French researchers tested the idea on 2141 lung-cancer patients, matched with 2168 subjects without the cancer, and discovered that a diet high in these vegetables could have a 72-per-cent protective effect.
The problem, as always, is in our genes. Enzymes encoded by GSTM1 and GSTT1 genes destroy isothiocyanates. Those with active GSTT1 enzymes enjoyed only 33-per-cent protection with the vegetables, and those with an active GSTM1 enzyme achieved slightly better 37-per-cent protection. However, those in whom both enzymes were inactive had a 72-per-cent protective effect, while those in whom both enzymes were active had no protection whatsoever from cruciferous vegetables (Lancet, 2005; 366: 1558-60).