Are You What You Eat, or What You Think? (The Answer is Both)

Have you ever paused to consider the intricate marvel that is the human brain? It is, without a doubt, the most complex and least-understood organ in our body. While its deepest secrets remain elusive, we have learned a great deal about how to influence its functions. This is where we can begin to understand ourselves not just as thinkers, but as biological beings driven by an ancient and intricate chemistry.

The Inner Dialogue: Desire, Logic, and Society

To make sense of our inner world, it helps to start with a classic psychological framework. You might have heard of Sigmund Freud’s model of the psyche, which, while not a map of the physical brain, provides a powerful metaphor for its functions. He proposed three competing forces within us:

• The Id (The Desires): This is the primal, instinctual part of us. It operates on the pleasure principle, seeking immediate gratification for our wants and needs. It’s the voice that says, “I want it now.”
• The Superego (The Conscience): This is the moral compass, the internalized voice of society, parents, and culture. It dictates how we should behave, what is proper, and what others might think. It’s the voice that says, “That’s not the right thing to do.”
• The Ego (The Pragmatist): This is the mediator, the logical and rational part of our mind that navigates the real world. It tries to satisfy the Id’s desires in a way that is realistic and socially acceptable, balancing them against the Superego’s restrictions. It asks: Is this expensive? Is it dangerous? Is it useful or harmful?

From a purely physiological standpoint, you cannot find the "Id" or "Superego" in a specific gyrus of the brain. A neurophysiologist knows this. However, this model has proven incredibly useful in psychotherapy because it gives us a language to understand our internal conflicts without needing a degree in neurology. It's a convenient and powerful schematic for the human condition.

The Chemistry of Our Feelings

What happens in our brain when we experience profound love, deep suffering, or pure happiness? These states are the result of different cocktails of neurotransmitters—chemical substances that nerve cells use to communicate.

• Love and Infatuation are often associated with a surge in phenylethylamine.
• Happiness and well-being are linked to high levels of serotonin and endorphins.
• Depression, conversely, is often characterized by low levels of serotonin and dopamine.

These chemicals are the filters through which we perceive the world. Consider serotonin, a key neurotransmitter for the limbic system, which governs memory, attention, and emotion. It fosters tolerance, calmness, and positive relationships. If your serotonin is low, your perception of reality shifts. Imagine someone returning from a wonderful vacation in the Maldives, yet they are irritable and unhappy. It’s tempting to judge their character, but the reality might be simpler: it’s not their personality; their brain chemistry is off. With low serotonin, every experience is filtered through a lens of negativity. Past slights feel more painful, and future plans are clouded by potential disasters.

While we can measure many hormones and neurotransmitter byproducts in blood or urine, it’s tricky with serotonin. About 80% of it is produced in the intestines, so tests often reflect gut health more than brain state. The best indicator remains a person's outlook on life.

The Surprising Link Between Sunlight, Food, and Your Mood

The good news is that we are not entirely at the mercy of our genetic predispositions. We can influence our brain chemistry. Serotonin is derived from an amino acid called tryptophan. Tryptophan is created in plants and animals primarily under the influence of sunlight. This has profound implications for our diet and well-being.

Think of a cow that grazed freely in a sun-drenched meadow. The meat from that animal will have a vastly different tryptophan content than a cow that spent its life in a stall eating processed feed. The same is true for a wild fish compared to one raised in a crowded, sun-deprived farm. This is why free-range and wild-caught foods often come with a higher price tag—they contain more of the natural building blocks our brains need.

This "sunlight" nutrient is also found in tropical fruits like bananas and mangoes. However, to be transported globally, these fruits are often picked green, packed in dark, gas-filled containers, and ripened artificially at their destination. Having never seen the sun, their tryptophan content is negligible. A lack of this crucial amino acid can lead to a cascade of problems: low serotonin, which disrupts the production of melatonin (the sleep hormone), resulting in poor sleep, bad moods, aggression, and a diminished sense of happiness.

This connection helps explain a grim reality for northern populations in places like Northern Europe and Canada. With long, dark winters, there is less sun exposure, which impacts the entire biochemical chain. These regions often see higher rates of depression and suicide, as people struggle against a chemically induced state of despair.

Future-Proofing Your Brain

Beyond mood, we can also take steps to protect our brain from age-related diseases. The two most common are Parkinson's and Alzheimer's.

• Parkinson's Disease is primarily caused by a lack of dopamine. Like serotonin, dopamine is synthesized from amino acids found in our food.
• Alzheimer's Disease can be fought with mental stimulation. The advice is simple but powerful: constantly load your brain. Learn new languages, solve crossword puzzles, memorize poems, play chess. By challenging your mind, you build cognitive reserve and resilience.

The Predictive Brain vs. The Reactive Brain

One of the most significant evolutions in the mammalian brain was the development of the cerebral cortex, which gave us the ability to anticipate the future. This is a fundamental difference between us and animals with more primitive, "reptilian" brains.

A crocodile’s brain is reactive. You can dangle bait in front of it a thousand times, and it will snap at it a thousand times. It doesn’t learn from the repeated failure because it cannot model a future outcome. It simply reacts to the present stimulus.

Now, consider a cat. If you tease it with a piece of sausage, pulling it away each time it reaches, after a few attempts the cat will likely get bored and walk away. It calculates the probability that the next attempt will also fail and decides to conserve its energy.

Our human brain is an incredibly powerful predictive machine. When you run through a forest, you don't consciously think about every single root and stone. You focus on your destination, and your brain works ahead, constantly calculating where to place your feet. This predictive function is key to our survival and success.

However, it comes with a downside. What happens when the brain cannot calculate a probable outcome? When the future is uncertain, the amygdala—the brain's fear center—triggers a state of anxiety. Your body prepares for a fight or for flight. This state of tension, this preparation for a potential threat that hasn't happened yet, is what we call stress. It is a direct result of our brain's sophisticated ability to live in the future.

This predictive mechanism even affects our basic physiology. Why is drinking plenty of water often recommended for weight management? After a few weeks of consistent hydration, the body predicts that water will be readily available. As a result, it stops holding onto excess water in the form of fat. Storing fat is a highly efficient way for the body to store water; its metabolism releases a significant amount of water as a byproduct. By ensuring a steady supply, you tell your predictive brain that it no longer needs to keep this emergency reserve.

Ultimately, this incredible capacity for prediction and social awareness allows us to function. Our unconscious desires push us forward, our superconscious social rules hold us together, and our conscious, logical mind makes the final decision. By understanding these interlocking systems—from ancient instincts to modern neurochemistry—we can begin to appreciate that the world is, in many ways, what our brain perceives it to be.

References

• Freud, S. (1923). The Ego and the Id.

  In this foundational work, Freud first outlined his structural model of the psyche. It details the dynamic relationship between the instinctual drives of the id, the reality-based functioning of the ego, and the moral and societal constraints of the super-ego. This text provides the original framework for the "inner dialogue" discussed in the article.

• Barrett, L. F. (2017). How Emotions Are Made: The Secret Life of the Brain.

  This book presents the theory of constructed emotion, arguing that emotions do not live in dedicated brain circuits but are actively constructed by our brain as it predicts our body's needs in a given situation. This directly supports the article's points on the predictive nature of the brain and how anticipation can lead to states like stress and anxiety. (See Chapter 3 for the core concept of the brain as a "prediction machine").

• Wurtman, J. J., & Marquis, N. (2010). The Serotonin Power Diet: Eat Your Way to Stop Cravings, Lose Weight, and Balance Your Mood.

  This book explores the direct biochemical link between diet, the amino acid tryptophan, and the brain's synthesis of the neurotransmitter serotonin. It provides practical evidence and explanation for how specific food choices can directly influence mood, feelings of well-being, and behavior, supporting the article's claims about nutrition's impact on brain chemistry.