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Eating potatoes four or more times a week may increase the risk for high blood pressure, a large new study has found.

Researchers pooled results from three observational studies involving 187,453 men and women followed for more than 25 years. The participants returned health and diet questionnaires every two years, including whether a doctor had diagnosed hypertension. The study is in BMJ.

After controlling for body mass index, physical activity, smoking and other factors, they found that compared to eating potatoes only once a month, having one potato — baked, boiled or mashed — four to six times a week increased the risk for hypertension by 11 percent. Eating four or more four-ounce servings of French fries a week increased the risk by 17 percent. Adjusting for salt and saturated fat intake did not change the results, but the authors acknowledge that they could not control for all possible variables.

The researchers suggest that potatoes cause a rapid rise in blood glucose levels, which is associated with blood vessel problems and inflammation. This may increase the risk for hypertension.

“We don’t completely know what a healthy diet is,” said the lead author, Dr. Lea Borgi, an associate physician at Brigham and Women’s Hospital in Boston, “and I have no opinions about what people should eat. It’s important that studies like this continue the discussion.”