- Potatoes aren’t all created equal. Most are high GI, with some such as desiree and mashed pontiac right up near the top of the GI scale. But other varieties such as nadine, as well as new potatoes boiled in their jackets, are almost down in the medium range.
- Nicola potatoes, now fairly widely available, are a good alternative with a GI of only 58 (medium range).
When starchy foods are cooked, the starch grains absorb water – the more they absorb, the easier the body finds it to get to the starch, and the higher the GI. So while most pasta falls into the low GI category, al dente pasta is even lower.
Different varieties of rice contain different types of starch, which is why jasmine rice is very high GI, while basmati and other rices high in amylose starch are medium.
Breads are mostly high. In both regular white and wholemeal breads, the grains are ground and the outer coating of the grain is broken, so digestive enzymes can get to the starch easily. Very grainy multigrain bread and sourdough are lower – it’s the acidity of traditional sourdough bread that results in lower GI. You can also buy specially developed low-GI white breads.
Most vegetables don’t contain much carbohydrate, so their GI is negligible. The exceptions are starchy vegetables such as potatoes, carrots, parsnips, sweet potato, pumpkin and corn. The old furphy that carrots (GI 42, not 92 as previously thought) have a higher GI than a Mars Bar (62) is demonstrably wrong.
At 65, sugar is actually only medium GI. This is because each molecule of table sugar (sucrose) is made up of one molecule of glucose (which contributes to the GI) and one of fructose. The fructose heads straight to your liver for burning and doesn’t change your blood sugar level. Even though many sugary foods have a moderate or even low GI, it doesn’t mean they are the best diet choices – sugar adds kilojoules but no valuable nutrients.
Fresh fruit is generally low GI, although a few such as cherries, apricots, pineapple and rockmelon are medium range. The notable exception is watermelon, which has a high value of 76. Dried fruits are mainly low or medium.
Roll over the "Low", "Medium" and "High" tabs along the bottom of the graphic below to see the GI for your favourite foods.