Thursday, November 8, 2012

Eating Right (Part 9)


GI Index


Foods with a high glycemic index (GI) contain carbohydrates that will dramatically raise your blood-glucose levels, while a low GI food will raise it much less.

The substance that produces one of the greatest effects on blood-glucose is glucose itself. Thus the glycemic index of pure glucose is set at 100, and every other food is ranked on a scale from 0 to 100 according to the actual effect on blood-glucose levels.


Testing:
  1. An amount of food containing an equivalent amount of carbohydrates (25 or 50 mg) is given to a volunteer.
  2. Over the next 2 hours blood is taken every 15 min to measure the blood glucose of these samples.
  3. The volunteer’s response to the food (spaghetti is used below) is compared with his or her own response to 50 mg of pure glucose.
  4. The average GI value found in 8-10 people is the GI value of the food.


Figure. Measuring the glycemic index value of a food

Hence GI of spaghetti is 41


Source: Brand-Miller, J et al. The New Glucose Revolution




Here are some of the GI indices of some foods. To find out more about GI Index I recommend The New Glucose Revolution by Jennie Brand-Miller et al.

G.I. RANGES: The figures form a continuum but in general:
LOW G.I.  FOODS                                 below 55
INTERMEDIATE G.I. FOODS         between 55 and 70
HIGH G.I. FOODS                                 more than 70






Jasmine rice sweeter than sugar ie >100 (GI of sugar is 100)


Wholemeal bread is made from highly refined wholemeal flour and hence high GI