Potatoes could lead to high blood pressure with as few as four spuds a week, new research concludes. Cooking methods were also shown to have little effect on how potatoes affect the body systems, the study determined.

Baked potatoes are often thought to be healthier than other methods of cooking the tubers. However, as far as high blood pressure is concerned, this may not be the case.

Hypertension affects roughly 80 million people in the United States. The condition has few symptoms, often leaving it undiagnosed. However, high blood pressure (HBP) can have deleterious health effects, potentially leading to serious health conditions, including premature death.

Replacing one serving of potato each day with non-starchy vegetables was found to reduce hypertension in study subjects.

The effect of potatoes on blood pressure presents an interesting dichotomy. While the food product raises blood sugar levels, tied to hypertension, they also contain potassium, which is known to lower blood pressure. This was the first major study to examine the long-term health effects of potatoes on hypertension.

Health records of over 187,000 people, covering 20 years, were examined as part of this latest study. None of the subjects examined had hypertension at the start of data collection.

Questionnaires recorded how often people in the study consumed various types of food. Potatoes were divided into three categories – potato chips, French fries, and spuds, which had been mashed, boiled or baked. Perhaps surprisingly, chips were found to be the one form of potato not associated with an increased risk of HBP.

Potential issues in the study include self-reporting by subjects of both their eating habits and blood pressure. People often forget what they ate, or may not report the truth.

"[The study could still] have potentially important public health ramifications, as they do not support a potential benefit from the inclusion of potatoes as vegetables in government food programs but instead support a harmful effect that is consistent with adverse effects of high carbohydrate intakes seen in controlled feeding studies," researchers suggest.

Examination of health effects from diet can be complex, and invoke a great deal of controversy.

Analysis of how potatoes could affect high blood pressure was profiled in The BMJ.