vitamin and Mineral Status in a Vegan Diet. Dtsch Arztebl Int. 2020 Aug 31;117(35-36):575-582.

Also Reviewed

Higdon J. Selenium. Linus Pauling Institute, Oregon State University. Updated November 2014.

Stoffaneller R, Morse NL. A review of dietary selenium intake and selenium status in Europe and the Middle East. Nutrients. 2015 Feb 27;7(3):1494-537.

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