Too much soft drink, juice and coffee can increase stroke risk

Frequent drinking of fizzy drinks, fruit juice and coffee is associated with an increased risk of stroke, according to the latest findings from the INTERSTROKE research project.

Stroke occurs when the blood supply to part of the brain is cut off and damages brain cells. Subtypes include ischemic stroke, which is usually due to a blood clot, and intracerebral haemorrhage, which is bleeding into the brain tissue.

INTERSTROKE is one of the largest international studies of risk factors for stroke, involving almost 27,000 people in 27 countries. Those who took part in the project came from a broad range of geographical and ethnic backgrounds, with different cardiovascular risk profiles.

The study that focused on people’s consumption of fizzy drinks and fruit juice, published in the Journal of Stroke, found that fizzy drinks (including both sugar-sweetened and artificially sweetened) were linked with a 22% increased chance of stroke, and the risk increased sharply with two or more of these drinks a day. The link between fizzy drinks and chance of stroke was greatest in Eastern/Central Europe and Middle East, Africa and South America.

Fruit juice drinks were meanwhile linked with a 37% increase in chance of stroke due to bleeding (intracranial haemorrhage). The risk triples with two of these drinks a day, with women showing the greatest increased chance of intracranial haemorrhage. The risk of stroke is likely to due to the fact that many products marketed as fruit juice are made from concentrates and contain added sugars and preservatives, offsetting the benefits linked with fruit consumption.

“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,” said the University of Galway’s Professor Andrew Smyth, lead researcher on both of the new studies.

“As a doctor and as someone who has researched the risk of stroke, we would encourage people to avoid or minimise their consumption of fizzy and fruit drinks, and to consider switching to water instead,” Smyth continued. Indeed, drinking more than seven cups of water a day was linked with reduced odds of stroke caused by a clot.

The study that focused on people’s consumption of coffee and tea, published in the International Journal of Stroke, found that drinking more than four cups of coffee a day increased chance of stroke by 37%, but lower intakes were not associated with stroke risk. Drinking tea was generally linked with an 18–20% reduced chance of stroke, although there were important geographical differences in the findings — tea was linked with lower chance of stroke in China and South America but higher chance of stroke in South Asia.

Drinking 3–4 cups per day of black tea was generally linked with a 29% lower chance of stroke, while drinking 3–4 cups per day of green tea was linked with a 27% lower chance of stroke. The reduced chance of stroke from drinking tea was lost for those that added milk, perhaps because this reduces or blocks the beneficial effects of antioxidants that can be found in tea.

The University of Galway’s Professor Martin O’Donnell, who co-leads INTERSTROKE, said a key goal of the project is to provide usable information on how to reduce one’s risk of stroke.

“While hypertension is the most important risk factor, our stroke risk can also be lowered through healthy lifestyle choices in diet and physical activity,” he said. “The current study adds further information on what constitutes healthy choices on daily intake of beverages.”

Image credit: iStock.com/zeleno