by Jack Norris, RD
Contents
- Essential Information
- Dietary Reference Intakes
- Selenium Content of Plant Foods
- Selenium Intakes and Status of Vegans
- Bibliography
Essential Information
Selenium is involved in protection from oxidative damage, reproduction, DNA synthesis, and thyroid hormone metabolism. Selenium levels have been positively associated with greater bone mineral density (Hoeg, 2012).
Selenium is lacking in the soil in many countries and so a multivitamin with selenium is the most reliable source. Soil in the United States and Canada has enough selenium for vegans there not to be concerned.
Dietary Reference Intakes
| U.S. Dietary Reference Intakes (DRI) for Selenium | ||
|---|---|---|
| Age | DRI (µg) |
Upper Limit (µg) |
| 0-6 mos | 15 | 45 |
| 7-12 mos | 20 | 60 |
| 1-3 | 20 | 90 |
| 4-8 | 30 | 150 |
| 9-13 | 40 | 280 |
| 14+ | 55 | 400 |
| Pregnancy | 60 | 400 |
| Breastfeeding | 70 | 400 |
It’s best not to ingest more than the upper limit as 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).
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.
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.
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).
The lowest selenium intakes in the world are in some parts of China where soil selenium is very low, 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).
Brazil nuts are the food highest in selenium, on average. 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. Selenium values in food composition tables mighty not reflect the actual selenium content of any specific food eaten by an individual.
Brazil Nuts
Summary: It’s not clear if vegans who live in selenium-depleted areas should rely on Brazil nuts for selenium due to the variability in selenium content and concerns about radium. Our suggestion is that if it’s just as convenient to obtain selenium from a supplement as from Brazil nuts, then a supplement is the more ideal option. If Brazil nuts are the more convenient option, then one Brazil nut per day seems like a reasonable amount to provide some selenium while not increasing the risk of harmful radiation to unusual levels.
Brazil nuts are the food most high in selenium, on average. Brazil nuts are almost exclusively grown in regions of South America where the soil content of selenium and conditions for selenium uptake by the nuts can vary widely (Alcântara, 2022).
One study found that Brazil nuts grown in selenium-poor, non-acidic soils contained appreciable amounts of selenium, whereas nuts grown in selenium-poor, acidic soil contained low amounts of selenium (Silva Junior, 2017). 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).
Thomson et al. (2008, New Zealand) conducted a 12-week trial comparing 2 Brazil nuts per day (containing an average of 53 µg selenium per day), 100 µg of a selenium supplement, and a placebo group. Plasma selenium increased by 64%, 61%, and 7.6% respectively. Plasma glutathione peroxidase activity (an indicator of short-term selenium activity) increased by 8.3%, 3.4%, and 1.2% respectively. Whole blood glutathione peroxidase activity (an indicator of longer-term selenium activity) increased by 13%, 5.3%, and 1.9% respectively. The authors recommended that in New Zealand, where dietary intakes of selenium and selenium status are low, daily consumption of 1 Brazil nut for increasing selenium intakes to recommended levels.
Radium in Brazil Nuts
Koeder and Keller (2024) conducted a literature review of the radioactive radium levels of Brazil nuts. They note that Brazil nuts may have higher levels of radium than other foods due to being grown in high-radium soils and because Brazil nut trees accumulate radium. One study found that Brazil nuts from trees grown at a botanical garden in Singapore also contained radium. Koeder and Keller note that radium levels can vary substantially among Brazil nuts even from the same batch. They contracted an accredited laboratory to measure the radioactive radium levels of 21 brands of Brazil nuts from Bolivia that they purchased in Germany.
Koeder and Keller were unable to determine if the level of radioactive radium in 1 to 2 daily Brazil nuts is harmful. Despite the Federal Office for Radiation Protection (BfS) in Germany recommends against eating Brazil nuts for pregnant, breastfeeding, children, and adolescents, Koeder and Keller didn’t find evidence to justify this recommendation although they say it might be justified as a precautionary measure. They determined that the amount of radiation provided by one to two Brazil nuts per day is roughly equivalent to that in 2 to 4 liters of drinking water and estimated that 1 Brazil nut per day would increase someone’s cancer risk from about 40% to about 40.02–40.06%.
Koeder and Keller point out that it’s not clear if the radium in Brazil nuts is absorbed in the intestine to any significant degree, and that it also might be that low levels of radiation can be protective (by maintaining the body’s DNA repair mechanisms, making them more effective in instances of higher radiation exposure).
Selenium Intakes and Status of Vegans
Summary: Vegans in the U.S. appear to have adequate intakes of selenium. Low intakes and lower blood concentrations have been reported in vegans and vegetarians in other areas of the world where soil selenium is low.
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., who found higher bone mineral density among women with higher selenium measurements, the vegans have low selenium plasma levels but adequate selenoprotein P levels. Weikert et al. didn’t provide reference ranges or selenium intakes.
A study from Sweden (Larsson, 2002) estimated selenium intakes and found them to be 10 µg/d (female) and 12 µg/d (male) for vegans compared to 27 µg/d (female) and 40 µg/d (male) for omnivores.
Last updated January 2019
Bibliography
Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academy Press, Washington, DC, 2000.
Mangels R, Messina V, Messina M. The Dietitian’s Guide to Vegetarian Diets, 3rd ed. Sudbury, MA: Jones & Bartlett Learning, 2011.
Rayman MP. Selenium and human health. Lancet 2012;379:1256-68.
Also Reviewed
Higdon J. Selenium. Linus Pauling Institute, Oregon State University. Updated November 2014.
4 thoughts on “Selenium”
Kia Ora from New Zealand
An increasing number of New Zealanders, including vegans, are eating gluten-free, (due to IBS sugars rather than Celiac gluten allergy – though most folk don’t know why gluten-free quells their symptoms). Might it be that we need more selenium, even though brown rice & beans, etc, are in our diets? Many people here cannot afford Brazil nuts, plus they are a high food-mile item, often involving child labour in Brazil. Perhaps our recommended level needs to be re-considered …
Since imported high-selenium wheat is an important source of selenium for those living in New Zealand, those who avoid wheat due to eating gluten-free are likely to need other sources of selenium. It may be that beans and rice are imported and supply selenium but without analyzing these foods, we don’t know how much selenium they provide. This is a circumstance where using a supplement that provides the RDA for selenium seems prudent.
What about selenium content for foods in the UK? Is it adequate for vegans?
Selenium adequacy will depend on individual food choices. For example, vegans in the UK who eat Brazil nuts regularly may have adequate selenium status based on one study that found that eating Brazil nuts can normalize selenium status (https://www.ncbi.nlm.nih.gov/pubmed/18258628) . According to the USDA National Nutrient Data Base, one Brazil nut supplies 95.8 mcg of selenium. The RDA for non-pregnant, non-lactating adults is 55 mcg/day.
Generally speaking, the UK is a low selenium area so crops grown in the UK are likely to be markedly lower in selenium than those grown in the US or other areas with higher soil selenium (https://www.ncbi.nlm.nih.gov/pubmed/22381456). This would affect foods commonly eaten by vegans such as locally-grown grains, fruits, and vegetables. One brief, older (1997) report finds lower selenium status in UK vegans than in UK non-vegetarians (https://www.bmj.com/content/314/7097/1834.2.long).