It has long been known that there is a connection between nutrition and well-being. A study on depression now claims to have discovered the extent to which the gut microbiome, the entirety of all microbial co-inhabitants in the gut, plays a role in this.
A thorough analysis—the most thorough to date—showed that individuals with depressive symptoms have a markedly different abundance or decrease of specific types of bacteria. The results can be read in the “Nature Communications” journal, published in December.
In fact, people with mental illnesses are particularly prone to gastrointestinal upset. Changes in weight and appetite are common in people suffering from depression, even in old age. Anxious people frequently experience nausea, heartburn, diarrhoea, or constipation in addition to their anxiety. Frustration eating or less excessive comfort food also illustrates the connection between eating and well-being.
Interest in the connection has recently increased again. Studies have given rise to an entire industry of probiotics and prebiotics, and Lactobacillus (a genus of lactic acid bacteria) has become a household name for more and more people. While most studies to date have been carried out on animals, such as rats, the new study is dedicated to humans. Data from the Rotterdam study, an extensive collection of health-relevant data, was also analysed.
As part of this study, 1000 stool samples were collected, and each participant gave information about their general health and any depressive symptoms. Together with her team, Najaf Amin from Oxford University investigated the relationship between the bacterial population in the samples and the results of the depression assessment. In addition, the same tests were carried out on a further 1539 people in the Netherlands.
Important types of bacteria
The researchers identified 16 types of bacteria as “important predictors” of symptoms of depression. For example, a reduction in Eubacterium ventriosum was found in depressed people. A decrease in the same type of bacteria has already been linked to brain injuries and obesity in previous studies. The bacterium Eggerthella, on the other hand, is abundant in people with depression.
It is impossible to say for sure whether a particular intestinal flora causes depression or vice versa. Depressive disorders are too complex and multifaceted for that. There is also a lack of technology that enables clear proof of causality. In any case, the gut and brain work together. Eating out of frustration can alter the microbiome, which in turn can worsen depression.
However, beneficial flora can also be rebuilt in a targeted manner. Even though this conclusion is sobering—a (reasonably) healthy diet is necessary—it needs enough fibre.
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