Inflammation — The Newest Theory of Disease

Does inflammation cause disease? That’s the newest idea to capture the imagination of medical investigators. Heart disease? Caused by inflammation of the lining of the arteries.  Peptic ulcers?  Inflammation of the lining of the stomach or small intestine.  Colon cancer? Inflammation of the colon’s lining.

Inflammation is the body’s reaction to irritants with a standard response that every medical person is taught to recognize – the simple flair and wheal – the redness and swelling seen in the skin after a scratch from a twig or the sting of a bee. When an irritant comes in contact with the body, the body responds with inflammation.

Chemicals released during this inflammatory response are anything but simple. So many substances are released that the outpouring is called a cascade. Chemicals and proteins release to increase blood clotting, summon white blood cells (body policemen), dilate and constrict blood vessels, increase output of hormones from the adrenal gland (steroids and epinephrine), the thyroid gland, the pancreas (insulin and digestive enzymes), and the pituitary gland. 

The inflammatory response is designed to launch when invaders (irritants – foreign bodies, foreign proteins) have entered the body and must be dealt with. As an acute reaction, it is very effective. But when irritants continue to enter the body over a prolonged period of time, the cascades get out of control – either growing tired and dull and not recognizing invaders who should be dealt with (bacteria, cancer cells, or others) or over-reacting to and attacking normal body proteins (such as the joint lining in arthritis, or pancreatic cells as in Type I diabetes).

There are four major body systems who are the first line of defense against outside invaders, and are most exposed to the outside world: the skin, the lining of the digestive system, the lining of the breathing system, and the blood vessels.

The outside lining of the body, the skin, is the most obvious first line of defense against invasion of irritants. It is thick and resistant to attack, only reacting if the tough outer layers are broken or have been soaked through (poison ivy juice or latex, for example). Even so, some people have sensitive skin that easily reacts to foreign proteins. We say these people are allergic. They over-react to invaders that most of us can shrug off.

The inside lining of the body, the lining of the gut from the mouth to the anus, is also bombarded constantly by foreign proteins and foreign particles that can attach to normal body proteins. The lining of the gut is very thin to absorb digested nutrients. The gut is flushed out on a regular basis by the large volume of water it secretes. But a slow or irregular flush cycle can leave it exposed to foreign particles causing inflammation.

The next obvious area exposed to outside irritants is the breathing system — the throat and lungs. This lining is also thin, to facilitate the intake of oxygen and the release of carbon dioxide. Its protective mechanism is a lining of small, ever-waving hair-like projections (called cilia) that move irritants up and out of the lung or down and out of the nose, sometimes producing a cough or a sneeze to expel them. Foreign proteins can cause a lung spasm, known as asthma.

The fourth system exposed to foreign invaders is the blood vessel system. Its lining is thin to allow nutrients and oxygen in. Except for the flow of blood, it has no natural flushing or cleansing mechanism. Blood vessels have to rely solely on white blood cells to seek out and destroy the foreign invaders. In the meantime, the blood vessels are at the mercy of the inflammatory response.

Why discuss this topic in a column normally focused on disease prevention? To lay a foundation for the next post — what to do when there is a prolonged, destructive inflammatory response.