Abstract:
Dietary glycemic load, the mathematical product of the glycemic index (GI) of a food and its
carbohydrate content, has been proposed as an indicator of the glucose response and insulin demand induced by
a serving of food. To validate this concept in vivo, we tested the hypotheses that 1) portions of different foods with
the same glycemic load produce similar glycemic responses; and 2) stepwise increases in glycemic load for a range
of foods produce proportional increases in glycemia and insulinemia. In the first study, 10 healthy subjects
consumed 10 different foods in random order in amounts calculated to have the same glycemic load as one slice
of white bread. Capillary blood samples were taken at regular intervals over the next 2 h. The glycemic response
as determined by area under the curve was not different from that of white bread for nine foods. However, lentils
produced lower than predicted responses (P < 0.05). In the second study, another group of subjects was tested
to determine the effects of increasing glycemic load using a balanced 5 x 5 Greco-Latin square design balanced
for four variables: subject, dose, food and order. Two sets of five foods were consumed at five different glycemic
loads (doses) equivalent to one, two, three, four and six slices of bread. Stepwise increases in glycemic load
produced significant and predictable increases in both glycemia (P < 0.001) and insulinernia (P < 0.001). These
findings support the concept of dietary glycemic load as a measure of overall glycemic response and insulin
demand.
