The impact of exercise on your gut bacteria

Having a healthy gut is about much more than just looking at the food you eat or probiotics you take. You have a win-win arrangement with your gut microbes. When you live a healthy life, these guys work super hard to keep you happy and healthy.

These microbes influence digestion, immune function, brain function, mood and overall health. The diversity of the microbes in your microbiome is a key parameter for measuring health. When this internal ecosystem is imbalanced, you can end of up with dysbiosis, digestive problems, Irritable Bowel Syndrome, weight gain, obesity, type 2 diabetes, autoimmune diseases, cardiovascular disease (CVD) and more.

We already know that diet, short chain fatty acids (SCFAs), prebiotics and probiotics can improve your internal ecosystem. Today, I want to share how a little exercise can positively impact your microbiome.

Exercise and your microbiome

Since 2010, there has been a number of studies investigating the impact of various forms of exercise on the microbiome. The type of exercise invariably impact results, but for the purpose of this post, I will focus on exercise in general.

Exercise has been linked to increases in the number of beneficial bacteria in the gut, thereby enriching microbial diversity. It is also associated with higher levels of firmicutes, a key bacterial phylum that is able to produce SCFAs, like butyrate.

In short, the intestinal microbiota is dominated by five phyla, of which firmicutes and Bacteroidetes make up more than 80%. Making these guys pretty important. Thanks to amazing advances in stool testing, you can now get a great deal of information about these phyla and thereby the health of your gut and immune function.

Let’s take a look at some of the science.

Study 1

A major study compared the microbiomes of 40 elite rugby players age 29 with control groups of similar age with either high or low BMI. It highlighted “significantly greater intestinal microbial diversity among the athletes”. Results also indicated higher levels of SCFAs, with ‘significantly higher levels of acetate, propionate, butyrate and valerate in athletes relative to controls”.

They also found that those individuals with a relatively lower BMI had significantly higher levels of akkermansia, compared to the higher BMI group. Akkermansia, is a key bacteria that helps to protect the gut lining and improve insulin sensitivity.

Extreme exercise is associated with leaky gut, so it is interesting to see that the body’s natural reaction in these athletes was to produce greater quantities of akkermansia. The body will always try and reach a state of balance/homeostasis and in this instance the akkermansia might well be there to protect these athletes from damage to the lining of the gut and therefore leaky gut. I think that’s pretty awesome.

Study 2

Researchers enrolled 32 (18 lean and 14 obese), previously sedentary women. They were asked to do six weeks supervised cardiovascular exercise for three days a week.

The exercises progressed from 30-60 minutes per day and then progressed in intensity over the duration of the programme. Therefore, from moderate (60% of HR reserve) to vigorous intensity (75% of HR reserve).

After six weeks, the participants returned to a sedentary lifestyle for a six-week washout period. During this period they revert back to whatever they ate prior to the study.

Stool samples are collected after the six weeks of exercise and again after the washout period. This was coupled with 3-day dietary controls before faecal samples. They found that exercise-induced alterations of the microbiome was subject to obesity status.

Exercise increased faecal concentrations of SCFAs in lean, but not obese participants. This was all independent of dietary changes (as diet was only logged for 3-days prior to stool collections).

This study therefore concludes that exercise training induces changes in the human gut microbiota but change is dependent on obesity status. These changes are also very short lived as results returned to baseline, after the washout period. Therefore, highlighting the need for consistency with exercise and as previously identified diet.

Study 3

In this study, 32 sedentary women aged 65 years and older participated in a 12-week study. The women were allocated to two groups receiving different exercise interventions of trunk muscle training (TM), aerobic exercise training (AE) or AE including brisk walking. Faecal samples were taken before and after the 12-week period. Other exercise measures were also taken.

The results indicated that the AE group had a significant increase in Bacteroides, especially in those who spent time brisk walking. Which concludes that “aerobic exercise training that targets an increase of the time spent in brisk walking may increase intestinal Bacteroides in association with improved cardiorespiratory fitness in healthy elderly women.”

Whilst it is clear that we don’t yet fully understand the exact mechanism by which exercise exerts its effect on the intestinal microbiota. It is clear that regular exercise can improve SCFA production, which can deliver a host of benefits to the immune system and overall health and wellbeing.

It is however really important to note that moderate to intense exercise can be beneficial, whilst extreme exercise, or even daily intense exercise can do the exact opposite. Extreme exercise can increase stress in the body and can damage the lining of the gut and negatively impact these key microbes.

To summarise, exercise can:

Improve microbial diversity in the gut
Enhance short chain fatty acid synthesis and carbohydrate metabolism
Improve butyrate production and therefore help with gut integrity
Protect from obesity and diabetes
Reduce inflammation
Reduce risk for colon cancer
Increase Akkermansia that protects the gut linings
Improve insulin sensitivity

How much should I exercise?

This is definitely a challenging question but listening to your body is a great place to start! By this I am not referring to the lazy inner voice, but more to an inner voice understanding your health limits and physical limitations.

Establishing a solid exercise routine might not be that straight forward for everyone. I know I struggle to fit mine in weekly. Whilst cardio/aerobic exercise are beneficial, so are weights and brisk walking. If the gym is not your thing, then make time for a brisk walk every day or run a couple of times a week. If you are ill and unable to exercise, then just focus on moving more where possible.

Happy Wellness Wednesday to you all.