The gut, also known as the digestive system, gastrointestinal tract, or even referred to as the “second brain” of the body serves many essential roles in sustaining our overall health and well-being.
Poor gut health has been linked to an array of health conditions. It can affect proper digestion and absorption of nutrients, aggravate inflammation, and is linked to our mental well-being. Modern lifestyles resulting in chronic stress, infections, diets high in processed foods, and the excessive use of antibiotics all negatively affect our guts.
Our bodies are home to over a hundred trillion tiny microbes made up of bacteria, fungi, and other microorganisms - most of which are found in our large intestine. These microbes promote normal gastrointestinal function and play an important role in our overall health and wellbeing.
Our mental health is largely affected by our gut health and vice versa. The bidirectional pathway between the gut and brain, otherwise known as the gut-brain axis, serves as a communication platform for many physiological processes. The two are so closely linked that the gut is often referred to as ‘the second brain’ of the body.
The gut and brain are in constant communication with each other through the use of communication chemicals such as hormones and neurotransmitters. Due to the high association between the gut and brain, the improvement of your gut environment can improve your mood.
Having optimal amounts of “good” gut bacteria will help with strengthening the immune system and improving conditions such as irritable bowel syndrome (IBS). Ideally, we require a diverse range of beneficial bacteria in our gut.
Food metabolism is regulated by the guts endocrine system. Hormones are produced that make us feel hungry or satisfied. If our guts endocrine system is not working optimally, feelings of unsatisfaction and continued hunger result. This ultimately leads to weight-gain or conditions such as type 2 diabetes1.
The gut’s immune system protects against pathogens and cells are tightly connected making up the gut epithelium1. There is also a protective mucus layer to add another layer of defense1. This barrier is compromised by diets high in sugar and emulsifiers and low in dietary fibre. Our gut microbes rely on dietary fibre, however, when our diets contain inadequate amounts of fibre the microbes start feeding on the components found in the protective mucosal layer1. This results in the release of inflammatory molecules which loosens the tight junctions that make up the epithelial layer1. Harmful microbes then come into contact with our gut immune cells causing further damage. This condition is known as leaky gut syndrome1.
Western diets high in sugar and fat and low in fibre have a negative impact on the diversity of the gut microbiome1. Modern day diets have a reduced diversity of gut microbiome species placing additional stress on our overall gut health. Studies have found an association between the Mediterranean diet and improved health. The Mediterranean diet is high in fruits, vegetables, nuts, seeds, and olive oil and includes lean animal protein sources primarily from poultry and fish1.
Poor diet as well as a lack of exercise cause abnormal communication between the gut microbiome and gut immune system1. Exercising has also been shown to benefit the gut microbiome and overall gut environment. Studies done on rats found that those who were active had improved gut microbiota compared to those whose activity was restricted1. The active rats were also found to have higher levels of the short-chain fatty acid, butyrate, in their guts. Butyrate improves our gut immune system, benefits cognitive functioning, and elicits feelings of satiety1.
The more plant-based fibre, polyphenols, phytonutrients, and anti-inflammatory foods we consume, the better for our gut health. For example, consuming a decadent dessert with roughly 50g of sugar will cause a spike in blood sugar levels and no nutrients for the gut microbiome. However, consuming a salad with beans, avocado, and nuts (with roughly the same caloric amount as the dessert) will provide the gut with absorbable micronutrients1. Nutrients are broken down by the gut microbiome into health-promoting molecules. This is one of the reasons why a calorie does not necessarily equal a calorie and not all calories can be considered the same.
Simple tweaks can be made to your diet in order to help your gut microbiome thrive. One of these would be to add a variety of plant-based foods to your diet. Different gut bacteria thrive on different foods so instead of reaching for the same fruit and veg we usually opt for, try to increase the variety of fruits, vegetables, whole grains, pulses, legumes, nuts, and seeds consumed.
Here are some other ways in which we can improve our gut health:
Polyphenols are plant-based molecules encompassing a variety of compounds such as flavonoids, quercetin, and anthocyanins1.
Flavonoids are bioactives found in certain foods that inhibit gut inflammation. A meta-analysis also concluded that flavonoid consumption enriches the beneficial gut microbiota known as Bifidobacterium and Lactobacillus. Not only are flavonoids good for the gut, they’re also anti-carcinogenic and antimicrobial.
Some polyphenols act as prebiotics which is food for our gut microbes1. Others suppress unhealthy microbes in our gut1.
Polyphenols are found in fruits (apples, pears, berries), leafy vegetables, red wine, nuts, and legumes.
Fermented foods can help to increase gut diversity and improve immune response. Eating fermented foods enhances the beneficial bacteria in our gut contributing to improved digestion and weight loss. Examples of fermented foods/drinks include kefir, kombucha, tempeh, miso, kimchi and sauerkraut.
The benefit of fibre for our gut health is indisputable. Not only does fibre regulate our bowel movements, but it also enables our gut microbes to thrive and perform at their best. It is essential to have a diversity of gut microbes for a healthy gut environment so ideally, we need to consume a variety of high-fibre plant-based foods for optimal gut health1. For example, consuming artichokes, broccoli and lentils will provide high amounts of microbiota-accessible carbohydrates (MACs) which the gut microbiota feed off and produce beneficial compounds. A diet rich in MACs will increase the amount of Bifidobacteria strains (healthy gut bacteria) available. Asparagus, leeks, and banana contain high amounts of fructans which are processed by the bacteria known as Faecalibacterium.
Spices such as turmeric, ginger, fennel, mustard, cardamon, and cumin have been used for years not only to add flavour to foods but also for their range of health benefits. They play a role in inflammation and contribute to an overall healthy gut microbiome1.
Omega 3 fatty acids
Omega 3 fatty acids are mostly absorbed in the small intestine however small amounts make their way to the large intestine1. It is here that they increase the diversity of the gut microbiome. Foods high in polyunsaturated fatty acids (PUFAs) include salmon, mackerel, herring, sardines, flaxseed, chia seeds, walnuts, and soybeans1. Omega 3 PUFAs result in the increased production of anti-inflammatory compounds and maintain the integrity of the intestinal wall.
1: Mayer, E 2021, The Gut-Immune Connection, Harper Collins publishers, New York
Written by Nicole Keeling, Registered Dietitian (HPCSA, ADSA)