From Harvest to Habits: How Autumn Influences the Gut Microbiome

Autumn is a season some dread, but others thoroughly enjoy; it is a season consisting of colder weather, a start to the new year for schools and universities and an increase in consumption of comfort food. Seasonal changes cause a shift in the composition of our microbiomes by changes in diet, stresses and shorter days – but some may question how this occurs.

The autumnal season is the time for schools returning and university life beginning, both of which can be stressful for students. The concept of the gut-brain axis is now well established, with a link between the gut and emotions proposed as far back as the 18^th century _[1]. In addition, as students transition into university life, they are more likely to engage in ‘freshers’ behaviour including smoking and consuming alcohol, which influences the gut microbiome. Cigarette smoking is significantly linked to a poor bacterial diversity of the upper small intestinal mucosa, with a higher prevalence of Streptococcus spp., Veillonella spp. and Rothia spp _[2]. Similarly, alcohol use is linked to a reduced number of key bacterial commensals, including Faecalibacterium, Bacteroides and Bifidobacterium spp., but an increased number of Pseudomonadota (Proteobacteria) - a phylum containing several human pathogens _[3].

A decrease in sunlight exposure in the autumn months diminishes the amount of vitamin D the human body can produce. Whilst low levels of vitamin D can cause low mood, fatigue and bone issues, there is a fundamental link between depletion of vitamin D and the function of the gastrointestinal tract. The vitamin D receptor (VDR) gene is fundamental to the gut microbiome; when the VDR gene is deleted, there is a distinct change to the composition of the gut microbiome _[4]. Homeostasis of the gut mucosa is regulated by vitamin D through increased expression of VDR-associated intracellular junction proteins such as occludin, vinculin and zonula occludens. Changes to vitamin D levels will impact the permeability of the mucosa and increase susceptibility to damage _[5]. Since VDR expression can be modulated by commensal and pathogenic gut microbes, probiotic use is more predominant in those with low vitamin D and is a potential avenue for those suffering in the autumnal months _[5].

Comfort foods and high-fat diets with low dietary fibre are common during autumn, but for decades, research has highlighted the detrimental impact these diets have on the gut microbiome and explored potential treatments to reinstate the beneficial microbes of the microbiome. As obesity and other diet-related diseases continue to rise, research into therapeutic applications of microorganisms remains clinically important. Kim et al. explored this by investigating the therapeutic effect of lactic acid bacteria on obesity. Lactiplantibacillus plantarum GBCC_F0227 was isolated from fermented foods and human faeces and grown in a Whitley A45 Workstation, where anaerobic conditions were maintained to promote growth. This strain was capable of catabolizing and reducing triglycerides, which are copious in high-fat diets. It could be suggested that this L. plantarum strain could be used in supplements, such as probiotics, during periods where high-fat diet consumption is high (e.g., during autumn) _[6]. Ultimately, prevention is always better than cure, so in the colder months, it is always advisable to practice a balanced diet and try to limit high-fat food intake.

Lifestyle, diet and stress depending on the season will continue to have a substantial impact on the gut microbiome, but it is important to educate and inform regarding how exactly this can occur, to allow informed decisions to be made.

Written by DWS Microbiologist Kirsty McTear

References

1. Verma A, Inslicht SS, Bhargava A. Gut-Brain Axis: Role of Microbiome, Metabolomics, Hormones, and Stress in Mental Health Disorders. Cells [Internet]. 2024 Aug 27;13(17):1436–6. Available from: https://www.mdpi.com/2073-4409/13/17/1436.
2. Shanahan ER, Shah A, Koloski N, Walker MM, Talley NJ, Morrison M, et al. Influence of cigarette smoking on the human duodenal mucosa-associated microbiota. Microbiome. 2018 Aug 29;6(1).
3. Jew M, Hsu CL. Alcohol, the gut microbiome, and liver disease. Journal of Gastroenterology and Hepatology. 2023 Apr 25;38(8):1205–10.
4. Chatterjee I, Lu R, Zhang Y, Zhang J, Dai Y, Xia Y, et al. Vitamin D receptor promotes healthy microbial metabolites and microbiome. Scientific Reports. 2020 Apr 30;10(1).
5. Akimbekov NS, et al. Vitamin D and the Host-Gut Microbiome: A Brief Overview. The Japan Society of Histochemistry and Cytochemistry. 2020 Mar 24;53(3):33–42.
6. Kim J, Jeon SG, Kwak MJ, Park SJ, Hong H, Choi SB, et al. Triglyceride-Catabolizing Lactiplantibacillus plantarum GBCC_F0227 Shows an Anti-Obesity Effect in a High-Fat-Diet-Induced C57BL/6 Mouse Obesity Model. Microorganisms. 2024 May 27;12(6):1086–6.