Selenium

An essential trace element necessary for the functioning of the glutathione peroxidase enzyme system, which protects cell structures from oxidative damage. It is obtained from foods such as vegetables, cereals, legumes, garlic, fish, seafood, eggs and meat. The amount of selenium in these sources depends on the concentration of selenium in the soil. The Brazil nut (Bertholletia excelsa) is the food with the highest known concentrations of selenium.

The daily selenium requirement for breastfeeding mothers is 70-75 micrograms (mcg) per day. For infants, it is 2-3 mcg/kg (10 mcg/day for the first 4 months) with a maximum of 30 mcg/day. ^{(MedlinePlus 2017, Kipp 2015)}

Selenium is found naturally in milk in its organic form as selenomethionine (Dorea 2002). The amount of selenium in colostrum is 80 mcg per litre and in mature milk 12-20 mcg/L, with no or very weak correlation with plasma selenium levels or daily selenium intake ^{(Ezeama 2025, Ish 2024, Wasowicz 2001, Bianchi 1999, Artaud 1993, Cummings 1992, Levander 1987, Higashi 1983)}. However, some authors have found that selenium supplements given to breastfeeding mothers increase selenium levels in milk, and infants may exceed their daily selenium requirements. ^{(Dorea 2002, Trafikowska 1996)}

Higher plasma selenium levels have been found in breastfed infants than in formula-fed infants ^{(Strambi 2004, Sorvacheva 1996)}. There are lower plasma selenium levels in infants born small for gestational age. ^{(Strambi 2004)}

A trend association, but not statistically significant, has been found between selenium concentration in breast milk and cognitive scores in infants. ^{(Lockyer 2021)}

Selenium deficiency is very rare. With a normal diet, selenium supplements are not necessary in the absence of disease or conditions that may promote deficiency, such as parenteral nutrition, Crohn's disease, or prematurity. ^{(MedlinePlus 2017)}

It has been found that about half of breastfeeding mothers have intakes below the estimated average requirement or adequate intake and are at risk of selenium nutritional deficiency, both them ^{(Jin 2025 and 2019, Ezeama 2025)} and their breastfed babies, as their average daily selenium intake is below their respective adequate intakes. ^{(Jin 2019, Daniels 2019)}

Excessive selenium intake can lead to selenosis, a disease that causes dermatological (alopecia, nail dystrophy), digestive, neurological and fatigue symptoms ^{(MedlinePlus 2017)}. Nutritional supplements containing excessive amounts of selenium have caused serious poisoning. ^{(Aldosary 2012, Senthilkumaran 2012)}

The possible effects of selenium in preventing cancer, cardiovascular disease and heavy metal and toxin poisoning have not been proven, so taking selenium supplements other than those found in a normal diet is not recommended. ^{(MedlinePlus 2017)}

See below the information of this related product:

• Brazil Nut (Fairly safe. Mild or unlikely adverse effects. Compatible under certain circumstances. Follow-up recommended. Read Commentary.)