Back in post-war Finland in the 1950s, it was hard to imagine a healthier lifestyle than that of the country’s thousands of forestry workers.
They spent all day outdoors in the fresh air, indulging in the kind of arduous physical labour many of us would balk at these days.
It should have been a recipe for good health and a long life. Yet, something was killing them well before their time. It wasn’t until a landmark study in 1953 by an American researcher called Dr Ancel Keys that the mystery was solved.
Keys compared the diets of men from seven different countries to try to work out why rates of heart disease appeared to be so much higher in some than others.
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