The digestive tract is emptied relatively rapidly, which causes hunger sensations to occur again soon after eating. If this large quantity of glucose in the blood is not effectively transformed into energy in the body cells, the circulating blood glucose levels remain high because of the absence of insulin or, as in the case of insulin resistance, this glucose is stored as fat in the body.
Carbohydrate-rich foods are divided into items with a low GI (55 or less), an intermediate GI (56 to 70) or a high GI (more than 70). From a practical point of view, carbohydrate-rich foods with a GI of up to 62 are regarded as foods with an acceptably “low GI”, based on the assumption that when they are combined with the other foods in a meal, they will be digested and absorbed at a slower rate.
In addition to better blood glucose control, a low GI diet also has other advantages. It protects against the development of obesity, and colon, prostate, ovarian and breast cancer.
Factors that influence the GI of foods
The following factors influence the digestion and absorption of carbohydrates, as well as the blood glucose level:
Cooking and gelatinisation of starch
When starch is cooked in the presence of water and heat, it causes swelling and gelatinisation of the starch granules (grains). This gelatinised starch contributes to faster and easier digestion by the enzymes in the digestive tract and this can then result in a higher GI.
Cooling and retrogradation of starch
Starchy foods that are cooked with moist heat, such as potatoes and maize (mealie) meal porridge, are more difficult to digest after they have cooled down, as a result of retrogradation of the starch. This starch resists rapid digestion and therefore contributes to a lower GI.
Types of fibre and fibre content
Water-soluble fibre (as in cooked dry beans, lentils, chickpeas, soya, etc.) lowers the GI because it delays the emptying of the stomach, while water-insoluble fibre (such as digestive bran) only lowers the GI when the food contains large quantities of this fibre.
Sugars
Not all sugars are absorbed at the same rate. Glucose is absorbed very rapidly and has a high GI (100), while fructose (fruit sugar) is absorbed more slowly and consequently has a low GI (23). Sucrose (cane or table sugar) is a mixture of glucose and fructose and has an intermediate GI (65). The addition of these sugars to starches with a higher GI can contribute to lowering the GI of the dish.(As a matter of interest, the GI of wheat flour is 70.)
Organic acids and fermented foods
Organic acids such as lemon juice and vinegar, as well as fermented foods like traditional fermented porridge (suurpap), lower the GI. By adding an acidic salad dressing and/or vinegar to salads, you can lower the GI of not only the dish, but the entire meal.
Where does sugar fit into the diabetic diet?
Cane/table sugar (sucrose) has an intermediate GI, which means that a diabetic does not need to totally avoid sugar, because a small amount will not cause the blood sugar to rise drastically. However, the concept of “less sugar” can be very misleading. From a more scientific point of view, it is recommended that not more than 10% of the total carbohydrates in your diet should be derived from sugar and sugar products.
A more practical guideline is that you should not consume more than 10 ml sugar per meal, that it must be part of a mixed meal and that it must be eaten with fibre. It is important to keep in mind that each teaspoon of sugar contributes both to your carbohydrate and kilojoule intakes of the day, but that it does not make any other contribution to your nutrient intake – such as fibre, minerals or vitamins.
Tips to reduce your sugar intake
•Learn to gradually use less sugar so that you lose your craving for sweet foods.
•Read the labels of products. Food legislation determines that the ingredients in a product must appear in descending order on the ingredients list. If an ingredient such as sugar appears at the end of the list, this probably means that the product contains only an insignificant amount of sugar.
•Avoid sugar in drinks such as tea, coffee and cold drinks.
•Avoid fruit that has been canned in sugar syrup. Rather choose fruit canned in fruit juice or artificially sweetened canned fruit.
•Clean, safe water should be your first choice to quench your thirst. You can also drink soda water and artificially sweetened cold drinks.
•Use low-kilojoule jelly.
•Enjoy a scraping of jam or honey on wholewheat or rye bread. There are a variety of jams on the market that are artificially sweetened or sweetened with fructose or which contain less sugar. Always keep your portion size small and rather store this type of jam in the fridge after opening it, to increase its shelf life. Also refer to the notes about fructose.
•Choose recipes with the least sugar, fructose or honey. In some recipes sugar can be replaced with fresh fruit, dried fruit, fruit purée, fruit juice or vegetables such as carrots, beetroot or pumpkin.
•Be aware of the sugar content of yoghurt and choose low-fat or fat-free, artificially sweetened yoghurt.
•Replace sugar in dishes with artificial sweetener or sugar substitutes in limited quantities.
Artificial sweeteners and sugar substitutes
Artificial sweeteners
Every so often a story does the rounds about how dangerous the prolonged use of certain artificial sweeteners can be. These findings are usually based on single cases and they are often not thoroughly investigated by means of additional research. In general, the consequences of obesity are regarded as a greater health risk than the possible negative effects of artificial sweeteners. It is, however, important to keep the use of these products to a minimum.
In my practice we use the guideline of not using more than eight to ten pills of artificial sweetener (which equals eight to ten teaspoons of sugar) a day. Heat (such as the boiling water you add to instant coffee), reduces the sweetness of sweetener pills. Test the sweetness of your tea or coffee by only adding the artificial sweetener when the beverage has reached drinking temperature. Artificially sweetened cold drink is also limited to not more than 500 ml per day.
Some artificial sweeteners consist of a combination of sweeteners, while others contain a filler, such as lactose or dextrose, which does provide some kilojoules and can have an effect on the blood glucose level. Read the labels of the products to obtain the necessary information. The brand names, contents of the products and combination of sweeteners change from time to time and new research results will appear in the lifetime of this cookbook. Where possible, I have indicated the amount of cane or table sugar in a recipe to enable you to work out a ratio to the sweetener of your choice.
Non-nutritive or artificial sweeteners include acesulfame-K, aspartame, sucralose, saccharin and cyclamate. These sweeteners do not contain any energy (kilojoules) and are very sweet even in small quantities. In pill form they often lose their taste when heated and in some cases they can cause a bitter taste in baked goods and cooked dishes. Sucralose is one of the sweeteners that is heat stable in any form.
Liquid sweeteners and some of the newer types of powder sweeteners are recommended for baking because they do not undergo taste chances during heating.
