In 1970-90, however, Japan’s cerebrovascular mortality rate fell towards the OECD average. With world-beating numbers on heart disease and fewer strokes, Japan soared up the longevity league table.

How did Japan overcome its cerebrovascular woes? Some of its gains simply mirror better treatments and reductions in blood pressure around the world, notes Thomas Truelsen of the University of Copenhagen.

However, another cause may be diets. Japan largely banned meat for 1,200 years, and still consumes relatively little meat and dairy. Too much of these can be damaging, since they contain saturated fatty acids, which correlate to heart disease. Studies have also tied eating lots of processed red meat to a greater risk of stroke. But too little may be unwise as well, because they provide cholesterol that may be needed for blood-vessel walls.

Some empirical evidence supports this view. One paper from the 1990s found that the parts of Japan where diets had changed most also had the biggest drops in cerebrovascular mortality. Another study, which tracked 80,000 Japanese people in 1995-2009, showed that strokes were most common among those who ate the least chops and cream.