Meat: Imam Ja'far As- Sadiq (as) - Detriments of Not Eating it.

Flesh produces flesh and increases the intellect.  Whoever gives up eating it for some days, his intellect will be impaired.

Imam Ja'far As-Sadiq (as)

In another report, from him (as),

"Whoever gives up eating flesh for forty days will become ill-natured and his intellect will be impaired.  Whoever becomes ill-natured, call to him in his ear with the iqama.' (call to prayer)