Get a Good Gut
Article By: Meghan Cook 02/08/2017
Your gut bacteria, while not the most alluring part of your body, play a huge role in your overall health. All but overlooked mere decades ago, the scientific world is now teeming with research that is beginning to explore just how crucial and influential these ‘good bacteria’ are.
Day to day, your intestinal bacteria, or microbiota, help keep you healthy and disease-free. They help you break down the food you eat, unlocking nutrients you would not have been able to alone. They also produce compounds that help regulate your metabolism, and are a key player in the immune system. For some time, their role in these health areas was thought to be limited to the intestine, but studies are demonstrating that gut bacteria are linked to other wide-ranging health concerns.
It’s now apparent that their involvement in the immune system stretches to processes that mediate bodily inflammation. The emergence and severity of most chronic disease is underscored by bodily inflammation. As such, gut health has been found influence the development and/or symptoms of diseases including arthritis, type-1 diabetes, allergies, IBS and cancer1.
Gut health also has a large effect on body weight and obesity. Some bacterial species have a more positive effect on metabolism and energy efficiency than others. Thus, manipulation of the microbial composition of the gut, to favour certain species over others, can induce weight gain or loss2. In one study, scientists recruited sets of human twins, where one twin was lean and the other was obese. Samples of microbiota from each twin were taken and transplanted into mice. Those mice that received samples from an overweight twin experienced gains in their fat tissue while the other mice stayed lean, even when fed a similar diet3.
Evidence from a range of studies is also demonstrating that gut bacteria have a large influence on mental health. The gut tissue contains a lot of nerve cells, more than the spinal cord. This facilitates a large amount of interaction across what’s been termed the ‘gut-brain axis’. Signalling from an inflamed gut can interfere with a number of neuronal pathways, including those regulating the production of serotonin4. As a major factor in the development of a mood disorder, disruptions in serotonin have long been linked to anxiety and depression. If that weren’t enough, unfavourable species of gut bacteria also produce their own neurotransmitters, which can travel to the brain and result in physiological and behavioural stress responses4.
So, what causes bad gut health? And how do you promote good gut health?
Overall, a healthy gut will have a good quantity of diverse beneficial species, each contributing different and positive effects. Conversely, bad gut health is defined by lower levels of bacteria overall, usually with the underrepresentation of beneficial species.
Bad gut health is thought to be a symptom of modern lifestyles. Part of this is our medication use, particularly antibiotics. Individual rounds of antibiotics have been found to significantly reduce bacterial abundance and diversity, taking the gut months to recover5. This decline, while temporary, results in large shifts of species composition that doesn’t seem to ever fully transition back. However, the primary factor that underlies gut health is diet1.
A healthy, balanced diet supports the growth of beneficial bacterial species, each of which has their own nutritional requirements. Eat a lot of vegetables and you will support bacteria that favour plant-based diets. Eat a lot of red meat or sugar, and you can inadvertently support bacterial species that are linked to inflammation. Much like the movie Idiocracy, you can’t water your garden with sugary drinks and expect good things to grow. But if there was one star of good gut health, even in terms of bacteria, it would be the positive effects of fibre. So upping your veg and wholegrain intake is an excellent first step.
Martínez, I., et al., The Gut Microbiota of Rural Papua New Guineans: Composition, Diversity Patterns, and Ecological Processes. Cell Reports. 11(4): p. 527-538.
Zhang, Y.-J., et al., Impacts of Gut Bacteria on Human Health and Diseases. International Journal of Molecular Sciences, 2015. 16(4): p. 7493-7519.
Ridaura, V.K., et al., Gut Microbiota from Twins Discordant for Obesity Modulate Metabolism in Mice. Science, 2013. 341(6150).
Foster, J.A. and K.-A. McVey Neufeld, Gut–brain axis: how the microbiome influences anxiety and depression. Trends in Neurosciences, 2013. 36(5): p. 305-312.
Dethlefsen, L. and D.A. Relman, Incomplete recovery and individualized responses of the human distal gut microbiota to repeated antibiotic perturbation. Proceedings of the National Academy of Sciences of the United States of America, 2011. 108(Suppl 1): p. 4554-4561.