Betaine
Specific molecules
A molecule the plant makes to withstand salt and drought; in us it takes part in the methyl cycle.
Not to be confused with betalains despite the name: same plant of origin, unrelated molecules.
Effects and benefits
The molecule that lets beets grow in salty soil also protects our kidneys. In us, from 1.5 g a day, it helps the cycle that recycles homocysteine by giving it its methyl groups.
Seaside plants and those of salty soils accumulate betaine to hold water in their cells. Our kidneys do exactly the same: in their deepest part, where urine is concentrated, the cells fill up with it so as not to dry out (Burg and Ferraris, 2008).
It gives a methyl group to homocysteine, which becomes methionine again. Betaine contributes to normal homocysteine metabolism, from 1.5 g a day; above 4 g a day, cholesterol may rise (Regulation 432/2012). Wheat bran, quinoa, spinach and beets are the richest; a plate never approaches the doses where caution is needed.
Sources: Burg and Ferraris, J Biol Chem, 2008 · EU Regulation 432/2012