Regarding all the foods that we consume as a drugs is a wondrous way to examine and comprehend the complex interactions and subtle forces behind how everything we put in our mouths affects “how our neurons behave and, subsequently, how we think and feel”.
In a compelling article that suggests our shared evolutionary history with the plants and animals that we eat is the root cause of them having an affect on our body’s behaviour, Gary Wenk, author of Your Brain on Food, briefly describes how some of the chemicals present in ‘drugs’ such as chocolate, bananas, alcohol and nutmeg affect us:
We have all experienced the consequences of our shared evolutionary history with the plants we eat. For example, unripe bananas contain the neurotransmitter serotonin. When you eat an unripe banana, its serotonin is free to act upon the serotonin neurons within your digestive tract. The consequence is likely to be increased activation of the muscles in the wall of your intestines, usually experienced as diarrhea.
Many plants contain compounds that should be able to enhance your brain’s performance. For example, potatoes, tomatoes, and eggplants contain solanine and α-chaconine, substances that can enhance the action of acetylcholine, a chemical in your brain that is vital to memory formation. Your mood might be enhanced slightly by eating fava beans because they contain L-DOPA, a precursor to the production of dopamine, the reward chemical in your brain. Whether these food-borne compounds actually affect your brain depends upon how much you consume and your own personal physiology. This might explain why some people find it quite rewarding to eat potatoes or eggplants.
Morphine-like chemicals capable of acting upon the brain are produced in your intestines when you consume milk, eggs, cheese, spinach, mushrooms, pumpkin, and various fish and grains. Dairy products in particular contain a protein known as casein, which enzymes in your intestines can convert into beta-casomorphin. In newborns, that beta-casomorphin can easily pass out of the immature gut and into the developing brain to produce euphoria.
There’s much more like that in the article, concluded with Wenk arguing that this shared evolutionary history is why plants and animals from other planets will probably not harm or sustain us if we ever travel to distant, Earth-like bodies.