It has often been noticed that differences along the historical borders exist in Poland. See for example this article.
Here's another article discussing the differences, and interestingly claims that the difference between the election result in former Prussian and Russian parts of Poland is likely due to other factors.
You think so? My impression of the Netherlands is that the staple food is fries with mayonnaise, maybe with some broodje kroket in between. In general the diet consists of a lot of butter, white bread and sugar. To me it does not seemt surprising at all that they eat least vegetables in Europe.