Good news for those who need a bit more coffee to get through their daily grind as the scientists have claimed that it may not increase your blood pressure. It's been suggested that coffee could cause high blood pressure, or hypertension, which has been linked to heart disease, strokes and shorter life expectancy.

But a new extensive study by a team from the Louisiana State University School of Public Health in New Orleans has now overturned this concern. It concluded that people who have several cups a day fare no worse than those who drink coffee less frequently.

For the study, the researchers pooled data from six old studies, covering 170,000 people, which asked participants how much coffee they drank each day and then followed them for up to 33 years.

According to their analysis, published in The American Journal of Clinical Nutrition, about one in five developed high blood pressure with the chance of diagnosis no different for people who said they drank more than five cups of a coffee a day compared with those who drank very little. But a member of the research team, Liwei Chen, said the relationship between coffee-drinking and blood pressure is complicated by the possibility that it does not work the same way for everyone.

"People with a different genetic background may react to coffee differently," she said. "For some people maybe it's safe to drink a lot of coffee, but not for other people." Blood pressure expert Lawrence Krakoff of Mount Sinai Medical Centre in New York, said: "I don't think of coffee as a risk factor for high blood pressure."