Potatoes from the Ösling, or apples from Luxembourg? Depending on the product and the season, the notion of a regional foodstuff may encompass a wide variety of distances. It is not useful to seek to pin the concept down to a precise number of kilometres.
Consequently, "regional" is a flexible concept; it is not defined in law. Basically, when we speak of regional foods, we mean foods which are produced, processed and marketed within a demarcated region.
So you shouldn't hesitate to ask your grocer straight out to explain where the products sold originate from and which criteria are applied in advertising the foodstuffs in question as "regional".
Does "regional" mean the same thing as "local"?
The term "regional" does not mean the same thing as "local", even though many consumers assume that the two expressions are synonymous. In point of fact, a "regional" purchase invariably connotes an extensive area in which the goods in question have been produced. By contrast, the term "local" means something more precise; it signifies a smaller geographical area, such as a specific place within a region.
A seasonal and regional diet is one where the food consumed is produced in one's region and in the current season. Accordingly, a regional diet is at the same time one which is consumed in season. By contrast, keeping to a seasonal diet does not automatically mean consuming only regional products, because it is always summer somewhere in the world.
Globalisation enables us to buy all sorts of fruit and vegetables all year round, and because of the increasing importation of foodstuffs cultivated in the southern hemisphere, we tend to forget that fruit and vegetables don't in fact have a year-round ripening phase. But is it really necessary to eat strawberries in winter, when they taste like nothing so much as strawberry-flavoured water?
A seasonal diet, by contrast, gives you a better feel for the passage of the seasons, and may even allow you to rediscover forgotten types of vegetables or fruit.