What is the link between gut health and depression?

Gut bacteria can affect all of our physiology from the fundamentals of when and how often we consume to how effectively we can produce important vitamins. It can determine the strength of our immune system and metabolism and it can also impact our mood. A study that is captured in the Human Microbiome Journal by Katerina Johnson, PhD (2019) states that gut bacteria influences the brain measurably, impacting stress, fear, symptoms of depression, social attitudes and behaviours. They were able to come up with this conclusion because different groups of bacteria had a strong correlation with certain behavioural characteristics. For example, they found that individuals with more social networks had a wider range of healthy gut bacteria, indicating that social interactions can alter the human gut microbial environment in a positive way. Additionally those who ate a wide variety of foods also had higher levels of good gut bacteria. 

In opposition they observed that anxiety, depression , and stress were strongly related to a decreased diversity of good gut bacteria. The study saw that people with lower levels of bacteria called Corynebacterium and Streptoccus were more likely to be moody. People who have lower amounts of Lactobacillus helveticus, bifidobacterium longum are known to have higher levels of anxiety according to a study conducted by Messaoudi et al in the British Journal of Nutrition (2011). There is also a known correlation between low levels of healthy gut bacteria and autism. The same goes for obesity. 

Dr Katrina observed that if specific bacteria are shared between two test subjects then they could swap behavioural traits. The specific type of bacteria that is used determines what trait will occur.  She was able to conclude this after giving a shy mouse bacteria from an aggressive mouse, whereby she noticed that the shy mouse later became aggressive. In this test it was clear that the bacteria was what influenced the hosts social behaviour. These findings together give a fresh perspective when it comes to trying to understand a personality.

Dr Katrina highlights that changing your diet can “improve your mood and change how you feel” to an extent but the results of this may not be long-term unless the diet is maintained. She also continues on to state that gut bacteria is only one section that influences our personality as there are many others, one of which happens to be genetics. 

A well-balanced diet is encouraged by Dr Katrina nonetheless to achieve good gut health. Benton et al recommend the daily consumption of probiotics to improve cognitive function and reduce moodiness, after his findings from a study in the European journal of clinical nutrition (2007). Cognitive impairment is common in patients who have Irritable Bowel Syndrome according to Kennedy, Clarke, O’neill et al (2014) so that leads me to assume that IBS patients will be able to improve this problem by consuming probiotics. Patients who have autism are said to see an improve in behaviour after being on gluten free and casein diets (Klein & Pennesi, 2012). There are a lot of other ways to improve gut bacteria but these are the ones I would like to focus on today. The bottom line is that gut health is very important and it can have a huge impact on our daily lives. It is essential that we try out best to form healthy gut bacteria in order to maintain overall well-being. 

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