Fructose intolerance can also affect our mood. Sugar helps the body absorb many other nutrients into the bloodstream. The amino acid tryptophan likes to latch on to fructose during digestion, for example. When there is so much fructose in our gut that most of it cannot be absorbed into the blood and we lose that sugar, we also lose the tryptophan attached to it. Tryptophan, for its part, is needed by the body to produce serotonin—a neurotransmitter that gained fame as the happiness hormone after it was discovered that a lack of it can cause depression. Thus, a long-unrecognized fructose intolerance can lead to depressive disorders. General practitioners and family doctors are only now beginning to include this knowledge in their diagnostic toolkit.
This raises the question whether a diet that includes too much fructose can also affect our mood, even in the absence of an intolerance. For more than 50 percent of people, eating 2 ounces (50 grams) of fructose or more per day (equivalent to five pears, eight bananas, or about six apples) will overtax their natural transporters. Eating more than that can lead to health problems such as diarrhea, stomachaches, and flatulence, and, over longer periods, to depressive disorders. The fructose intake of the average American is currently close to 3 ounces (80 grams) a day. Our parents’ generation, consuming just honey on their toast, far fewer processed foods, and a normal amount of fruit, took in no more than ½ to 1 ounce (only around 16 to 24 grams) a day.
Serotonin not only puts us in a good mood, it is also responsible for making us feel pleasantly full after a meal. Snack attacks or constant grazing on snacks may be a side effect of fructose intolerance if they are accompanied by other symptoms, such as stomachaches. This is also an interesting hint for all diet-conscious salad eaters, since many salad dressings found on our supermarket shelves or at fast-food outlets now contain fructose-glucose syrup (often known as high-fructose corn syrup). Studies have shown that this syrup can suppress leptin, the hormone that makes us feel full, even in people who are not fructose intolerant. A salad containing the same amount of calories but with a homemade vinaigrette or yogurt dressing will keep you feeling full for longer.
Like everything else in the world, food production is constantly changing. Sometimes those changes are good for us and sometimes they are bad. Curing was once the state-of-the-art way of ensuring people were not poisoned by eating rotten meat. For centuries, it was common practice to cure meats and sausages with large quantities of nitrite salts. This gives them a pinkish red, fresh color, and explains why products such as ham, salami, tinned pork, or gammon do not turn the same brown-gray color in the frying pan as an unprocessed chop or steak.
Use of nitrites for food preservation has been highly regulated since the 1980s, due to concerns about possible negative effects on human health. In the United States, sausage and cold meat products must contain no more than 156 parts per million of nitrite salt, approximately one-fifth of the level allowed twenty-five years ago. Rates of stomach cancer have fallen considerably since these regulations were introduced. This shows that what had once been a very sensible meat-preserving technique was in drastic need of correction. Today, canny butchers mix large amounts of vitamin C with small amounts of nitrite to cure their meats safely.
A similar modern reassessment of ancient practices may be in order in the case of wheat, milk, and fructose. It is good to include these foodstuffs in our diet, since they contain valuable nutrients, but it may be time to reassess the quantities we consume. While our hunter-gatherer ancestors ate up to five hundred different local roots, herbs, and other plants in a year, a typical modern diet includes seventeen different agricultural plant crops at most. It is not surprising that our gut has a few problems with a dietary change of that scale.
Digestive issues divide society into two groups: those who worry about their health and pay great attention to their nutrition, and those who get annoyed by the fact that they can no longer invite a group of friends round for a meal without having to go shopping at the pharmacy. Both groups are right. Many people err on the side of caution after hearing from their doctor about a food intolerance and then noticing that they do feel better if they avoid certain foods. They might decide to cut out fruit, wheat, or dairy products, and then often act as if they were poisonous. In fact, most people react to excessive amounts of these foodstuffs without being genetically intolerant to them. Most have enough enzymes to process a small portion of creamy sauce, the occasional pretzel, or a fruit pudding.
However, this does not mean that real intolerances should be ignored. We do not need to swallow every new development in our food culture blindly. Wheat products for breakfast, lunch, and dinner, fructose in practically all processed foods, or milk products long after weaning—it is not surprising that our bodies sometimes rebel. Symptoms like regular stomachaches, repeated bouts of diarrhea, or severe fatigue do not occur for no reason, and nobody should be expected to just accept them as “one of those things.” Even if your doctor has ruled out celiac disease or hereditary fructose intolerance, nobody can deny you the right to avoid certain foods if you notice that doing so improves your general well-being.
Apart from this general overconsumption, antibiotics, high stress levels, or gastrointestinal infections, for example, can also trigger temporary sensitivities to certain foods. When the body has returned to a healthy equilibrium, even a sensitive gut can usually sort itself out. Then there is no need to impose a lifelong ban on certain products, but simply to make sure you consume them in quantities your system can easily cope with.
A FEW FACTS
ABOUT FECES
COMPONENTS
COLOR
CONSISTENCY
GENTLE READER, it is now time to get down to the nitty-gritty. So, hitch up your suspenders, push your glasses up the bridge of your nose, and take a good gulp of your tea. While maintaining a safe distance, we must now take a closer look at the mysteries of number twos!
COMPONENTS
Many people believe feces are made up mainly of what they have eaten. That is not the case.
Feces are three-quarters water. We lose around 3½ ounces (100 milliliters) of fluid a day. During a passage through our digestive system, some 10 US quarts (9.8 liters) are reabsorbed. What we deliver into the toilet bowl is the result of an absolute maximum level of efficiency. Whatever fluid is left in the feces belongs there. This optimum water content makes our feces soft enough to ensure our metabolic waste products can be transported out of our bodies safely.
A third of the solid components are bacteria. They are gut flora that have ended their careers in the digestive business and are ready to retire from the workplace.
Another third is made up of indigestible vegetable fiber. The more fruit and vegetables you eat, the more feces you excrete per bowel movement. Increasing the proportion of that food group in the diet can raise the weight of a bowel movement from the average 3½ to 7 ounces (100 to 200 grams) to as much as 17 or 18 ounces (500 grams) per day.
The remaining third is a mixed bag. It is made up of substances that the body wants to get rid of—such as the remains of medicines, food coloring, or cholesterol.
COLOR
The natural color of human feces ranges from brown to yellowish-brown—even when we have not eaten anything of this color. The same is true of our urine—it always tends toward yellow. This is due to a very important product that we manufacture fresh every day: blood. Our bodies create 2.4 million new blood corpuscles a day. But the same number are broken down every day, too. In that process, the red pigment they contain is first turned green, then yellow. You can see the same process in the various stages of a bruise on your skin. A small portion of this yellow pigment is excreted in your urine.
Most of it, though, passes through the liver and into the gut. There, bacteria change its color once again—this time turning it brown. Examining the color of feces can provide a useful insight into the goings-on of our gut.
LIGHT BROWN TO YELLOW: This color can be the result of the harmless disorder called Gilbert�
��s syndrome (or Gilbert-Meulengracht syndrome). In this condition, one of the enzymes involved in the breakdown of blood works at only 30 percent of its normal efficiency. This means less pigment finds its way into the gut. Affecting around 8 percent of the world’s population, Gilbert’s syndrome is relatively common. This enzyme defect is not harmful, causing barely any problems for those who have it. The only side effect is a reduced tolerance for acetaminophen, which should be avoided by those with Gilbert’s syndrome.
Another possible cause of yellowish feces is problems with the bacteria in the gut. If they are not working as they should, the familiar brown pigment will not be produced. Antibiotics or diarrhea can cause such an alteration in fecal color.
LIGHT BROWN TO GRAY: If the connection between the liver and the gut is blocked by a kink in the tubes or by pressure (usually behind the gall bladder), no blood pigment can make it into the feces. Blocked connections are never a good thing, and those who notice a gray tint to their feces should consult their doctor.
BLACK OR RED: Congealed blood is black and fresh blood is red. In this case, the color is not due to the pigment that can be turned brown by bacteria, but to the presence of entire blood corpuscles. For those with hemorrhoids, a small amount of bright red blood in the stool is no reason to worry. However, anything darker in color than fresh, bright red blood should be checked by a doctor—unless you have been eating large amounts of beetroot.
CONSISTENCY
The Bristol stool scale was first published in 1997, so it is not very old if you consider the millions of years that feces have existed. The scale classifies the consistency of feces into seven groups. A chart like this can be a useful tool, since most people are reluctant to talk about the appearance of their bowel movements. That’s perfectly natural. There are some aspects of private life we prefer not to rub other people’s noses in! But such a reticence to talk about what we find in the toilet bowl means that people with unhealthy looking feces are often unaware of it. They think everybody’s business looks like their own. A healthy digestive system, producing feces with the optimum water content, will produce types 3 or 4. The other types are less than ideal. If they do appear, a good doctor should be able to find out whether your loose stool or constipation is the result of a food intolerance, for example. The chart was developed by Dr. Ken Heaton at the University of Bristol in the United Kingdom.
TYPE 1
Separate hard lumps, like nuts (hard to pass)
TYPE 2
Sausage-shaped, but lumpy
TYPE 3
Like a sausage but with cracks on its surface
TYPE 4
Like a sausage or snake, smooth and soft (author’s note: like toothpaste)
TYPE 5
Soft blobs with clear-cut edges (passed easily)
TYPE 6
Fluffy pieces with ragged edges, a mushy stool
TYPE 7
Watery, no solid pieces, entirely liquid
The type a person’s feces belong to can be an indication of how long indigestible particles take to pass through their gut. According to this, in Type 1 digestive remains take around one hundred hours to pass through the system (constipation). In Type 7, they pass through in just ten hours (diarrhea). Type 4 is considered the ideal, because it has the optimum ratio between fluid and solid content. Those who find types 3 or 4 in the toilet bowl may also want to observe how quickly their feces sink in water. Ideally, they should not plummet straight to the bottom, as this would indicate the possibility that they still contain nutrients that have not been digested properly. Feces that sink slowly contain bubbles of gas that keep them afloat in water. These gas bubbles are produced by gut bacteria that mostly perform useful services. So this is a good sign, as long as it is not accompanied by flatulence.
THESE HAVE BEEN a few selected facts about feces, gentle reader. You can now loosen your suspenders and let your glasses slide back down your nose to where they are most comfortable. Here endeth the first chapter of the story of the gut and its goings-on. We now turn to an electrifying topic: the nerves.
(PART TWO)
THE NERVOUS
SYSTEM
OF THE GUT
THERE ARE PLACES where the unconscious and the conscious meet. When you are sitting at home, eating your lunch, you may be unaware that your next-door neighbor is just a short distance away, beyond the dividing wall, chomping away on his lunch, too. You might hear the faint creak of his floorboards and suddenly, your awareness reaches out beyond your own four walls. Similarly, there are areas of our own body we are simply unaware of. You don’t feel your organs working away all day long. When you eat a piece of cake, you taste it while it is still in your mouth, and you are also conscious of the beginning of its journey as it passes down your throat after you swallow it. But then, as if by magic, the cake is gone! From then on, what we eat disappears into the realm of what scientists call smooth muscle.
Smooth muscle is not under our conscious control. Under the microscope, it looks very different from the tissue of the muscles we can control consciously, such as the biceps. We can flex and relax the muscles in our upper arms at will. Such muscles are made up of the tiniest little fibers, lined up so neatly they look as if they were drawn using a ruler.
The microscopic structure of smooth muscle resembles an organic network, and it moves in mellifluous waves. Our blood vessels are surrounded by smooth muscle tissue, which explains why we blush when we are embarrassed. Smooth muscle tissue slackens in response to emotions such as embarrassment, causing the blood capillaries in the skin of the face to dilate. In many people, stress has the opposite effect, causing the muscles surrounding the blood vessels to contract, restricting the flow of blood. This can lead to high blood pressure.
The gut is cosseted by no fewer than three coats of smooth muscle tissue. This makes it incredibly supple and able to execute different choreographies in different places. The choreographer directing these muscles is the gut’s own (enteric) nervous system. The enteric nervous system controls all processes that take place in the digestive tract, and it is extraordinarily autonomous. If the connection between the enteric nervous system and the brain is severed, the digestive tract carries blithely on as if nothing has happened. This property is unique to the enteric nervous system and is found nowhere else in the human body—without directions from our brain, our legs would be lame and our lungs would no longer be able to breathe. It is a shame that we are oblivious to the workings of these independent-minded nerve fibers. Burping or breaking wind might sound a bit gross, but the movements involved are as delicate and complex as those of a ballerina.
How Our Organs Transport Food
ALLOW ME TO take you on a journey. Let us accompany that piece of cake on its travels in the realm of smooth muscle.
Eyes
PARTICLES OF LIGHT bouncing off the piece of cake hit the optic nerves at the back of the eyes, generating a nerve impulse. This first impression travels right through the brain to the visual cortex at the back, just below where a high ponytail would be. There, the brain interprets the nerve impulses to form an image. It is not until that happens that we really see the piece of cake. This delicious news is then passed on to the systems that control salivation, with mouth-watering results. Similarly, the mere sight of a yummy treat also causes the stomach to produce some digestive juices in anticipation.
Nose
IF YOU STICK your finger up your nose, you will notice that the cavity continues upward far beyond the reach of your finger. This is where the olfactory nerves are, which are responsible for smelling. They are coated in a protective layer of mucus, so anything we smell must first be dissolved in that slimy substance if it is to get through to the nerves.
Olfactory nerves are specialists. There are specific receptors for a large range of individual smells. Some spend years hanging around up your nose, waiting for their chance to shine. When that single, long-awaited lily-of-the-valley scent molecule finally attaches itself, the receptor pro
udly calls out “lily-of-the-valley!” to the brain. Then it might be idle again for the next couple of years. (Incidentally, although we are equipped with a large number of olfactory cells, dogs have inconceivably more.)
For us to smell it, molecules from the piece of cake first have to drift into the air, to be sucked in through our nostrils as we breathe. They may be aromatic molecules of vanilla, minute plastic molecules from cheap party forks, or evaporating alcohol fragrances from the cake’s rum filling. Our olfactory organ is a royal taster with a thorough knowledge of chemistry. The closer we bring the cake-laden fork to our cake-hole, the more detached cake molecules stream into our nose. If we detect tiny traces of alcohol as the cake covers the last small gap between our fork and our mouth, we may back our arm up in suspicion to allow our eyes to inspect the cake again, just to check whether it is supposed to contain alcohol or whether the fruit in it has started to rot. With all checks passed, it’s mouth open, fork in, and let the ballet begin.
Gut: The Inside Story of Our Body's Most Underrated Organ (Revised Edition) Page 6