As I previously wrote in my blog, you might have heard about selenium many times as an ingredient in antioxidant supplements, but you probably don’t know that this mineral has an enormous importance for the correct functioning of the thyroid gland as well. This mineral is incorporated into at least 25 selenoproteins[1] involved in different processes such as protection against lipid peroxidation, thyroid hormone metabolism, T cell immunity as well as the modulation of the inflammatory response[2].
In this post, I would like to give you some ideas about how you can get enough of this nutrient from food and how your current nutritional status can be assessed. For starters, the current recommended dietary intake in adults is about 55 and 75 micrograms per day (see table 1). More than 850 micrograms per day are instead considered toxic.
In its organic form, selenium is present in food as selenomethionine, whereas selenite is selenium’s inorganic form which is not naturally present in the diet and is metabolized differently[3]. Foods rich in selenium include Brazil nuts (25 mcg/nut on average), eggs (13.9 mcg/egg), oysters (63.7 mcg/100 g), tuna (80.4 mcg/100 g), salmon (41.4 mcg/100 g), shrimps (39.6 mcg/100 g), whole-wheat bread (70.7 mcg/100 g), sunflower seeds (53 mcg/100 g), oats (34 mcg/100 g) and whole-grain rye (35.3 mcg/100 g). Finally, most kinds of meat (pork, beef, lamb, turkey, chicken) and mushrooms contain selenium as well.
| Population group | Daily recommended intake (mcg) | Maximum daily intake level including supplements (mcg) |
| Men and Women aged 19+ | 55 | 400 |
| Pregnant Women | 60 | 400 |
| Breastfeeding Women | 70 | 400 |
Table 1: daily recommended intake (mcg) and maximum intake levels in different population groups.
Based on the above, it seems that selenium is contained in several types of food. Therefore, people eating a varied diet should not have any problem at all.
What happens if your intake does not meet the recommendations? Clinical signs of deficiency include Keshan disease, a cardiomyopathy, mainly affecting young children and women of childbearing age, which is apparent in areas of China in populations with particularly low intakes[4]. An inadequate selenium status has also been inversely associated with cancer, infertility, impaired immune function, not to mention a higher risk of mortality[5],[6],[7].
You’d better make sure you get enough of this mineral into your diet!
How is it possible to know whether our selenium status is currently good enough? The answer is, it is not easy. Many studies have been performed over the years, although many of them are inconsistent with each other, with different units used for the same measurements (e.g., urinary selenium measured either in micromoles per day or in micromoles per gram creatinine) making it difficult to combine the estimates in a meta-analysis. Despite the fact that plasma levels have been widely used as a marker for selenium status in several studies, it is not considered a reliable. Alternatively, whole-blood concentrations, plasma selenoprotein P, and plasma, platelet, and whole-blood activity of glutathione peroxidase have been used. All these measurements can mirror the selenium status, but it’s difficult to assess which is the most reliable[2].
Scientists will someday come up with a reliable test for measuring selenium status. On our side, what we can do is to munch a few Brazilian nuts while waiting for this new test!
[1] Kryukov GV, Castellano S, Novoselov SV, et al. Characterization of mammalian selenoproteomes. Science 2003;300:1439–43.
[2] Ashton K, et al. Methods of assessment of selenium status in humans: a systematic review. Am J Clin Nutr 2009;89(suppl):2025S–39S.
[3] Burk RF, Norsworthy BK, Hill KE, Motley AK, Byrne DW. Effects of chemical form of selenium on plasma biomarkers in a high-dose human supplementation trial. Cancer Epidemiol Biomarkers Prev 2006;15:804–10.
[4] Yang GQ, Xia YM. Studies on human dietary requirements and safe range of dietary intakes of selenium in China and their application in the prevention of related endemic diseases. Biomed Environ Sci 1995;8: 187–201.
[5] Brown KM, Arthur Jr. Selenium, selenoproteins and human health: a review. Public Health Nutr 2001;4:593–9.
[6] Akbaraly NT, Arnaud J, Hininger-Favier I, Gourlet V, Roussel AM, Berr C. Selenium and mortality in the elderly: results from the EVA study. Clin Chem 2005;51:2117–23.
[7] Bleys J, Navas-Acien A, Guallar E. Serum selenium levels and all-cause, cancer, and cardiovascular mortality among US adults. Arch Intern Med 2008;168:404–10.
