How Gut Bacteria Affects Depression

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It all seems to be about the gut these days doesn’t it? There are copious adverts for yogurts with “friendly bacteria” or pro-biotic capsules to restore your gut flora. It’s no secret that when we’re feeling a bit under par our digestive system plays up and we all know that what we put into our bodies can also have an effect on our moods. But now new evidence shows that the bacteria in depressed people is actually different to those who are not suffering from depression.

We know there is a link between stress and the gut. When your brain is stressed it sends messages to your gut – for instance, butterflies in your stomach, stomach cramps, constipation – or the other way - an increased need to go to the toilet. But can it operate in reverse? Can the gut also send messages to the brain and affect our mental wellbeing?

Research from the APC Microbiome Institute in University College Cork in Ireland recently showed that this is indeed the case. They found that rats that had no bacteria in their microbiomes had an exaggerated stress response, and confirmed that some microbes – especially one called lactobacillus rhamnosus - have an ability to dampen down anxious behaviour and regulate stress.

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They also discovered that the bacteria in our gut is linked through the vagus nerve. The nerve signals go two ways – it can travel from the brain stem all the way down through all the key organs but it can also go from the gut to send signals to the brain. And they found that the microbes – the bacteria in the gut – could also send signals to the brain via this vagus nerve.

The researchers then took the gut microbes from a depressed person and transplanted it into a rat. Very soon this rat began exhibiting signs of depression too – lethargy, loss of appetite and an inability to experience pleasure. How did they discover that? Well, they tried to tempt the rat with sugar water (which most rats cannot resist as it’s akin to a massive rat pleasure-high) but the depressed rat was not bothered by the sugar water at all. This is a similar symptom of depression – being unable to find joy in the things that were once pleasurable.

They found that the diversity of microbes in a depressed person was lower than in a person who is not depressed. So if you think about your gut in terms of a garden, you need a good diet that allows for nutrient rich soil to allow your gut flora to flower in abundance with lots of different species. A depressed person has a gut that doesn’t have nutrient rich soil so the bacteria flora that grows is limited. (Just like the rats that had no bacteria felt more stressed.) And it’s this limited amount of friendly bacteria that may go some way to explaining why some people feel depressed.

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It’s official - the gut communicates to the brain, and those bacteria in our gut really do influence our mood. Therefore, feeding ourselves well is definitely one way we can help our mental wellbeing. Research has shown that the foods that help our gut to produce friendly bacteria are fermented foods of all types such as pickled vegetables and natural yoghurt plus polyphenols which can be found in foods such as nuts and onions. Other foods that can help depression are ones that contain omega 3 fatty acids which are found in oily fish, soya beans, flaxseed and linseed, and a Mediterranean diet with lots of fresh vegetables and fruit has been pinpointed to contain many of the foods that can lift your mood.

So if you’re feeling the slide into depression, as well as seeking professional help, you can help your body to help your mind by making sure your gut flora is blooming and flowering full of friendly bacteria that will send all the right signals to your brain.

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