by In a recent review published in Nutrients, researchers reviewed preclinical and clinical data to analyze gut microbial changes in different dietary conditions.
Study: Beneficial Effects of Nutritional Interventions on Gut Microbiota – A Critical Review of Advances and Future Perspectives. Image Credit: LightField Studios/Shutterstock.com
Background
Intermittent fasting (IF), a popular dietary intervention, has been studied for its impact on gut microbial composition and host physiopathological processes.
Studies show that dietary ingredients modulate the gut microbial community, and that nutrient transformations in microbes have a major impact on host metabolism.
This reciprocal association could affect chronic drug metabolism, which would greatly affect human health and disease. Nutritional interventions for various disorders could be tailored to improve overall health by restoring gut microbial balance and diversity.
Regarding the review
In the current review, researchers described the impact of diet on the intestinal microbiome by reviewing preclinical and clinical studies published in the PubMed database in English from 2015 to 2023. For preclinical data, only studies that published between 2021 and 2023.
Two researchers independently screened data, and discrepancies were resolved by consensus. Protocols, studies, and case reports with inaccessible full text were excluded, and eligible records were screened for full text. In total, 17 preclinical records and 26 clinical records were analyzed.
Preclinical studies on the effects of dietary intervention on animal gut microbiota
In six-week-old C57BL/6J mice, high-fat (HF) diet interventions increased CR Facts, Actinobacteria, Firmicutes: Bacteroidetes ratio, Bifidobacteriaceae, Lactobacillus johnsonii, Bifidobacterium pseudolongumand Faecalibaculum abundance in the cecum. However, these interventions have declined Bacteroidetes and Parabacteroides count.
In male Fisher 344 x Brown Norway F1 hybrid rats, Keto diets reduced time-restricted feeding (TRF) in fecal Actinobacteria and Patescibacteria counting and multiplying Verrucomicrobia count. Western diet reduced fecal TRF (16:8). Bacteroidota, Proteinaseand Cyanobacteria count and increase Verrucomicrobia count.
A regular chow diet increased TRF Lactobacillus, Muribaculaceae, Dubosiella, Clostridia, and Facalibacterium count. Maternal feeding was reduced with intermittent fasting (M-IF). Lactobacillus intestinalis abundance in mice offspring.
In male Wistar rats, IF decreased Firmicutes: Bacteroidetes ratio and Bacillus velezensis counting, increased Lachnospiceae and Lactobacillaceae count, and increase Lactobacillus and Akkermansia muciniphila count. CR and IF increased helicopter, Bacteroidetesand Facts count in rainbow trout as it decreases Actinobacteria count in the proximal intestine.
The intervention of 16:8 and 24:24 IF increased the abundance of different microorganisms in the feces of allergic mice and decreased Facts count. Short term IF reduced Facts, Verrucomicrobia, Lachnospiceae, Ruminococcaceaeand Ruminiclostridium count in C57BL/6 mice with induced colitis, and long-term IF is reduced Akkermansiaceae and increased Lactobacillaceae count.
Preclinical studies of gut microbial composition in C57BL/6J mice found adaptation to dietary changes. However, there was a lack of consistency and homogeneity in the results regarding bacterial strains/group dynamics.
Different types of fasting have different effects on gut microbiome, and study protocols involving different feeding restrictions, periods and diets make it challenging to draw conclusions. In addition, several animal models, which may be specifically sensitive to calorie restriction (CR), have been evaluated.
Effects of dietary interventions on the human gut microbiota
A randomized controlled trial (RCT) reported that fasting for five days increased Buchinger Proteinase and Christensenellaceae count but reduced Firmicutes: Bacteroides ratio. Only water fasting was reduced Fusobacterium count and increase of homogeneous gut microbiota.
Ramadan intermittent fasting increased alpha diversity, Lachnospiceaeand Ruminococcaceae count but decrease Bacteroidales. In other studies, intermittent fasting reduced Ramadan Coprococcus, Clostridium_XlV spp., and Lachnospiceae count only increase Dorea, Klebsiella, Facalibacterium, Sutterella, Parabacteroides, Alistipe, bacteria, and Facts count.
Ten days of Buchinger fasting and three months of reduced feeding Facts count only increase Bacteria, Proteinaseand Bacteria. Buchinger fasting and a Mediterranean-like diet for hypertensive patients with metabolic syndrome can reduce Bifidobacterium, Coprococcus comes, and Rosebury count.
In obese postmenopausal women, VLCD increases for 46 days Christensenellaceae count. In overweight and obese adults, a six-week caloric restriction diet reduces and stabilizes weight Akkermansia muciniphila count.
Dietary restriction can influence the gut microbiota by reducing pro-inflammatory cytokines, improving short-chain fatty acid (SCFA) production, increasing intestinal barrier integrity, and exhibiting immunomodulatory effects.
Reduce long-term dietary restriction for a year Actinobacteria count and Firmicutes: Bacteroidetes ratio as it increases Bacteria, Rosebury, Facalibacteriumand Clostridium XIVa ratio. No specific pattern was established for changes in gut microbiota; However, health benefits have been demonstrated, including reduced risk factors for age-related diseases and increased lifespan.
Based on the review findings, dietary interventions such as time-limited fasting and caloric restriction were studied for their effects on markers of metabolic health and gut microbiota composition. These programs alter the gut environment by altering nutrient availability, energy sources, microbial growth and SCFA production.
They can reduce inflammation, regulate metabolism, and improve circadian rhythm. However, data are insufficient to establish a typical pattern of gut microbiota changes.
More research is needed, especially in obese and metabolically compromised patients, to identify long-term changes and to assess different molecules of gut microbiota.
