A massive study of more than 200,000 US adults has revealed that not all potatoes are created equal – because different forms will dramatically shift your risk of developing type 2 diabetes. But there's some good news for spud-lovers, showing that it all comes down to preparation and that the often maligned root vegetable has some significant health benefits, too.
Researchers from Harvard University analyzed data from 205,107 healthy adult men and women – free from diabetes, cancer or cardiovascular disease – in the long-term Nurses’ Health Study (NHS), Nurses’ Health Study II (NHSII) and Health Professionals Follow-up Study (HPFS).
Across these studies, dietary intake and health outcomes were tracked for up to 36 years, with data collected between 1984 and 2021, and questionnaires and new information entered every two-to-four years. Over the course of this period, 22,299 cases of type 2 diabetes (T2D) were documented.
What they found was that while higher overall potato intake was associated with a modestly increased risk of developing T2D, this risk was almost entirely driven by French fries.
People who ate fries five or more times a week had a 27% higher risk of developing T2D, compared to those who rarely indulged. And for every additional three servings a week, the risk jumped 20%. The results, however, showed there was a cap on the risk increase – the highest intake group remained set at the 27% risk level.
But in contrast, people who ate baked, boiled or mashed potatoes had no significant risk in developing T2D, when researchers adjusted the data to consider other lifestyle and dietary factors.
“We’re shifting the conversation from, ‘Are potatoes good or bad?’ to a more nuanced – and useful – question,” said researcher Seyed Mohammad Mousavi. “'How are they prepared, and what might we eat instead?'”
This study is the first of its kind to not just assess the risk of T2D and potatoes but quantify the benefits of replacing fries with other foods.
While it may seem obvious – fries are often deep-friend in oils with added salt – the researchers noted that potatoes aren't inherently bad for health. Fries come loaded, so to speak, with a bunch of added health risks, such as trans fats from frying and acrylamide when prepared at very high temperatures. However, even baked and boiled potatoes – which have a natural high glycemic index – don't deliver the same T2D risk.
"Limiting French fries – and choosing healthy, whole grain sources of carbohydrate could help lower the risk of type 2 diabetes across the population,” said lead researcher Walter Willett, a professor of epidemiology and nutrition at Harvard. "The need to move beyond broad food categories and pay closer attention to how foods are prepared and what they’re replacing. Not all carbs – or even all potatoes – are created equal, and that distinction is crucial when it comes to shaping effective dietary guidelines.”
The researchers found that substituting fries with other forms of carbohydrates could significantly lower T2D risk – by 19% if all servings were swapped with non-rice whole grains.
And it's worth noting, potato skins contain nutrients such as fiber, which helps with blood sugar control. And potatoes that aren't deep-fried or covered in butter are a useful source of potassium, which helps regulate blood pressure.
“The public health message here is simple and powerful,” said Willet. “Small changes in our daily diet can have an important impact on risk of type 2 diabetes.”
The study was published in the journal BMJ.
Source: Harvard University
