Ultra-processed foods (UPFs) are products that have undergone a series of industrial processes, including physical, biological, or chemical processes, coupled with the use of additives such as colorings, emulsifiers, and preservatives. UPF consumption has grown dramatically over the last few decades worldwide. This growth is accompanied by the increasing prevalence of non-communicable diseases (NCDs) such as cardiovascular diseases, hypertension, and type 2 diabetes. UPFs represent three main health concerns: (i) they are generally high in non-nutritive compounds such as sugars, sodium, and trans fat and low in nutritional compounds such as proteins and fibers, (ii) they contain different types of additives that may cause severe health issues, and (iii) they are presented in packages made of synthetic materials that may also cause undesirable health side-effects. The association between the consumption of UPF and the risk of developing diabetes was discussed in this review. The high consumption of UPF, almost more than 10% of the diet proportion, could increase the risk of developing type 2 diabetes in adult individuals. In addition, UPF may slightly increase the risk of developing gestational diabetes. Further efforts are needed to confirm this association; studies such as randomized clinical trials and prospective cohorts in different populations and settings are highly recommended. Moreover, massive improvement in foods’ dietary guidelines to increase the awareness of UPF and their health concerns is highly recommended.
Study Design/Follow-Up/ |
UPF Intake Assessment |
Main Results |
References |
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Participant Characteristics |
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Cross-sectional/- n = 13,608 adults (age ≥ 19 years) Diabetic (7%) (50% women) |
24 h recalls/NOVA/ proportion of TEI |
↑ DM risk by 37% (with high vs. low intake, 73% vs. 24% of TEI) An absolute 10% increase in UPF intake increases the risk by 6% (p < 0.05) |
Nardocci et al. [31] (2021, Canada) |
Prospective cohort/6 years n = 104,707 adults (age ≥ 18 years) Non-diabetic (79.2% women) |
24 h recalls/NOVA/ proportion of weight |
An absolute 10% increase in UPF intake was associated with 15% higher risk of T2D (p = 0.001) |
Srour et al. [34] (2020, France) |
Prospective cohort/5.4 years n = 21,730 adults (age 40–69 years) Non-diabetic (52.9% women) |
24 h recalls/NOVA/ proportion of weight |
↑ T2D risk by 44% (with high vs. low intake, 41.9% vs. 7.7% of diet proportion) (p < 0.028) |
Levy et al. [35] (2020, UK) |
Prospective cohort/12 years n = 20,060 adults (age ≥ 18 years) Non-diabetic (61.5% women) |
FFQ/NOVA/ proportion of weight |
↑ T2D risk by 53% (with high vs. low intake, >323.3 vs. <214.6 g/day of diet proportion) (p = 0.024) |
Llavero-Valero et al. [36] (2021, Spain) |
Prospective cohort/41 months n = 70,421 adults (age 35–70 years) Non-diabetic at baseline (58.6% women) |
FFQ/NOVA/ proportion of weight |
↑ T2D risk by 80% (with high vs. low intake, 48.7% vs. 23.7% of diet proportion) An absolute 10% increase in UPF intake increases the risk by 25% (p < 0.001) |
Duan et al. [37] (2020, The Netherlands) |
Cross-sectional/- n = 785 pregnant women (age ≥ 20 years) Non-diabetic at baseline |
24 h recalls/*/ proportion of TEI |
↑ gestational obesity risk by 3 times (with high vs. low intake, 47% vs. 18% of TEI) (p < 0.05) No association with GDM (p > 0.05) |
Sartorelli et al. [38] (2019, Brazil) |
Prospective cohort/7.2 years n = 3730 pregnant women (age 18–49 years) Non-diabetic |
FFQ/NOVA/ proportion of weight |
↑ GDM risk by 10% (with high vs. low intake, >4.5 vs. <3.3 serving/day)(p = 0.818) women aged ≥30 years had a doubled risk (p = 0.041) |
Leone et al. [39] (2021, Spain) |
Cohort/- n = 42 pregnant women (age ≥ 20 years) pre-gestational diabetics |
FFQ/NOVA/ proportion of TEI |
Each 1 kcal from UPF in the 3rd trimester (mean intake, 15.2% of TEI): ↑ 1-h PPG level by 0.143 (p = 0.011) ↑ HbA1c by 0.007% (p = 0.025) ↑ gestational weight by 0.11 kg (p = 0.006) |
Silva et al. [40] (2021, Brazil) |
Abbreviations: UPF: Ultra-processed foods; FFQ: Food frequently questionnaires; TEI: Total energy intake; DM: Diabetes mellitus; T2D: Type 2 diabetes; GDM: Gestational diabetes mellitus; PPG: Postprandial glucose; HbA1c: glycosylated hemoglobin; (↑): Increased. *Classified based on the 2014 Guia Alimentar para a População Brasileira; see Louzada et al. [41] for the detailed method.
The Canadian cross-sectional study by Nardocci and colleagues [31], based on the 2015 Canadian Community Health Survey–Nutrition data, showed a strong association between high UPF consumption and obesity and reported a significant association with developing diabetes. Those who consumed a high level of UPF (average UPF intake, 73% of TEI) had an increased risk of developing diabetes by 37% compared to those who consumed the lowest level of UPF (average UPF, 24% of TEI). With each 10% increase in energy intake derived from UPF intake, there was an increase in both obesity and diabetes risk by 6%. These findings align with a large French cohort [34] where adult individuals were followed up for a median of six years, and UPF consumption was measured based on grams percentage (in weight). The higher UPF consumption (average proportion (in weight) in the diet was 17.29%) showed a significant linear relationship with developing T2D. Results remained statistically significant even after further adjustment of multiple covariates, including the nutritional quality of the diet. The nutrient intake profile was also similar to the previously mentioned studies; the high UPF consumption was significantly associated with a higher intake of energy, saturated fats, sodium, and sugars and a lower fiber intake. Another cohort carried out in the UK [35] also revealed a strong relationship between high consumption of UPF and the development of T2D. The findings showed that for every 10% increase in UPF consumption, the incidence of T2D increased by 12%. More remarkably, over 5.4 years of follow-up, individuals who consumed the highest levels of UPF (average proportion (in weight) in the diet was 41.9%) had an increased risk of developing T2D by 44% compared to those who consumed the lowest levels of UPF (average UPF proportion was 7.7%). A recent cohort carried out in Spain [36] also found that individuals who consumed a high level of UPF had an increased risk of developing T2D by 53% relatively compared to those who consumed a lower level of UPF. This relationship was in a significant dose-dependent manner (p = 0.024). Higher BMI levels were also observed in those who consumed a high level of UPF. Surprisingly, the mean UPF proportion (in weight) in the diet was 9.5%, which is less than that found in both the French [34] and the British [35] cohorts, yet showed a significant association with the risk of T2D. On the other hand, the nutritional intake of those who consumed the highest levels of UPF had elevated levels of fats and decreased levels of proteins.
From another point of view, and due to similarities between the results of the British [35] and the French [34] cohorts, it was indicated that increased risk of T2D might be associated with all kinds/categories of UPF products (e.g., beverages, sugary products, processed meats, or processed bakery products) [35]. The differences in types of UPF consumed between these two cohorts are the main reason; the consumed UPF products in the French cohort were mainly sugar-based, ultra-processed fruits and vegetables and beverages, which represented 28%, 18%, and 16%, respectively, of total UPF consumption. In comparison, the most consumed UPF products in the British cohort were beverages, industrial processed bakery products, breakfast cereals, and industrial-processed frozen/shelf-stable prepared meals, which represented 39.1%, 29.9%, and 19.3%, respectively, of total UPF consumption. Hence, it is likely that the type/category of UPF consumed does not alter the association with the increased risk of T2D. However, another large cohort carried out in the Netherlands earlier this year [37] showed that the types of UPFs were significantly altering the results. However, in this study, the difference was between savory snacks, high in salt and sodium content, and traditional Dutch cuisine. The savory snacks showed a significant positive relationship with the incidence of T2D, while the traditional Dutch cuisine had no relation. According to the authors, sliced bread was the main product consumed in traditional Dutch cuisine, and because the majority of sliced bread consumed in the Netherlands is brown bread, which is made of a combination of whole-wheat and white flour or whole-wheat flour only, it is higher in fiber and micronutrients. High fiber intake is beneficial for preventing and managing T2D [42,43]. Therefore, nutritional quality is a key factor in altering the effect of UPF on developing T2D. The Dutch participants who consumed the highest levels of UPF (mean UPF proportion (in weight) in the diet was 48.7%) had a remarkably increased risk of developing T2D by 80% compared to those who consumed the lowest level of UPF (mean UPF proportion was 23.7%). It is worth mentioning that for each 10% increase in UPF consumption, the risk increased by 25%.
Consumption of sweet drinks and salty processed foods was found to enormously increase the risk of prediabetes by 248% and 48%, respectively, and the risk of T2D by 219% and 600%, respectively, compared to individuals who did not consume these products or had a rare consumption ratio. In contrast, the consumption of at least three servings or more each of fruit and vegetables a day decreased the risk of prediabetes by 26% and 5%, respectively, and the risk of developing T2D by 12% and 5%, respectively, compared to those who did not [44]. Consistently, consumption of an unprocessed diet among diabetic outpatients led to a significant reduction in fasting plasma glucose, glycosylated hemoglobin (HbA1c), and low-density lipoprotein (LDL) cholesterol compared to patients who consumed an unhealthy diet that mostly consisted of high levels of sweets and desserts, refined carbohydrates, and UPFs [45]. It was indicated that reduced LDL cholesterol levels are highly related to consuming an unprocessed diet. The administration of cholesterol-lowering drugs was not different among these participants, and thus, the results could not be related to drug usage. In addition, the patients who consumed the non-healthy diet had a nutritional profile significantly higher in saturated fats, which has been linked for decades with elevated LDL levels [46]. Adherence to dietary recommendations was shown in a French cohort to be significantly related to the development of T2D [47]. Participants were followed up for a median of 6.7 years, and their adherence to dietary guidelines of a French nutrition and health program, Programme National Nutrition Santé (PNNS), was assessed. After adjusting several covariates, including BMI, those who had high adherence to these guidelines had a significantly decreased risk of developing T2D by 49% compared to those who had the lowest adherence ratio, indicating that following the nutritional recommendations is strongly related inversely to developing T2D.
Another matter of interest, high consumption of UPF, might also be associated with developing gestational diabetes; a cross-sectional study [38] showed that UPF consumption strongly increases gestational weight but with no association with gestational diabetes. However, the classification of foods based on the degree of industrial processing was not fully achieved in this study. Therefore, misclassification may alter or attenuate the association between UPF and gestational diabetes. In contrast, a recent cohort [39] found that high UPF consumption was significantly associated with developing gestational diabetes (p = 0.041); however, this association was not observed among women under 30 years old. This could be explained by changes in the immune system that are reported with aging [48,49]. Cytokine dysregulation is one of the remarkable changes that lead to a chronic low-grade inflammatory state due to elevated pro-inflammatory cytokines, thus increasing the risk of comorbidities, including insulin resistance. Furthermore, another cohort that investigated the effect of UPF consumption on glycemic control among pregnant women with pre-gestational diabetes [40] showed that in the third trimester, each kcal of energy intake derived from UPF consumption significantly increased the one-hour postprandial glucose level, HbA1c, and gestational weight by 0.143 mg/dL, 0.007%, and 0.11 kg, respectively. Yet, the overall results showed that high UPF consumption is mostly associated with gestational weight gain.
The findings of the presented studies showed a strong association between UPF consumption and the incidence of diabetes. Almost all of these studies had adjusted their results for various covariates, which increased the significance of the findings. However, these studies were mainly conducted in Europe and America; other studies conducted in regions such as East Asia and/or the Middle East or other different regions are lacking. Recent investigations show that genetic differences between European and Asian populations, for example, play a significant role in the pathogenesis of diabetes [50]. Therefore, further studies in different populations and settings are highly needed to confirm the association. In addition, studies related to UPF intake and gestational diabetes are lacking worldwide. More studies on this particular point are also required.
The relevant findings showed that UPF consumption is significantly associated with the incidence of obesity, increasing insulin resistance, BMI levels, waist circumference, and LDL cholesterol levels while reducing HDL cholesterol levels, leading to a potential increase in the risk of T2D. Multiple investigational studies have revealed an association between the consumption of UPF and the risk of T2D, where the mean contribution of UPF proportion (in weight) in the diet ranged from 9.5% to 48.7%. In addition, there might be a slight association between high UPF consumption and gestational diabetes. These findings could be related to the significant and remarkable increase in the non-recommended nutrients found with high UPF consumption. Although this is not the only concern, additives included in this industry may cause health issues that have not been adequately investigated. Additionally, the packaging of UPFs may contain harmful chemicals, which have also not been well studied. Further studies, such as randomized clinical trials and prospective cohorts in different populations and settings, are needed to confirm these findings and take urgent actions to improve future dietary guidelines to emphasize the detrimental effects of UPF to limit their consumption as much as possible.
This entry is adapted from the peer-reviewed paper 10.3390/nu14122366