New research suggests that fortifying food with folic acid may help to prevent stroke death.
The study, reported in the Circulation journal, suggests that the acid, which is often added to breads, cereals and spreads, lowers the risk of stroke by reducing the body's homocysteine levels.
The research found that the average annual decline in stroke deaths in the US rose from 0.3 per cent between 1990 and 1997 to almost three per cent between 1998 and 2002 when folic acid fortification was made mandatory.
The findings were not matched in England and Wales, where fortification of foods is not yet compulsory.
Head researcher Dr Quanhe Yang commented: "If folic acid fortification is responsible for even a fraction of the accelerated improvement we observed, this public health benefit is an important bonus to the reduction in neural tube defect rates."
Around 150,000 people in the UK have a stroke each year and it is the nation's third biggest killer.