David and Austin Perlmutter argue that modern dietary patterns — high in sugar and processed carbohydrates — are a major, underappreciated contributor to widespread brain fog, mood disorders, and cognitive decline.

The core mechanism they describe:

• Chronic low-grade inflammation, substantially driven by diet, is presented as a root cause connecting numerous seemingly unrelated brain health complaints
• This inflammatory process operates gradually and often invisibly until symptoms become noticeable
• Many people attribute symptoms like brain fog purely to psychological or lifestyle stress, missing a significant dietary contributing factor

This framing positions diet as a genuine, underexplored lever for addressing common but often unexplained cognitive and mood complaints.