Is there any dietary recommendation for psoriasis?

Yes. A diet high in zinc can help, but my recommendation is to take a 50mg zinc gluconate supplement, together with 5000-7500mcg of biotin. Generally avoid high glycemic foods (sugar and starch-flour), eat plenty of vegetables, lean meat (including fish and poulry), and also make sure you get plenty of omega-3s. I supplement myself to get 1500mg/day.
Yes, a few. It is generaly recommended to follow a heart-helathy diet: plenty of fruits and vegetables, minimal saturated fat, hardly any trans fat. Some people benefit from eliminating gluten. For more information, check http://www.Psoriasis.Org/page.Aspx?Pid=1910.