Boiled or fried: which potatoes are more dangerous for health

Potatoes have long been part of the diet of millions of people around the world, but their association with the risk of developing type 2 diabetes is a matter of debate.

A new large-scale study from the Harvard T.H. Chan School of Public Health, published in The BMJ, sheds light on this issue by focusing on the way potatoes are prepared.

The study analysed data from more than 205,000 adults whose diet was tracked over decades in three large cohort studies (Nurses' Health Study, Nurses' Health Study II and Health Professionals Follow-up Study). For more than 30 years, participants regularly completed questionnaires about the frequency of consumption of various foods, including fries, baked, boiled and mashed potatoes, and whole-grain products.

The results were quite revealing. Regularly eating Chips three times a week increased the risk of developing type 2 diabetes by 20 per cent. In contrast, boiled, baked and mashed potatoes showed no significant association with increased risk of the disease. During the follow-up, 22,299 participants were diagnosed with type 2 diabetes.

The scientists also analysed how replacing potatoes with whole-grain products affected health. For example, replacing a serving of baked, boiled or mashed potatoes with wholemeal pasta, bread or farro reduced the risk of developing diabetes by 4 per cent. But replacing Chips with wholemeal products reduced the risk by 19%. Even when replacing Chips with regular refined cereals, the risk of developing diabetes also decreased.

To confirm their findings, the researchers conducted a meta-analysis of data from 13 previously published cohort studies on potatoes and 11 on whole-grain products, covering more than 500,000 people and 43,000 cases of diabetes worldwide. The findings were similar to those of the main study.

According to the lead author of the study, Dr Seyed Mohammad Mousavi, it is important to pay attention not only to the product itself, but also to the way it is prepared and what exactly it is replaced with in the diet.

He was supported by Walter Willett, Professor of Epidemiology and Nutrition, who emphasised that even small changes in the daily menu, such as reducing the consumption of Chips and replacing them with whole-grain products, can significantly reduce the risk of developing type 2 diabetes across the population.