How to Boost Your Gut Microbiota and Improve Your Health

More than ever, we’re being inundated with advice on what to eat and what to avoid, and “gut health” has become something of a hot topic. However, with so much contradictory information surrounding it, we wanted to cut through the chaos and provide you with a simple, yet scientific guide to gut health and the simple steps you can take to boost your gut microbiota. 

We’ve teamed up with qualified dietitian Roseanna Henderson, who shares her insight and the latest scientific research into gut health. 

The Gut

The digestive system is the group of organs via which food is broken down, nutrients are absorbed and waste products are expelled.  The term “gut” is used to refer to the intestines or bowels, which are host to a large number of microorganisms known as the gut microbiota. The gut microbiota has important roles in the immune system, digestion of nutrients and the production of vitamins. Scientific research has found links between an unhealthy gut microbiota and health conditions including obesity, cancer and mental health issues (1,2). A healthy gut microbiota is one that is diverse, ie. has lots of different types of microorganisms (3). By improving and maintaining a healthy gut microbiota, it may be possible to reduce the risk of developing health issues.

Diet and the Gut Microbiota

The gut microbiota is affected by lots of different factors including smoking, medication and diet. Diet is thought to be one of the most powerful ways to change the gut microbiota (4), and scientific studies have shown that changing your diet and incorporating “gut beneficial” foods can change your gut microbiota in a matter of hours. However, the effect of a dietary change on the gut microbiota seems to last only whilst the dietary change takes place, so any benefit stops if you return to your previous diet (5). This suggests that long-term dietary change is required for a sustained improvement in gut health.

One of the key actions of the gut microbiota is breaking down food components that are not digested by the gut. Different types of gut microorganisms break down different food components. Gut microorganisms that break down food components into compounds that have a positive effect on health are considered beneficial, such as Bifidobacterium and Lactobacillus bacteria. These can produce short chain fatty acids (e.g. butyrate), which have effects including reducing inflammation, protecting against bowel cancer, boosting the immune system and benefits to heart health, mental health and bone health  (3,6).

So What Can We Eat That Is “Gut Beneficial”?

Polyphenols

Polyphenols are found in foods including fruits and vegetables, tea, cocoa and wine. They are thought to have health benefits for humans, including anti-inflammatory and anti-cancer properties. Scientific studies have found that polyphenols can change the gut microbiota, increasing the amounts of beneficial Bifidobacterium and Lactobacillus bacteria (3). A small study in healthy and obese individuals looked at the effect of polyphenols from red wine. It found that after taking polyphenols for 30 days, both healthy and obese groups had increased amounts of beneficial bacteria in their stools. There were also improvements in blood sugar and “good” HDL-cholesterol levels for both groups, which were found to be linked to the increase in beneficial bacteria (7). This suggests that the health benefits of polyphenols could, in part, be due to changes to the gut microbiota.

Prebiotics

Prebiotics are a form of fibre which are digested by the gut microbiota and have a positive effect on health (6). Prebiotics essentially provide a food source for the gut microbiota, which break them down into short chain fatty acids. Scientific studies have found that dietary interventions with prebiotics increase the amounts of beneficial Bifidobacterium and Lactobacillus bacteria in the gut and the production of the short chain fatty acid, butyrate (8).

Prebiotics are found in foods such as garlic, onions, leeks, artichokes, asparagus, chicory, bananas, agave and wheat (9). They can also be taken in the form of a supplement (6).

Probiotics

Probiotics are defined as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host” (10). So, when probiotics are consumed, they pass into the gut alive, where they have the potential to settle and increase in number. This can change the makeup of the gut microbiota by boosting the number of beneficial microorganisms (such as Bifidobacterium and Lactobacillus) and inhibiting the growth of potentially harmful ones (11).

Probiotics are taken as probiotic yoghurts and drinks, or in the form of a supplement. There are many types of microorganisms used as probiotics; some of the most common strains include those in the Lactobacillus family (e.g.  L. acidophilus) and those in the Bifidobacterium family (e.g. B. bifidum) (11). Probiotic supplements are not regulated like medicines, which means that the amount and type of probiotic in different supplements will vary, so it’s worth checking the back of the packet to find out what you’re buying!

For people with a healthy diverse gut microbiota, consuming probiotics may not have much effect, but, if you have a low number or variety of gut microorganisms, the benefit may be greater 5. Probiotics are particularly beneficial after taking antibiotics. Antibiotics disrupt the gut microbiota and can cause diarrhoea (12), so it is important to only take antibiotics when necessary. Taking a course of probiotics after finishing a course of antibiotics will help to re-establish a healthy and diverse gut microbiota (12).

 Fermented foods

Fermentation is the process where food or drinks are changed by microorganisms. There are two types of fermented foods; those which naturally contain and grow microorganisms, such as sauerkraut and kimchi, and those which have microorganisms added to them in the form of a “culture”, such as kombucha and kefir. There are a few ways in which fermented foods may have a beneficial effect on gut health. Firstly, they may be able to act as probiotics, i.e. the microorganisms in the fermented food reach the gut alive and are able to provide a health benefit. Secondly, the process of fermentation itself may produce compounds which have a positive effect on health. Finally, fermentation may reduce the amount of toxins in the fermented product (13).

Currently, there is limited scientific evidence for the effectiveness of fermented foods in improving gut health. There are only a few scientific studies and those that have been done are often lab- based and not in humans. High quality studies are needed to determine the effect of fermented foods on gut health in humans (13).

Summary

The gut microbiota has important roles in the normal functioning of our bodies and there are links between an unhealthy gut microbiota and numerous health conditions. Diet can affect the balance of “good” and “bad” microorganisms in the gut, so by optimising our diet we can improve the makeup of our gut microbiota. A varied diet containing polyphenols, prebiotics, probiotics and perhaps fermented foods may have a beneficial effect on the gut microbiota and our health. Further scientific research is required to determine the extent of the benefits.

References

1.       Marchesi JR, Adams DH, Fava F, et al. The gut microbiota and host health: A new clinical frontier. Gut. 2016;65(2):330-339. doi:10.1136/gutjnl-2015-309990
2.       Illiano P, Brambilla R, Parolini C. The Mutual Interplay of Gut Microbiota, Diet and Human Disease.; 2020. doi:10.1111/febs.15217
3.       Yang Q, Liang Q, Balakrishnan B, Belobrajdic DP, Feng QJ. Role of Dietary Nutrients in the Modulation of Gut Microbiota : A Narrative Review. 2020. doi:10.3390/nu12020381
4.       Zhernakova A, Kurilshikov A, Bonder MJ, et al. Population-based metagenomics analysis reveals markers for gut microbiome composition and diversity. Science (80- ). 2016;352(6285):565-569. doi:10.1126/science.aad3369
5.       Leeming ER, Johnson AJ, Spector TD, Roy CIL. Effect of diet on the gut microbiota: Rethinking intervention duration. Nutrients. 2019;11(12):1-28. doi:10.3390/nu11122862
6.       Gibson GR, Hutkins R, Sanders ME, et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nat Rev Gastroenterol Hepatol. 2017;14(8):491-502. doi:10.1038/nrgastro.2017.75
7.       Moreno-Indias I, Sánchez-Alcoholado L, Pérez-Martínez P, et al. Red wine polyphenols modulate fecal microbiota and reduce markers of the metabolic syndrome in obese patients. Food Funct. 2016;7(4):1775-1787. doi:10.1039/c5fo00886g
8.       So D, Whelan K, Rossi M, et al. Dietary fiber intervention on gut microbiota composition in healthy adults: A systematic review and meta-analysis. Am J Clin Nutr. 2018;107(6):965-983. doi:10.1093/ajcn/nqy041
9.       Holscher HD. Dietary fiber and prebiotics and the gastrointestinal microbiota. Gut Microbes. 2017;8(2):172-184. doi:10.1080/19490976.2017.1290756
10.   Hill C, Guarner F, Reid G, et al. Expert consensus document: The international scientific association for probiotics and prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506-514. doi:10.1038/nrgastro.2014.66
11.   Azad MAK, Sarker M, Li T, Yin J. Probiotic Species in the Modulation of Gut Microbiota: An Overview. Biomed Res Int. 2018;2018. doi:10.1155/2018/9478630
12.   Kim SK, Guevarra RB, Kim YT, et al. Role of Probiotics in Human Gut Microbiome-Associated Diseases. J Microbiol Biotechnol. 2019;29(9):1335-1340. doi:10.4014/jmb.1906.06064
13.   Dimidi E, Cox SR, Rossi M, Whelan K. Fermented Foods : Definitions and Characteristics , Gastrointestinal Health and Disease. Nutrients. 2019;11(1806):26. doi:https://doi.org/10.3390/nu11081806

Rosie graduated with a postgraduate diploma in Dietetics from King’s College London in 2017, having previously gained a Master’s degree in Nutrition and a First Class Honours degree in Biomedical Sciences.