The researchers say that according to a long-term study of nearly 85,000 US women, the risk factor is especially applicable to obese women who may already be at risk of the disease.
They say a diet high in potato equates to a modestly elevated risk of developing type 2 diabetes.
This is they say is because although potatoes have healthy qualities, they also have a high glycemic index (GI) - meaning they cause a rapid, strong rise in blood sugar.
Such surges over a period of time can cause damage to the pancreatic cells that produce the hormone insulin, which is needed to metabolize blood sugar.
People who are overweight or have sedentary lifestyles may be particularly vulnerable to the effects of high-GI foods because they often have underlying insulin resistance which is a precursor to diabetes, in which body cells lose their sensitivity to insulin.
The researchers say it makes sense then to cut down on foods such as french fries.
According to Thomas L. Halton, the lead author of the new study, he and his colleagues found that women with the highest potato intake were 14 percent more likely than those with the lowest intake to develop diabetes over 20 years.
Also the women who specifically ate the most french fries, had a 21 percent greater risk of diabetes than those who ate the fewest.
The researchers say that general diet and lifestyle habits did not explain the link, and potatoes seemed to be more problematic when a woman ate them instead of whole grains.
Halton's team concludes that whole grains along with many high-fiber vegetables, fruits and legumes, have a lower GI than potatoes and white-flour products and eating such foods could potentially cut diabetes risk.
The findings are published in the American Journal of Clinical Nutrition.
"We thought that the idea itself was important, that this is a really powerful approach to a very major question," says Funk, "but we thought that there was no way in the world that we were actually going to get statistically significant results."
The reason for his doubt was the incompleteness and lack of uniformity of ecological data. "There are all these species out there and so few of them are known in intimate detail, so any kind of ecological characterization, through no fault of ecologists, will be limited in accuracy and precision," Funk says.
Nevertheless, the researchers decided to do the best they could with the information available. So they collected information from the published literature on three basic ecological variables: habitat, diet and size. Then they used this information to calculate the differences in ecological adaptation between the hundreds of pairs of related species in the original studies.
When they compared these differences in adaptation with the degree of reproductive isolation for each pair and then added them up, the researchers found that the overall association was positive with a surprisingly high level of confidence: The odds that the association is simply due to chance are only one in 250, substantially higher than the standard confidence level of one chance in 20 that scientists demand.
"The fact that the association is statistically significant despite the crudeness of our estimates suggests that the true biological association is very strong," Funk says. "Darwin's famous book was called 'On the Origin of Species,' but it was really about natural selection on traits rather than species formation. Since our study suggests that natural selection is a general cause of species formation, it seems that Darwin chose an appropriate title after all."
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