Many popular diet books give you a list of foods based on the Glycemic Index, and recommend avoiding all foods that have a high glycemic index.

When you eat a food, your blood sugar level rises. The food that raises blood sugar the highest is pure table sugar. So Glycemic Index is a ratio of how high that food raises blood sugar in comparison to how high table sugar raises blood sugar levels. Foods whose carbohydrates break down slowly release glucose into the bloodstream slowly, so blood sugar levels do not rise high and therefore these foods have low glycemic index scores. Those that break down quickly cause a high rise in blood sugar and have a high glycemic index.

Most beans, whole grains and non-starchy vegetables have low glycemic index; while sugars, refined grains made from flour, fruits and root vegetables have a high glycemic index.

If you look at glycemic index food lists, you will see things that should bother an intelligent person. A carrot has almost the same glycemic index as sugar does. That is ridiculous. You know that a carrot is far safer for diabetics than table sugar. So nutrition scientists developed a new measure to rank foods called Glycemic Load. It tells you how much sugar is in the food, rather than just how high it raises blood sugar levels. To calculate Glycemic Load, you multiply the grams of carbohydrate in a serving of food by that food's Glycemic Index.

Carrots and potatoes both have a high Glycemic Index (GI), but using the new Glycemic Load (GL), carrots dropped from high GI of 131 to a GL of 10. Potatoes fall from a GI of 121 to a GL of 45. Air-popped popcorn, with a glycemic index of 79, has a GL of 4.

Foods that are mostly water or air will not cause a steep rise in your blood sugar even if their glycemic index is high. That's why the new measure, Glycemic Load, is more useful. However, all of these tools are more important for research than for your daily selection of foods. Use your own common sense and eat plenty of fruits, vegetables, whole grains, beans and other seeds. Avoid the refined carbohydrates -- foods made with extracted sugars, flour, white rice or milled corn products.

Gabe Mirkin, M.D.

Dr. Gabe Mirkin has been a radio talk show host for 25 years and practicing physician for more than 40 years; he is board certified in Sports Medicine and three other specialties.

Dr. Mirkin's daily features on fitness have been heard on CBS Radio News stations since the 1970's. He has written 16 books including The Sportsmedicine Book, the best-selling book on the subject that has been translated into many languages. His latest book is The Healthy Heart Miracle, published by HarperCollins.

Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. A Boston native, Dr. Mirkin did his residency at the Massachusetts General Hospital. He has served as a Teaching Fellow at Johns Hopkins Medical School, Assistant Professor at the University of Maryland, and Associate Clinical Professor in Pediatrics at the Georgetown University School of Medicine. He has run more than forty marathons and is now a serious tandem bicycle rider with his wife, nutritionist Diana Mirkin.