DEAR DR. DONOHUE: What causes Crohn’s disease? What is the treatment?

My son has it. — F.H.

ANSWER: Crohn’s disease is one of the two inflammatory bowel diseases. The other is ulcerative colitis. Both have some common signs and symptoms, but they are quite different illnesses. Inflammation is the body’s response to something that causes it harm. Inflammation, therefore, is good. However, when inflammation gets out of hand, it becomes a destructive process. In Crohn’s disease, the inflammation can attack any section of the digestive tract, from the mouth to the lowermost part of the colon. The small intestine and the colon are the two areas affected most often by Crohn’s.

Deep ulcers that penetrate the tract’s wall form. Tunnels connecting organs with the digestive tract often develop. Those tunnels are called fistulas.

Abdominal pain with diarrhea and weight loss are prominent symptoms. Passing stool often alleviates the pain for a while. People also might develop a fever. Naturally when all this happens, Crohn’s patients have little energy to do anything.

You have to put treatment into the plural when speaking of Crohn’s. It has many treatments. I’ll give you a very brief outline, because a long list of medicines will only confuse you. One of the first medicines chosen for treatment is Asacol, which calms the inflamed tract. If a more potent remedy is needed, prednisone, one of the cortisone drugs, often is used. A new group of medicines called biologicals is highly effective when the more common ones aren’t making a dent in improving symptoms. Remicade (infliximab) is one example.

DEAR DR. DONOHUE: Is 1,000 IU of vitamin D too much? The doctor recommended it. I am 84. — F.H.

ANSWER: The new recommendations for vitamin D are 600 IU for adults up to 70 years of age, and 800 IU for those older than 70. Your dose is not excessive. The upper limit is set at 4,000 IU a day.

DEAR DR. DONOHUE: Please enlighten me on the pros and cons of iodized salt versus salt without iodine. I used very little iodized salt in my cooking and rarely at the table. What is the use of salt without iodine? — B.S.

ANSWER: In the early years of the 20th century, hypothyroidism (a sluggish thyroid gland) and goiter (thyroid enlargement) were rampant. This was due to iodine deficiency.

In the 1920s, the government felt that adding iodine to salt would solve this problem. Salt was cheap, and everyone used it. So iodized salt became standard. It worked. The incidence of hypothyroidism and goiter was greatly reduced. Iodine doesn’t affect the taste of salt.

Even if you don’t use iodized salt today, you still get enough from diet. Ocean fish, shellfish, milk, cheeses, yogurt and eggs have a good supply of iodine. Furthermore, most commercial baked goods and other foods contain iodized salt.

People on a low-salt diet often wonder if they are getting enough iodine. They are.

You use salt without iodine for the same reasons you’d use iodized salt — because the recipe calls for salt.

DEAR DR. DONOHUE: My eyesight has been getting worse in the past few months for no apparent reason. I had an eye exam four months ago. At the two previous exams, the doctor suggested getting over-the-counter reading glasses. Now it seems like I need them all the time to read labels and cooking directions on packages. I can see to drive and do regular things. What’s going on? They blame it on age. I’m in my mid-50s. — G.L.

ANSWER: You can believe the doctor. I’m sure you have presbyopia, a change in your eyes’ lenses that happens after age 45. They have lost the ability to focus up-close images like print and the eye of a needle. It’s the fate of everyone. Distant vision is unaffected. It’s not a sign of future blindness. Reading glasses are the answer.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.