Fermented herring, known to the Swedes as surströmming, is a Swedish specialty. It's loved and loathed, putrid yet popular.
And like moist snus, it's one of the crazy concoctions Swedes love so much that they fight the EU in able to keep them.
But it can also be poisonous. The fish contains high levels of PCB and dioxin, environmental pollutants with the potential to be highly toxic - and seriously harm fetuses and infants.
The Swedish National Food Agency (Livsmedelsverket) declared on Monday that young women should eat herring, stinky or otherwise, no more than two or three times a year, and should try to eat the fish only at the late-August herring celebration - when it's practically mandatory.
The herring in pill form was reported to be just as risky as the "fresh" varieties.
Herring, Baltic Herring, wild-caught salmon, trout, and whitefish from the Vänern and Vättern lakes of Sweden also should be eaten with caution, the agency said.
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Children should also stay away from the fish.
But grown men and women passed child-bearing age can do as they like - as long as they don't eat herring more than once a week - perhaps just as much out of consideration for their neighbours as for the sake of their health.