Amino acid
Histidine
Histidine is an essential amino acid that has to come from food. The body uses it, among other things, to make histamine.
Also listed as L-Histidine
Food needs and trial doses are different questions
The Norwegian VKM assessment cites a WHO adult requirement of 10 mg/kg daily and lists meat, fish, dairy, legumes, nuts and seeds among food sources. The gram-level amounts used in supplementation experiments should not be mistaken for this nutritional requirement. 1