From Mike Quastel:

Re: “Last Supper” got ever bigger in paint: study (March 24): The last supper was almost certainly the passover meal (seder), and would of course not have included bread. The picture by Duc­cio and Ti­tian clearly shows a large chunk of bread on the corner of the table. Therefore I submit that the artist’s rendition is inaccurate and one cannot deduce anything from the sample of 2 paintings.