About the Glycemic Index

glycemic index

  • The glycemic index (GI) is a ranking of carbohydrates on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating.
  • Foods with a high GI are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels.
  • Low-GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels, and have proven benefits for health.
  • Low GI diets have been shown to improve both glucose and lipid levels in people with diabetes (type 1 and type 2). They have benefits for weight control because they help control appetite and delay hunger.

PDF Download a Table of Glycemic Index and Load Values

Low GI diets also reduce insulin levels and insulin resistance making the body more insulin sensitive.
Recent studies from Harvard School of Public Health indicate that the risks of diseases such as type 2 diabetes and coronary heart disease are strongly related to the GI of the overall diet.

In 1999, the World Health Organization (WHO) and Food and Agriculture Organization (FAO) recommended that people in industrialized countries base their diets on low-GI foods in order to prevent the most common diseases of affluence, such as coronary heart disease, diabetes and obesity.

High GI vs Low GI Foods

What is the GI?

Carbohydrates are one of the best sources of energy for our bodies. The simplest form of carbohydrate is glucose, which is:

  • A universal fuel for most organs and tissues in our bodies.
  • The only fuel source for our brains, red blood cells and a growing fetus, and is
  • The main source of energy for our muscles during strenuous exercise.

GI ChartSurprisingly, most of us don’t eat too much carbohydrate, but all too often we eat the wrong kind, because not all carbohydrates are created equal. This is where the glycemic index or GI comes in. It’s about recognizing the ‘smart carbs’ – the low GI ones – and making sure we include them in our main meals and snacks.

The GI is simply a dietary tool that helps us differentiate between the various carbohydrate foods we eat and how our bodies use them.

  • Carbohydrates with a low GI (55 or less) don’t make our blood glucose levels rise very high for very long. They provide sustained energy.
  • Carbohydrates with a high GI (70 or more) are the ones that cause our blood glucose levels to go higher for longer. High blood glucose may cause damage to vital organs.

change in blood glucose

Good sources of carbohydrate

good carbs
Carbohydrate foods come mainly from plants – cereal grains, legumes, fruit and starchy vegetables. Some dairy foods like milk and yogurt also contain carbohydrate.

Common sources of carbohydrate include:

  • Whole wheat bread
  • Breakfast cereals
  • Brown rice
  • Whole wheat pasta
  • Noodles
  • Fruits and their juices such as apples, pears, oranges, plums, peaches and nectarines, berries and bananas
  • Starchy vegetables such as potatoes, sweet potatoes, yams, taro, sweet corn, parsnips, pumpkin and carrots
  • Legumes (pulses) such as beans, chickpeas, lentils and split peas
  • Dairy foods like milk, yogurt, ice cream and their alternatives
  • Sugars, honey and confectionery
  • Starchy snack foods like potato and corn chips

The health benefits of low GI eating

The scientific evidence supports healthy low Glycemic Index diets:

  • Help to fill you up and keep you feeling satisfied for longer, avoiding over eating or too much snacking.
  • Lower your insulin levels which makes fat easier to burn and less likely to be stored.
  • Help you to lose body fat and maintain lean muscle tissue.
  • Reduce your triglycerides, total and ‘lousy’ (LDL) cholesterol.
  • Increase your levels of ‘healthy’ (HDL) cholesterol.
  • Reduce your risk of developing type 2 diabetes.
  • Help to manage your blood glucose levels and reduce your risk of developing diabetes complications.
  • Reduce your risk of developing cardiovascular disease.
  • Reduce your risk of developing some cancers
  • Reduce your risk of developing certain eye diseases.
  • Improve your skin
  • Sustain your energy levels longer, improving both mental and physical performance.

Using the GI is easy

It’s all about balance. To achieve any of the health benefits of low Glycemic Index eating, you need to make sure that you include plenty of low GI ‘smart’ carbs as part of a healthy balanced diet.

How to choose low glycemic index smart carbohydrates?

Step 1. Swap high GI foods for low GI ones in the same food group. There are plenty to choose from. The foods you choose should also be low in saturated fat, moderate in sodium (salt) and high in fiber. Foods that meet all of these requirements carry the GI Symbol.

Breakfast, Lunch, and Dinner

Step 2. Consume at least one serving of a low GI carbohydrate food at each meal and choose low GI carbohydrate foods for your snacks.

Step 3. Keep your eyes on that serving size. Be conscious of the quantity of carbohydrates you eat. Eating too much food, even healthy choices, will most likely pile on the pounds/kilos.

An easy way to keep up with your portion sizes is to only use ¼ of your plate for carbohydrate foods.  Save half the plate for non-starchy veggies and the other ¼ of the plate for lean proteins.

And get moving. Make sure you include at least 30-60 minutes of planned exercise like walking, swimming or riding a bike in your daily routine, plus 30 minutes of incidental exercise like using the stairs instead of the lift or going over to talk to a colleague instead of sending an email.

Important highlights of the Glycemic Index (GI)

The GI only applies to carbohydrate-rich foods.

It is not possible to obtain a Glycemic Index value for foods which contain almost no carbohydrate.

Foods with minimal carbohydrates and no glycemic index:

  • important highlights of the glycemic indexMeats
  • Fish
  • Chicken
  • Eggs
  • Cheese
  • Nuts (most nuts)
  • Oils/butter
  • Cream
  • Vegetables(most vegetables)

The GI of a food does not make it good or bad for you. High GI foods such as most potatoes and wholemeal breads still make valuable nutritional contributions to your diet. And low GI foods such as pastry that are high in fat (usually saturated fat) are no better for you because of their low GI. The nutritional benefits of different foods are many and varied, and we suggest you base your diet on a wide variety of foods that are low in salt and saturated fat, high in fiber and have a low GI.

You don’t need to avoid all high GI foods

There is no need to eat only low GI foods. While you will benefit from eating low GI carbs at each meal, this doesn’t have to mean excluding all others. A meal that includes a high GI food such as a typical potato and a low GI food such as sweet corn will result in a lower GI meal overall.

You don’t need to add up the GI each day

The GI value of a food can be altered by the way it is processed or cooked, so we don’t believe it is possible to calculate a precise GI value for recipes or to predict the GI of a menu for the whole day. That’s why we prefer simply to categories foods as low, medium or high GI in most circumstances. We have also seen the benefits people gain by simply substituting high GI foods for low GI foods in their everyday meals and snacks without more complicated dietary changes.

Are foods containing sugar excluded?

Not all sugars are the same. Many foods naturally high in sugars are very nutritious like fruit, milk and yogurt. Unfortunately food labels don’t help you distinguish between the low or high GI sugars or tell you whether the sugars are naturally occurring or added. It’s more useful to focus on a food’s overall GI (rather than the sugars), and if you need to watch your blood glucose levels, also look at total carbohydrate. Therefore nutritious foods high in sugar are not excluded.

10 tips for reducing the GI of your diet

vegetables1. Pile half your dinner plate high with vegetables or salad
Aim to eat at least five serves of vegetables (this doesn’t include the starchy ones like potatoes, sweet potatoes or sweet corn) every day, preferably of three or more different colors.


2. Be wise with your potatoes

potatoesIf you are a big potato eater and can’t bear the thought of giving them up, you don’t have to. Just choose wisely, and be careful with the quantity. Choose one or two medium-sized low GI potatoes such as Carisma, or a lower GI potato such as Nicola or Marfona or have one or two baby new potatoes with a small cob of corn or make a cannellini bean (they are white beans) and potato mash replacing half the potato with cannellini beans. Don’t be afraid of trying other starchy vegetables like sweet potato, yams or taro – steamed, roasted or mashed.

bread3. Swap your bread
Instead of high GI white and wholemeal breads, choose a really grainy bread where you can actually see the grains, granary bread, stone-ground wholemeal bread, real sourdough bread, soy and linseed bread, pumpernickel, fruit loaf or bread made from chickpea or other legume-based flours.

4. Replace those high Glycemic Index crunchy breakfast flakes
These refined breakfast cereals spike your blood glucose and insulin levels. Replace them with smart carbs like natural muesli or traditional (not instant) porridge oats or one of the lower GI processed breakfast cereals that will trickle fuel into your engine.

5. Make your starchy staples the low GI ones
Look for the low GI rice’s, serve your pasta al dente, choose less processed foods such as large flake or rolled oats for porridge or muesli and intact grains such as barley, buckwheat, bulgur, quinoa, whole kernel rye, or whole wheat kernels and opt for lower GI starchy vegetables.

6. Learn to love legumes (pulses)
Include legumes like beans, lentils and chickpeas in your meals two or three times a week, more often if you are vegetarian. Add chickpeas to a stir-fry, red kidney beans to a chili, a 4-bean salad to that barbecue menu, and beans or lentils to a casserole or soup.

7. Develop the art of combining
No need to cut out all high GI carbs delicious classic Italian soup), rice with beans and chili (go Mexican), tabbouli tucked into pita bread (with falafels of course and a dash of hummus), baked beans on toast or piled on a jacket-baked potato for classic comfort food.

8. Incorporate a lean protein source with every meal
Eat lean meat, skinless chicken, fish and seafood, eggs, milk, yoghurt or cheese, or legumes and tofu if you are vegetarian. The protein portion should make up around a quarter of the plate/meal.

9. Tickle your taste buds
Try vinaigrette (using vinegar or lemon juice with a dash of extra virgin olive oil) with salads, yoghurt with cereal, lemon juice on vegetables like asparagus, or sourdough bread. These foods contain acids, which slow stomach emptying and lower your blood glucose response to the carbs in the meal.

10. Go low GI when snacking
If it is healthy and low GI, keep it handy. Grab fresh fruit, dried fruit, or fruit and nut mix, low fat milk and yoghurt (or soy alternatives), fruit bread etc for snacks. Limit (this means don’t buy them every week) high GI refined flour products whether. The trick is to combine them with those low GI ticklers to achieve a moderate overall GI. How? Lentils with rice. (think of that home baked or from the supermarket such as cookies, cakes, pastries, crumpets, crackers, biscuits, irrespective of their fat and sugar content). These really are the ‘keep for the occasional treat’ foods.

Keep your eye on the serve size. Remember portion caution with carb-rich foods such as rice, al dente pasta and noodles, potatoes etc. Eating a huge amount of these foods, even of the low GI variety, will have a marked effect on your blood glucose. A cup of cooked noodles or al dente pasta or rice plus plenty of mixed non-starchy vegetables and a little lean protein can turn into 3 cups of a very satisfying meal.

How low should you go?

Because a low Glycemic Index food is defined as 55 or less, people have made the reasonable assumption that a whole diet that averages less than 55 is ‘low enough’. In fact the AVERAGE American diet already has a GI of 56 to 58 because we all eat low GI fruits and dairy products and of course table sugar (GI 65). So to reduce the risk of chronic disease, a low GI eating pattern/diet must have a much lower number.

What we now know from research is that the GI of the diet of people in the lowest quintile (20% of the population) is about 45. Since this reduces the risk of chronic diseases like type 2 diabetes and heart disease, and people can achieve it in real life, it’s a reasonable definition of a low GI diet (i.e., 45 or less).

How do you achieve this? Simply substitute high for low GI foods in your everyday meals and snacks. Breakfast in particular is your opportunity to go for low GI ‘Gold’ by selecting a low GI breakfast cereal. Don’t assume that just adding milk makes it a low GI meal!

Making healthy food choices

While most of us know that our health and well being will improve if we eat more nutritious foods, the reality is that a lack of time and busy lifestyles often contribute to poor food choices. Unfortunately, poor food choices are a major cause of overweight/obesity and associated conditions like type 2 diabetes and heart disease.

But working out exactly what you should be eating can be confusing these days with so many product options on the supermarket shelves and brightly colored ‘nutrition’ messages on the packages.

Are foods containing sugar excluded?
No. This is because all sugars are not the same. Many foods naturally high in sugars are very nutritious like fruit, milk and yoghurt.

Unfortunately food labels don’t help you distinguish between the slowly absorbed and the rapidly absorbed sugars or tell you whether the sugars are naturally occurring or added.

It’s more useful to focus on food’s GI, and the amount of total carbohydrate.

Healthy eating

A healthy, balanced diet should be delicious, varied and flexible. The following tips, based on the dietary guidelines/food pyramids from most countries around the world, provide the basis for healthy eating whoever you are and wherever you live.

  • Enjoy a wide variety of nutritious foods
  • Eat plenty of vegetables and fruits
  • Consume only moderate amounts of added sugars and refined starches
  • Eat plenty of legumes (pulses) such as peas, beans, lentils, chickpeas, and split peas
  • Eat plenty of cereal grains including breads, rice’s, pasta and noodles – preferably the wholegrain variety, and choose the low GI options
  • Include lean meats, poultry without skin and fish or appropriate vegetarian protein alternatives. Make sure you eat at least 2 servings of fish a week
  • Include milks, yoghurt’s, cheeses or calcium-enriched soy alternatives; and choose the reduced fat varieties where possible
  • Drink plenty of water
  • Limit saturated fat and moderate your total fat intake
  • Choose foods low in sodium (salt), and try to limit to 1,500mg/day
  • Reduce serving sizes – portion caution is an important part of healthier eating
  • Limit your alcohol intake if you choose to drink alcohol

And make sure you include at least 30 minutes of planned exercise like walking, swimming or riding a bike in your daily routine, plus 30 minutes of incidental activity like using the stairs instead of the lift.

Eat more of the healthy foods (such as fruit and non-starchy vegetables)

vegetablesIt isn’t all about cutting back. Most people don’t eat anywhere near enough fruits and vegetables. Fresh, dried and canned fruits are all suitable, and you  can eat as much as you like of most non-starchy vegetables (leafy greens, carrots, tomatoes, onions, etc).

Modify your carbohydrate intake

This means thinking about carb quality and quantity and getting familiar with the sources and amounts of carbohydrate in your diet. There’s no point buying the ‘99 per cent fat free’ product if it packs in 120 g of high GI carbs per serving. For carb quality, make sure that you are eating the low GI ones as much as possible. As for quantity, 35–45 g of carbohydrate at any one sitting is a good average.  The brain needs about 130g of carbs/day.  Choosing 35-45 per meal and 15g or less per snack (if needed) will get you to that total.  Replacing some carbohydrate in your diet with monounsaturated fat can reduce your post-meal blood glucose levels and lower your triglycerides, but you have to be careful with this. Too much added fat may lead to weight gain. Talk to your dietitian about the proportion of fat to carbohydrate that’s right for you.

Moderate your protein intake

Protein won’t increase your blood glucose level and is valuable for satisfying appetite. The usual recommended protein intake is 15–20 per cent of your total energy intake. Most people in the developed world already eat this amount, so there is no need to eat more. People with kidney disease (about 1 in 3 people with diabetes) should avoid a high protein intake, because research shows that a more moderate intake helps preserve kidney function.

Limit saturated fats and cholesterol

trans fat and cholesterolThis is absolutely essential for everyone with type 2 diabetes or cardiovascular disease. You must get and keep your LDL (bad) cholesterol down. Don’t obsessively avoid high cholesterol eggs and prawns. It’s the saturated fats in those lamb chops and chocolate chip cookies that are having the greatest effect on your cholesterol levels. If you’ve been eating healthily and doing regular exercise for at least three months and your cholesterol levels still haven’t improved, talk to your doctor about cholesterol-lowering medications. A practical intermediate step may be to try one of the reduced fat margarine’s that have added phytosterols for a further three months. Provided you can eat the 4–5 teaspoons a day of margarine without gaining weight, these margarine’s can reduce your blood cholesterol levels by around 10%.

Cut back on salt

limit your saltHigh blood pressure is a common risk factor for cardiovascular disease around the globe. Reducing your sodium intake by not adding salt to food when cooking or at the table, and choosing salt reduced or low salt foods at the supermarket, will help lower it. If you think you have done this but your blood pressure is still high, you might need medication as well. See your doctor for further advice.

Limit your consumption of alcohol

limit your alcoholLike most things in life, moderation is the key. One or two drinks each day may actually help prevent or delay the development of diabetes, and some of its more common complications, by decreasing insulin resistance. It may also decrease the risk of developing heart disease, by providing small amounts of powerful anti-oxidants and thinning the blood. On the other hand, excessive amounts of alcohol may increase the risk of pre-diabetes and diabetes by contributing to weight gain – particularly if you’re drinking goes along with eating energy-dense foods. If you have diabetes or pre-diabetes, it’s important to limit your consumption of alcohol to no more than one standard drink a day if you are a woman and two standard drinks if you are a man.  And, beware, alcohol may cause a low blood sugar even hours after consumption so be sure to have a handful of nuts or drink only with meals.