The glycemic index was created in 1981 as a tool to help those with diabetes better control their blood sugar levels. The glycemic index ranks carbohydrates -- the macronutrient that provides the body with energy -- based on how high and how fast they increase blood sugar levels. Consuming high glycemic index foods rapidly increases blood sugar levels, triggering the pancreas to secrete large amounts of insulin -- the hormone needed to help cells utilize glucose. Due to this physiological response, eating low glycemic index foods can help reduce the risk for chronic diseases.
Diabetes
Diabetes, specifically type 2 diabetes, occurs as a result of insulin resistance and beta cell exhaustion. Consuming high GI foods may contribute to the onset of type 2 diabetes. The sharp rise in blood sugar levels triggered by high GI foods causes the beta cells in the pancreas to produce more insulin. Over time, the high demand for insulin causes the beta cells to lose their ability to secrete insulin. A decline in insulin production leads to more glucose remaining in the blood -- the characteristic feature of diabetes.
Heart Disease
The cells in the body require glucose for energy. Glucose circulating in the blood needs the help of insulin to get into the cells. When blood glucose levels rise and insulin levels rise in response to high GI foods, the body uses as much energy as possible. The remaining glucose gets converted into triglycerides and stored in fat cells. High triglyceride levels, defined by MayoClinic.com as levels greater than 200 mg/dL, contribute to the thickening of artery walls, a process known as atherosclerosis. Atherosclerosis increases the risk of heart disease, stroke and heart attack.
Obesity
As of 2008, approximately one-third of the adults in the United States were classified as obese, according to the Centers of Disease Control and Prevention. Obesity, defined as a body mass index of greater than 30, increases the risk for many chronic diseases including heart disease, diabetes, cancer, stroke, osteoarthritis and liver and gallbladder diseases. Diets that contain a high proportion of high GI foods can contribute to obesity. The sharp rise in blood glucose and resulting increase in insulin causes glucose levels to rapidly fall. This triggers feelings of hunger sooner than foods with a low GI, which slowly release glucose. This can lead to the consumption of more food and more calories, causing obesity.
Cancer
The relationship between high GI diets and the incidence of cancer remains an issue of debate. The Linus Pauling Institute reveals studies that find no correlation between high GI foods and breast cancer and other studies, like one conducted in Italy that shows a correlation between a high GI diet and breast cancer. Current studies are also being conducted to determine if there is a relationship between high GI food consumption and colorectal cancer.
References
- Linus Pauling Institute: Glycemic Index and Glycemic Load; Victoria Drake; 2009
- MayoClinic.com: Triglycerides; June 2010
- Centers for Disease Control and Prevention: Obesity Statistics
- Centers for Disease Control and Prevention: Health Consequences of Obesity
- "American Journal of Clinical Nutrition": Glycemic Index, Glycemic Load, and Chronic Disease Risk; Barclay et. al.; March 2008
