What is the Glycemic Index?
By Andrea Stewart, RD
The Glycemic Index (GI) is not new and has remained controversial among health professionals. Last month, a study published in the American Journal of Clinical Nutrition, found that a diet with a high-glycemic load - a diet low in fiber and high in processed foods - was linked to a greater risk of developing type II diabetes. While this is consistent with past research, is utilizing the Glycemic Index an appropriate and effective way of managing blood sugar or helping to ward off diabetes? Let’s take a closer look.
What is the Glycemic Index?
The GI is a measure of how certain foods, particularly carbohydrates, affect blood sugar levels. Foods with a higher GI ranking are said to cause a rapid increase in blood sugar, requiring more insulin secretion by your body to usher that sugar into your cells to use for energy. This is followed by a dramatic drop of blood sugar which can leave you feeling hungrier, sooner. A food with a lower GI ranking is said to slow the digestion and distribution of sugar into the blood, giving way to prolonged periods of fullness and satisfaction.
Of course, the repercussions go beyond your hunger levels. Eating too many foods that have a higher GI ranking may put too much work on your pancreas, the organ which secretes insulin, and over time that can set you up for insulin resistance. That means, your body doesn’t respond to insulin as it should, resulting in poor blood glucose control and altered fat metabolism. Insulin resistance is not only a contributing factor for type II diabetes, but also for obesity, stroke, high blood pressure and heart disease. The Center for Disease Control and Prevention shows that close to 25.8 million people, or 8.3% of the U.S. population, have diabetes, while almost 7 million people remain undiagnosed.
The Highs and Lows
Higher GI ranking-foods include table sugar, refined flour, many shelf stable crackers, pastries, desserts, candy, sodas, sweetened beverages, and certain low fiber fruits and vegetables.
Lower GI ranking-foods include beans, nuts, fiber rich vegetables & fruit, most dairy and cheese, meat, fish and unrefined complex carbohydrates.
Seems like a no-brainer, right? Focusing on low-GI foods seems to focus mostly on foods that are naturally higher in fiber. Doing so can help protect against insulin resistance, your risk for developing diseases, as well as promoting weight loss.
But it’s not as simple as it appears. Firstly, you’d need to remember the GI ranking for each food or combinations of foods. The ranking changes depending on these combinations as well as the ripeness of a vegetable or fruit (ie. a ripe banana contains more sugar than one that's green). In fact, some low GI foods are actually less nutritious than high GI foods. For example, one slice of a common name brand supreme pizza as well as a leading brand vanilla cake with frosting have a lower GI ranking than an average sized baked potato, small bowl of wholegrain wheat-barley cereal, or watermelon Harvard Health Publications Glycemic Index chart. There’s no reason those lower GI foods should be chosen over the latter more nutritious options.
The Bottom Line
There is much more required to healthy eating and weight management than the GI ranking system alone.
While it is absolutely important to understand how certain foods affect your blood sugar, you don’t want to restrict nutrient dense foods just because they have a higher GI ranking. The emphasis must be on choosing the right types of carbohydrates and limiting simple, nonnutritive carbs, such as table sugar, high sugar granola bars, desserts, most refined flours, sodas and sweetened beverages that contribute little to zero nutrition. The best way to keep your blood sugar stable is with small frequent meals consisting of a small serving of complex carbohydrates, a lean protein and some colorful produce. The combination of these foods will help keep you feeling fuller longer and your blood sugars more stable throughout the day. This will keep you satisfied, content and not looking for the next sugar high.
We want to hear from you! Do you apply the GI Index to your diet? Why or why not?
Andrea Stewart, RD is a registered dietitian who is passionate about helping others filter through the endless nutrition information available so they can be their healthiest. Andrea places a huge emphasis on eating a colorful, whole foods diet as a primary method for disease prevention and wellness. For more information go to Andrea’s website, follow her on Facebook, or Twitter.