Ultra-processed foods linked to increasing type 2 diabetes risk
Extensive research has demonstrated that the consumption of ultra-processed foods (UPFs) has a detrimental impact on the development of type 2 diabetes mellitus (T2D). However, the exact influence of other levels of food processing on T2D risk remains uncertain. A recent study published in The Lancet Regional Health sheds new light on this issue, exploring the association between varying degrees of food processing and the risk of developing T2D.
Food Processing and Its Relationship with Type 2 Diabetes
The Nova classification system is widely used to categorise foods based on the extent of their processing. According to this system, foods are divided into four categories: unprocessed or minimally processed foods (MPFs), processed culinary ingredients (PCIs), processed foods (PFs), and ultra-processed foods (UPFs). Research has long associated higher consumption of UPFs with weight gain, obesity, T2D, and cardiovascular diseases. A study conducted as part of the European Prospective Investigation into Cancer and Nutrition (EPIC) initiative revealed that a higher intake of UPFs is also linked to an increased risk of cancer and cardiometabolic multimorbidity.
Despite these findings, the link between T2D and all categories of processed foods, including MPFs, PCIs, and PFs, has yet to be fully elucidated. Further research is necessary to determine whether UPFs or other processed foods are most closely associated with adverse health outcomes. Gaining a deeper understanding of the impact of different types of processed foods may provide researchers with crucial insights into the benefits of replacing UPFs with healthier alternatives, such as MPFs, PCIs, or PFs.
The Study Overview
The recent cohort study used data from the EPIC project to explore the relationship between various food processing categories and T2D risk. Researchers assessed participants’ dietary intake at the start of the study by administering comprehensive dietary questionnaires. Based on this information, food consumption patterns were categorised according to the Nova classification system.
In order to identify cases of T2D, researchers relied on multiple data sources, including participants’ self-reports, primary and secondary care registers, hospital admission records, medication registers, and mortality data. The analysis used Cox regression and statistical substitution models to estimate the associations between T2D risk and the intake of MPFs, PCIs, PFs, and UPFs. Sub-group analyses were also conducted to identify any potential variations in the association between different UPFs and T2D risk.
The average age of the study participants was 52.5 years, and 63.5% of them were female. The average body mass index (BMI) was 25.7 kg/m², indicating that most participants were classified as being slightly overweight. Over the course of a 10.9-year follow-up period, 4.6% of participants were diagnosed with T2D. On average, MPFs and PCIs contributed to 72.1% of participants’ daily dietary intake, while UPFs accounted for 13.0%, and PFs made up 14.9%.
Key Findings of the Study
In examining the relationship between food processing and the development of T2D, the researchers conducted restricted cubic spline analyses to assess the intake of MPFs and PCIs. These analyses revealed a linear relationship between higher consumption of MPFs + PCIs and a lower risk of T2D up until very high intakes. Additionally, the study found that increased consumption of MPFs + PCIs, as well as PFs, was linked to a reduced risk of T2D. In contrast, a higher intake of UPFs was associated with an elevated risk of developing T2D.
To better understand the impact of replacing certain food groups on T2D risk, the researchers performed statistical substitution analyses. These analyses revealed that substituting 10% of UPFs with either MPFs + PCIs or PFs significantly reduced the risk of T2D. Moreover, replacing MPFs + PCIs with PFs also resulted in a reduction in T2D risk. These results held even after accounting for confounding factors such as saturated fat intake, sugar consumption, and adherence to a Mediterranean diet.
When investigating different sub-groups of UPFs, the study uncovered significant heterogeneity in their relationship with T2D. For instance, an increase in the consumption of savoury snacks, ready-to-eat or heat dishes, animal-based products, and artificially or sugar-sweetened beverages (ASBs/SSBs) was associated with a higher risk of T2D. On the other hand, lower T2D risk was linked to the consumption of plant-based alternatives, sweets and desserts, biscuits, breakfast cereals, and breads. Interestingly, no significant association was found between T2D and the consumption of sauces, spreads, condiments, alcoholic beverages, or other miscellaneous UPFs.
The Role of Adiposity in the UPF-T2D Relationship
To further understand the mechanisms underlying the association between UPF consumption and T2D, the researchers conducted mediation analyses focused on the waist-height ratio (WHtR), a measure of adiposity. These analyses revealed that WHtR mediated 46.4% of the association between UPF consumption and T2D risk. This suggests that body fat distribution may play a significant role in the relationship between UPF intake and the development of T2D.
Despite the robustness of the findings, some inconsistencies were noted in sensitivity analyses. For example, in France and Italy, the study did not find a statistically significant association between UPF consumption and T2D risk. Additionally, when the intake of MPFs + PCIs was modelled as kcal/day, %kcal/day, or g/day, no significant association with T2D risk was observed.
Conclusions
This study reinforces the growing body of evidence linking higher consumption of ultra-processed foods with an increased risk of type 2 diabetes mellitus. At the same time, it highlights the protective effect of consuming less processed foods, such as minimally processed or processed culinary ingredients, against the development of T2D.
Importantly, the findings point to the significant heterogeneity within the category of UPFs, suggesting that not all UPFs pose the same level of risk. This variability underscores the need for more nuanced public health guidelines, which should focus on reducing the intake of specific harmful UPFs rather than treating UPFs as a single, homogenous group. By encouraging people to make healthier food choices and reduce their consumption of certain types of UPFs, it may be possible to mitigate the rising global incidence of type 2 diabetes.