One of the extremely annoying symptoms of many digestion-related diseases is a lack of mental clarity or brain fog. There have been a number of explanations for why this might be the case, from die-off symptoms of bacteria in the gut, to a leaky gut, to an infection of the brain itself.
Paul Jaminet from The Perfect Health Diet writes about this subject on his blog, here:
Be sure to read the comment section, because he goes into detail on the subject of ketogenic fasting, which he suggests to help trigger your body to start consuming the bad bacteria. He also mentions how bad reactions to ketogenic fasting may signify a brain infection.
There is lots of interesting material here. For instance: if you have an infection and you take Doxycycline and it does not help, then you probably have a parasitic rather than a bacterial infection. Parasites can live off the ketones created by carb fasting, and bacteria, apparently, cannot.
You might want to read this over a few times if you are feeling brain fog at the moment.