Cheers - this is what I found:
Inject instant flavor to your dukan diet menu by adding a small amount of seeded mustard. Both French and English mustards are allowed during most phases of the Dukan diet. Horseradish adds its own unique heat to meat and is actually also permitted during all phases. Just like in Japanese foods, wasabi, the kind of horseradish sauce, and ginger are both allowed. These go good together with fish, that is actually why they are often served with sushi