The connection between culture and the composition of our gut microbiome

The Oxford Dictionary defines ‘culture’ simply as the ‘way of life’ of a particular nation or community. Our way of life is a vast and overarching umbrella term that includes our beliefs, traditions, art and the organisation of society. One very distinct aspect of every country’s culture is the food that makes up a sizable portion of the collective diet. Historically, what we consume has varied depending on our geographical location, as the availability of crops and wildlife varies due to topography and climate. Today we have access to international trade and biotechnology, which has allowed us to sample foods that were previously inaccessible. But even in the age of modern innovation, we cannot erase the impact that culture-based diets have on our lives - food is not only a signifier of our lifestyle but also reflects the memories of our families and our connection to our heritage. While it is an enjoyable experience to taste different cuisines, most of us will inevitably return to our default diets. Therefore, it may not be overly presumptuous to connect these differences in culture with the state of health across various populations. Our gut microbiome is a major modulator of health, and the food we eat, of course, plays a significant role in its configuration. The primary responsibility of our gut microbiota is to promote digestion by breaking down our food and absorbing its nutrients. The bacteria in the gut can also produce vitamins and amino acids, degrade toxic compounds, and even stimulate the immune system. But first, we need to investigate what happens to the microbes in our gut following a meal. 

As its name implies, the gut microbiome spans the entirety of our digestive tract. Starting from the top of the small intestines, our gut microbiota can easily break down different kinds of sugars, such as sucrose or lactose. The rapid absorption of calories from sugar causes the surge of energy felt when one indulges in a dessert. But as what we have ingested descends towards the large intestine, fibrous and starchy foods have a more difficult time being digested due to their complex chemical structure. These foods require the aid of specialised microbes, which break down the molecular structure of the foods and extract the required nutrients. As is true, particularly in the case of fiber, some components cannot be degraded further, so they are fermented instead and converted to short-chain fatty acids. These acids are beneficial for muscle health and are known to prevent certain cancers and chronic diseases. And finally, the deoxygenated environment of the colon is home to anaerobic bacteria like Clostridium and Lactobacillus. At this point, there is little to digest, so the role of these microbes is to prevent the growth of harmful bacteria by out-competing them with regard to attaining nutrients. In some cases, the bacteria can produce vitamins that plants and animals cannot, such as vitamin B12. Considering how immensely beneficial these microbes are for our health, we, in turn, need to ensure that they survive and thrive in our gut. If you have seen any yoghurt or health supplement commercials, there is a good chance you may have encountered the term ‘probiotic’. Probiotic foods or pills contain active microbiota, like the bacteria found in yoghurt. The main function of these probiotics is to replenish our microbiome, which can be negatively affected by factors such as bowel diseases, aging or the overuse of antibiotics. Now that we have learned the basic facts about the gut microbiome and culture-specific cuisine let’s travel around the globe in our imagination to discover how the foods that are commonly found in various cultures can affect our physical well-being. 

In recent years, there has been a surge in the popularity of Southeast Asian culture. Everything from fashion to music and, most importantly, food from this cluster of nations is in vogue. Kimchi is a Korean side dish composed of fermented and salted vegetables, the most prominent being the napa cabbage. Fermentation is an ancient technique for food preservation used across a multitude of cultures. And while it is currently redundant due to the use of refrigeration, its unique flavour has enabled it to remain firmly in our collective consciousness. The salty brine used to create kimchi turns it into a probiotic as microbial growth is promoted. This is in contrast to pickled foods, which are fermented in vinegar, a weak acid that is lethal to bacteria. As a result, the foods pickled with vinegar do not provide the benefits kimchi does. In a 2021 research study conducted by Pennsylvania State University, metagenomic comparisons between the gut microbiomes of East Asians and Caucasians living in the US revealed that the former had more bacteria belonging to a variety of phyla. Interestingly, this disparity was more prominent for individuals with a lower BMI, and the gut microbiome of obese participants was more homogenous in both groups. If we move westwards across the globe, we find that okra is a beloved vegetable used in many traditional dishes. It is enjoyed across many regions but is particularly prevalent in South Asian countries. Okra is high in mucin, which is consumed by the bacterial species Akkermansia muciniphila. This specific strain is highly advantageous for us. In fact, metagenomic analyses have found that a higher amount of A. muciniphila in the body decelerates the progression of diabetes, inflammatory bowel disease and obesity. As more mucin is taken up, additional mucin is secreted by the epithelial cells, thus reinforcing the walls of the intestines. This is extremely crucial, as this wall is a selectively permeable barrier that absorbs nutrients, electrolytes and water while keeping out toxins and bad microbes. So those who eat more okra are likely to have a stronger gut. 

In contrast, some foods that we eat are detrimental to our microbiome. A notorious example of this is red meat, a common ingredient across various cultures, which is most common in the West. The overconsumption of red meat has been linked to the development of heart disease, stroke and colon cancer. Interestingly, the populations that eat the largest quantity of red meat in the world are Argentina and Uruguay, which also have some of the highest colon cancer rates. But what exactly makes red meat so dangerous? Scientists hypothesise that a carbohydrate called N-glycolylneuraminic acid (abbreviated as Neu5Gc) is involved. This sugar is not only impossible to pronounce but is also impossible for humans to synthesise. As a species, we have lost the gene coding for this compound, thereby causing our immune system to view Neu5Gc as a foreign body. This carbohydrate thus causes inflammation, which explains why inflammatory conditions like heart disease and colon cancer are so common. In 2019, researchers at the University of California genetically engineered mice to only take in Neu5Gc from their diets. They were then split into groups, either consuming a lot of red meat or a lot of soy, and the results showed a difference in their gut microbiome. The red meat groups had fewer microbes in general but possessed more sialidase, a Bacteroides enzyme. Sialidase is thought to aid in the release of Neu5Gc from the cells, a natural consequence of our bodies rejecting it. 

It is clear from our cross-cultural journey that our diet does affect the microbiota in our digestive tract. There are differences that are deep within us, and the years we have spent consuming certain culturally significant foods evidently reflect that. But the main reason researchers concern themselves with this phenomenon (apart from this simply being interesting) is the way this impacts our healthcare system. These differences can manifest in the diseases that are prevalent in each population and the types of drugs that need to be administered. The cuisine stemming from our cultural roots not only evokes visceral memories of our experiences but can even alter the course of our lives. And that is a truly amazing phenomenon.

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