Glycemic index, or GI, is a ranking of carbohydrate containing foods on a scale of zero to 100 according to how quickly these foods raise your blood sugar level after consumption. A low GI diet is believed to protect you from the various health complications caused by unstable blood sugar levels like diabetes and obesity. A low GI diet alone is not conclusively proven effective for weight loss, but it may be helpful in managing existing diabetes.
Glycemic Index and Blood Sugar
A diet that follows the glycemic index is intended to help regulate your blood sugar, or glucose, levels. Glucose is a primary energy source for your cells, muscles and tissues. You get the majority of your glucose from carbohydrate containing foods. Your body breaks these foods down into glucose, which is then passed to your bloodstream. Unused glucose is stored in your liver or muscles in the form of glycogen. Your pancreas regulates the level of glucose in your blood with the help of the hormone insulin. When too much glucose in is your blood, the insulin moves it into your cells. Excess glucose or rapid changes in glucose can alter the way insulin is released and works to regulate your blood sugar levels, resulting in insulin resistance.
Glycemic Index Ranks
A low GI food is ranked numerically as 55 or under. A medium GI food is 56 to 69 and a high GI food is 70 and above. A high GI food is rapidly digested and absorbed but raises your blood glucose level quickly and is followed by a sugar crash. Conversely, low GI foods are slow to digest and absorb, resulting in sustainable energy from a gradual rise in blood glucose levels. Slow absorbing foods remain in your digestive system longer, which may help delay hunger cues to control your appetite. This is not only a benefit for losing weight, but also to prevent your body from becoming insulin resistant and increasing the risk of health conditions like heart disease, stroke or high blood pressure.
Low GI Foods
Peanuts and cashews rank from 14 to 22 on the GI scale for a 1 oz. serving. Whole grains like bran cereal, wheat bread or pasta and barley rank from 35 to 40. Beans are generally low GI and rank from 20 to 45 for kidney beans, navy beans, black beans or baked beans per one cup serving. Vegetables like one whole carrot, one medium sweet potato and one stalk of corn or medium sized fruits like pears, plums and peaches rank from 16 to 48. Animal-based foods like meat and dairy are not ranked on the GI.
Finding Low GI Foods
In general, foods with added sugars, processed or white grains and preservatives likely have a high GI. The majority of foods are not labeled with a glycemic index rank. You can conduct online searches to find comprehensive GI food charts, but use credible sources like the University of Sydney database or the international table in the "American Journal of Clinical Nutrition." Consult your physician before starting a low GI diet to determine safety for your health. Some low GI foods are high in calories and saturated fats, which could increase your risk of health conditions related to high cholesterol or high blood pressure.
References
- "American Journal of Clinical Nutrition"; International Table of Glycemic Index and Glycemic Load Values; Kaye Foster-Powell et al.; July 2002
- MayoClinic.com; Glycemic Index Diet; Losing Weight with Blood Sugar Control; Nove. 24, 2009
- Glycemic Index Foundation; University of Sydney: List of Glycemic Index for Foods
- Linus Pauling Institute; Glycemic Index and Glycemic Load; April 2010
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