A balanced diet of B12, folate and choline is critical to ensuring the benefits of methylation (known as single carbon metabolism).
There are several very important metabolic reactions that depend on transferring a solitary carbon molecule to genes or amino acids (the building blocks of proteins). This single carbon has 3 hydrogens attached to it and is called a ‘methyl group’ (or CH3). Adding a methyl group is called ‘methylation’ and methyl groups come from an essential nutrient called choline, found in high concentration in foods like liver, egg yolks, wheat germ, cruciferous vegetables, meat and fish. Methyl groups from choline get passed to betaine (made from choline) or an essential B group vitamin called folate.
Folate can’t methylate directly and passes its CH3group (like a relay runner passing the baton) to Vitamin B12 to methylate an amino acid called homocysteine. This transforms homocysteine into methionine, which is a key to making many other amino acids for the body and also the reading of the genetic code. If there is a shortage of methyl groups, like in B12, folate or choline deficiency, then homocysteine levels can rise, causing damage to the brain and cardiovascular system, among others. So a balance of these three nutrients is very important.