Do you suffer from depression? Dr. Michael Greger teaches us the scientific reasoning behind why eating an animal-protein diet may exacerbate the problem.
Tryptophan is one amino among many found in proteins, and they compete with one another for transport across the blood-brain barrier into the brain. And since tryptophan is present in most animal proteins in relatively small quantities, it gets muscled out of the way. If you eat plant foods, though, the carbohydrates cause a release of insulin, which causes your muscles to take up the nontryptophan amino acids as fuel, and so your tryptophan can be first in line for brain access.
Animal foods can even make things worse: “When tryptophan is ingested as part of a protein meal, serum tryptophan levels rise, but brain tryptophan levels decline due to the mechanism of transport used by tryptophan to cross the blood–brain barrier.”
The tryptophan levels in those given a high protein turkey, egg, and cheese breakfast dropped whereas in the waffle-OJ group, their trytrophan levels went up.
This may actually explain the carbohydrate cravings one sees in PMS—your brain may be trying to get you to boost tryptophan levels to feel better. “Consumption of a carbohydrate-rich, protein-poor evening test meals during the premenstrual period improved depression, tension, anger, confusion, sadness, fatigue, alertness, and calmness scores—significantly–among patients with premenstrual syndrome.”
“Because synthesis of brain serotonin, which is known to be involved in mood and appetite, increases after carbohydrate intake, premenstrual syndrome subjects may overconsume carbohydrates in an attempt to improve their dysphoric mood state.”