Women who regularly eat potatoes are more likely to develop Type 2 diabetes when they fall pregnant, research reveals.
Those who enjoy two to four servings of potato a week are 27% more likely to get the disease when pregnant, according to a major US study published in the British Medical Journal.
Harvard University researchers suggested substituting potatoes with other vegetables, legumes like peas, beans and lentils, or whole grain foods might lower the risk.
Experts analysed total potato consumption, including baked, boiled, mashed and fried, of 15,000 women who later became pregnant over a 10-year period.
One serving included one baked or boiled potato, 237ml of mashed potatoes or 113g of fries.
Even one serving a week before pregnancy appeared to increase the risk by 20% compared with women eating less than one serving a week. Those eating more than five servings a week had a 50% increased risk.
How eating potato before pregnancy increases chances of developing diabetes during it
The experts said: “Though potatoes are rich in vitamin C, potassium, dietary fibre and some phytochemicals, unlike other vegetables they can have detrimental effects on glucose metabolism because they contain large amounts of rapidly absorbable starch.”
When women substituted two servings a week with other vegetables, pulses such as beans, lentils and peas, and whole grain foods, they had a 9% to 12% lower risk.
In the study of more than 21,000 pregnancies, published in the British Medical Journal (BMJ), 854 were affected by gestational diabetes.
Experts said higher potato consumption before pregnancy “was significantly associated with an increased risk” of the condition.
They said high potato consumption had already been associated with insulin resistance and an increased risk of Type 2 diabetes.
The women in the study were asked about potato consumption in the previous year as part of a questionnaire, looking at how often they ate certain foods.
The experts concluded: “Higher levels of potato consumption before pregnancy are associated with greater risk of (gestational diabetes), and substitution of potatoes with other vegetables, legumes, or whole grain foods might lower the risk.”
However, the authors stressed that the study did not positively prove that potatoes caused diabetes.
The NHS says up to 18% of women giving birth in England and Wales are affected by gestational diabetes. The condition can increase the risk of stillbirth, miscarriage and premature labour.
Emily Burns, research communications manager at Diabetes UK, cautioned: “This study does not prove that eating potatoes before pregnancy will increase a woman’s risk of developing gestational diabetes, but it does highlight a potential association between the two.
“However, as the researchers acknowledge, these results need to be investigated in a controlled trial setting before we can know more.
“What we do know is that women can significantly reduce their risk of developing gestational diabetes by managing their weight through eating a healthy, balanced diet and keeping active.”
Women giving birth affected by gestational diabetes
Meanwhile, the Government’s public health agency said its advice remained “the same”.
Dr Louis Levy, head of nutrition science at Public Health England, said: “As the authors acknowledge, it is not possible to show cause and effect from this study.
“The evidence tells us that we need to eat more starchy foods, such as potatoes, bread, pasta and rice, as well as fruit and vegetables to increase fibre consumption and protect bowel health.
“Our advice remains the same: base meals around a variety of starchy foods, including potatoes with the skin on, and choose wholegrain varieties where possible.”
Prof Judith Buttriss, director general of the British Nutrition Foundation, which receives some funding from food producers and manufacturers, said: “It’s important to recognise that the main nutrition-related determinant of gestational diabetes is pre-pregnancy body weight where the risk far exceeds the level of risk reported in the paper from potato consumption.”