Live Wisely: Three-Brain Dictionary: Key Terms for Nourishment & Well-Being

This dictionary serves as a guide to the hormones, nervous system functions, and key concepts that impact our head brain, heart brain, and gut brain—helping us understand how food, stress, and emotions shape our well-being.

HEAD BRAIN (Cognitive Clarity & Mental Well-Being)

Dopamine

A neurotransmitter that fuels motivation, pleasure, and focus. Found in reward-based behaviors (like eating delicious food), but can also be depleted by stress or overstimulation (like constant social media scrolling).

Serotonin

A neurotransmitter often called the "feel-good" chemical. It regulates mood, sleep, and digestion. Interestingly, 90% of serotonin is produced in the gut, linking digestion to emotional well-being.

Cortisol

The primary stress hormone, released during the fight-or-flight response. It increases blood sugar for energy but suppresses digestion, making it harder for the body to absorb nutrients when stressed.

Adrenaline (Epinephrine)

A hormone that kicks in during stress or danger, increasing heart rate and redirecting energy away from digestion to focus on immediate survival.

HEART BRAIN (Emotional Balance & Connection)

Oxytocin

Known as the "love hormone", it promotes bonding, trust, and relaxation. Released through touch, connection, and even mindful eating, oxytocin enhances digestion and helps shift the body into a parasympathetic (rest-and-digest) state.

Heart Rate Variability (HRV)

A measure of how well your nervous system adapts to stress. Higher HRV = better resilience, emotional regulation, and digestion. Deep breathing, relaxation, and connection improve HRV.

Vagus Nerve

A major nerve connecting the head, heart, and gut brains. It plays a key role in switching between stress (sympathetic) and relaxation (parasympathetic). Activating the vagus nerve (through deep breathing, humming, or mindful eating) enhances digestion and emotional well-being.

GUT BRAIN (Intuition, Digestion & Immune Function)

Gut Microbiome

The ecosystem of trillions of bacteria in your digestive tract. A balanced microbiome supports digestion, immunity, and even mental health (since gut bacteria produce serotonin and dopamine).

Ghrelin

The hunger hormone, signaling when it’s time to eat. It rises when the stomach is empty and falls after a satisfying meal.

Leptin

The satiety hormone, telling the brain when you're full. Balanced leptin levels prevent overeating and support long-term energy regulation.

Insulin

A hormone that regulates blood sugar levels. Whole foods help maintain balanced insulin levels, while processed sugars and stress can cause spikes and crashes.

Inflammation

A natural immune response to injury or stress. Chronic inflammation (from processed foods, stress, or poor gut health) can contribute to digestive issues, brain fog, and fatigue. Anti-inflammatory foods (like turmeric, olive oil, and fermented foods) help keep it in check.

NERVOUS SYSTEM (Balancing Stress & Relaxation for Digestion)

Sympathetic Nervous System (Fight-or-Flight)

The body's stress response, designed for survival. When activated, it releases cortisol and adrenaline, increasing alertness but shutting down digestion. Eating in this state (rushed, distracted, or anxious) makes it harder to absorb nutrients.

Parasympathetic Nervous System (Rest-and-Digest)

The healing state where digestion thrives. Activating this system (through deep breathing, gratitude, and mindful eating) increases serotonin and oxytocin, improving nutrient absorption and gut health.

Vagal Tone

The strength of your vagus nervRee activity, affecting how quickly you recover from stress and shift into relaxation. Higher vagal tone = better digestion, emotional regulation, and resilience. Activities like humming, slow breathing, and cold exposure can improve vagal tone.

How This All Comes Together

When we eat in a parasympathetic state, with mindfulness and connection, we allow our three brains to work together:

• The head brain stays clear and focused.

• The heart brain feels nourished and emotionally balanced.

• The gut brain digests efficiently, producing the right hormones for well-being.

By understanding these key terms, we can make more informed choices about how we eat, not just what we eat—turning food into fuel for our best, most vibrant selves.