Lutefisk is the least effective food item, regenerating only 1 Life point. However, it is useful in that it can be tithed to the Lutefisk God in return for (eventual) gifts of fishy-smelling artifacts. Whether or not that makes it worthwhile to lug around these disgusting, gelatinous lumps is, of course, up to you.

The Horadric Lutefisk Cube can be used to generate Lutefisk from other items.