Selenium Status Should Be Assessed

We would like to add two important aspects to the meaningful conclusions drawn by the authors concerning the essential trace element selenium (1).

Besides a single assessment of baseline micronutrient supply, explicit attention should be paid to potentially demanding and stressful situations, such as pregnancy, chronic or acute illness, or convalescence. In particular during pregnancy, there is high risk for selenium deficits when the additional needs of the fetus are not met by adequate supply (2). Moreover, selenium deficiency constitutes an established risk factor for infections, autoimmune disease and malignancy, and poor Se status is associated with increased morbidity and mortality, as just reported in regards to COVID-19 (3).

Adequate selenium supply needs to be adapted also after pregnancy, disease and therapy, in order to cope with the particular challenging follow-up conditions. This notion is of particular relevance to those patients with proven deficits, e.g., due to vegan diet. The reported median serum selenium values of 68 µg/l (vegans) and 77 µg/l (mixed diet) are in our view critically low, because they indicate a suboptimal supply and insufficient biosynthesis of important selenoproteins, such as the glutathione peroxidases and the transport protein selenoprotein P (3, 4).

Especially in those patients who live on a vegan diet during tumor therapy, supplemental selenium intake should be recommended to compensate for an existing selenium deficiency, since the clinical data indicate an improved tolerance of chemotherapy and radiotherapy under supplementation without impairment of the main biological effect (4). The same applies equally to tumor patients on a mixed diet. In our view, there is no risk of selenosis when a daily supplementation of 200 µg selenium is not exceeded and, ideally, the selenium status is monitored every three months (4).