I was recomemded to take Vit A as Retinol rather than Beta-Carotine. However, carrots are important too. It neutrolizes endotoxins. I am taking about 200g of carrots (not every day. too lazy) with coconut oil.
Another anti-serotonin agent is gelatin. So, headcheese, soup mande from marrow bones, etc. are good. I take Red Lake gelatin as supplement (in red cylinders).
Klauss.
P.S. Serotonin is not a "happy" hormon. It is rather "misery" hormon. High serotonin, for example, means low dopamine (that would explain why i don't have adrenaline rush), low testosterone, etc.