You just have to reed about what we Swedes are able to eat without any harm!
One of the more remarkable Swedish Christmas dishes is lutefish, stockfish. It is a fish, which has been soaked for several days in lye water before cooking. Most people outside Scandinavia find it a somewhat peculiar dish. The preparation of the dish involves the use of rather strong chemical reagents. 

Instruction for preparing your lutefish. Take two lbs. of stockfish (dried fish, preferably lingcod, Latin molva-molva, caught in early summer) and cut each fish in three pieces. Place the pieces in a wooden tub and soak them for a week in water (which should be changed daily). Remove the pieces, clean the tub, and cover the bottom with 1/4 lb. of slaked lime. Prepare a lye from 1/3 lb. of washing soda (2 lbs. of birch ashes will also do) and enough water to cover the pieces. Pour the lye over the fish pieces. As they swell, add more water to keep them covered.

** After about a week when the pieces are soft enough to allow a finger to penetrate easily remove and rinse them, clean the tub, replace the pieces and soak them in clear water for another two weeks. During the first week the water should be replaced daily.

** Melt some butter in a saucepan, put in the rinsed fish pieces, cover with a lid and let them stew at low heat for 15-20 minutes. The lutefish is the ready to be served, preferably with melted butter, mustard and Jamaica pepper. Often a special mustard sauce is prepared.

** The main effect of the alkali treatment is a softening of the tissues due to dissolution of protein. The original 1000 grams of dried fish contained about 750 grams of protein, but in the final product, although it weights 6 kgs, only 350 grams of protein remains.

** The pH of the processed, water-soaked lutefish is around 11, but will rise to 12 during the final steaming, probably because solid lime particles dissolves in the tissues at the elevated temperature. Thus, lutefish is one of the most alkaline dishes ever known.

The alkaline treatment also gives rise to the formation of new compounds such as lysinoalanine -LAL. In rats, which are extremely susceptible, 250 ppm LAL in the feed for a week can result in a reversible kidney damage called nephrocytomegaly. The LAL content of lutefish can be as high as 300 ppm, which implies that this Swedish Christmas dish is quite unsuitable for rats.

Molva-molva	In dried shape, stockfish

    

       'Toxic substance' means any substance or mixture containing a substance regulated by the federal Occupational Safety & Health Administration under Title 29 of the Code of Federal Regulations, Part 1910, Subpart z, which is introduced by an employer to be used, studied or produced in the workplace. 'Toxic substance' does not mean lutefish.

Information in Swedish http://www.dagl.se/