Mercola sells supplements lol

Excessive inflammation doesn't help mental health .... no real surprise there

Antidepressant drug papers have overstated the success of medications ... again no surprises there.

If you want to take a position on the role of gut health, vitamin d or fish oil or exercise in depression then you need systematic reviews or metanalysis to support those views. Not selectively choosing articles and bits of info and then cobbling together a narrative.