Glycemic index, how high food elevates blood sugar


DEAR DR. DONOHUE: Would you explain the glycemic index? I have two friends who know everything there is to know about food and healthful eating. They are now onto this glycemic index thing. I tried to get them to explain it to me, but it was less clear after their explanation. I don’t think they know what they’re talking about. Will you give me a basic course on it? – R.K.

The glycemic index indicates how fast and how high a given food raises blood sugar. It applies only to carbohydrates. Carbohydrates are sugars or starches.

We’re told to go easy on foods with a high glycemic index. Since those foods raise blood sugar to high levels shortly after eating them, the body has to release large amounts of insulin to keep blood sugar in the normal range. Foods with high indexes cause peaks and valleys in blood sugar. Such great fluctuations in blood sugar are not good.

A glycemic index of 70 or higher indicates a food with a high index; values between 56 and 60 are medium glycemic foods; values of 55 or less are low glycemic foods.

The only way to know a food’s glycemic index is to look it up on a chart with such values. These charts are in nutrition books and on the Web. You can’t guess at a food’s index. For example, you would think that table sugar has a high glycemic index. It doesn’t. It has a medium value. On the other hand, a baked potato has a high glycemic index.

I really don’t know how much practical value this has for the ordinary person. We have turned eating into a science project when it should be an event for pleasure and health.

DEAR DR. DONOHUE: My 8-year-old nephew recently died from intussusception. No one knows exactly what happened. Apparently he complained of a stomachache. It didn’t go away. My sister took the boy to the doctor, who had him hospitalized immediately. They worked on him for many hours, and eventually he underwent surgery. He didn’t make it.

My sister will never get over this. How could he have died so quickly? – V.N.

You can get an idea of what intussusception is from a telescope whose smaller sections fold into the adjacent larger sections. In intussusception, parts of the intestine telescope into adjacent sections.

The initial signs are crampy stomach pain, sometimes with vomiting.

Intussusception is not an easy diagnosis to make. Ultrasound pictures of the digestive tract can provide good evidence that it’s the cause of the stomach pain.

Your nephew’s illness ran a very rapid course. That’s not the usual story. His telescoped intestine must have suffered a cut-off of blood supply. Those parts of the tract died and released bacteria into the abdominal cavity and into the blood. Under those circumstances, death often results.

Your sister and her husband have endured a tragedy. I am floundering here, trying to explain something whose details aren’t clear.

DEAR DR. DONOHUE: My mom passed away a few weeks ago in the hospital. She was 102. On the death certificate, the attending physician wrote that the cause of death was a “cardiovascular accident.” Would you please explain this medical term? – T.G.

A cardiovascular accident usually means a heart attack. A similar term, a cerebrovascular accident, is a stroke.

DEAR DR. DONOHUE: I am 78 and have recently been diagnosed with blocked arteries. I have had one artery bypass operation already. Can a needle be inserted into the artery to suck out the plaque? Or can the plaque be injected with fluid that dissolves it? – I.L.

What arteries are blocked? Sometimes the blockage can be surgically scooped out – an endarterectomy. Or the blockage can be squashed with a balloon (angioplasty) and a stent inserted to keep the artery opened. Or the blocked artery can be removed and replaced with a graft.

Dissolving the plaque with a medicine is something that lies in the future.

DEAR DR. DONOHUE: I am in my rusty years, not golden. I am writing about something important to me – SVT (supraventricular tachycardia). I would like to respond with a simple explanation to people who question me about it. What brings it on? Can I take something to stop it? – I.Y.

The “supra” of supraventricular tachycardia tracks the problem’s origin to the parts of the heart above (supra) the ventricles, which are the two lower heart chambers that pump blood out of the heart. That upper region is the heart’s atria, the place where the heartbeat arises. “Tachycardia” is a fast heartbeat.

There are many different kinds of supraventricular tachycardia – atrial fibrillation, atrial flutter, sinus tachycardia and many more. I suspect that the one you have is paroxysmal supraventricular tachycardia, a heartbeat that speeds up abruptly for no good reason and continues to beat fast for minutes to hours. Your heart has two pathways that the heartbeat can take in reaching the lower heart chambers. Those alternate paths confuse the heart and, from time to time, without any warning, cause it to accelerate suddenly.

Medicines can often keep these racing episodes to a minimum or even eliminate them. Two that are frequently chosen are beta blockers or calcium channel blockers.

If medicines can’t rein in the speeding heart, doctors can obliterate the extra pathway with a catheter equipped with a special tip that delivers radio waves or electric current that permanently closes the redundant path.

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