What is the Glycemic index? It is a numerical measure of the rate i.e. how fast and to what extent the intake of carbohydrate rich foods may affect your blood sugar levels. A food with a high GI raises blood sugar levels
more than a food with a medium or low GI. Glucose has been given a numerical value of 100, because it is absorbed immediately into the bloodstream and all carbohydrate containing food such as fruit are compared to glucose, which is used as a reference.
Factors affecting the absorption and digestion of fruit, which in turn may influence the GI of foods include:
- The amount of cooking (cooked apple versus raw apple); processing
(fruit versus fruit juice); ripeness and storage time — the more ripe a fruit the higher the GI; the type of fibre (soluble – citrus fruits); the more acid a food is, the lower the GI value. E.g. lemon juice lowers the GI of the food or meal, the presence of fat, protein or low GI foods consumed with the fruit. The GI of a fruit is different when eaten alone than it is when combined with other foods. When eating a higher GI fruit, you can combine it with other low GI foods or protein and fat to balance out the effect on blood glucose levels. E.g. eating a fruit salad and yoghurt; and portion sizes are still relevant for managing blood glucose.
The low GI index fruits fall below the reference range of 40 (<40) and are given the green to go! Whereas Intermediate GI Fruits fall within the reference range of 56-69 and get the orange for slow down and proceed with caution; and the high GI fruits with a reference range of above 70 (70+) get the red for halt – unless portion control is noted strictly or these frutis are eaten in combination with proteins or other low GI foods.
|FOOD||GLYCEMIC INDEX (glucose=100)||Serving size in gram|
|Peach, canned in light syrup||40||120|
The table above shows the average GI of fruits commonly eaten.
A word on Acidity…
The more acid the fruit is, does not necessarily mean it is also acid forming. Most fruits such as apple, banana, grape juice, grapes, raisins, apricots, berries, cantaloupe, melon, lemon, orange, peach, pear, watermelon are potassium-and bicarbonate-rich and therefore are alkaline forming and thus have become part of the “so called” Alkaline diet. This diet claims to help combat the acidic environment, the Westernised lifestyle (high in sugar, dairy, gluten, creates, alcohol, caffeine, and animal meats) creates.
Taking a closer look at pH, pH level measures how acid or alkaline something is. A pH of 0 is totally acidic, while a pH of 14 is completely alkaline. A pH of 7 is neutral. Those levels vary throughout your body. Your blood is slightly alkaline, with a pH between 7.35 and 7.45; and your stomach is very acidic, with a pH of 3.5 or below, so it can break down the food. Your urine pH levels change, depending on what you eat. An example of this is seen in a high-protein, low carbohydrate diet, which may lead to a high acid load, which has a small effect on blood pH, but a larger effect on urine pH levels.
For additional information regarding GI of fruit or foods, or before starting the alkaline diet consult your dietitian.