Capsaicin can have a beneficial effect when part of a regular diet, previous studies have shown. The effects include having an anti-inflammatory potential and protection against obesity – both attributed to the gut microbial community response to capsaicin. However, there is no consensus on the mechanism behind the protective effect and in this study, an in vitro model of the human gut was used to work out how eating capsaicin regularly can affect the gut microbiota.
The researchers used a combination of NextGen sequencing - fragmenting DNA/RNA into multiple pieces, adding adapters, sequencing the libraries, and reassembling them to form a genomic sequence - and metabolomics to discover that regular consumption changed the structure of the gut microbial community by increasing diversity – and certain short-chain fatty acids (SCFA) abundances.
They say the changes in the gut may be responsible for health benefits associated with consuming capsaicin.
The capsaicin compound is what provides the associated pungent flavour in red chilli pepper – historically it has been used to mask the poor taste in deteriorated food, add flavour to enhance cuisine and also for medicinal purposes. It has also been associated with lowered cholesterol and obesity as well as having antioxidant, anti-inflammatory and anti-hypertensive effects.
The researchers said: "The gut microbiota is an impactful mediator of health and human disease and when there is an imbalance between the types of organism present in a person’s natural microflora, especially in the gut, this is believed to contribute to a range of poor health conditions. This can occur when there is a lack of diversity which can be due to increasing age, the western diet or adverse health issues such as obesity, diabetes or irritable bowel syndrome."
Studies have shown that capsaicin can alter the gut microbial population.
For this study, the effect of capsaicin on the gut microbial community from two independent donors were evaluated and faecal samples were donated by both. The effect of capsaicin was analysed at the beginning and at the end of 14 days and to understand how it impacts the gut microbial community structure, the researchers performed shotgun sequencing and used both alpha and beta diversity measures to assess the results.
Changes in gut microbiota
The researchers said there had been significant changes in community diversity consistent with previous reports that found consumption of the pepper in mice and humans changed the gut microbial community.
They said: “The corroboration of our findings with those of other researchers illustrates the ability of this in vitro model to mimic the in vitro model gut microbial community response to capsaicin. Observed shifts in the community in this study indicate that capsaicin increases diversity in the gut microbial community. An increase has been associated with better health, whereas a decrease in gut microbial diversity is associated with some illnesses, particularly in relation to type 2 diabetic individuals. Thus, an increase in the diversity is indicative of the ability of capsaicin to modulate the gut microbiota beneficially.”
Studies have shown that using capsaicin in diet can change the abundance of SCFAs and it has been speculated that this shift in production is the reason for the positive health impacts when eaten. It is well-established that SCFAs are a major component in the regulation of gut health and overall health.
The researchers found this study is in agreement with previous work but also finds that the way capsaicin can shift SCFA abundance is a potential explanation for its beneficial health effects. The researchers observed that there have been recent efforts to determine the mechanisms behind these positive health impacts.
Overall, they found that capsaicin significantly altered the gut microbial structure and SCFA levels but did note that these changes were donor dependent.
They added: “While performing an in vitro study does remove the host component from our analysis and therefore is limited in scope, our study design has several advantages. The removal of the host tissues allows the effects of the compound on the bacterial community alone to be discovered. It is also advantageous to perform metabolics and the SCFA analysis from a culture microbiome, as analysing from faecal samples alone will illustrate what compounds last until collection. This work identified multiple microbial changes, as a function of capsaicin that may prove beneficial to host physiology.”
'Analysis of the Ability of Capsaicin to Modulate the Human Gut Microbiota In Vitro'
Authors: Karley K. Mahalak et al