Positives

• One patient exploring supplements for Long COVID found that a combination including hydroxytyrosol and L-carnitine had an “amazing effect on brain fog,” significantly improving their cognitive clarity Reddit.
  
  
• In another report, a patient with Long COVID and mast cell activation syndrome (MCAS) reported benefits from a supplement containing hydroxytyrosol, which was part of a regimen that helped manage their symptoms Reddit.
  
  

Negatives

• Patients buying isolated hydroxytyrosol capsules commonly see less benefit than expected, because EFSA only approved health claims for hydroxytyrosol consumed within olive oil, not from isolated supplements PMC.

Hurdles & Side Effects

• Supplement-grade hydroxytyrosol commonly costs $45-60/month and varies dramatically between brands due to narrow specifications and source materials needed to produce it consistently FDA.