Five Things You Didn’t Know About Digestion

By Dina Cheney

Eat, absorb nutrients from food and poop out the rest. If only digestion were that simple. Thanks to recent research advances in the brain-gut connection, we now know that the mind plays a key role in processes along the digestive tract. Read on for insights from Kristin Kirkpatrick, registered dietician at the Cleveland Clinic Wellness Institute; Scott Anderson, author of “The Psychobiotic Revolution: Mood, Food, and the New Science of the Gut-Brain Connection  (National Geographic, November 2017); and Marc David, founder of the Institute for the Psychology of Eating and author of the books “Nourishing Wisdom” (Random House, December 1991) and “The Slow Down Diet” (Healing Arts Press, March 2005), as we delve deep into the complexities of digestion.

1. The large intestine plays a larger role in digestion than many of us realize

Sure, the small intestine is responsible for the majority of nutrient absorption. Yet its counterpart has been gleaning more attention of late. “We now know that much of the energy we get from our food is a product of bacterial fermentation that takes place in the large intestine,” Anderson says.

And those bacteria are nothing to sneeze at. Anderson explains that about 3 pounds of these bugs inhabit the colon (another name for the large intestine). “They ‘love’ the fiber and complex sugars that our gut cannot absorb, converting them into short-chain fatty acids, which are like ambrosia to the cells lining the gut,” he continues. “Some of these bacteria even produce chemicals, such as serotonin and dopamine, which can directly affect our mood.”

2. Our digestive system needs foreplay

“Flavors and especially aromas prime the gut for food, initiating all sorts of digestive secretions from the stomach, pancreas, liver and cells lining the gut to get ready for a meal,” Anderson explains. “In fact, the gut has special cells in its lining that ‘taste’ food all the way through the system and know what’s passing by. It then secretes specific enzymes, acids and bases to properly digest them.” That’s why people who cannot smell often undereat, he says. Since food does not entice them, their guts are not properly primed for digestion.

3. Pleasure increases nutrient absorption

If we don’t derive pleasure from our food, we won’t absorb as many nutrients, explains David in his article “The Metabolic Power of Pleasure.” As proof, David cites a scientific study in which one group of rats was rendered unable to taste. Although these rats ate the same amount of food as the control group, all he desensitized rats died of clinical rat malnutrition.

For further validation, David mentions a study of Swedish and Thai women. When given Swedish meals, the Swedish group absorbed more iron from the food than the Thai group. Conversely, when offered Thai meals, the Thai group absorbed more iron from the food than the Swedish group. Similarly, the two sets of women absorbed more iron from their meals when they were served intact, as opposed to blended into mush.

Relishing food also makes us feel satisfied and signals our bodies to stop eating, David explains. Specifically, the chemical cholecystokinin (produced by the body when protein or fat are ingested) stimulates the small intestines, pancreas, gallbladder and stomach to digest food; shuts down the appetite; and creates a pleasure sensation in the brain. “[This chemical] shows us how pleasure, metabolism and a naturally controlled appetite are interwoven to the core,” he says.

4. You’ll help your body by chewing slowly

Eating slowly impacts digestion, Kirkpatrick explains. First, pacing yourself “slows the entire process of digestion and allows time for the brain to send the signal that you’ve fueled enough and it’s time to stop eating,” she says. Similarly, she says that studies have shown that when people hear the sound of themselves chewing, they stop eating sooner.

Another benefit of eating slowly? “Chewing helps release the maximum amount of nutrients from our food. … The mouth can absorb nutrients, too, so the longer food remains in our mouth, the better the absorption of certain sugars and starches,” Anderson explains.

To experience how this works firsthand, Anderson recommends chewing on a cracker and holding it in your mouth for a few minutes. “Chemicals in your saliva will start to break down the starches into sugar, which you can actually taste,” he says. “It’s a fun example of the digestion process that starts as soon as you pop food in your mouth.”

5. Manage stress for a healthier gut

Stress (plus a poor diet and antibiotics) can negatively impact the bacteria in our gut—and these bacteria are critical for digestion, Kirkpatrick explains. “Stress has been well-established in research as a factor in gastric mobility, delaying the rate of and perhaps hindering proper absorption [of nutrients].”

Anderson agrees that mood can affect the composition of our gut bacteria, which he says explains how stress can give us a feeling of butterflies in our stomach, and may exacerbate Crohn’s disease and irritable bowel syndrome.

Plus, eating when stressed often causes us to ingest more calories. As David explains in the same article, “A stressed eater produces more circulating cortisol, our main stress hormone. What’s amazing is that cortisol desensitizes us to pleasure. When you’re in ‘fight or flight’ response and trying to escape the hungry wolf, you don’t want your brain to be in a ‘feel good’ mode and get sidetracked looking for chocolate. All of you needs to be focused on survival. So when cortisol desensitizes us to pleasure in our day-to-day stresses, we need to eat more food to feel the same amount of pleasure as when we’re relaxed.”

The bottom line?

Choose food with enticing aromas, flavors and textures—and don’t omit protein, fat and fiber. Take the time to chew slowly. Maintain a healthy diet, avoid antibiotics (if you can) and manage your stress levels. Your gut will thank you.

Video credit: AlexMaster, Adobe Stock
Photo credit: catalina m., Shutterstock; takasuu, Thinkstock; rawpixel, Unsplash;, Shutterstock; Jelena Danilovic, Thinkstock; fizkes, Thinkstock; Parilov, Shutterstock


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Dina Cheney

Dina Cheney is a writer and recipe developer whose cookbooks include “The New Milks,” “Mug Meals,” “Meatless All Day,” “Year-Round Slow Cooker,” “Williams-Sonoma New Flavors for Salads,” and “Tasting Club.” She has contributed articles and recipes to Every Day with Rachel Ray, Parents, Fine Cooking, Clean Eating, Specialty Food, Coastal Living, The Huffington Post, and more. Cheney is a graduate of The Institute of Culinary Education and Columbia University. Find her online at, and her complete collection of non-dairy resources at