The theory is that sugar and high glycemic carbs that rapidly convert to sugar trigger a release of insulin to control the level of sugar in the bloodstream. Excess sugar in the bloodstream is inflammatory and causes a cascade of free radical damage.

To explain how dangerous this is, Dr, Perricone points out that diabetics with poorly controlled blood sugar age one third faster than nondiabetics and are prone to kidney failure, blindness, heart attack and stroke.

So insulin comes to the rescue to clear the excess sugar from the bloodstream. And what do you suppose the insulin does with all this sugar? It stores it as fat. And worse yet, until the insulin sweeps up the excess sugar, it runs rampant throughout the body causing glycation and cross-linking of the body's collagen.

The effect is visible on the skin, which becomes leathery and inflexible as we age. Though it can't be seen, the same damage is taking place inside the body where it affects other vital organs including the kidneys, lungs and brain.

So far, so good. Nutritionists have recommended that people cut their consumption of sugar for decades. The surprise when one ranks sugars and carbs by their glycemic index, is that some foods we normally think of as healthy show up as being bad for you.

The glycemic index is a ranking from 1 to 100, with 100 indicating the increase in blood sugar from eating table sugar (or white bread in one scale). Whichever scale is used, the important thing is a rank ordering of a food's effect on blood sugar.

The low glycemic food diets mentioned above have different cut off points. For example, Dr. Perricone's 28-day program prohibits any foods that score above 50 on the glycemic scale. That leaves out such things as bananas, bagels, carrots, corn, potatoes, rice and watermelon.

You can read more about the glycemic index (GI) and view the whole table http://www.mendosa.com/gi.htm here. This site is authored by David Mendoza, a freelance medical writer and consultant specializing in diabetes. The site is a gold mine of information.

Mr. Mendoza points out that a food's glycemic index tells you how rapidly a particular carb turns into sugar, but not how much of that carbohydrate is in a serving. In other words, it's not just the quality of the carb, but also the quantity, that counts.

The version of glycemic index on his site (courtesy of Professor Jennie-Brand Miller of the University of Sydney) includes a column called glycemic load (GL) as well as a column of serving size in grams. A glycemic load of 20 or more is considered high; 11 to 19 is medium; and 10 or less is low.

Looking at this bigger picture, some of the ?bad? carbs in low-glycemic food diets turn out to be not so bad. A 120g serving of watermelon has a horrible GI of 74 but a very low GL of 4. A medium banana (129g) has a bad GI of 51 but a medium GL of 13. An 80g serving of carrots has a borderline GI of 47 but a low GL of only 3. The same amount of corn has a GI of 47 but a low GL of 7.

On the other hand, some carb foods look bad whether you go by the GI or the GL. A 70g bagel has a high GI (72) as well as a high GL (25). A 150g serving of boiled white rice has a GI of 56 and a GL of 24. A medium baked potato (159g) has a high GI (60) and a marginal GL (18).

If you decide to concentrate on low-glycemic foods, I recommend you focus on a food's glycemic load. Just be careful to adhere to the indicated serving sizes (or adjust the calculation accordingly), GL is a better measure of how much sugar in total is being poured into the bloodstream and the amount of sugar that will be stored as fat.

This article is for informational purposes only. It does not purport to offer medical advice.