Selenium: daily dose and safe limits

For most adults, the recommended daily dose of selenium is 55 micrograms (mcg) per day. In the UK, the reference nutrient intake for adults is 55 mcg, though some international bodies suggest up to 60 mcg. The safe upper limit – the dose above which adverse effects may occur – is 300 mcg per day for adults, according to the European Food Safety Authority (EFSA). You don't need more than that, and taking more brings no added benefit – quite the opposite, it can be harmful.

How much selenium should I take per day?

The recommended daily amount (RDA) of selenium varies with age and physiological state. For healthy adults, the figure is 55 mcg per day. During pregnancy and breastfeeding, needs rise slightly: 60 mcg per day during pregnancy and 70 mcg per day while breastfeeding. These are European reference values, based on the amount needed to ensure maximal activity of selenoproteins, which depend on this mineral to function.

If you get selenium from food, know that the amount varies greatly with the soil where crops are grown. Brazil nuts are famously rich in selenium – a single nut can contain between 68 and 91 mcg, which already covers an adult's daily need. But you don't need to eat Brazil nuts every day; a varied diet with cereals, meat, fish, and eggs usually provides enough selenium.

What is the safe upper limit for selenium?

The safe upper limit for selenium intake in adults is 300 mcg per day. This figure was set by EFSA and represents the highest dose that, based on available data, does not cause adverse effects in most people. Above this limit, selenium can cause symptoms such as garlic-like breath, a metallic taste in the mouth, hair loss, and brittle nails. In more severe cases, it can lead to neurological and gastrointestinal problems.

It's important to stress: the 300 mcg limit refers to total intake, meaning the sum of selenium from food and supplements. If your diet is rich in foods like Brazil nuts, tuna, or sardines, your dietary intake may already be considerable. Adding a 200 mcg supplement on top of that could bring you dangerously close to the limit, especially if you also consume other fortified foods.

What happens if you take too much selenium?

Selenium toxicity is a real risk, though rare. Selenosis, as chronic poisoning is called, manifests with symptoms that may go unnoticed at first: fatigue, irritability, and a characteristic garlic odour on the breath. Over time, changes appear in nails and hair, which become brittle and may even fall out. At very high doses, selenium can cause nervous system damage, with tremors and coordination difficulties.

That's why you shouldn't take selenium supplements without need. If you don't have a diagnosed deficiency, or if your diet is varied, you probably don't need to supplement. And if you do take supplements, never exceed the dose on the label, and avoid combining several products that contain selenium (for example, a multivitamin and an isolated supplement).

Who might need selenium supplements?

There are situations where supplementation may be justified, but these should be assessed by a doctor. People with conditions affecting intestinal absorption, such as Crohn's disease or coeliac disease, may struggle to get enough selenium from diet. Patients on kidney dialysis also often have low levels. And in regions with selenium-poor soils – rare in Europe but present elsewhere – food may not supply the mineral adequately.

For most people, though, supplementation is unnecessary. If you suspect you might be deficient, the best step is to talk to your doctor and ask for a blood test. Self-medicating with selenium, especially at high doses, is not advisable and can do more harm than good.

Selenium and beauty: what does the science say?

Selenium is often linked to skin, hair, and nail health, which is why it appears in many beauty supplements. The rationale is that selenium participates in the production of selenoproteins, some of which have antioxidant action, protecting cells from oxidative stress. But the evidence that selenium improves skin or hair appearance in healthy people is still emerging – that is, there are promising hints, but nothing conclusive.

Some small studies suggest selenium may help in specific conditions, such as certain types of hair loss, but results are preliminary. There is no solid proof that taking high doses of selenium makes skin more radiant or nails stronger. In fact, excess selenium can cause the opposite: hair loss and brittle nails are symptoms of toxicity. So if your goal is beauty, more selenium is not better.

If you're considering a beauty supplement with selenium, such as Collagen Gummies or Glow Up, check the selenium dose on the label. Most supplements contain between 50 and 100 mcg per serving, which is safe for most adults. But remember: beauty doesn't come from a pill, and a balanced diet, adequate sleep, and sun protection remain the pillars of healthy skin.

How to choose a selenium supplement?

If, after talking to your doctor, you decide you need a supplement, there are a few practical considerations. Selenium comes in two main forms: selenomethionine and sodium selenite. Selenomethionine is the organic form, found naturally in foods, and is generally well absorbed. Sodium selenite is an inorganic form, also used in supplements, but with less efficient absorption.

As for dose, choose a supplement that provides between 50 and 100 mcg per day, unless your doctor advises otherwise. Avoid products with more than 200 mcg per serving, unless there is a clear medical reason. And always check the label for the form of selenium used and the exact dose per portion.

Remember that supplements are not medicines and should not be used to treat or prevent disease. If you have a health condition or take medication, talk to your doctor or pharmacist before starting any supplement. They can assess whether selenium is safe for you and whether it interacts with other medicines.

What if I don't know the right dose?

The honest answer is: don't guess. The recommended daily dose of selenium is 55 mcg for adults, and the safe upper limit is 300 mcg. But everyone is different, and factors like age, health status, and diet influence individual needs. If you have doubts about how much selenium to take, or if you're considering supplements for specific purposes, the best thing is to consult a healthcare professional.

A pharmacist can help you interpret labels and check whether a supplement is suitable for you. A doctor can order tests to assess your selenium levels if deficiency or excess is suspected. Don't rely on generic internet advice, including this article, for important health decisions. The information here is a starting point, not a substitute for professional advice.

In summary: for adults, 55 mcg per day is the reference dose, and 300 mcg is the upper limit not to exceed. Most people get enough selenium from food and don't need supplements. If you're still considering supplementation, talk to your doctor or pharmacist first. And remember: more isn't better, and excess can be harmful.