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  • Karen Haralson

Digestive Health: Understanding the First Phase of Digestion

Updated: Jun 12, 2023

The digestive system breaks down food into its building blocks for absorption and then eliminates the waste. This process is called digestion.

Digestion is essential in obtaining energy, repairing tissues, and growing. The digestive system employs chemical, biological, and mechanical processes and nerve impulses to use our food.

Within each phase, the processes are different according to where digestion takes place:

1. Cephalic (head) phase – the sensory organs (taste, smell, etc.) and mouth.

2. Esophageal phase – the esophagus.

3. Gastric phase – the stomach.

4. Intestinal phase – the small and large intestines.

This article discusses the cephalic, pronounced sə-ˈfa-lik, phase of digestion. Find out how rituals around food, senses, vagus nerve, and chewing play an essential role in digestive health. There are also simple tips worth digesting (yes, pun intended) that can help to prevent digestive symptoms.

Understanding how the digestive system functions and practicing healthy eating habits is vital to optimizing long-term health.

Come to Your Senses for Digestive Wellness

The cephalic phase is the first of four phases of digestion, starting when we anticipate eating and ending once food is swallowed. The word cephalic comes from the Greek word kephalḗ, meaning “head.”

Before eating your next meal, take this invitation to pause. Get to know the food you eat through your senses. Before tasting, what does it look, smell, sound, or feel like? Using sensory organs, the parts that send your brain information about the world and memories about food, are potent ways to jump-start digestion.

Are the aromas savory like a peppered steak, sweet like baked cookies, or fruity like a juicy pineapple? Do the colors look bright, like steamed broccoli, or darker, like beans in chili? Is the texture soft like a ripe banana, crunchy like fresh celery, or dry like a tortilla chip? Do you have any positive or fond memories of certain foods or events with food? Maybe you ate a cool, crisp watermelon on a hot day. Or perhaps, this meal is the same one made for you when you were a child. Are you beginning to salivate? Is your stomach growling?

Gratitude practices before eating can have a significant impact. A 2019 study found that teens made healthier food choices after giving thanks for their food. The study’s authors attributed gratitude’s effect on the participant’s moods. Practicing gratitude, a form of mindfulness, can not only help reset negative emotions but also help with digestion and prevent overeating. Other benefits include appreciating where food originates, the environment raised from farm to table, and all the hard-working hands that helped get it to you.

Rest and Digest with the Vagus Nerve

The vagus nerve runs from the brain stem to the lower part of your intestine or colon inside the digestive tract. The vagus nerve is a vital part of the rest and digest response system in your body and stimulates many functions in digestion:

1. It triggers stomach acid secretion and intestinal contractions, which thereby help with elimination.

2. This nerve also tells other digestive organs, such as the pancreas, liver, and gallbladder, to assist in chemical reactions needed for food breakdown.

3. Saliva production is facilitated as well by the vagus nerve. Saliva helps break down carbohydrates and fats.

4. It is also assisting in dilating your blood vessels, protecting your teeth from decay, and maintaining pH balance.

5. The nerve allows communication from the brain to and from the gut.

When stressed, our bodies get ready for a fight or flight situation. The digestive system is slowed by decreasing muscle contractions, redirecting blood flow to other organs, and decreasing chemical secretions. This can lead to poor digestion. Symptoms, including painful spasms, gas, belching, bloating, constipation, or diarrhea, can be avoided or eliminated by stimulating your vagus nerve before eating.

By slowing down, the body gets warmed up to eat by secreting essential chemicals, breaking down and absorbing food, and eliminating unused portions. All of this occurs before you put the bite in your mouth, which is made possible with help from the vagus nerve.

For Mindful Digestion, Chew on This

“Remember to chew your food,” Mom said. It turns out she’s right. Chewing your food well before swallowing serves several functions in the body. Chewing is studied at length and found to be beneficial for several reasons. The first and most apparent is that food gets broken down by your teeth into smaller particles which makes it easier for the body to process. The food mixes with saliva and allows enzymes in your mouth to start digesting fats and carbohydrates. These enzymes also help prevent tooth decay. The more we chew, the more saliva is secreted. You may not know that chewing well also:

1. Stimulates digestive system blood flow and increases intestinal movement. This study from Science Daily in 2022 shows that chewing well increases the energy of metabolism and is essential in limiting weight gain and obesity.

2. Helps strengthen the immune system by producing cells called Th17. The mouth can be a gateway for different infectious microbes that Th17 works against.

3. Promotes the feeling of fullness and prevents overeating, as shown in this study. Chewing well helps your digestive system release hormones that affect satiety.

The cephalic or first digestion phase is completed once the food is swallowed and enters the esophagus. Read below for helpful tips on what you can do to keep your digestive system moving for long-term health and wellness and chronic disease prevention.

Helpful Tips for Digestive Health

1. Mindful eating, in which we slow down the mind, helps us to be present. This reduces stress and encourages the rest and digest functions of the digestive system.

- Use your senses before you eat. Take a few moments to notice aromas, textures, colors, sounds, etc.

- Practice gratitude before eating.

- Take three deep breaths when you sit down to help stimulate your vagus nerve.

- Practice non-judgment. Negative thoughts during mealtimes increase stress.

2. Chew your food thoroughly.

- Chewing helps mix food with saliva, which also helps to digest and break down food. Failure to chew well can lead to problems with nutrient absorption and cause digestive symptoms such as painful spasms, gas, belching, bloating, constipation, or diarrhea.

- Chew until you have no more lumps or texture in your mouth.

- If you want to count, experts recommend chewing food an average of 30 times, depending on the food’s hardness.

3. Allow time to eat.

- Give yourself at least 20-30 minutes to eat a meal. This will give your body time to awaken your digestive system and chew food thoroughly.

- This gives the brain time to sense fullness and prevents overeating.

- See this as an investment in your overall long-term health.

The Takeaway

The cephalic, or first, phase of digestion starts in the head and ends when food is swallowed. In this phase, sight, sound, taste, touch, and hearing help to turn on our digestive system engines. Having an appreciation for our food before eating helps with mindfulness and creates feelings of relaxation, which boosts digestion.

The vagus nerve also plays a role in the rest and digest actions of the digestive system, helping to secrete saliva, stimulating digestive contractions, and improving blood flow. Chewing food well leads to better breakdown and nutrient absorption, improves your immune health, and plays a role in weight management.

Taking care of your digestive health is an excellent step to enjoying a healthy life. If you have any severe digestive system symptoms or symptoms that do not go away, get advice from a medical doctor.

Understanding the digestive system and practicing healthy eating habits can reduce or avoid digestive symptoms, optimize digestive system wellness, and improve long-term health.

Robin Fillner, RN, BSN is passionate about wellness and being outside. She is a health writer and oncology nurse at Salinas Valley Memorial Hospital. She is also a Certified Functional Nutrition Counselor through the Functional Nutrition Alliance. Find her at:



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