Study links potato consumption to lower mortality in Norwegians

Potatoes are often considered to be less healthy compared to other vegetables. In 2000, Dr. Fedon A. Lindberg created a stir in Norway when he announced that a large proportion of the population ought not to eat so many potatoes. Many of us can gain weight and develop type 2 diabetes, he believed.

A major study has now looked at how 77,000 Norwegians have fared over a period of 40 years.

"Those who ate at least two potatoes a day during the 1970s and 80s turned out to have a 12% lower mortality rate during the subsequent 40 years. Eating more potatoes was also linked to a lower mortality due to heart disease.

"This lower mortality rate is roughly the same as we find among people with a high consumption of vegetables in general," says Erik Arnesen, research fellow at the Institute of Basic Medical Sciences at the University of Oslo.

Potatoes are not among the recommended fruits and vegetables on the '5-a-day' list

In the past, people thought that a proper dinner had to include potatoes. Six days a week, it was therefore normal to serve potatoes at dinnertime. According to consumer surveys from the 1980s, 9 out of 10 fish dinners and 8 out of 10 meat dinners were eaten with potatoes.

"Potatoes have often been thought to be less healthy than other vegetables and the Norwegian dietary guidelines do not include potatoes among the recommended '5-a-day' fruits and vegetables.

"However, though the most recent Nordic dietary recommendations do say that people can include potatoes as an important part of a healthy diet, there is not enough evidence to conclusively determine that potatoes in themselves affect the risk of chronic diseases. That is why we wanted to investigate this particular question," says Arnesen.

The correlations were the same among women and men

The study was recently published in the Journal of Nutrition. In collaboration with other researchers at the University of Oslo and the Norwegian Institute of Public Health, Arnesen collected data from county-wide surveys carried out between 1974 and 1988 by Norwegian National Health Surveys. The researchers then linked the participants to the Cause of Death register 40 years later, to see how things had turned out.

"Those who ate on average two potatoes a day were shown to have a reduced risk of dying. Our estimates are also that for every 100 grams of higher potato intake, the mortality risk and the risk of dying from precisely heart disease, were 4% lower, explains the research fellow."

Arnesen emphasizes that the researchers took into account the participants' age, gender, smoking habits, physical activity and their intake of meat, fish and melted butter or margarine for dinner. The correlations were the same for both women and men and across the various categories of body mass index, smoking and physical exercise.

Potatoes provide vitamin C, potassium and dietary fiber

During the 1970s and 80s, boiled potatoes were one of the primary sources of dietary fiber in Norwegian food. Among other things, they also provide vitamin C and potassium, which promote good heart health.

Professor Kjetil Retterstøl at the Department of Nutrition, the last author of the study, says that one of the strengths of the study is the large number of participants and the long follow-up period.

"This is probably the largest study ever on the link between potatoes and heart disease," says Retterstøl.

Other studies included French fries and mashed potatoes

A number of previous studies have indicated that you run a higher risk of developing diabetes type 2 if you eat a lot of potatoes. Arnesen points out that a consistent weakness of these studies is that they also include products derived from potatoes, such as French fries and mashed potatoes.

"Nutritionally, these products are very different from simple, boiled potatoes since they are high in both fat and salt," he explains.

The scientist emphasizes that more research is needed in order to understand the underlying mechanisms involved, so that we can find out just how healthy potatoes are from all points of view.