Ramadan fasting reshapes gut microbiome

In a recent study published in Frontiers in Microbiology, scientists from the Acibadem Mehmet Ali Aydinlar University in Istanbul, Turkey, explore the impact of Ramadan intermittent fasting on the composition of the gut microbiota.

Background

The human gastrointestinal (GI) microbiome is comprised of trillions of microorganisms. Bacteroidetes and Firmicutes are the most abundant bacterial species in the GI tract, followed by Proteobacteria, Verrucomicrobia, Fusobacteria, and Actinobacteria.

The gut microbiome composition typically remains stable throughout adulthood. However, the microbiota can be affected by various factors ranging from age, dietary habits, and physical exercise to body mass index (BMI) and genetics.

Diet is one of the most significant factors influencing the composition of the gut microbiota. Previous studies have reported that while the Western-style diet reduces the proliferation of beneficial bacterial populations within the gut, the Mediterranean diet differs significantly in its effects on the gut microbiome, as it maintains the balance between beneficial and harmful bacterial populations.

Fasting is also an important factor that can considerably influence the gut microbiota composition. Fasting is defined as voluntary food deprivation for therapeutic, cultural, or political reasons. Ramadan intermittent fasting is a time-restricted feeding pattern in which food and liquid consumption is restricted from dawn to sunset during the entire month of Ramadan, which occurs during the ninth month of the Muslim calendar.

Previous studies investigating dietary patterns indicate that intermittent fasting can alter gut microbiota composition, increase short-chain fatty acid (SCFA) production in the GI tract, and reduce an individual’s risk of certain cardiovascular and metabolic diseases.

Study design

In the current study, scientists investigate the effects of Ramadan intermittent fasting on the gut microbiota composition in the Turkish Muslim population.

The current study included 12 healthy adults who practiced 15 hours of fasting every day for 29 consecutive days during Ramadan. All study participants were asked to follow their routine diets and avoid exercise during the study period.

Anthropometric measurements, including body weight and height, three-day dietary records, and fecal samples, were collected from the participants the day before Ramadan fasting initiation, denoted as the baseline time point, as well as after the completion of Ramadan fasting.

Three-day dietary record data were used to assess food intake during the study period. Fecal samples were analyzed by 16S ribosomal ribonucleic acid (rRNA) gene sequencing and bioinformatics to determine any potential changes in the gut microbiota composition.

Altered gut composition after fasting

The analysis of the gut microbiota composition revealed that Ramadan intermittent fasting significantly enhanced the alpha and beta diversity of gut microbiota at the phylum level. However, at the genus level, fasting-induced changes were more heterogeneous among participants.

At the phylum level, a reduction in Firmicutes and induction in Proteobacteria were observed at the end of fasting as compared to baseline levels. Induction in the Bacteroidetes/Firmicutes ratio was also observed among participants at the end of Ramadan fasting.

At the genus level, reduced levels of seven bacterial genera, including Blautia, Coprococcus, Dorea, Faecalicatena, Fusicatenibacter, Lachnoclostridium, and Mediterraneibacter were observed at the end of the fasting period. Comparatively, increased levels of two bacterial genera of Escherichia and Shigella were observed at this same time point in fasting individuals.

Impact of dietary intake

The correlation analysis between dietary composition and gut microbiota diversity revealed that carbohydrate-enriched diets were associated with reduced genera diversity. Comparatively, high-fat diets were associated with more diverse genus composition.

Further analysis between the dietary intake and relative abundance of bacteria at the genus level revealed negative correlations between protein consumption and Ihubacter, vegetable consumption and Fusicatenibacter, and nut consumption and Intestinibacter. In fact, nut consumption was found to affect six out of the 13 detected genera.

Study significance

Intermittent fasting during Ramadan is associated with rich and diverse gut microbiota. Importantly, significant differences in food consumption habits were observed among study participants; however, the duration of fasting was similar.

The observed changes in the gut microbiota are likely due to the differences in consumed foods. Thus, future studies that include people who follow similar dietary practices during Ramadan are needed to determine the effect of intermittent fasting on the composition of the gut microbiota more precisely.

Journal reference:

Saglam, D., Colak, G. A., Shain, E., et al. (2023). Effects of Ramadan intermittent fasting on gut microbiome: is the diet key? Frontiers in Microbiology.

doi:10.3389/fmicb.2023.1203205

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