Digestion 101: Digestion Starts Before the First Bite

This article is part of a 3-part series that walks you through what I call Upper Digestion. When we suffer from bloating, stomach pain, gas, or irregular bowel movements, our instinct is to look at the exit point. But we actually need to look at what’s happening with the first three phases of digestion: cephalic, chewing, and stomach acid. Often, downstream digestive issues entirely resolve when we optimize these initial three phases.

Most people think digestion begins when food hits the stomach, but it actually begins long before your first bite.

_{Please note: This post may contain affiliate links, meaning I may earn a commission on your purchase.}

The Brain-Gut Connection (And Why Stress Short-Circuits It)

Simply seeing, smelling, thinking about, or preparing food activates what's known as the cephalic phase of digestion. During this phase, your brain sends a massive highway of electrical signals down the vagus nerve to prepare your gastrointestinal tract for the meal ahead. Saliva increases (this is why Pavlov's dogs started to salivate at the sound of a bell, in anticipation of a meal), stomach acid levels begin to elevate, pancreatic enzymes are signaled into production, and bile is readied by the liver and stored in the gallbladder for release into the small intestine.

The digestive tract completely shifts into "rest and digest" mode. All of this happens before you actually take a single bite!

But here's the catch: most of us (myself included before I became aware of this!) multi-task while eating. We scroll our phones, answer emails, or eat on the run. It's rare these days to set aside a separate moment each meal away from distractions to allow our bodies to enter the relaxed state that is essential for these digestive juices to be released in the first place!

When you eat while stressed or distracted, your autonomic nervous system shifts into sympathetic (fight-or-flight) mode. Your body cannot tell the difference between a high-stress work deadline and a real physical emergency. In this state, it prioritizes immediate survival, which means it redirects blood flow away from your core and digestive organs and straight to your limbs, so your muscles can be ready to fight or flee.

As a result, your body completely shuts down "non-essential" functions like stomach acid production and gut motility. You end up swallowing food into an under-acidified stomach. The food just sits there and ferments, which leads directly to the bloating, gas, and indigestion you feel later. Your body simply cannot prioritize digesting food when it believes it is under pressure.

What the Clinical Proof Shows

A 2020 systematic review article called "Endocrine Cephalic Phase Responses to Food Cues" examined 50 human studies to better understand how the body begins preparing for digestion before food is actually consumed.

The authors found that the sight, smell, thought, and taste of food activate the brain, which then signals the digestive system through the vagus nerve to initiate a range of anticipatory responses. These include increased salivation, gastric acid secretion, pancreatic enzyme release, bile secretion, changes in gut motility, and the release of hormones such as insulin and pancreatic polypeptide.

The review concluded that the broader cephalic phase response is a well-established physiological process that helps prepare the gastrointestinal tract to digest, absorb, and metabolize nutrients more efficiently. The data reinforces the idea that digestion begins well before the first bite, proving that slowing down, engaging the senses, and eating in a relaxed state directly optimizes these natural preparatory processes.

Moving Beyond "Soulless" Food to True Nourishment

There is a deeper reason why modern eating leaves our digestion compromised: we have completely disconnected our food from our environment. Much of the food we consume today has become "soulless" food, pre-packaged, hyper-processed, devoid of life, and eaten out of plastic wrappers while sitting under artificial, fluorescent lighting. It carries no information about the world outside, and our bodies register that lack of connection.

Digestion is meant to be an act of true nourishment, which goes far deeper than simply ticking off a list of macronutrients or counting calories. True nourishment is about entering into a beautiful, intentional relationship with your environment.

Every local, seasonal food you eat contains a specific "light code", molecular information about the time of year, the soil microbiome, and the sun exposure of the region you live in. When you choose local, whole foods instead of packaged items like a local tomato in the summer or root vegetables in the autumn, you are feeding your gut microbiome the exact seasonal data it expects. This environmental information helps synchronize the body's peripheral clocks in organs such as the stomach, liver, pancreas, and intestines, letting them know exactly what kind of fuel is coming and how to process it efficiently.

Circadian rhythm and meal timing play a massive role in this process. We are biologically designed to eat during daylight hours when our digestive capacity is naturally strongest. Morning sunlight helps synchronize the brain and autonomic nervous system, supporting healthy vagal tone and preparing the digestive system for the day ahead.

Circadian research from experts like Dr. Satchin Panda, Frank Scheer, and Leon Kreitzman suggests that many digestive functions, including salivary secretion, gastric acid production, digestive enzyme release, bile acid synthesis, intestinal motility, and insulin sensitivity, all follow robust circadian rhythms and are generally more active during the biological daytime. Regular meal timing during the day helps synchronize these internal peripheral clocks, allowing digestion and nutrient metabolism to begin preparing before a meal is consumed.

In contrast, irregular meal timing or eating late at night under artificial blue light disrupts these rhythms, reducing digestive efficiency, impairing nutrient absorption, and compromising glucose regulation. Together, cephalic phase physiology, local seasonal eating when possible (trust me, I am never 100% seasonal and local) and circadian biology suggest that true nourishment is optimized not only by engaging our senses before eating, but also by eating at consistent times and aligning meals with our internal biological clock.

Your Step-by-Step Upper Digestion Support

To support the overlooked circadian aspect of digestion and activate the neurological pathways that tell your digestive system, "The day has started. Food is coming," use this simple five-step checklist to guide your daily routine:

• Set your daily clock: Step outside into direct morning sunlight for 10–15 minutes without sunglasses within an hour of waking. I use the MyCircadianClock app every single day, it is my #1 tracking app to make sure I’m setting my biological clocks correctly.
• Clear the space: Disconnect completely before you plate your food. Put your phone in another room, close your laptop, and commit to eating in a calm, quiet environment without screens. (Outside whenever possible!)
• Shift your nervous system:Take 5 slow, gentle breaths right before your first bite, making your exhales longer than your inhales to drop your body out of a stressed state. If you want a little extra support, using high-quality herbal bitters  right before your meal (more about this in a future blog) can beautifully help shift you into this state and prep your stomach acid production simultaneously, as can  applying a grounding essential oil (use code CARRIEB) directly to the sides of your neck to stimulate and support your vagus nerve.
• Anchor your senses: Take a moment for prayer, meditation, or simple gratitude. Look closely at your food and intentionally take in the aroma. I literally like to examine the different colors and smells in each bite, this sensory input is the exact spark that tells your stomach to begin pumping out gastric juices.
• Protect the evening window: Block artificial light after nightfall and wrap up your eating window early so your body can rest during the biological night. Wearing orange-toned blue blockers after dark is an absolute must for me to protect my sleep and circadian rhythms; I highly recommend Ra Optics  (use code CARRIEB ) or VivaRays (use code CARRIEBWELLNESS).

By changing how and when you approach your food, you give your upper digestive tract the ultimate head start.

But once your brain has signaled your gut and those preparatory juices are flowing, the biological baton is officially passed to your mouth. And unfortunately, this next step is exactly where most people completely sabotage their digestive fire without ever realizing it.

It is beautiful to see how much our environment influences our gut. But once the internal juices are flowing, we want to make sure we are fully supporting the physical gateway of digestion so all that amazing prep work can do its job.

Stay tuned for Part 2 of this series: How Chewing Saved My Stomach Acid. (Because how you break down your food changes absolutely everything.)

  
Want to Dive Deeper?

• Good Read: If you want to explore how your biological clock dictates your digestive fire and overall health, I highly recommend checking out this book: "The Circadian Code" by Dr. Satchin Panda. It will completely change how you view the timing of your day.
• Free Challenge: New here and want to see how supportive light and hydration can be in your daily life? Join my free 5-Day Intro Challenge to learn one foundational circadian concept each day, delivered straight to your inbox!
• Community: You don't have to navigate your health journey alone. Inside my private online community, Sol Circle, we walk hand-in-hand to help you reclaim your energy, ease your digestion, and find your natural rhythm again. 👉 Come hang out and heal with us inside Sol Circle! 
  
  

Scientific References & PubMed Support:

• Study: "Endocrine Cephalic Phase Responses to Food Cues: A Systematic Review." PubMed ID (PMID): 32152865

• Study: "The Circadian Clock Network in the Gastrointestinal Tract and Its Impact on Health and Disease." PubMed ID (PMID): 30489552

• Study: "Circadian Rhythms in Gastrointestinal Health and Disease." PubMed ID (PMID): 33830206