The European food safety authority (EFSA) last evaluated vitamins and minerals for safety in 2006 and set a so-called Tolerable Upper Intake Level (UL) for each micronutrient, provided sufficient data were available. This UL reflects the maximum safe level of a micronutrient that will not cause adverse effects when taken daily from all sources for a lifetime.
| The maximum safe daily intake for selenium is 300 µg. The maximum safe daily intake for selenium is 5.5 times the EU recommended daily intake (Nutrient Reference Value, NRV). |
The above safe maximum daily amount applies to adult males and females 18 years of age and older, as well as pregnant and lactating women. Furthermore, the safe maximum daily amount applies only to dietary selenium as well as sodium selenate, sodium selenite, and sodium hydrogen selenite.
Selenium oversupply is generally not to be expected in the dietary pattern common in Germany. In a long-term study over at least 4.5 years, the administration of 200 µg selenium per day in addition to the conventional diet remained without undesirable side effects.
The so-called LOAEL (Lowest Observed Adverse Effect Level) – the lowest dose of a substance at which adverse effects were just observed – was set by EFSA at 1,200 µg of selenium per day. Based on the LOAEL, a NOAEL (No Observed Adverse Effect Level) – the highest dose of a substance that has no detectable and measurable adverse effects even with continued intake – of 850 µg of selenium per day was derived for selenium and corresponds to just under three times the safe maximum daily intake.
Adverse effects of excessive selenium intake
Selenoses (selenium toxicity with alopecia/hair loss, altered nail growth, mottled teeth, skin sores, and nerve changes) have been observed above an excessive selenium intake of 1,200 µg selenium per day.
Single ingestion of 250 mg (250,000 µg) of selenium and multiple ingestions of 27 to 31 mg of selenium resulted in symptoms of poisoning such as nausea (nausea), vomiting, soft nails, dry hair, alopecia (hair loss), and fatigue. In addition, a garlicky odor of the breath is characteristic of selenium poisoning. The same symptoms have been observed after inhalation of selenium-containing vapors in the selenium-processing industry.
In China, daily intakes of at least 5,000 µg of selenium per day resulted initially in brittle hair and nails, sore skin with swelling and blisters, and in later stages in neurological and motor disorders, pain, cramps, numbness, and even paralysis. Symptoms subsided after cessation of use and affected individuals recovered.
