Baked, boiled, or mashed, new research indicates potatoes raise the risk of high blood pressure, suggesting they be removed from school lunch and food stamp programs.

Potatoes — one of the most ubiquitous foods in the world — may need to be reevaluated for people who need to be more heart healthy.

A new study released today examined the diets of people who included potatoes as a staple in their meals — eating four or more servings a week — and found they had an increased risk of high blood pressure.

Researchers at Brigham and Women’s Hospital and the Harvard Medical School found those who replaced one serving of boiled, baked, or mashed potatoes per day with a nonstarchy vegetable had a lower risk of hypertension.

Lead study researcher Dr. Lea Borgi, a physician at Brigham, said few independent studies have examined the impact of potatoes and this new research could be part of the conversation about what constitutes a healthy diet.

“Potatoes are very nutrient rich for sure, but one should also know they’re very high on the glucose index,” she told Healthline.

Her team’s results were published in the British Medical Journal.

Until recently, federal school lunch programs restricted white potatoes to one cup a week and the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) excluded white potatoes.

The restriction on starchy vegetables in school lunches was lifted in 2012 and white potatoes were included in WIC vouchers in 2015.

Read More: Get the Facts on a Balanced Diet »

Researchers used data from 187,453 participants with more than 20 years of follow-up research.

Two of the three studies involved focused primarily on nurses, most of whom were women.

None of the study participants reported high blood pressure at the start of the study. At the end, 77,726 reported they had been diagnosed with hypertension.

Researchers discovered those who consumed four or more servings of baked, boiled, or mashed potatoes had an 11 percent increase in hypertension. Oddly, this risk only translated to women, not men.

“That was quite surprising,” Borgi said.

For french fries, that risk was 17 percent for both genders.

Interestingly enough, researchers didn’t discover any association between consuming potato chips and higher blood pressure.

In the subject pool involving men aged 40 to 75 at the beginning of the study, potato chips were associated with an overall lower risk of developing hypertension.

“That was another unexpected result,” Borgi said.

She said the shift in healthier oils to make potato chips might have helped.

While further study is needed to confirm the findings, Borgi says there were several possible ways potatoes could increase a person’s blood pressure, including a high glycemic load and the potential to contribute to weight gain.

The increased risk could also be explained by the fact potatoes are often consumed with high amounts of salt and fats, like butter or sour cream.

Overall, it’s too early to recommend a diet low in potatoes, or especially one high in potato chips, Borgi said.

“These studies are a good start to a conversation,” she said.

Read More: Get the Facts on High Blood Pressure »

Dr. Mark F. Harris, a professor of general practice at the University of New South Wales in Sydney, Australia, wrote in an editorial accompanying Borgi’s research that too much emphasis is often placed on isolated food items and not dietary patterns.

“Prevention and early management of hypertension is a major priority of governments and international organisations in their attempts to reverse the rising prevalence of chronic disease. Diet has an important part to play,” he wrote. “However, dietary behaviour and patterns of consumption are complex and difficult to measure. We will continue to rely on prospective cohort studies, but those that examine associations between various dietary patterns and risk of disease provide more useful insights for both policy makers and practitioners than does a focus on individual foods or nutrients.”

Borgi agrees a person’s diet should be examined in its totality, not merely a single food item.

“I think it’s become difficult to identify a healthy dietary pattern, but patterns are made up of individual foods,” she said.

As potatoes are often touted for their ability to decrease blood pressure, the study adds to the debate about what aspects of a person’s diet can either increase or decrease their risks for diseases later on.

Other research has found that purple potatoes, a boutique variety becoming increasingly popular in high-end food stores, have the ability to lower blood pressure in obese people or those who already have hypertension.

Potatoes are natural sources of important minerals, including magnesium and potassium. That’s why organizations like the American Association of Retired People (AARP) recommends baked potatoes for heart health.

Potato industry-funded research argues white potatoes have earned their spot on American’s dinner plate because of their macronutrients, while other studies cite their calories and starches as reasons for concern.

The World Health Organization (WHO) doesn’t classify the potato — including sweet potatoes and other starchy tubers — as a vegetable. They recommend 400 grams of fruits or vegetables a day, none of which should be potatoes.

U.S. dietary guidelines, however, recommend five cups of starchy vegetables like potatoes each week.

Read More: New Dietary Guidelines Released »