Selenium: the key trace element for thyroid, fertility and pregnancy

It is incorporated into specialised proteins called selenoproteins, several of which are directly involved in the conversion of thyroid hormones, the antioxidant protection of cells and the regulation of immune defences.

Its role in the thyroid is particularly critical: without selenium, the thyroid gland cannot efficiently convert T4 into T3, the active form of thyroid hormone, which affects all metabolic functions and the neurological development of the baby. A selenium deficiency can furthermore amplify the effects of an iodine deficiency, two trace elements whose requirements increase significantly during pregnancy and breastfeeding. The chemical form of selenium used directly determines its bioavailability and its benefits.

In its natural form, the main dietary sources of selenium are Brazil nuts, by far the most concentrated source, fish and seafood, offal such as liver and kidneys, lean meats, eggs and certain wholegrains grown in selenium-rich soils. The selenium content of plant foods is directly linked to the richness of the soil in which they were grown, and European soils are generally low in selenium compared to North American or Brazilian soils. This is one of the reasons why selenium deficiencies or insufficient intakes are common in European populations, particularly among pregnant women and vegetarians. The absorption of dietary selenium depends on its chemical form, organic or mineral, and the food matrix in which it is found.

In supplement form, selenium is found in two main forms: organic forms, including selenomethionine and selenocysteine, and inorganic forms, including sodium selenate and selenite. Organic forms, and selenomethionine in particular, have a markedly superior bioavailability, with an absorption rate of up to 90% according to studies, compared with only 50 to 60% for inorganic forms. It is the form of choice in a pregnancy vitamin. Selenomethionine is incorporated into the body's proteins in the same way as methionine, making it a particularly well-absorbed and well-tolerated form. In Baby Bump by Jolly Mama, it is precisely this highly bioavailable form that is used, to ensure a genuinely effective intake during pregnancy. It is advisable to check the chemical form of selenium in any supplement, the presence of a quality certification and the absence of excessive doses, as selenium can become toxic at very high quantities.