Healthy eating is difficult to achieve because we have so many health factors to consider and food choices to make. We know antioxidants are good for us so we want to eat lots of colorful fruits and vegetables because they contain phytochemicals like carotenoids and flavonoids which neutralize the free radicals that cause the age-related degenerative diseases. We know that we may not get all the antioxidants that we need in our food so we take supplements to ensure an adequate supply of antioxidants. But what about the actual food we eat. One of the major problems with our modern diet is that the food we eat is a tasty combination of saturated fats and highly processed and quickly digested carbohydrates. However in the last several years, people have become so concerned about fats in their diet that they have substituted carbohydrates and avoided even the good unsaturated fats in lean meat, olive oil and other plant oils.
Now everybody seems to be eating a medium- to high-carbohydrate diet without giving proper attention to the type of carbs that they eat. Not all carbohydrates behave the same in our bodies. We have been told for years to avoid simple carbs like honey and white bread and eat complex carbohydrates that our body doesn’t digest and turn to glucose as quickly. However determining whether a food containing carbohydrates is absorbed and raises our blood sugar quickly or slowly is not at all intuitive. Scientists have done a lot of rigorous testing over the past several years and have found that white bread and baked potatoes raise our blood sugar level much faster than honey, jams and chocolate bars.
These scientists developed a numerical index called the Glycemic Index or GI to compare the ability of different carbohydrate containing foods to raise the body’s blood sugar levels – or in other words the speed of conversion to glucose. GI values are determined by feeding human subjects who have fasted overnight a fixed amount of the food and then measuring their blood glucose levels at fixed intervals of time. Pure glucose is set at 100 and then other foods are compared to this profile. Testing is time consuming and the tests have to be averaged for a number of individuals. However these studies have yielded some surprising results such as the fact that the starches in rice, bread, potatoes and many types of cereals were absorbed and raised blood sugars very quickly but the sugars in fruit, candy, chocolate and ice cream did not result in prolonged rises in blood sugars. In other words many of the starchy foods had a much higher Glycemic Index than many of the sugary foods. Needless to say these results seem counter intuitive and have caused a lot of controversy in the food industry. The rate of absorption is very dependant on how the carbs are bound up with the food fiber and the particle size. For example less gelatinized products like al dente spaghetti and oatmeal have lower GI values and stone ground flours have lower GI values than finely ground flours. The fibrous coat surrounding beans and seeds stop enzymes from getting at the starchy carbs inside and will slow the digestion of grainy breads, legumes and barley.
The acidity of foods also slows down digestion and vinegar, lemon juice, pickles and sourdough bread will result in lower GI meal values. The Glycemic Index is important not only to diabetics but also to non-diabetics because we need to know what foods will keep our blood sugars on an even keel and not raise them too high and then have them plummet down again causing hunger. The slow digestion of low GI foods and the gradual rise and fall in blood-glucose response helps people with diabetes control their blood sugar levels and increase their sensitivity to insulin. Low GI foods will help healthy people delay hunger pangs and promote weight loss in overweight individuals. In addition low GI carbohydrates can reduce blood cholesterol levels and also reduce our risk of heart disease. High blood glucose spikes can result in oxidative stress leading to the formation of plaque that can cause atherosclerosis and even blood clots. So keeping our blood sugar levels fairly level and low seems like what we should be trying to achieve through healthy eating. How do we go about achieving this? The first step is to look at what carbohydrates we are consuming and the GI levels of the meals that we are eating. Then we should try and ensure we have at least one low GI food in each meal to keep the overall meal GI close to 50. Most fats and proteins have no effect on the GI level of our meal because they don’t contain carbs.
However watch out for saturated fats and too many calories. Let’s look at some meals and see what substitutions we could make. The GI values are shown in brackets. Breakfast Cut back on Corn Flakes (92), Rice Krispies (82) and substitute All-Bran (32) or switch to a cereal based on oats, barley or bran. Stop eating white bagels (72), white bread (70) or whole-wheat bread (77) and switch to pumpernickel (50) or sourdough (55). Fruits are mostly low GI foods and surprisingly orange juice (46) is very good. Lunch and Dinner Eat your colored vegetables and make your salad dressings with olive oil and vinegar. Avoid parsnips (97) and substitute pastas like al dente white spaghetti (38), linguini (46) or macaroni (47) for Instant white rice (87) and potatoes – baked (85), red-skin peeled and boiled (88). Except for parsnips and potatoes most vegetables have a low GI value. Additional information on GI values can be found at the University of Sydney website http://www.
glycemicindex.com/ or in the “The New Glucose Revolution: Shopper’s Guide to GI Values 2006.