FAD

What it isFlavin adenine dinucleotide, the major active form of riboflavin (vitamin B2).

Why it mattersIt is the electron carrier for flavoprotein oxidases — including monoamine oxidase, which degrades dopamine, norepinephrine, and serotonin.

What it changesRiboflavin deficiency therefore reaches wide: energy metabolism, monoamine turnover, and the metabolism of other vitamins all run through flavins.