Do you know how long you can survive without food or water? The answer may vary depending on how well stocked you are to start (and the environment – how hot/dry it is), but on average, we can survive about a month without food, and 10-14 days without hydration. When you think about it, we are all pretty close to death if we ignore our intestines.
The intestines are soft, mucous-coated, muscular tubing that connect the stomach to the anus. The intestine performs different functions depending on where it is along the digestive tract. The small intestine (it’s called small because it has a relatively small diameter) is about 22 feet long, and the first foot or so (called the duodenum) is responsible for initiating nutrient absorption. In our previous reviews of the liver and pancreas we learned that food is broken down in the small intestine with the help of bile (a kind of soap produced by the liver) and pancreatic enzymes that are squirted into the small intestine when food passes by.
The duodenum absorbs most of our food’s iron and calcium, as well as some minerals, and neutralizes the acidic food mixture from the stomach. The next segment of the small intestine (the jejunum) is responsible for the majority of nutrient absorption including sugars, amino acids, and fatty acids. And the final segment (ileum) absorbs vitamin B12 and reclaims bile. The inner lining of the intestine has microscopic folds that serve to increase the surface area in contact with food, so that nutrients can be actively or passively transported across the wall and into the bloodstream where they can travel to all the cells of the body. If we spread out all the folds, the intestines of one human would actually cover an area the size of a tennis court!
The small intestine empties into the colon (which has 3 segments: ascending, transverse, and descending) which is about 5 feet long. The colon primarily extracts liquid from food, absorbing most of its water content. The colon is an important storage system for waste, and is home to thousands of kinds of healthy bacteria that influence and strengthen our immune systems.
The most common problems that occur with our intestines include:
- Ulcers: food that has been mixed with stomach acid, bile, and strong pancreatic enzymes can be irritating to the intestinal lining. If the lining does not produce enough protective mucous, this highly acidic sludge can cause painful ulcers, chronic bleeding, and eventual anemia.
- Muscle contraction issues (too much/too little). Constipation and diarrhea are both related to food transit time. When intestinal muscles contract slowly, food passes through them more slowly and their water content has more time to be absorbed.
Constipation results, with hard stool caused by dryness. Diarrhea, on the other hand, may be caused by overactive muscle contractions that move food along very quickly.
Irritable bowel syndrome can be a result of both fast and slow contracting muscles. In rare cases, the bowels can twist on themselves and cut off their own blood supply (called an
ileus) or telescope into themselves (called an intussusception). These twists are very painful and represent a surgical emergency.
- Malabsorption: autoimmune diseases (such as Crohn’s disease and
ulcerative colitis), allergies (such as Celiac disease or gluten allergy) and bowel surgeries (including bariatric surgery) can affect the absorption of nutrients in the intestine. Nutritional deficiencies can cause anemia, with calcium, iron, and magnesium often being too low.
- Food Intolerance: some of us have difficulty digesting milk protein (lactose intolerance), or high fiber foods. Cheese, caffeine, or certain plants (such as soy) can cause bloating, gas, and abdominal pain for some people.
- Food Allergies: food allergies (as opposed to intolerances) are more than uncomfortable, but dangerous. Peanut and shellfish allergies, for example, can cause a rapid immune response that can affect the entire digestive tract, including the mouth and throat, and cause difficulty breathing and sudden swelling.
- Wall herniations: as we age, intestinal walls (especially in the colon) tend to weaken. Small outpouchings called diverticula can trap food and become infected (known as
diverticulitis). When antibiotics are not enough, sometimes parts of the colon need to be removed.
- Infections: intestinal infections are very dangerous because of the bacteria that live inside the small intestine and colon. When these bacteria (such as E. coli) get outside the intestine and into the blood stream, they can cause rapid sickness, fever, and even death if not treated quickly.
Appendicitis is an infection of a worm-like outpouching near the attachment of the small and large intestines. More common outside the U.S.,
parasites can be accidentally ingested and cause bleeding or diarrhea, and spores from
clostridium difficile (known as c.diff) or cholera bacteria are contagious and may require hospitalization due to severe dehydration.
- Polyps and Cancer: intestines are very active tissues, and they replace the first layer of cells in their lining every four to five days. Since these cells are rapidly dividing and replacing themselves all the time, it makes sense that they are at risk for dividing incorrectly, and causing polyps (growths) to develop. Most cancers develop from inside these polyps, so removing polyps is a priority during colonoscopies.
How can you keep your intestines healthy?
- Eat a healthy, high-fiber, low processed food diet. High
fiber diets, lower in red meat have been associated with a reduced risk of colon
cancer. Whenever possible, eat whole foods (as opposed to highly processed,
canned or pre-prepared food), grains, plants, and lean fish and poultry
- Drink plenty of water. Water assists in absorption of
nutrients and helps to prevent constipation.
- Avoid trans fats and charred meat. Partially hydrogenated
oils in baked goods and margarines are absorbed by the intestines and increase
the risk of diabetes, heart disease, and stroke. Charred and pickled meats may
increase the risk for colon cancer as well.
- Get regular colonoscopies starting at age 50, or sooner if you
have colon cancer in your family.
- Limit alcohol intake. Alcohol is associated with a higher
risk of colon cancer.
- Take vitamin supplements if you have a malabsorption problem.
For some people who can’t absorb B12 or iron, IV or injectable versions of these
vitamins and minerals are available to bypass the gut. For most Americans, all
the vitamins and minerals necessary for good health are available in a healthy
- Take probiotics. Good gut bacteria are important to maintain,
especially after a course of antibiotics. You can restore your gut flora by
eating yogurt with live cultures or acidophilus tablets. Probiotics can
reduce your risk of colon infections like C. diff after antibiotic treatments.
- Report blood in your stool to your doctor. Bloody or
black stool may be caused by hemorrhoids, ulcers, or colon cancer. Either way,
don’t be shy to talk to your doctor right away if you see blood in your stool.
With 25 feet of gut tubing and a tennis court-sized absorptive area, shedding all its inner lining cells every 4-5 days, and moving about 5 pounds of food per day through the system via muscular contractions, the human intestinal tract is an amazing piece of engineering. Keeping it running smoothly can be challenging, but luckily there are effective dietary and over-the-counter medication options to keep us out of most trouble. For other issues, we can rely on our primary care physicians or friendly neighborhood gastroenterologists and surgeons.
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