- Dietary Reference Intakes for Selenium
- Selenium Content of Plant Foods
- Selenium Intakes and Status of Vegans
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|
|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|
|Pinto beans, cooked||1 cup||11|
|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.
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).
Last updated January 2019
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