Glycaemic Index

Glycaemic index or GI is a ranking of carbohydrate in food and how it affects blood glucose levels. Low GI diets are growing in popularity since eating low GI foods can help to keep blood sugar levels steady and provide sustained energy.

What is GI?

Carbohydrates are an essential part of our diets, providing the main fuel for our brain and the preferred source of fuel for our muscles during exercise.  The GI is a measure of the rate at which we break down carbohydrates in food.  When carbohydrates are metabolised they release glucose into the blood and it is the speed and rate of this, which determines the GI value.

Glucose has a GI value of 100 and is the reference point at which all other GI values are measured against.

Several factors influence how quickly a carbohydrate food raises blood glucose levels.  Processing, refining and cooking food makes the carbohydrate more digestible, and also raises the GI.  High-fibre and natural wholefoods (whole grain or whole wheat) take longer to digest so have a lower GI. These foods raise the blood sugar level slowly, making them the best choice for people with diabetes and those seeking to manage their weight and improve their overall health.

How does it work?

High GI foods cause a rapid rise in blood glucose that triggers a rush of insulin.  The insulin removes surplus glucose from the blood but the rush in insulin also causes you to feel lethargic and crave more sugar.  And so the cycle continues!

Eating low GI foods causes a steady rise in blood glucose which in turn leads to a gentle rise in insulin. Small increases in insulin keep you feeling fuller for longer, energized and also encourages the body to burn fat.

Diabetes and GI

Understanding how different types of carbohydrate affect blood sugar levels is particularly important for people with diabetes. Some scientific studies have shown that meals containing low GI foods are helpful for managing diabetes by improving both blood-sugar levels and the rate of fat metabolism. Studies have also identified that diets favouring low GI foods are an important factor in preventing the onset of Type II diabetes.

How do I follow a low GI diet?

- Replace highly refined carbohydrates such as white bread, sweet treats, highly processed cereals, mashed potatoes and white rice with less processed carbohydrates like wholemeal bread, wholemeal pasta, brown rice, beans, lentils and fruit & vegetables

- Combine carbohydrate rich meals with protein such as meat, fish and dairy

- Keep the skins on fruits & vegetales to increase the fibre content

- Snack on nuts & seeds rather than sweet treats

You don't have to completely cut out high GI foods, just combine them with low GI foods to achieve a moderate GI meal


Low GI breakfast ideas

  • Add sliced fruit, nuts & seeds to wholegrain, fibre rich cereal
  • Smoothie made from semi-skimmed milk, yogurt and banana
  • Fresh fruit salad with natural low fat yogurt
  • Porridge with raisins
  • Mixed grain bread topped with avocado and pumpkin seeds

Low GI lunch ideas

  • Wholemeal pitta bread with houmous and tomatoes
  • Mixed bean & tomato soup
  • Salad Nicoise - salad, tuna, new potatoes, egg
  • Scrambled egg and smoked salmon on wholemeal toast

Low GI dinner ideas

  • Spaghetti Bolognese served with a green salad
  • Stir-fried chicken breast with mixed green vegetables and noodles
  • Grilled steak with new potatoes, sweetcorn and peas
  • Spicy dahl with basmati rice and yogurt & mint dressing
  • Grilled fish served with sweet potato chips and pea puree

Lower GI recipes

Try these delicious recipes containing low GI ingredients

Find GI values of common foods at (this link opens a new window).