Glycaemic index, glycaemic load, carbohydrate counting and artificial sweeteners
GI shows how fast a food raises blood sugar; GL adds how much carbohydrate a serving holds. Carbohydrate counting and sweeteners help diabetics plan meals and insulin.
GI vs GL
GI values change with variety, ripeness and cooking, so use them to compare foods, not as exact numbers.
What changes GI, with Indian examples
| Factor | Effect | Example |
|---|---|---|
| Type of starch | More amylose, lower GI | Parboiled rice tends to have a lower GI than polished raw rice |
| Processing and cooking | Grinding, flaking, puffing and overcooking raise GI | Puffed rice and cornflakes are high; whole grains and dalia are lower |
| Fibre | Soluble fibre lowers GI | Oats, barley, pulses, methi seeds |
| Fat, protein and acid in the meal | Slow stomach emptying, lower GI | Rice with dal and curd raises sugar less than plain rice |
| Ripeness | Riper fruit, higher GI | Ripe banana is higher than a firm one |
| Cooling cooked starch | Forms resistant starch, lowers GI a little | Cooled rice in curd rice |
| Low-GI foods | Raise blood sugar slowly | Most pulses (rajma, chana, moong), milk, curd, apple, orange, guava, barley |
| High-GI foods | Raise blood sugar fast | Glucose, white bread, cornflakes, puffed rice, mashed potato, many polished rice varieties |
Worked example 1: glycaemic load
Watermelon has a high GI (about 72 in the international GI tables), but a 120 g serving has only about 6 g carbohydrate. Cooked white rice has a GI of about 73, and a 150 g serving has about 42 g carbohydrate. Find the GL of each.
- Watermelon: GL = 72 × 6 ÷ 100 = 432 ÷ 100 = 4.3 (low).
- White rice: GL = 73 × 42 ÷ 100 = 3,066 ÷ 100 = 30.7 (high).
- Both foods have almost the same GI, but the rice serving carries seven times more carbohydrate.
Watermelon GL about 4 (low); white rice GL about 31 (high). Portion size matters as much as GI.
Worked example 2: carbohydrate counting
A type 1 diabetic on rapid-acting insulin eats 2 phulkas (30 g atta each), 1 bowl dal (30 g raw), 100 g vegetables and 100 mL curd. Count the carbohydrate and carb choices. Use the exchange values: cereal 20 g, pulse 18 g, vegetable 5 g, curd 5 g carbohydrate.
- Phulkas: 2 × 20 g = 40 g.
- Dal: 18 g. Vegetables: 5 g. Curd: 5 g.
- Total = 40 + 18 + 5 + 5 = 68 g carbohydrate.
- Carb choices = 68 ÷ 15 = 4.5, about 4½ choices.
- Record the count: the doctor uses it, with the patient's own insulin-to-carbohydrate ratio, to set the meal-time insulin. The dietitian counts; the doctor decides the dose.
68 g carbohydrate, about 4½ carb choices. The doctor uses this count to set the meal-time insulin.
Artificial (non-nutritive) sweeteners
| Sweetener | Sweetness vs sugar | Energy | Notes |
|---|---|---|---|
| Saccharin | About 300-500 times | None | Heat-stable; bitter aftertaste; ADI 5 mg/kg body weight |
| Aspartame | About 200 times | 4 kcal/g, but used in tiny amounts | Loses sweetness on heating; contains phenylalanine, so labelled for people with phenylketonuria (PKU); ADI 40 mg/kg; IARC (2023) called it possibly carcinogenic but JECFA kept the ADI |
| Acesulfame-K | About 200 times | None | Heat-stable; often blended with aspartame; ADI 15 mg/kg |
| Sucralose | About 600 times | None | Made from sugar; heat-stable, used in cooking and baking; ADI 15 mg/kg |
| Steviol glycosides (stevia) | About 200-300 times | None | From the stevia plant; heat-stable; ADI 4 mg/kg (as steviol) |
| Sugar alcohols (sorbitol, mannitol, xylitol) | Half to equal | About 1.6-2.6 kcal/g | In sugar-free sweets and gum; excess causes gas and diarrhoea |
In the diabetes clinic, teach swaps by GL, not just GI: a small serving of watermelon is fine, a large plate of white rice is not. Sweeteners can replace sugar in tea, but WHO (2023) does not advise them for weight loss, and they do not make sweets or bakery items safe.
2 marks: “Define glycaemic index.” The blood-glucose rise over 2 hours after a food with 50 g available carbohydrate, compared with 50 g glucose (GI 100). Low 55 or less; high 70 or more.
5 marks: “Write a note on artificial sweeteners.” Define, then saccharin, aspartame, acesulfame-K, sucralose, stevia and sugar alcohols with sweetness, energy, heat stability, ADI, PKU warning and WHO 2023 advice.
10 marks: “Explain glycaemic index, glycaemic load and carbohydrate counting in the management of diabetes.” Define GI and GL with cut-offs and formula, factors affecting GI with Indian foods, a GL calculation, carb choices with an example, and how the doctor matches insulin to the count.
GI is speed, GL is speed × amount. Cut-offs 55 and 70 for GI, 10 and 20 for GL. One carb choice = 15 g.