Ultra-processed foods: Implications for gastrointestinal health

Table 3 Summary of available studies on the effect of ultra-processed food on the gut microbiome[43-46]

Ref.	Alpha diversity	Beta diversity	Bacterial composition changes about UPFs		Composition changes related to specific UPFs	Clinical outcome
			Increases	Decreases
Atzeni et al[44], 2022	No significant difference	No significant difference	Positive association between Alloprevotella spp. (P = 0.041) and Sutterella spp. (P = 0.116) vs tertile 2; Positive association between Alloprevotella spp. (P = 0.065), Negativibacillus spp. (P = 0.096), and Prevotella spp. (P = 0.116) vs tertile 3		No significant differences found between bacterial taxa and UPFs categories	UPFs consumption is positively associated with higher total energy intake; No significant differences in cholesterol, TG, or HbA1c between the tertiles. No association between bacterial taxa and cardiovascular risk factors
Cuevas-Sierra et al[43], 2021	Men consuming > 5 servings/day of UPFs showed lower richness compared to men consuming < 3 servings/day (observed P = 0.03, Shannon P = 0.01, Chao1 P = 0.04). No differences in women or the whole population	No significant difference	Gemmiger spp. (P < 0.001); Granulicatella spp. (P < 0.001); Parabacteroides spp. (P < 0.001); Shigella spp. (P < 0.001); Bifidobacterium spp. (P < 0.001); Anaerofilum spp. (P = 0.001); Cc_115 spp. (P = 0.007); Oxalobacter spp. (P = 0.008); Collinsella spp. (P = 0.008)	Lachnospira spp. (P = 0.003); Roseburia spp. (P = 0.003)	Women: Dairy and pizza positively correlated with Actinobacteria (P < 0.05), and pizza positively correlated with Bifidobacterium spp. (P < 0.05)	Consumption of UPFs is associated with ↑ serum triglycerides (P = 0.004) and ↓ HDL-c levels (P = 0.04). UPFs consumption is associated with ↑ depression, anxiety, and weight in women, while ↑ weight and BMI in men
Fernandes et al[45], 2023	No associations between food processing level and alpha diversity	NA	Clostridium butyricum; Odoribacter splanchnicus, Barnesiella intestinihominis, Alistipes onderdonkii, Alistipes indistinctus	Ruminococcus sp., (Ruminococcus) gnavus Bacteroides vulgatus Bacteroides plebeius	NA	Consumption of UPFs is associated with leptin resistance
García-Vega et al[46], 2020	Higher in females than males (Shannon, P = 0.046), higher in middle-aged than younger individuals (Shannon, P = 0.012). No significant association between diet quality (including UPFs intake) and alpha diversity	Differences according to participants’ city of origin (P = 0.001), sex (P = 0.001), socioeconomic level (P = 0.024) and BMI (P = 0.002). No significant association between diet quality (including UPFs intake) and beta diversity	Bifidobacterium adolescentis, Prevotella melaninogenica, Subdoligranulum variabile, Veillonella dispar, Ruminococcus spp., Bilophila spp., Oscillospira spp.	Prevotella copri Clostridium hathewayi, Ruminococcaceae unclassified spp. Gemella spp. Lachnospira spp. Oscillospira spp.	OTUs from Oscillospira spp., Unclassified Ruminococcaceae, Ruminococcus spp., Lachnospira spp. Positively associated with the intake of plant-derived food groups, rich in dietary fiber; Bifidobacterium adolescentis is associated with plant-derived food groups; Bile-tolerant Bilophila sp., Prevotella copri, and the opportunistic pathogen Prevotella melaninogenica were associated with increased intake of animal-derived foods	Diets enriched with plant-derived foods have more diverse gut microbiota and ↑ levels of SCFA-producing bacteria

HDL-c: High-density lipoprotein cholesterol; OTU: Operational taxonomic unit; SCFA: Short-chain fatty acid; TG: Triglyceride; UPFs: Ultra-processed food; BMI: Body mass index; HbA1c: Glycated hemoglobin.