The brain needs energy. It uses 20% of the body’s supply, 50% of the sugar in the blood, 20% of all inhaled oxygen, and 25% of the body’s metabolic activity takes place there. Proteins are crucial to the brain. They are composed of amino acids and there are ten essential ones obtained only from the diet. Foods contain different combinations of them but they must be balanced and over the limiting amount to prevent deficiencies of them. Lack of certain amino acids causes depression. You might think that gobbling up a lot of them will load up the brain. But there is a brain-blood-barrier that prevents water-soluble toxins from entering. Since most major brain nutrients are water-soluble this complicates things. For this reason, if you wanted to manufacture brain neurotransmitters you’d have to use precursor loading which involves eating more of the nutrients that the body converts to neurotransmitters.
In order to be processed efficiently these amino acids cannot be bound up in molecular chains but must be in free form. A proper precursor is the chemical starting point for changes made which result in the desired neurotransmitter. Serotonin is an important end product. L-tryptophan is its precursor which, midway through its conversion process, becomes 5-hydroxytryptophan. Today there is a product called 5-HTP which represents this state and would create serotonin. Another important neurotransmitter is norepinephrine and a precursor to it is L-tyrosine which goes through a couple of conversions requiring additional chemical input. You can increase the effectiveness of the process by ensuring that the required vitamins (e.g. vitamin B6) and other ingredients are present. A factor to consider is that amino acids compete with one another for absorption by the body, so the precursors should be taken at different times to avoid conflict. However, self-medication may, at best, just be supplemental. Proper treatment should be by a doctor and possibly a therapist.