The idea is to eat at least 350 grams of fish a week, which is around one-and-a-half cups—and it should be a fatty fish, such as herring or mackerel, or a mix with leaner cuts such as plaice and pollock. But don't make tuna your first choice; it's low in the fatty acids we need, and it can also have high concentrations of methylmercury.
Switching from meat to fish doesn't have a profound impact on health, although the researchers reckon it could prevent 170 deaths from heart disease every year among Denmark's population of 5.74m people, say researchers from the country's Technical University.
Although red meat is an important source of iron, it also raises the risk of some cancers, the researchers say, while fish is an important source of healthy fatty acids and vitamin D.
People over the age of 50 and younger women could especially benefit from the change in the diet, the researchers say.