Written by: Roshni Patel
Email:proshni0714@gmail.com
Introduction One of the lesser known but one of the most integral parts of the human body is the gut microbiome. Through niche exclusion, antimicrobial peptide production, energy harvest and metabolism, immune system development, etcetera, the gut microbiome proves itself as one of the most important parts of the human body (Kedia & Ahuja, 2023). The microbiome develops into a gender specific one as an individual matures through puberty; it weakens after the age of 65 (Kedia & Ahuja, 2023)[DR1] . There are many factors that go into how well the microbiome works. Some of the most common gut bacteria are Bacteroides, Escherichia, Streptococcus, Ruminococcus, Bifidobacterium, Clostridium, and Bifidobacterium (Conlon & Bird, 2014). As the benefits of the gut microbiome are discovered, research and data analysis become increasingly important, and essential questions are asked such as the cause for the gut microbiome differing in developing countries versus developed countries.
Figure 1: Different types of gut micrbiome
Diet/ lifestyle has been proven to have one of the heaviest impacts on the gut microbiome. A simple diet alteration can result in a large, albeit temporary microbial shift within 24 hours (Singh et al., 2017). Eating certain foods produces a predictable shift in host bacteria. SCFAs (short chain fatty acids) are a major energy source and have been shown to be anti–inflammatory with the addition of butyrate; people with an unhealthy diet reportedly had less SCFAs present in the microbiome (Kedia & Ahuja, 2023).
Mental health also has a significant impact. The brain and gut work in a bi-directional manner known as the gut brain axis (Limbana et al., 2020). This means that they can impact each other’s functions as well as stress, anxiety, etc. Many people who struggle with their mental health tend to lose their appetite, which is considered a change in diet and can result in a change in the gut microbiota (microbial shift). Data demonstrates that patients with diagnosed mental health issues have shown gut microbiome dysbiosis (microbial imbalance).
Per this discussion, there are also many cultural implications to be noted. Most developing countries have poor infrastructure and a weak and/or dictator-run government. This results in a substantial difference in the quality of life across the wealth gap. The poor tend to grow their own food, meaning that they eat less processed food and animal products (Conlon & Bird, 2014). Much of the population in these developing countries tend to lead agriculture-based lives, so they do not have a reliable source of income throughout the year due to issues such as drought, flooding, etcetera (World Bank, 2023). Many couples have more children because they view them as a form of economic security . Additionally, male babies are still preferred in certain cultures and often parents will keep trying until a boy is born (Brink, 2015). With more children, comes the responsibility of school fees, dowry (still prevalent), clothes, shoes, etcetera. Depression and psychological rates are high especially in women due to their experiences with domestic and sexual violence (Kopinak, 2015). Cultural stigma and lack of access to proper facilities often prohibits people from seeking the help they need to overcome their mental battles. People living in developing countries have limited access to running water and electricity. There is a substantial difference in lifestyles and diets when compared to that of the average person living in a developed country such as the USA.
Impact of Diet and Lifestyle on Gut Microbiome
People in developed countries tend to have a diet rich in processed foods, energy-dense, and an elevated level of fat (Shi, 2019). The NOVA system, which classifies foods into 4 groups based on the extent of how processed food is, has brought attention to ultra-processed foods (Zinöcker & Lindseth, 2018). These foods are known to have a long shelf life and a poor nutritional profile. This is most common in high income countries such as the USA, Australia, and France, which had an average energy intake from ultra-processed foods of 57.9, 42, and 29.1 percent, respectively (Shi, 2019). The composition of diet greatly influences the type of bacteria developing in the gut as well as how much they grow and thrive (Singh et al., 2017). This has also resulted in various health issues such as obesity and inflammatory diseases through a diet low in fiber and fruits/vegetables (Shi, 2019). The Western-style diet has been shown to have higher tendencies of dysbiotic bacteria (Garcia-Montero et al., 2021). For instance, North America, considered one of the most developed areas in the world, has some of the highest rates of IBD (irritable bowel disease), i.e., an inflammatory disease, which stems from a change and/or inflammation of gut microbiota (Khan et al., 2019). Most people in developed countries are not malnourished and still have the necessary fiber for at least a marginally healthy gut microbiome. As time goes on, healthy eating has become more common, so it is likely that the gut microbiome will diversify.
Alternately, the diet of people in developing countries tends to consist of less processed foods and more vegetables and fruits due to many families leading an agricultural life. However, people tend to be malnourished, which impacts the gut microbiome. As the gut microbiota are disturbed, they could make malnutrition and growth failure a more prevalent issue. This was later proven as gut microbiota dysbiosis was causally connected to childhood undernutrition through a study involving Malawian (Malawi is a developing country in Africa) children and infants with varying degrees of undernutrition (Wilson et al., 2020). Butyrate is the most common type of SCFA (short chain fatty acid) that acts as a major energy source for epithelial cells and strongly influences immune tolerance and anti-inflammatory protective properties (Constanzo et al., 2021). SCFA’s are mainly created through fermentation of dietary fibers and carbohydrates. While not all areas of Africa are underdeveloped, the overall diet is similar to a Mediterranean diet - low in fat and high in fiber (Wilson et al., 2020). This means that the gut microbiome should be healthy and diverse. Due to malnutrition, the SCFA’s do not function properly or there is a lack of them, which points to a weakened gut microbiome. In many underdeveloped parts of Africa, butyrate can be less prominent and have a heavy negative impact on the immune system. This is partly why many people in rural Africa have deficiencies, microbial dysbiosis, metabolic diseases, etc (Wilson et al., 2020). Overall, a common diet high in fiber and vegetables and fruits is quite beneficial to the gut microbiome, but malnutrition and/or undernutrition has a harsh impact on it, leading to diseases such as obesity, asthma, inflammatory bowel disease, etc (Allali et al., 2021). There are also other factors that influence this, such as the vast use of antibiotics from a young age as well as environmental factors.
There were multiple studies conducted on the specifics of the comparisons in diet and its corresponding impact on the gut microbiome. The gut microbiome of Hadza hunter-gatherers of Tanzania was compared to that of urban Italians (Wilson et al., 2020). The Hadza gut microbiome showed more SCFA potential while the urban Italian microbiome showed a tendency in xenobiotic metabolism. The diet of the Hadza people has been shown to be rich in fiber, which is important for SCFA function. This further emphasizes the impact diet has on the gut microbiome. A study conducted in Russia compared the microbiotal composition of rural Russians and urban Russians (Tyakht et al., 2014). It was noted that the urban Russians had more of a Western style diet consisting of meat and processed foods while the rural Russians consumed more produce. Lactobacillus and Phascolarctobacterium were found to be the most abundant genus in rural communities such as the Omsk region and Khakassia, respectively. This was also the case in Mongolia: these bacteria dominated the gut microbiome of the rural population. On the other hand, it was shown that the gut microbiome of people of urban areas such as Saint-Petersburg had many pathogenic compositions such as Escherichia coli, which is associated with inflammatory bowel diseases. Gathered from 14 data sets, scientists were able to analyze 586 different gut microbiomes that represented hunter-gatherers, pastoral, urban, agricultural, and agropastoral populations (Plaza, 2022). It was shown that industrialized populations had less diversity than those from a non-industrialized background. Certain groups such as Lanchospirae and Rickenellaceae were found to be more common in modern societies, virtually having evolved. Even over a brief period, a change in the Western diet resulted in elevated levels of BA-tolerant bacteria, a disruption in the intestinal barrier, a pro-inflammatory environment, and lowered SCFA levels (Garcia- Montero et al., 2021). There were also more dysbiotic bacteria in the gut microbiome of those following the Western diet rather than the eubiotic bacteria found in those following the Mediterranean diet. For reference, the Western diet is characterized by developed/urban areas while the Mediterranean diet is characterized by developing/rural areas.
Effect of Mental Health on Gut Microbiome
Mental health and the gut microbiome interact in many ways. The gut brain axis is a bi-directional network connecting the enteric and central nervous systems (Appleton, 2018). Mood disorders such as anxiety and depression have been proven to be linked to gastrointestinal disruptions. Diet has been shown to impact the gut-microbiome's influence on cognitive function. Studies have shown that people in developing countries have less access to mental health care than developed countries (Kopinak, 2015). This is due to stigma and lack of awareness (Krendi & Pescosolido, 2020). It was reported that people of Eastern nations believed that having mental health issues was shameful, even believing that they do not exist. However, developing countries such as Uganda are improving this by opening clinics that offer mental health services in addition to regular medical care (Kopinak, 2015). There are many hormones such as serotonin, melatonin, histamine, etc, that regulate the gut-brain axis (Appleton, 2018). Some of these hormones, such as serotonin, are mostly produced by the gut (approximately 95%). Due to an imbalanced diet and other issues, sometimes people do not produce enough of a certain hormone, so things such as mental health, sleep, and appetite can be impacted.
Mental health in developed countries is heard of more due to the lack of stigma. For example, according to data from 2021, approximately 61% of Americans with mood/mental disorders received treatment of various forms (2021 National Survey of Drug Use and Health). As mental health awareness has become more prominent, more people are likely to receive therapy/counseling in Western countries. However, many people living in developing countries/ Eastern areas have a culture that believes that having mental health issues is shameful and should not be mentioned. While there are underlying issues such as racial and sexual discrimination, these problems are present in all countries regardless of the degree of severity. Data shows that while 1 out of 4 people globally experience a mental disorder at least once during their lives, only 2/3 of these people receive treatment (Krendi & Pescosolido, 2020). This impacts the gut microbiome in many ways. As mentioned prior, the gut brain axis is a bi-directional network that connects two systems – the enteric and central nervous systems (Appleton, 2018). If mental health is poor, the gut microbiome will also be imbalanced, which could cause many issues such as irritable bowel syndrome. If treatment is not received, then there will be other physical issues alongside the potentially harmful changes in the gut microbiome. For example, an alteration within the gut microbiome could be a change in SCFA metabolism (Appleton, 2018). Disruptions to the metabolism of SCFA’s have been linked to the development of autism as microglial function is impaired.
Conclusions
Essentially, diet and lifestyle have a major impact on the gut microbiome such as its composition and diversity. Studies and data clearly showed the disparity between the gut microbiome of people living in developed/urban areas versus developing/rural areas. A more fibrous diet was found to be more common in unindustrialized areas, which lead to an abundance of SCFA’s and microbial diversity. However, due to circumstances such as malnutrition and environmental factors, many people in developing countries such as Malawi have a weakened gut microbiome which affects the immune system, which is a potential reason as to why so many people in developing areas have diseases (aside from lack of preventative measures. Certain bacterial groups were found to be more common in rural areas while more pathogenic groups were found in urban areas (based on Western - style diet versus natural diet). The Western-style diet tended to result in dysbiotic bacteria while those following the Mediterranean/ natural diet tended to display more eubiotic bacteria in the microbiome. Diet is quite different between developed countries and developing countries, and the effect of it on the gut microbiome is prominent. Another important aspect of the gut microbiome is mental health. Mental health issues are perceived differently in developed countries and developing countries as characterized by the comparisons between Western and Eastern areas, respectively. Mental health impacts the gut microbiome and vice versa. Disruptions in the gut microbiome from mental health issues can lead to an onslaught of issues including Crohn’s disease. People in developed countries are more likely and have received more treatment for mental health issues compared to those living in developing countries. Diet/lifestyle and mental health have contributed significantly to the differences between the gut microbiomes of people living in developed countries and developing countries.
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