Drinking more than four cups of coffee per day increases the risk of stroke by more than a third, according to new research from the University of Galway.
New findings from global research studies co-led by University of Galway, in collaboration with McMaster University Canada and an international network of stroke researchers, highlighted the impact different drinks can have on stroke risks.
Stroke occurs when the blood supply to part of the brain is cut off and damages brain cells – it can either be ischemic stroke, which is usually due to a blood clot, or when there intracerebral haemorrhage, which is bleeding into the brain tissue.
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The findings come from two analyses of the Interstroke research project, one of the largest international studies of risk factors for stroke, involving almost 27,000 people in 27 countries, including Ireland.
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According to the research, fizzy drinks, including both sugar-sweetened and artificially sweetened such as diet or zero sugar, were linked with a 22 per cent increased chance of stroke, and the risk increased sharply with two or more of these drinks a day.
Fruit juice drinks were linked with a 37 per cent increase in chance of stroke due to bleeding known as intracranial haemorrhage. With two of these drinks a day, the risk triples, the research showed.
According to the research on coffee, drinking more than four cups of the beverage a day increased the chance of stroke by 37 per cent, but lower intakes were not associated with stroke risk.
Drinking between three and four cups per day of breakfast and earl grey teas was linked with a 29 per cent lower chance of stroke, while consuming the same amount of green tea was linked to a 27 per cent lower chance.
However, the research found the addition of milk can reduce or block the effects of antioxidants found in tea.
Prof Andrew Smyth, professor of clinical epidemiology at University of Galway and consultant physician at Galway University Hospital, said “not all fruit drinks are created equal”.
“Freshly squeezed fruit juices are most likely to bring benefits, but fruit drinks made from concentrates, with lots of added sugars and preservatives, may be harmful,” he said.
Prof Smyth said the increased stroke risk due to coffee consumption is “probably linked to caffeine, which can increase blood pressure”. However, he stated the research did not look at the effects of different types of coffee, which could have varying impacts.
The study on the effects of fizzy drinks and fruit juice was reported in the Journal of Stroke and the findings related to tea and coffee were published in the International Journal of Stroke.
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