What affects the gut microbiome?

Authors: Sharon Jang , Vanessa Mok , Dominik Zbogar | Reviewer: Phillip Popovich | Published: 5 May 2020 | Updated: ~

Lifestyle factors can have a large impact on the bacterial composition in the gut. This in turn can cause biological changes that may predispose an individual to long-term diseases.¹¹

The numerous factors known to affect the balance of the gut microbiome, and their relationship to SCI are discussed below.

Diet has a large impact on the composition of the bacteria in the gut. In particular, processed foods in the Western diet may contribute to decreases in microbiome function and diversity. Conversely, a diet that is comprised of a variety of whole foods and probiotics can promote a diverse community of bacteria. Many studies with weak to moderate evidence have demonstrated an association between the bacterial community in the gut and the development of diseases such as diabetes and obesity. However, there is still much to learn about the functions of the gut microbiome before we can find an optimal approach to diet that will control microbiome-induced chronic diseases.

Drinking alcohol can affect the integrity of the gut microbiome, but these effects may be dependent on the type of alcohol consumed. One study in able-bodied males found that those who consumed gin had decreased numbers of beneficial gut bacteria. On the other hand, those who consumed red wine had decreased numbers of harmful bacteria and increased numbers of beneficial bacteria. The researchers believed that moderate consumption of red wine provided a source of polyphenols which may explain differences seen between the two groups. Polyphenols are compounds found in plants that may have prebiotic-like effects. While the effects of alcohol on the microbiome in SCI are unknown, alcohol should be limited to avoid the known health risks on other body systems.

Antibiotics are a well-known class of drugs that can disrupt the growth of both harmful and beneficial organisms in the gut. This can effectively decrease the number and diversity of the bacteria. Susceptibility to urinary tract and lung infections and pressure ulcers is increased following SCI. Because antibiotics are frequently used to treat these conditions, people with SCI may experience further disruptions to an already disrupted microbiome. Some may also report fatigue, emotional, or neurological issues with antibiotic use, suggesting that what is happening in the gut can have an effect in other parts of the body.

There is large variability in the amount of exercise performed by people with SCI, but most do not engage in any. Various studies on able-bodied individuals report a greater amount of certain healthy gut bacteria in physically active people compared to less active people. Thus, in SCI there may be a missed opportunity for physically inactive people to benefit from these healthy bacteria in their gut, some of which have anti-inflammatory effects and can protect from obesity.

Refer to our chapter on Exercise Guidelines to learn more about physical activity following SCI.

Sleep problems occur more commonly in individuals with SCI compared with the general population. This is important because sleep deprivation can cause disruptions in cognition, immune function, and many other body functions. A recent study looked at how the lack of sleep impacted bacteria in the gut among the general population. It found that just two consecutive days of sleep deprivation lead to increased amounts of bacteria that are implicated in conditions such as weight gain and diabetes. These conditions are already prevalent in people living with SCI.

Smoking can lead to unwanted effects on the gut microbiome.¹⁴

There is evidence that smoking can cause negative changes in the diversity of the gut microbiome. Notably, the bacterial composition changes caused by smoking appear to be similar to the changes brought about by conditions like inflammatory bowel disease and obesity. Not only does smoking upset the balance of the microbiome, but it can lead to many short-term and long-term consequences like pneumonia which is especially harmful in people with SCI who have pre-existing breathing problems.

Recent evidence suggests a link between stress and negative changes in the gut microbiome. Stress may play a role in gut bacteria disruptions following spinal cord injury as people with SCI experience both massive physical stress from the injury itself and significant psychological stress due to dramatic life changes.