Potatoes Tied to Higher Risk of Type 2 Diabetes; French Fries Worst

Veronica Hackethal, MD

December 24, 2015

Eating potatoes may increase the risk of type 2 diabetes and replacing them with whole grains may lower this risk, according to a study published online December 17 in Diabetes Care.

"Although potatoes are considered a vegetable in the US Guideline of Healthy Eating, potatoes should not be regarded as a key component of a healthful diet. These data support the notion that potatoes should be considered a source of carbohydrates like grains, especially refined grains, rather than vegetables," commented first author Isao Muraki, MD, PhD, of the Osaka Center for Cancer and Cardiovascular Disease Prevention, Japan, and Harvard TH Chan School of Public Health, Boston, Massachusetts.

"Potatoes contain a large amount of starch and a relatively small amount of fiber, vitamins, minerals, and polyphenols," he added, "Lower quality and quantity of carbohydrate is associated with a higher risk of type 2 diabetes."

Moreover, when potatoes are served hot their starch becomes more easily digestible and raises blood glucose levels more quickly, he explained.

Are Potatoes a Vegetable or Not?

Whether to consider potatoes as a vegetable in dietary recommendations has recently been a point of contention in the United States and United Kingdom, with the two countries coming to different conclusions.

The US national food guide MyPlate and Review of Special Supplemental Nutrition Program for Women, Infant, and Children Food Packages by the Institute of Medicine consider potatoes to be a "healthful vegetable."

In contrast, the UK national food guide, the Eatwell plate, lists potatoes as a cereal, according to background information in the article.

The current study combined data from three US cohort studies on 70,773 women from the Nurses' Health Study (1984–2010), 87,739 women from the Nurses' Health Study II (1991–2011), and 40,669 men from the Health Professionals Follow-Up Study (1986–2010).

Participants did not have diabetes, cardiovascular disease, or cancer at the start of the study. Researchers assessed potato consumption using validated food frequency questionnaires. Total potato consumption did not include potato chips (crisps), because the questionnaire combined potato and corn chips into one question.

Researchers also evaluated 4-year change in potato consumption. They identified type 2 diabetes using self-report and confirmed it with a validated questionnaire.

French Fries Associated With Greatest Risk of Diabetes

The results showed that participants with a higher consumption of potatoes (baked, boiled, mashed, or french fried) had a significantly higher risk of type 2 diabetes.

After adjustment for demographic, lifestyle, and dietary factors, participants who ate less than two to four servings of potatoes per week had a 7% increased risk of type 2 diabetes (pooled hazard ratio [HR], 1.07), while those who ate seven or more servings per week had 33% increased risk (pooled HR, 1.33) compared with those who ate less than one serving per week.

Participants who ate french fries had a higher risk of type 2 diabetes (pooled HR for every three servings/week, 1.19) than those who ate baked, boiled, or mashed potatoes (same HR, 1.04), respectively.

Adjusting for individual dietary factors, changes in body mass index over time, and glycemic load from all foods except potatoes (to account for the quality and quantity of total carbohydrate) did not change the results.

Participants who increased their potato consumption over time — especially french fries — had an increased risk of diabetes. For every three-servings/week increase, they had a 4% increased risk of diabetes compared with those who ate the same amounts of potatoes over time.

Estimates showed that replacing three servings per week of potatoes (regardless of type) with whole grains would decrease the risk of type 2 diabetes by 12%. Similar findings resulted from analyses by potato type (french fries and baked, boiled, or mashed).

Because study participants were health professionals of European ancestry, these results may not extend to other ethnic and demographic groups, the authors note.

"Potato food consumption should be reduced for people with elevated risk of developing diabetes or insulin resistance," Dr Muraki emphasized. "Healthy foods such as vegetables, fruits, whole grains, and nuts, rather than potatoes, should be encouraged for the prevention of type 2 diabetes."

The authors report no relevant financial relationships.

Diabetes Care. Published online December 17, 2015. Abstract

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