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Too much selenium in the body: an underestimated risk. Selenium plays an essential role in immunity and the fight against oxidative stress, but an excess can quickly become toxic. Here's what you need to know.
Selenium: an essential but delicate mineral to dose
Selenium plays a fundamental role in the body's defense. It protects cells from oxidative stress by supporting the action of key enzymes, such as glutathione peroxidase, which neutralizes free radicals. It is also involved in the production of thyroid hormones and the proper functioning of the immune system.
But as is often the case with micronutrients, the balance is fragile. A selenium deficiency can lead to weakened immunity, hormonal disorders, and even chronic fatigue. Conversely, an excess of selenium can have harmful effects on health.
What are the dangers of excess selenium?
Too high a selenium level in the blood can occur from excessive intake of food supplements, or from regular consumption of foods very rich in selenium such as Brazil nuts (up to 100 µg per nut). However, the recommended intake is approximately 70 µg per day for an adult.
Beyond that, selenium becomes a danger. This is called selenosis, a form of progressive intoxication that can cause:
- gastrointestinal problems (nausea, diarrhea, abdominal pain)
- hair loss and brittle nails
- garlic-smelling breath (classic symptom of intoxication)
- chronic fatigue or unexplained irritability
- neurological disorders in the longer term
Even more worrying, some studies suggest that chronic excess could increase the risk of developing certain pathologies, particularly an increased risk of prostate cancer in men (in case of regular overdose over several years).
How to identify selenium overdose?
If you take food supplements, or if you very frequently consume seafood, liver, or Brazil nuts, it is advisable to monitor your selenium intake. In case of doubt, a blood test can be prescribed to evaluate your level.
A selenium level above 150 µg/L of plasma is considered high. It is not uncommon to exceed this threshold if you combine several sources of selenium in the same day.
What to do in case of excess selenium?
The first step is simple: immediately stop any supplement containing selenium. Then, limit the consumption of highly concentrated foods, such as Brazil nuts, which alone can exceed the maximum tolerable intake.
Adopt a more diversified diet, maintaining good mineral coverage without excess. Medical monitoring may be necessary if symptoms are already present.
In the majority of cases, the effects of moderate excess gradually disappear once the intake is normalized. But be careful not to alternate deficiency and excess: the goal is always stability, aiming for an adapted and regular intake of around 70 µg per day.
