Importance of your gut for performance – What GCSE and A-Level Biology doesn’t tell you
The majority of GCSE and A Level syllabuses cover digestion from mouth to large intestine by looking at the enzymes and mechanisms the body uses to break down our food into small enough molecules to be absorbed. What is missed or only covered in passing, is our reliance on the hundreds of thousands of micro-organisms that live in the digestive system. Research clearly shows that without them our digestion simply doesn’t work properly. The more we study these populations of microflora, the larger the role we find that they may have.
The gut microbiota or microflora
The human digestive system is home to trillions of micro-organisms. The average adults gut population has 10 times more cells than the host’s body, weighs more than 1kg and their waste accounts for about half of our faeces. Around 40 common species account for approximately 98% of most populations, but over 500 different species have been identified and scientists believe that these may account for as little as 20% of the total number found across all world populations.
The microflora live in highly organised and complex colonies, with some species dominating and controlling the population of others. The precise organisation and mix of species appears to be individual and although similar in members of the same family, population or closely related groups, everyone’s balance of micro flora is unique and will depend on their lifestyle, home and diet. For example a gut microbe recently identified in a small population of people in Japan has the ability to break down the structure of seaweed, which is an important part of their diet. Although highly beneficial in this population, it hasn’t been found elsewhere in the world, where seaweed is not eaten as regularly. In a perfect world our individual microflora should contain a mix of species that are beneficial to each of us in our specific environment.
The traditional role of the microflora
It has been known for some time that most complex carbohydrates are only broken down by gut microfloral fermentation in the lower intestine and that the rate and extent of this process depends on the composition of the food and mix of micro-organisms present. Without gut microflora we would not be able to utilise all the carbohydrate we eat, as we lack enzymes to break down polysaccharide starches, fibre, oligosaccharides and sugar alcohols. Microorganisms turn these carbohydrates into short-chain fatty acids (SCFAs), such as acetic acid, propionic acid and butyric acid. These can be absorbed but also provide a major energy source for local muscle and gut cells, improving digestion, supporting a healthy intestinal barrier and inhibiting the growth of harmful bacteria. Microflora are thought to be responsible for around 10% of energy production.
New Roles – The Importance for Optimal Health and Performance
Research over the last decade has found that micro-organisms living throughout the digestive system (from mouth through to colon) have a number of other important roles….
- Gut microflora are responsible for a large proportion of our Vitamin K production and are important in the manufacture of all B Vitamins.
- The right balance of favourable gut microflora have also been shown to improve nutrient absorption, particularly of Calcium (maybe by as much as 50%) and Magnesium. Which are both particularly important during adolescence and are often deficient in sports people.
- A wide volume of research shows that eating a wide variety of colourful fruit and vegetables, containing a good variety of phytonutrients is linked to lower disease risk, better health and improved academic and sports performance. However, eating lots of phytonutrients isn’t the whole story, as in many cases the nutrient in our food is not in its bioactive form. More research is needed but one idea being looked at, is that the action of beneficial gut microflora maybe needed, for us get all the benefit from the foods we eat. Differences in microfloral population are one explanation as to why some some individuals do not respond in the same way to supplementation studies. Using antibacterial mouth washes have been found to prevent the performance benefits of beetroot juice anthocyanins and supplementing with probiotics has been found to boost the performance benefits of many natural sports supplements. There is also evidence that high intakes of polyphenols may support beneficial gut bacteria.
- Gut microflora are vital for the proper functioning of our immune system. Initially it was thought that they improved immunity by maintaining the gut barrier and providing a layer of defence against pathogenic micro-organism invasion but it is now thought the balance of the gut microbiome is also vital for the proper development of the immune system. The mechanism is complex and more research is needed but it would appear that the wrong balance of microflora maybe responsible for the development of some types of autoimmune and allergic diseases. Infants with less diverse gut bacteria at the age of 3 months have been shown to be more likely to have food sensitivity to allergens at 1yr, including egg, milk and peanut. Lack of gut bacteria diversity in early life may be a driver for food allergies. Some probiotic species have been shown to shorten or reduce the risk of certain infections, particularly those of the GI tract.
- It would appear that there are differences in how individuals digest food depending on which microbes they have in the gut and that these differences may have a role in weight gain & obesity. Short-chain fatty acids (SCFAs) affect lipid, glucose, and cholesterol metabolism. SCFAs have been shown to beneficially affect glucose metabolism; normalising blood glucose levels and increasing the efficiency of glucose handling. They also increase fatty acid oxidation in tissue, decreasing fat storage in white adipose tissue and increasing loss of heat energy through the brown adipose tissue.
- Gut microflora break down proteins such as enzymes, bile salts, dead host and bacterial cells and the collagen and elastin found in food. Over the last two decades eating a diet high in meat and processed meat products has been linked to increased disease risk, particularly for cancer. Inadequate fermentation of protein by the wrong balance of bacteria has been shown to produce toxins and carcinogens, which may be the reason for this increased cancer risk in some people. More research is needed.
- Lack of SCFAs causes poor gut mobility and possibly gut damage and has been linked to IBS.
- Gut bacteria produce many of the neurochemicals’ used by the brain to regulate mental processes such as learning, memory and mood. Poor diversity of gut bacteria has been associated with a number of mental health problems, including eating disorders, anxiety and depression. Research has found that boosting microflora diversity results in lower perceived stress and anxiety. Individuals given prebiotic supplements were also found less likely to ‘pay attention to negative comments’ than those who received a placebo and had lower levels of the stress hormone cortisol. Animal studies have shown that early exposure to normal gut bacteria is important for brain development and the development of ‘normal’ behaviour. Mice bred to be germ-free (no microflora in the gut) are found to be excessively active and show greater risk-taking behaviour. Poor gut microfloral diversity has been found in autism, ADHD and dyslexia.
- Beneficial flora increase the gut’s absorption of water, lessening the risk of dehydration.
100s of pieces of research looking at the micro-organisms living on or within our bodies have been published this year. Many of these studies are strong but there is still a huge amount we don’t know. I have tried to summarise this research as simply as possible, to give an idea of how important gut health is. I have not included references but I have these for anyone who is interested and would be very happy to discuss the research in more detail.
What is clear is that gut health is important…..
Prebiotics and Probiotics
Prebiotics are substances which feed and so boost the number of beneficial bacteria which naturally exist in the gut, suppressing the growth of other less useful bacteria. The most common types of prebiotics are inulins, fructo-oligosaccharides, (FOS) and galacto-oligosaccharides (GOS). Inulin is a natural storage carbohydrate present in more than 36,000 species of plants, including wheat, onion, bananas, garlic, asparagus and chicory. Oligosaccharides are complex carbohydrates composed of short chains of sugars linked by bonds that are difficult for the human digestive enzymes to break. FOS are short chains of fructose and GOS short chains of galactose. FOS and GOS are common in fruit and vegetables. GOS can also be synthesised from lactose in milk. There are also lots of supplements on the market.
Probiotics are live bacteria and yeasts that boost beneficial gut bacteria. Probiotics often contain specific species of Bifidobacteria and Lactobacilli, which help “balance” gut flora, increasing the number of helpful, and inhibiting the growth of harmful bacteria. The most common natural probiotics are live cultured yogurt, Miso (fermented rye, beans, rice or barley), Sauerkraut (fermented cabbage), Kifir (goat’s milk and fermented kefir grains), Microaglae (spirulina, chorella, and blue-green algae) and green pickles. A large number of specialist foods and supplements are also available.
Both pre- and pro-biotics have been shown to have beneficial effects on gut flora. Much of the research has been done by supplement manufacturers but natural products maybe just as, if not more effective. When choosing a natural product or supplement watch the amount of sugar. Refined sugar boosts unfavourable micro-organism growth.
Physical Activity and Vitamin D – Being fit and active has been found to improve gut microfloral diversity and lessen gastrointestinal disorder risk. Vitamin D has been shown to regulate the micro biome. Vitamin D deficiency results in a drop in the number and diversity of species.
Gut Microflora and Sport
Extreme exercise or training is found to suppress the body’s immune response and probiotics have been found to help, particularly with the type of respiratory tract infections that are common in youth athletes. Pro and prebiotics may also help with sport related gastrointestinal distress, particularly as high protein intakes are common in athletes. Many professional sports teams now take both pre and probiotics on a regular basis and they have been found to boost the effect of some ergogenic aids.
Gut Microflora and Dyslexia
Microbial community diversity has been widely linked with autistic spectrum disorders (ASD) but at the moment the evidence is mostly associative. There is definitely reduced diversity but its difficult to know whether this occurs because of the disorder (poor eating or stress) or whether the low microfloral diversity it is the cause. In dyslexia, I feel probiotics/prebiotics use may be worth trying. Dyslexia is often linked to poor blood glucose regulation, migraine and anxiety, all of which are also associated with poor micro-biome diversity. Omega3s, B Vitamins, Magnesium and phytonutrient polyphenols have been all been linked to positive outcomes in dyslexia fitting into this story but much more research is needed.