CHAPTER 6:
THE GUTS OF THE MATTER
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“Because of my Crohn’s disease, I was in so much pain that I couldn’t stand up straight. Every time I ate something, it hurt. In 1999, I had surgery to remove two and a half feet of intestine, including part of my colon. The surgery relieved the severe pain, but I still dealt with intestinal spasms and gut pain after eating. I completed my first Whole30 in March 2010. Through the process, the intestinal pain, gas, and bloating completely went away—and did not return. The constant underlying fear of Crohn’s returning is gone because now I understand its root cause.”
—Sarah G., Fort Collins, Colorado
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Our third Good Food standard evaluates the effect of certain foods on the digestive tract. We believe you should consume only foods (and drinks) that support normal, healthy digestive function; eating anything that impairs the integrity of your gut impairs the integrity of your health.
Let’s discuss normal gut function first, and then talk about how your food choices can disrupt it.
THE GUT
The purpose of your digestive tract (or gut) is to absorb nutrients from food, but it is also a prominent part of the immune system. (Didn’t know that, did you?) These two functions—digestive and immune—are inextricably intertwined, though the gut’s critical role in regulating immune response often goes underappreciated. We’ll talk more about that in the next chapter.
You’re probably already familiar with the major components of the digestive system: the stomach, small intestine, and large intestine. Let’s take a digestion road trip, shall we?
You take a bite of food and start chewing. Chewing breaks your food (i.e., the mishmash of macronutrients, water, fiber, and micronutrients) into smaller pieces, and an enzyme in your saliva starts to break the carbohydrates down into simple sugars.
When you swallow that food, it moves into your stomach. Essentially nothing happens to carbohydrate and fat in the stomach, but protein gets some attention—the acidic environment of the stomach, plus some digestive enzymes, start to break the protein down into smaller pieces.
Your stomach also acts as a sensor for satiety, talking to your brain through both the nervous system and hormones. The stomach’s message that you’ve eaten also tells your brain to allow more energy to be used.
Your stomach then releases a controlled flow of this mixture of food and digestive enzymes into your small intestine, where bile salts and pancreatic enzymes help break food down even further. The carbohydrates are completely broken down into individual sugars; smaller protein molecules are broken down into peptides or individual amino acids; fats are broken down into glycerol and fatty acids.
When everything is properly broken down, most of the useful parts are absorbed through the lining of the small intestine and eventually end up in the bloodstream, which is the primary means of transporting nutrients from place to place.
The remainder of your meal then passes into the large intestine, which reabsorbs water and some minerals. The rest of the solid waste is excreted via, well … you know.
THE LIVER AND GALLBLADDER
Almost everything that goes from your gut into your bloodstream then goes directly to your liver, a critical metabolic regulator and filtration system. One of your liver’s many jobs is to detoxify compounds in your blood that managed to improperly pass through your gut barrier into your bloodstream before that blood goes to the rest of your body. For example, bacteria that manage to barge their way through your intestinal lining are mostly destroyed by your immune system, but some leftover (toxic) components of those cells can still make their way into your bloodstream. Your liver filters them out before they get into the rest of the body. Your liver is also responsible for producing bile (which is stored in the gallbladder and helps to digest fats) and cholesterol (which is critical for normal cellular and hormonal function). It also forms fats (triglycerides) out of excess dietary carbohydrate and stores important substances like vitamins A, D, and B12 and copper and iron.
INSIDE OUTSIDE
Your small intestine is the key to a healthy digestive tract. It is long and convoluted, with an enormous surface area. (In fact, if you stretched it all out, it would be the size of a tennis court!) The small intestine functions as a “holding tank,” keeping your food in place until it’s fully digested, but its most important job is to help you effectively absorb nutrients.
Think of the intestinal lining as similar to the skin on your body—a highly flexible, resilient, semi-permeable membrane that acts as a barrier between your insides and the outside world. Skin is designed to keep good stuff (fluids, tissues, etc.) inside your body and bad stuff (bacteria, viruses, etc.) out.
Your small intestine does pretty much the same thing—except on a much larger scale. Yep, your gut is your largest interface with the outside world, more so than your skin or respiratory tract. This is why your gut is so critical to your immune system.
IT STARTS IN YOUR GUT
About 70 percent to 80 percent of your entire immune system is stationed in your gut. That’s because there are all kinds of nasty beasties that would love to use your body as base camp, and most of them come in with your food and drink. So your immune system fortifies your intestinal wall with immune cells, which seek out and destroy pathogens trying to get through the intestinal lining. Any bad guys who make it past these immune cells into the bloodstream then have to travel through the liver, where even more immune cells are on hand to protect you. If they get past all of those defenses and manage to infect other tissues, a full-body immune response is triggered.
Think of food that is still inside your small intestine (in the lumen) as technically still outside your body. That’s right, until your food passes through the lining of your intestine and into your bloodstream, it is technically not yet in your body.
Here is another critical point: The entire process of digestion takes place while your food is still inside the long tube that passes from the one end of your digestive tract to the other. If undigested food somehow finds its way into the body, well, it’s as good as wasted.
Useless.
And probably harmful.
Keeping the right stuff in and the wrong stuff out is critical to a healthy gut.
Let’s go back to talking about skin. Think about what would happen if your skin was “leaky,” for example, if you crashed your bike and had major road rash. That road rash would expose your unprotected insides to the outside world. If some bacteria found their way inside, they could cause a pretty ugly infection, which your immune system would then have to work hard to fight off.
Well, a similar thing could happen if your gut was damaged and “leaky,” to the extent that it was no longer able to keep the bad stuff out. If that were the case, your immune system would (again) have to deal with the foreign invaders that got “inside,” where they didn’t belong.
LEAKY GUT SYNDROME
Leaky gut syndrome is not generally recognized by mainstream medical practitioners, which is probably frustrating for those of you who experience the consequences on a daily basis. Leaky gut (a simple way of saying “ongoing increased intestinal permeability”) occurs when the intestinal lining is abnormally permeable or structurally damaged, leaving the small intestine unable to do its job of nutrient absorption while maintaining inside-outside order. As a result, some bacteria and their toxins, undigested food, and waste may “leak” out of the intestines into the bloodstream, triggering an immune reaction. This is how leaky gut syndrome is related to immune-mediated problems in the body.
So if the lining of your gut is the physical barrier between your insides and the outside world, it should be clear why the integrity of this barrier is pretty darn important. You must be able to maintain control over what is allowed inside your body.
Without that control, there is chaos, which starts in your digestive tract and spreads throughout the body.
The good news is that a healthy gut is very well adapted to filtering out the bad guys while still absorbing the stuff from your food that you need. Let’s use another analogy to show how a healthy intestinal lining manages the process of selective absorption.
THE PARTY IS ROCKIN’ (SECURITY ON THE INSIDE)
Think of your body as an exclusive members-only nightclub in the rough part of town. At Club Body, there is a security force on patrol inside the club at all times (immune cells circulating throughout the body) that watches over the members and deals with any riffraff that happens to sneak in. But the big, muscular bouncers at the doors (a collection of immune cells that form a part of your intestinal barrier) are your first line of defense: they decide who can enter Club Body (members) and who can’t (anyone else).
Some substances—properly digested food, for example—are recognized as members and allowed to come inside, while strangers and troublemakers (like bacteria and viruses) are denied entry. Other things we can’t make use of inside, like undigested food and fiber, are also turned away.
The bouncers take their jobs very seriously, as experience has taught them that all outsiders have the potential to cause a lot of trouble if they get inside. There are only so many ways into the club, however, so as long as the bouncers guard all the doors and screen out any unsavory characters, things inside should (theoretically) stay healthy and safe.
BACTERIAL FRIENDS AND FOES
Since keeping your inside healthy and secure is so important, your body has assigned your security force some additional agents—a group of unlikely allies on the outside. Your body is home to trillions (yes, trillions) of bacteria, and most of them are in your gut. Over the course of a very long time, our immune system has developed a working relationship, an alliance of sorts, with some of these bacteria. Their presence does not trigger an immune response—they’re considered trusted friends, and are a vital component of a healthy human body. We consider them our BBFs (Best Bacterial Friends), and we’d rather go without our big toes than give up these “friendlies”—they are that important.
Our alliance with these friendly bacteria is largely what helps regulate our delicately balanced immune activity. These bacterial undercover agents hang out in the intestine just outside the door to Club Body, helping your security staff by discouraging the bad guys from loitering and starting trouble. Friendly gut bacteria help us digest our food, absorb micronutrients, manufacture vitamins, stabilize immune function, and generally take up space that would otherwise be snapped up by pathogenic bacteria.
GOOD GUYS, BAD GUYS
Researchers are rapidly growing to appreciate the centrality of the gut’s bacterial population (microbiota) in determining many aspects of health, including metabolism, psychological well-being, and … immunity. Balanced gut bacteria (the right kinds, in the right amounts) help to promote balanced immune function, which leads to a more relaxed, finely-tuned immune system. If we compromise our population of good bacteria on the outside, the bad guys would have the opportunity to multiply. As the bad guys pile up just outside the doors, they put a lot of stress on our security team. Balance is key. It’s a Goldilocks kind of situation: not too much, not too little … we need just the right amount.
HOW THINGS GO WRONG
So it seems as if your body (and your club) has a pretty good system for keeping itself healthy and safe. You’ve got the secure structure of the club itself (your intestinal lining), bouncers at the doors (immune cells in the lining), and a security force on the inside (circulating immune cells). Plus, you’ve got your friendly bacterial allies (BBFs) on the outside, helping to maintain law and order.
Your body’s gut defense system generally works very well.
Until it doesn’t.
There are a few ways bad guys can get into this exclusive nightclub. They might assault a bouncer, or wear a mask pretending to be a member, or pry open a locked (unused) door that was left unguarded. Or, if your gut is leaky (picture a sieve), all the doors and windows are wide open, and there’s no way to control who comes in. This spells big-time trouble for the in-house security force.
In this situation, your club is no longer healthy and safe. Letting bad guys in (through what should be tightly controlled entry points) leads to fights and destruction of property and could eventually overwhelm the rest of the security staff inside.
The same thing happens inside your body if your intestinal lining is compromised.
Once they’re in, the bad guys run rampant through the whole body.
And that is a very bad situation—but do you want to know the worst part?
Poor food choices are to blame.
Poor food choices flood your gut with bad guys, overwhelming your immune system. Bad food is what brings in the hoodlums, impersonators, and lock pickers, all of whom do what they are biologically designed to do—get in and wreak havoc. You create this condition of increased gut permeability, digestive distress, and systemic inflammation just by choosing the wrong foods. And it’s not your fault, because you didn’t even know you were doing it. (Not to worry—we’ll explain which foods disrupt your gut in Part 3.)
WHY IT MATTERS
Some overly optimistic folks may wonder at this point if there could be an advantage to increased intestinal permeability. We get where they’re coming from—like maybe if that barrier were a little more lenient, you could potentially absorb more nutrients, or digest your food a little bit faster. But that’s not how the body is meant to work. Again, let’s talk about skin. Is there ever a biological advantage to having an open wound? The answer is, of course, no.
Increased gut permeability is always a problem because it means your body no longer has control over what comes in and what stays out. Increased gut permeability (and the ensuing inflammatory chaos) is linked not only to intestinal inflammatory conditions like Crohn’s disease, ulcerative colitis, and irritable bowel syndrome (IBS), but also chronic diseases like cardiovascular disease and diabetes, hypersensitivities like asthma and allergies, and autoimmune conditions like Hashimoto’s thyroiditis, rheumatoid arthritis, and type 1 diabetes.
In fact, this third Good Food standard is directly linked to the fourth, because increased intestinal permeability provokes systemic inflammation. (You’ll learn why that’s bad soon enough.)
The importance of your gut as a healthy, intact barrier cannot be overstated.
One last thing—and the final nail in your leaky gut coffin. Remember how excessive abdominal fat (central obesity, or what the media calls being “apple shaped”) is a clear risk factor for heart disease, high blood pressure, stroke, and diabetes?
Deposition of visceral fat (which contributes to that sexy apple shape) is one of the direct effects of increased gut permeability.
Over time, with ongoing gut leakage, your liver and surrounding fat deposits act like a spongy trap for some of the bad guys that get in. This leads to significant inflammation in those tissues, as well as excessive deposits of fat in both the liver and surrounding adipose tissue.
That means your leaky gut also plays a major role (along with cortisol) in your stubborn belly fat and directly contributes to your risk of conditions like heart disease, high blood pressure, stroke, and diabetes.
We should have your attention by now—but once again, there is good news. Much like with your hormones, even after decades of poor diet and in the face of a gut leaking like a sieve, in most cases, the situation is all highly reversible. You can heal your intestinal lining, reinstate a high-functioning security system, and restore a thriving population of healthy bacteria if you do the same simple thing:
Change the food you put on your plate.
THE SCIENCE-Y SUMMARY
The food you eat should foster a healthy gut and digestive system.
Maintaining a healthy gut barrier is critically important to your health.
Certain foods can unbalance your healthy gut bacteria and/or promote intestinal permeability, compromising gut integrity.
Compromised gut integrity and bacterial imbalance lead to digestive distress and can promote chronic disease, hypersensitivities, and autoimmune conditions in the body.
Most of your immune system is located in your gut, which means our third and fourth Good Food standards are very closely linked.