Sliding on

Enjoy your cup of java

Professor John D Brooks, FNZIFST

John Brooks' view of the food world through the lens of a microbiologist.

Much of my work as a food microbiologist has involved food spoilage and food poisoning, with from time to time a large helping of singlecell protein and biofilm research. I have written about these things both in Sliding on and my own food safety blog here. As Monty Python would say “Now for something completely different”. There is mounting evidence that our gut biome significantly impacts our health and may even affect our brains. It follows that our food and drink may interact with our gut biome and thus indirectly affect our behaviour.

In the past it has been claimed that coffee can cause cancer. It will no doubt come as a relief to many of us that a review of more than 1,000 studies by the International Agency for Research on Cancer (IARC) in humans and animals failed to find adequate evidence to indicate that coffee is a carcinogen. There may indeed be an inverse relationship between drinking coffee and some cancers.

In a relatively small survey, a team from Baylor College of Medicine in Houston, Texas examined “the association between caffeine consumption and the composition and structure of the colonic-gut microbiota.” They managed to find 34 male participants with a normal colon in one hospital, prepared to undergo a screening colonoscopy and endoscopy to determine the health of their colons. The researchers obtained snap-frozen colonic mucosa biopsies from various segments of these individuals’ colons, and extracted microbial DNA, then performed 16s rRNA gene sequencing analysis. The researchers claimed that their work was different from most studies which focus on the faecal biome. In addition to this invasive investigation, the participants completed a food frequency questionnaire that was actually designed to evaluate the daily intake of coffee. The results were divided into “high” and “low” coffee consumption’ based on the resultant intake of caffeine. The questionnaire did not reveal any information on how the coffee was prepared or the brands used.

Perhaps not surprisingly, a high intake of caffeine did have an effect on the gut microbiome but the effect was independent of the participants’ age or the quality of their diets. High caffeine consumption was associated with high levels of the bacterial genera Faecalibacterium and Roseburia, but low levels of Erysipelatoclostridium. These bacteria are regarded as part of the normal gut flora, but elevated levels of E. ramosum have been linked with metabolic syndrome and were found in animal studies to be associated with diet-induced obesity. Several other genera of bacteria were also found to be present at higher levels in the flora of the high-intake volunteers.

The authors concluded that “Higher caffeine consumption was associated with increased richness and evenness of the mucosaassociated gut microbiota, and higher relative abundance of antiinflammatory bacteria, such as Faecalibacterium and Roseburia, and lower levels of potentially harmful Erysipelatoclostridium.”

Many studies now are suggesting that there is a two-way interaction between the gut microbiome and the brain. Some of it reads like science fiction, but there is good evidence to support this. For example, production of short-chain fatty acids, such as butyrate, by bacteria in the gut when they break down fibre, may be associated with brain function. Butyrate-producing Faecalibacterium and Coprococcus bacteria were consistently associated with higher quality of life indicators. Depletion of Dialister and Coprococcus spp. is consistently associated with depression. The term ‘psychobiotic’ has been coined for microbiota-based interventions that have a beneficial effect on the human brain (2). We know that certain microbes in the gut can modulate the immune response in ways that affect the brain and also produce signalling molecules that regulate neuron activity.

Of course, studies with humans are fraught with difficulty. We eat a wide variety of foods and consume all sorts of alcoholic and nonalcoholic beverages and all of these in different amounts. Some of us take medication or have high-stress jobs, while others are able to take life at a much slower pace. There appears to be no barrier to our effecting change in our gut biota by altering our diets and this doesn’t involve buying special foods from specialist stores. A Mediterranean diet that's high in fibre, particularly from vegetables, is thought to be beneficial and in a small study in which subjects were given high fibre, prebiotics and fermented foods, the experimental group reported being less stressed than the control group. Perhaps it’s time for us to concentrate more on looking after our microbiota.

Now, I’m off to make a strong cup of coffee with cream.

References:

1. Dai, A. Et al. (2023) The Association between Caffeine Intake and the Colonic Mucosa-Associated Gut Microbiota in Humans – A Preliminary Investigation. Nutrients, 15, 1747. https://doi. org/10.3390/nu15071747

2. https://www.bbc.com/future/article/20230120-how-gut-bacteria -are-controlling-your-brain Caffeine. (2023, May 2). In Wikipedia. https://en.wikipedia.org/ wiki/Caffeine