Type 2 Diabetes Risk: Carb Quality Counts

Among people with a family history of type 2 diabetes, genetics plays a role in disease risk, but poor diet, lack of exercise, and obesity are far more important for tipping the balance toward developing the disease. And once you have diabetes, heart disease, blindness, kidney disease, nervous system damage, and other complications may not be far behind. This is why it’s so important to pinpoint which of our choices can best keep diabetes at bay.

Proof of principle

Glycemic index (GI) and glycemic load (GL) are measures of how carbohydrates affect our blood sugar levels. GI refers to how quickly 50 grams of carbohydrate from a food will raise blood sugar levels and how high those levels will go. The higher the GI, the higher the blood sugar and the more quickly it will rise. But GI doesn’t account for the carbohydrate content in a typical serving size, which is where GL comes in.

Health experts have long suspected that GI and GL are related to type 2 diabetes risk and now they have added ammunition that this connection is real.

To study carbohydrate quality and diabetes risk, researchers collected diet information from 37,846 healthy, diabetes-free 21- to 70-year-old adults. After following the group for 10 years, the researchers found:

• A higher GL diet significantly increases risk of developing type 2 diabetes.
  
  
• A higher GI diet increases the risk of developing type 2 diabetes, though not as much as higher GL.
  
  
• Eating more dietary fiber significantly decreases the risk of developing type 2 diabetes.
  
  
• Eating more starch significantly increases the risk of developing type 2 diabetes.

You don’t have to count carbs to make your carbs count

Exhaustive glycemic index lists are available, but as this study shows, glycemic load may be the more important number. The GI for carrots is 131. For white pasta it’s 71. But a serving of carrots contains 4 grams of carbohydrate vs. the 40 grams found in a 1-cup serving of pasta. You’d have to eat several pounds of carrots to get 40 grams of carbohydrates!

The GL, which adjusts for the carbohydrate content in a serving size, tells the true story. Carrots have a GL of 5. Pasta’s GL is quite high at 28.

To avoid driving yourself crazy with GI lists, consider the three things that lower overall GL of the diet: protein, fat, and fiber. This is one reason why the GL of carrots is so low. The carrot fiber blunts the blood sugar effects of carrot carbohydrate. And, of course, the total amount of carbohydrate in a serving of carrots is low. This also explains some of why whole foods, like oranges are a better nutrition choice than orange juice, which offers minimal fiber.

Focus on getting protein, healthy fat, and fiber into all of your snacks and meals. For a snack think apple and peanut butter rather than apple juice and crackers. Ditch the processed foods and white (enriched) flour snacks. Focus on food that looks like, well, food!

And finally, don’t forget about your waistline. Overweight and obesity, which affect close to 70% of adults in the US, are leading risk factors for type 2 diabetes.

(Am J Clin Nutr; E-pub Ahead of Print August 4, 2010)

September 2, 2010

Suzanne Dixon, MPH, MS, RD, an author, speaker, and internationally recognized expert in chronic disease prevention, epidemiology, and nutrition, has taught medical, nursing, public health, and alternative medicine coursework. She has delivered over 150 invited lectures to health professionals and consumers and is the creator of a nutrition website acclaimed by the New York Times and Time magazine. Suzanne received her training in epidemiology and nutrition at the University of Michigan, School of Public Health at Ann Arbor.

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