COVID depletes your NAD+. The body hijacks tryptophan trying to make NAD+. This is one cause of post-COVID anxiety.
There are other causes of post-COVID low tryptophan levels.
“Low serum and muscle tryptophan levels, as well as elevated kynurenine levels, may be to blame for COVID-19’s most common long-term symptoms, such as depression, sleep disturbances, fatigue, and muscle weakness—which are similar to the symptoms of tryptophan deficiency,” as reported in Altered tryptophan absorption and metabolism could underlie long-term symptoms in survivors of coronavirus disease 2019 (COVID-19).
Tryptophan