Glykemický index - GI

• Way to measure the quality of a carbohydrate
• Represents the area under the curve produced when:
• 50 g of the carbohydrate is eaten by an individual
• Regularly measure the blood sugar over a period of 2 hours
• Glucose produces a curve with the greatest area
• It is assigned the value of 100
• All other carbohydrates are then compared with this value [1]

Stanovení GI

• 50 g of carbohydrate from oat flakes
• The area under the oat flakes curve is only 40% of the area under the glucose curve
• Oat flakes have a glycemic index of 40 [1]

Co srovnává GI

• 50 g of glucose are being compared to 50 g of carbohydrate from oat flakes
• And NOT with 50 g of oat flakes !!! [1]

Kritika GI

• The glycemic index did not prove suitable for providing nutritional recommendations
• Entirely different portions were being compared !!! [1]

Příklad

• White bread and watermelon have an almost identical glycemic index
• In order to obtain 50 g of carbohydrate from white bread
• Eat 111 g of white bread
• To obtain 50 g of carbohydrate from watermelon
• Eat 1 kg of watermelon [1]

• Because of this a new measurement was introduced: glycemic load - GL [1]

Study by Prof. David Ludwig

• Two groups of rats
• The same weight
• Over 18 weeks
• Same amounts of calories, carbohydrate (69%), protein (20%) and fat (11%)
• Two groups:
• 1) carbohydrates with a high glycemic index (100% amylopectin)
• Počáteční váha 548 g
• 2) carbohydrates with a low glycemic index (40% amylopectin and 60% amylose)
• Počáteční váha 549 g [1]

Výsledky:

• Difference in fat content 71%
• Weight difference was only 8%

1)

• After 8 weeks gained so much fat that the investigator lowered the calories for this group by 5%
• Final weight at the end of the study of 450 g
• 97.8 g of fat [1]
• Had greater increases over time in the areas under the curve for blood glucose and plasma insulin after oral glucose [2]
• Lower plasma adiponectin concentrations [2]
• Higher plasma triglyceride concentrations [2]
• Severe disruption of islet-cell architectur [2]
• Had almost twice the body fat of those on the low-GI diet after 9 weeks [2]

2)

• Final weight of 491 g
• 57.3 g of fat [1]

Závěr:

• The rats were not fat from consuming too many calories, but from eating carbohydrates with an excessively high glycemic index. [1]
• The first group moved about significantly less than the second group, which can be explained by the higher insulin level in the first group resulting in lower production of the movement-stimulating protein, Foxa 2. [1]

Literatura: