Carbohydrates & blood sugar: it’s not the amount alone

Of all nutrients, carbohydrates raise blood sugar the most, they’re broken down into glucose that passes into the blood. So it helps to understand which carbohydrates act how.

The three basic types

Traditionally we distinguish simple carbohydrates (sugars, e.g. in sweets, but also in fruit and milk), complex carbohydrates (starch, e.g. in grains, potatoes, legumes) and fibre.¹ Simple sugars are usually absorbed quickly, starch more slowly, and fibre delivers barely any glucose to the blood.¹

Glycaemic index and glycaemic load

The glycaemic index (GI) ranks foods by how fast they raise blood sugar. The glycaemic load (GL) is more meaningful because it also accounts for how many carbohydrates a normal portion contains.²³

The classic example is watermelon: high GI but low GL, because a normal portion contains few carbohydrates.³ A low GL is 10 or below, medium 11–19, high from 20.

What counts in practice

The blood-sugar effect depends not only on the carbohydrate but on its companions: fibre, protein and fat slow absorption. A lower-carb or higher-fibre combination lowers the spike – shown in several intervention studies.⁴ In practice: more wholegrain, legumes, vegetables and fruit with skin; less refined sugar, white flour and white rice.²

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