Glucoraphanin → sulforaphane
Sulfur compounds
The dormant molecule of broccoli, which only becomes sulforaphane the moment it is broken.
Chew well, and cook briefly: above 70 °C the vegetable's enzyme is dead. Broccoli sprouts carry ten to a hundred times more than broccoli.
Effects and benefits
Broccoli carries a weapon in kit form: two parts stored apart, which only come together when you chew it. The sulforaphane that results flips the switch of hundreds of protective genes in our cells; in one trial, a broccoli sprout drink made people excrete 61% more benzene.
In the plant, glucoraphanin and the enzyme that transforms it, myrosinase, are stored in different cells. When an insect bites the leaf, or when we chew it, the two meet and produce sulforaphane, bitter and repellent to the insect.
In us, sulforaphane activates Nrf2, a protein that controls hundreds of defense genes: antioxidant enzymes, enzymes that neutralize and clear foreign substances (Fahey et al., 1997).
The effect was measured in Qidong, China, a region heavily exposed to air pollution: twelve weeks of a broccoli sprout drink increased urinary excretion of benzene by 61%, and of acrolein by 23% (Egner et al., 2014).
A proven kitchen trick: a pinch of ground mustard seed on overcooked broccoli gives back the enzyme it lost (Okunade et al., 2018).
When cooking has destroyed the plant's myrosinase, it is bacteria of the colon — Bacteroides thetaiotaomicron among others — that do the conversion in its place, in far smaller amounts.
Sources: Fahey et al., PNAS, 1997 · Egner et al., Cancer Prev Res, 2014 · Okunade et al., 2018