All you need to know about GI

Learn about the Glycaemic Index: what is is; why it matters and how healthy it is to follow…

All you need to know about GI

What is the Glycaemic Index (GI)?

It’s a ranking of carbohydrate foods based on the speed at which they effect blood sugar levels. Low-GI foods release sugar into the bloodstream slowly and steadily, while high-GI foods are absorbed quickly, rapidly raising blood sugar levels. Low/medium-GI foods include

seeded bread




basmati rice


beans and pulses



, fruit and vegetables, while those with a high GI include white bread and white rice, cornflakes, cakes, biscuits and baked potatoes.

Why does GI matter?

Low-GI diets help people with diabetes keep their blood sugar levels stable and may also help boost levels of HDL or ‘good’ cholesterol. And because they help you feel full for longer, low-GI foods may also aid appetite control.

Does anything else affect GI?

As with most things diet-related, it’s a complex issue. Although GI ratings apply only to carbohydrates, combining carbs with protein or fat can lower the GI. Many things can influence a food’s GI, from the way you cook it to its ripeness – especially with fruit.

So is it healthiest to eat mainly low-GI foods?

Yet again, it’s not as simple as that. Because fat lowers GI, some less healthy foods actually have a lower GI than healthier ones – for instance, chips have a lower GI than plain boiled potatoes. But no one would recommend chips as part of your everyday, balanced diet. At the same time, some vitamin-rich foods, such as watermelon, have a surprisingly high GI. But you’d need to eat a lot of it to have an effect. “Instead of focusing on GI, think about what you’re eating overall,” says Dr Elisabeth Weichselbaum of the British Nutrition Foundation. “Go for a healthy balanced diet and you can’t go wrong.”

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