The glycemic index (GI) of foods has important implications for the prevention and treatment of the major causes of morbidity and mortality in western countries, including non-insulin-dependent diabetes, coronary heart disease, and obesity. The recent United Nations FAO/WHO Consultation on Carbohydrates recommended that “the glycemic index of foods be used in conjunction with information about food composition, to guide food choices.”
Specifically, it recommended that “at least 55% of energy be derived from carbohydrates and that the bulk of carbohydrate foods be those rich in dietary fiber (non-starch polysaccharide and with a low glycemic index.” Although these recommendations are designed for the general population, there is persuasive evidence that they are even more applicable to people with weight issues and / or diabetes. Vegetables are low on the Glycemic Index.
What exactly is the glycemic index (GI), and why has it become so important? In this article, we show how foods are classified according to their GI, summarize the health benefits and criticisms of the GI, and consider the practical aspects of putting GI into nutrition therapy for diabetes.
What is the GI?
The GI is an established, physiologically based method used to classify foods according to their blood glucose-raising potential. It compares the level of glycemia after equal carbohydrate portions of foods and ranks them relative to a standard (usually glucose or white bread). Over the past two decades, the GI concept has been subjected to extensive research confirming its reproducibility, application to mixed meals, and clinical usefulness in the treatment of diabetes and hyperlipidemia. More than 600 individual foods have been tested for their GI. Concerns about using high-carbohydrate diets in diabetes (because of adverse effects on triglycerides [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][TG] and high-density lipoprotein cholesterol [HDL] levels) are overcome by recommending low-GI instead of high-GI carbohydrate foods.
The GI concept has been widely adopted in diabetes management in Australia, New Zealand, Canada, the United Kingdom, and France. Dietitians at the International Diabetes Institute in Melbourne, Australia, headed by Professor Paul Zimmet, were among the first to take GI from theory to practice. The GI remains controversial in the United States, where it is perceived as too complex for health professionals as well as for ordinary people or simply not worth the trouble. Inexplicably, food exchanges and carbohydrate counting are regarded as less complicated.
The average American diet has a high GI, and the adoption of a low-GI diet will entail some adjustments, but our experience suggests that this is not difficult and may be facilitated by simple “take home” messages.
Contrary to popular belief, low-GI foods are not the same as foods based on high complex carbohydrate and fiber, nor are high GI foods those based on simple sugars. The foods that produce the highest glycemic responses include many of the starchy foods consumed by people in industrialized countries, including bread, breakfast cereals, and potatoes, whether high or low in fiber. This is because the starch is fully gelatinized and can be rapidly digested and absorbed.
The foods with the lowest GI values include pasta, relatively unprocessed cereal foods, baked beans, dairy products, and many types of fruit and vegetables. Sugary foods often cause lower levels of glycemia per gram of carbohydrate than the common starchy staples of western diets. This is because up to half of the weight of carbohydrate is fructose, a sugar that has little effect on glycemia. In fact, the overall GI of the diet has been shown to have an inverse correlation with total sugars (refined plus naturally occurring) expressed as a proportion of total carbohydrate.[This does not mean that sugar is good for you, just that not all sugars are created equal. Further, some grains (e.g. refined bread) is higher on the glycemic index.
How quickly do foods raise your blood sugar?
The glycemic index measures how fast a food is likely to raise your blood sugar and can be helpful for managing blood sugars. For example, if your blood sugar is low and continuing to drop during exercise, you would prefer to eat a carb that will raise your blood sugar quickly. On the other hand, if you would like to keep your blood sugar from dropping during a few hours of mild activity, you may prefer to eat a carb that has a lower glycemic index and longer action time. If your blood sugar tends to spike after breakfast, you may want to select a cereal that has a lower glycemic index. Better yet, eat some fruit and/or vegetables.
The numbers on the attached Glycemic Index Chart give that food’s glycemic index based on glucose, which is one of the fastest carbohydrates available. Glucose is given an arbitrary value of 100 and other carbs are given a number relative to glucose. Faster carbs (higher numbers) are great for raising low blood sugars and for covering brief periods of intense exercise. Slower carbs (lower numbers) are helpful for preventing overnight drops in the blood sugar and for long periods of exercise.
Reminder: Our bodies have to work hard to digest food. Calorie restriction is good for our health and our body systems. Calorie restriction is also the only proven anti-aging practice in that it has been shown to increase life span as well as quality of life.
If you have any questions about the glycemic index or sugar convention, please email your question or questions to firstname.lastname@example.org.
By NBH, Director of Education & Research
NBH Lifetime Health Weight Loss & Hormone Clinics, Medline South