Good carb, bad carb

June 28, 2013

 

San Diego-In an Optometric Nutrition Society course at the American Optometric Association, Paul Chous, OD, FAAO, borrowed the words made famous by author Michael Pollen: “Eat real food, not too much. Mostly plants.” This also happens to be the advice Dr. Chous gives his patients with diabetes.

A diabetic himself, Dr. Chous explained the intricacies of dietary glycemic index and diabetic glycemic load. Glycemic index (GI) is a measure of how much your blood glucose rises after you eat a specific food. Glycemic load (GL), on the other hand, is determined by portion size since some foods have a very high glycemic index but a low load. Watermelon, for instance, has a very different glycemic index vs. glycemic load.

There is a lot of controversy surrounding the utility of the glycemic index because it varies based on a number factors, such as how the food is prepared, what time of day you consume, and what you along with it.

But to what extent do GI and GL matter? They matter quite a bit, said Dr. Chous. Low GI is <55, medium is 55-69, and high >70.

High glucose causes excess mitochondrial reactive oxygen species formation. Oxidative stress leads to endothelial dysfunction. When you consume a lot of sugars you get oxidative stress. You also get advanced glycation endoproducts (AGE), which is a plaque implicated in everything from Alzeimers and stroke to AMD and cataract. In essence, AGEs cause aging.

Specific to the eye, studies have found a 52% reduced risk of diabetic retinopathy when comparing highest to lowest dGI and dGL. The Blue Mountains Eye Study also found that AMD is strongly associated with high dGI. High dGI also increases incidence of AMD and advancement of AMD according to AREDS. In fact, one in five cases would not have advanced if GI was controlled.

Finally, GI also matters in the formation of cortical cataract (not in other forms of cataract), which means a patient’s Snellen may be good, but his contrast sensitivity may be very poor.

Dr. Chous currently wears a continuous glucose monitoring system, which he said is very helpful in making patients aware of how their bodies respond to certain foods. While GI is important, Dr. Chous said a primary goal should be to minimize spikes, since that is what causes the greatest damage.ODT