Can your food decide your mental health?

Doctor: Eat non-veg, it will give you protein, calcium, vitamins, and will keep you healthy.

Chintu: Which health sir? Physical or mental?

Before I tell you what did the doctor reply, let's first appreciate Chintu for his good question, smart kid, huh. Now let's try to see if we can arrive at an answer for this based on the logic of Evolution. Don't worry, I won't go into morality behind killing life and all.

Let's go back in time, humans are evolving, still living in caves, and struggling for the basic needs of life. Problems like less number of likes on profile pictures are waiting for them in 2.5 lac years, future. Two herds are there, let's name them Rock and Water. People of Rock herd are primarily non-vegetarians relying on hunting for food, while the people of Water herd are vegetarians who depend on fruits for food.

Each time people from Rock herd think of food, they will inevitably start thinking of elaborate plans to hunt and kill, their blood flow and heartbeat will rise with a rise in adrenaline to get their body ready for the act of hunting. Their mind will be filled with violent thoughts as the following act is of such kind.

Now let's see what happens to the people of the Water herd. Whenever they want food, they will think of just going to the forest and find some fruits. So in contrast to Rock herd, these guys will not go through elevated heartbeat and adrenaline with violent thoughts. Effectively a calmer mind.

As time passes their brains evolve, with readymade mindsets to switch onto, based on the type of food they desire. After 2.5lac years when Facebook is there and basic needs do not require hunting anymore (at least not for all the people), still our brain has the same structure that we have evolved in the past 2.5lac years. So effectively whenever we take a non-veg meal, our brain switches to a Rock herd mindset and whenever we take a vegetarian meal, it stays in a Water herd mindset. What I mean is, vegetarian meal potentially keeps you in a calmer state of mind. 

This is an answer that we can arrive at with rudimentary logic. Of course, if you want to know what Doctor replied then you will have to ask a doctor. Chintu is anyway left puzzled.