Updated: Apr 28, 2020
My name is Tiffany Anne Smith. I’m a Registered Dietitian + the world’s worst nutritionist because I think that, while important, food is actually NOT the most important thing in a healthy lifestyle, especially if you’re starting from scratch.
Think I’m crazy? I’m kinda used to that, but hear me out anyway…
First, it’s important to understand a little bit about how your body digests + absorbs the fresh, healthy food that you feed it, because if your body can't digest, absorb and assimilate all those nutrients, you’re straight up wasting your time + money.
Your Ancient, Evolved Digestion
The human metabolism is an efficient, holistic biological system that consists of countless chemical reactions every microsecond that greatly affect your nutritional status.
Biologically, you have one long tube from your mouth to your anus, and all of the food in that tube is technically still OUTSIDE of the system until those tiny particles cross through a layer of mucus and into the intestinal cells. When absorption isn’t working well, you lose valuable nutrients — they go right out of the end of the tube.
In the hospital, if a patients gut is working, we always use it because when your digestive system doesn’t get to do the work is was created to do, it dies. That’s why there will never be a magic pill that will give you all of the nutrients you need to be healthy, because when you’re not smelling the food or feeling the texture in your mouth, your esophagus doesn’t have to push the food down, your stomach doesn’t churn and your intestines don’t move.
We can’t bypass a part of the system or the whole system suffers. Every part of a biological system affects the system as a whole and every piece is important.
The first step in digestion is crushing the big pieces of food and soaking them in saliva. From there, it goes into your esophagus where muscles contract in a wave like motion to push it down. Then it gets into your stomach where it churns every kind of way and gets soaked with more enzymes. When it finally reaches your intestines, transporters + receptors attach to nutrients and carry them to the tissues.
Amazingly, when there’s a significant increase in sugar (and our modern diet is more saturated than ever before), your intestines adapt instantly to dispatch more transporters to carry all that extra glucose into the body! Like magic!
There are dozens of hormones and enzymes, cholecystokinin, gastrin, secretin, peptidases, lipases, amylases, all increase + decrease as you need them, just like the transporters — this is how our ancient bodies have evolved to accommodate our modern diet.
Digestion Starts in the Eyes
Eating is an complete experience and all of your senses contribute that experience. (That’s how we become so emotionally attached, because it engages us on so many levels.) The way you think about your food, whether it looks appetizing on the plate, the aroma of it, all prime your body to digest and absorb the nutrients from the food you eat.
According the Journal of the American Dietetic Association, mere exposure to the sight, smell, taste, and textural attributes of foods elicits myriad digestive, endocrinologic, thermogenic. cardiovascular, and renal responses.
The Cephalic Phase
Absorption begins in your mind, in the cephalic phase — the head phase.
In 1987 two researchers in Britain decided to see what would happened to intestinal nutrient absorption when humans are in a stressful situation. Each subject drank a glass of salt water as they were listening to an audiobook through headphones, then the researchers kept switching the audio books, and took small samples from their intestines at different points to see how absorption was affected.
Per that study published in my favorite journal, Gastroenterology, “We used dichotomous listening as a psychological stress because it mimics the experience of a busy person trying to perform several tasks at once while being continuously interrupted.” They knew they were doing it right when subjects started to experience “significant increases in blood pressure, pulse, respiration, and anxiety score.” The result?
“Dichotomous listening significantly reduced [intestinal] absorption of water, sodium, chloride, and potassium. We conclude that the autonomic nervous system may have a physiologic role in the control of intestinal absorption.”
Can you imagine what that means when you’re working while eating? Or watching an emotional TV show?
According to Today’s Dietitian, mindful eating is “being aware of the process of food preparation and feeding yourself choosing enjoyable and nutritious foods, acknowledging food preferences without judgment, recognizing and honoring physical hunger and satisfaction cues and using wisdom to guide your eating decisions.”
Research shows that just being mindful, relaxing and enjoying the experience of your meal, improves the food choices that you make, how your body uses that food, and how the system biologically responds.
The Transit Phase
The time after the food leaves your head and travels down the esophagus, before it reaches your stomach, is called the transit phase. I like to think of this as when the food goes past the heart — when your emotions can affect your absorption.
Your brain uses the information it gets through your senses to make decisions about what you need to do to survive based on your understanding of that information. When you sense danger, your sympathetic nervous system gets ready to either stay + fight, or run away. It then moves the blood away from your digestive system, and sends it to your lungs + muscles. Essentially, it makes a judgment call that you don’t need to digest food right now because your priority is survival, instead you need to take big breaths + move quickly.
Research shows that an ability to tolerate uncomfortable internal emotional reactions are effective for weight loss. If you can become aware of how you think about the world around + learn to be comfortable with being a little uncomfortable, your sympathetic nervous system will relax, and all of that blood will go back into you “rest + digest” functions.
The Gut Microbe
There are millions of bacteria in your intestinal “gut” — about four pounds worth of tiny bugs that regulate intestinal cell functions. In fact, you have 10 times more bacteria cells in your body than human cells, so much that the microbiome is called a “forgotten essential organ.”
As we’re learning in The Time of Corona, this world belongs to microorganisms — we just pretend to run shit.
The bugs in your gut are special. The good ones manufacture vitamins B12 (cobalamin), B9 (folate), B7 (biotin), B6 (pyridoxine), B5 (pantothenic acid), B3 (niacin) and K. They enhance the absorption of minerals, digest food and metabolize drugs. They even fight off pathogens (bad bugs that make you sick).
How efficiently your body does the job of absorbing + using the nutrients from your diet greatly depends on the bacteria in your gut!
The Enteric Nervous System
In the gastrointestinal (GI) tract, the enteric nervous system is your body’s “second brain.” It functions independently of the central nervous system (your brain, spinal cord, nerves) and it controls the blood circulation in the gut, the movement of food through it, hormones + enzymes, and helps regulate immunity + inflammation throughout the entire body. (Chronic systemic inflammation is a small fire that’s always burning in your body and some very smart people believe that slow-burn is the root of all disease.)
Your GI tract is a completely independent system — it even has its own communication network! There are more nerve (communication) cells in your bowel than there are in your spine!
Ohhhhhh, and 70% of all our immune cells live in or around the gut. Think about that for a second…
Both the microbiome and the enteric nervous system are directly affected by your diet, so if you’re not only unable to absorb healthy, life giving nutrients, your crippling your immunity + putting your whole health at risk.
Insulin is your body’s most important anabolic (building) hormone, and it “opens up” your red blood cells, heart, muscles, and fat tissue to absorb + use the nutrients from the food you eat. How your cell respond to insulin is called insulin sensitivity.
The trouble happens when your cells no longer respond well to insulin (this is called insulin resistance), and all those nutrients stay in the bloodstream instead of going into the tissues where they are needed. That leads to highly preventable, chronic “lifestyle diseases” such as cardiovascular disease, diabetes, and Alzheimer’s (which it being called Type 3 Diabetes).
Research shows that just one night of poor sleep reduces insulin sensitivity (and the ability to absorb nutrients) by 25% and shifts the body toward the sympathetic nervous system, away from “rest + digest” functions, reducing absorption even further.
(Another study reports that people who get less than 6 hours of sleep consistently have significantly higher risk of stroke, cancer, diabetes, cardiovascular disease, and all chronic diseases than those who get 7 to 8 hours consistently.)
Movement improves blood circulation throughout the whole system and speeds up digestion.
After just six weeks of regular exercise, there’s an increase in the beneficial gut bacteria that reduces the risk of all inflammatory (read: all) diseases. After just one exercise session, there’s an increase of insulin receptors, improved insulin sensitivity, and red blood cells, liver + skeletal muscles all take in more nutrients from the blood.
(As an added bonus, exercise releases endorphins serotonin, both improve our overall mood and sense of willpower, making difficult challenges feel easier!)
Sunshine + Vitamin D
Vitamin D acts in your body like a hormone. Nearly every tissue and cell in your body has receptors for vitamin D, and it plays a critical role in HALF of all chemical reactions in your body.
In your gut microbiome, Vitamin D reduces pathogenic bacteria + increases the overall diversity of the community of bugs. When you reduce the disease causing harmful bacteria in the gut, you shift the ratio toward the healthy bacteria, which in turn lowers local + systemic inflammation.
Good bacteria multiply + create a diverse, rich, healthy, life giving environment. They have a positive influence on GI diseases such as inflammatory bowel disease + bacterial infections. (It almost goes without saying, but GI distress is one of the top things that affect your absorption. If your bowels are sick, they’re not absorbing nutrients.)
These same strategies also determine whether your immune system can protect you from infectious disease, read my other article, How What You Eat Determines If a Coronavirus Infection Kills You, to learn more.
What you eat is obviously very important to your health, but when you put it into perspective with your whole biological system, many other lifestyle choices you might not have considered determine the benefits + outcomes of even the most carefully planned diet.