Depression is a serious mood disorder affecting millions around the world in one form or another.
The usual treatment includes different kinds of therapy as well as medication.
However, many antidepressants are not well-tolerated and cause adverse side-effects, which is why the search for an effective treatment is ongoing.
Emerging evidence points towards the fact that diet plays a major role in the prevention and/or treatment of depression.
For example, the fast-food diet, which is characteristic of having high fat and sugar content and processed foods, is linked to an increased risk of depression and anxiety. 
On the other hand, the Mediterranean diet, known for including a lot of whole foods, fiber, and healthy fats, like fruits, veggies, and legumes, is associated with fewer depressive symptoms. 
Dietary fiber is a type of carbohydrate found in the edible part of plants, that cannot be digested and absorbed by the body, and it helps to maintain gut health.
Insufficient fiber intake has been associated with different chronic diseases, like diabetes and heart disease, as well as impaired immune system function.
Fiber modulates the gut flora, which, in turn, affects the gut-brain axis.
This is why there has been an association between fiber intake and mental health in previous studies.
However, the results have been inconsistent, partly because different fiber sources were used in all of the studies.
A recently published study aimed to investigate and compare the effects of several fiber sources and identify the link with depression.
The study included a total of 2414 participants between the ages of 19 to 64.
They were screened for symptoms of depression and their fiber intake from each fiber subtype (crude, cereal, vegetables, fruit, seaweed, and mushroom) was calculated.
According to the depression symptoms, the participants were divided into two groups - normal, mild, and moderate to severe.
The tests and assessments showed that mushroom and seaweed fiber lowered the depressive symptoms in the participants.
Additionally, seaweed fiber also lowered depressive symptoms in participants who were diagnosed with clinical depression by a physician.
There seems to be an undeniable connection between the gut and the brain.
Even though there is much more to be discovered, the results of this study seem to offer a new glimpse into how diet can help mental health.
Resource: Kim, C.-S.; Byeon, S.; Shin, D.-M. Sources of Dietary Fiber Are Differently Associated with Prevalence of Depression. Nutrients 2020, 12, 2813. doi:https://doi.org/10.3390/nu12092813References: