Vitamin B12, which the body receives via food, provides important coenzymes for isomerisation processes. Since only specific microorganisms are able to build vitamin B12, the body cannot produce a sufficient amount of this vitamin by itself. Therefore, it is important to consume enough food containing vitamin B12.
An adequate supply of iodine is crucial for babies’ healthy development –deficiencies bear the risk of hypothyroidism and brain damage. Parents should therefore ensure that their child receives enough of this mineral (e.g. via saltwater fish and seafood).
The trace element selenium is particularly important due to its role as an antioxidant and its effect on the immune system. It appears in a number of compounds, for example in proteins and inorganic selenium salts. The body counteracts selenium deficiency by strict regulation of selenoproteins.
Vitamin B12 (cobalamin) describes a group of compounds with a cobalt atom inside a porphyrin-like ring. Cobalamins involved in nutrition are transformed into the active coenzymes adenosyl and methylcobalamin, which are required for two reactions: i) the isomerisation of methylmalonyl-CoA to succinyl-CoA by mitochondrial methylmalonyl-CoA mutase, and ii) the methylation of homocysteine to methionine by methionine synthase. Vitamin B12 also plays an important role in the metabolism of folate.
Only certain microorganisms are able to build vitamin B12. Orally ingested vitamin B12 creates a complex with a factor in the gastric mucosa (gastric intrinsic factor (GIF)) and is absorbed in the jejunum. This is the reason why microbial production of vitamin B12 in the gut can never make the organism self-sufficient. Vitamin B12 always has to be ingested orally and is supplied by nutrients of animal origin, especially by liver, fish, eggs, cheese and dairy products.
Even at high doses, no adverse effects of vitamin B12 have been observed (DGE, 2015). However, insufficient supply of the vitamin, which is common in vegans, may require supplementation, otherwise megaloblastic anaemia may result. Recommended dosages are listed below:
Iodine is an element that is essential to the thyroid gland. Its metabolism is closely related to the one of selenium – mainly due to the existence of selenium-containing iodothyronine deiodinases, which activate the transformation of the prohormone thyroxin (T4) into its active T3-form. A well-functioning thyroid gland is highly important because its hormones T3 and T4 influence a number of bodily processes such as metabolism, cognitive development, and pleiotropic effects in many different organs (Boelaert and Franklyn, 2005). Iodine deficiency may lead to hypothyroidism and the development of a goitre. Iodine deficiency disorders are often of particular concern in infancy because of the risk of developmental brain damage.
The average iodine content of breast milk is around 50-100µg/l. Infants require an intake of 50µg per day of iodine, which is adequate for the majority of infants from birth to 12 months of age. An exclusively breastfed infant would consume 40-80µg of iodine per day during the first six months of life. Its fully or partially bottle-fed counterpart would receive 35-94µg per day (Hilbig 2005; Noble and Emmett, 2006). Accordingly, the recommended dosages are:
Iodine content in food varies according to the supply of iodine to the original food product. Two good sources of iodine are saltwater fish and seafood.back
Selenium is an essential trace element appearing in many compounds. As selenocysteine, it is incorporated into different proteins; 25 different genes for selenoproteins exist. Selenium can also appear in albumin as selenomethionine, which is non-specifically bound into the polypeptide chain instead of sulphur-containing methionine. Selenium can be bound to selenium-binding proteins, although their function is currently unknown.
Selenium sources are the aforementioned amino acids (selenocysteine or selenomethionine) and inorganic selenium salts. Selenium metabolism is regulated in a fairly complex way. If sources of selenium are limited, selenoproteins are made based on a clear hierarchy: some proteins such as GPx1 are down-regulated, while others such as GPx4 and deiodinases are still produced further on.
Selenium is an important antioxidant; an inadequate supply has a negative effect on immunological responses.
Selenium overdose is not expected in real-life conditions. DGE (2015) recommends the following dosages: