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What is a glycemic index?

The glycemic index (GI) is a scientific ranking of foods based on their immediate effect on blood sugar levels. Many everyday carbohydrate-based foods have been tested and given a ranking between 1 and 100, depending on the speed at which they release their sugars into the bloodstream. Carbohydrate foods that break down quickly during digestion have the highest glycemic indexes (GIs of 70 or above). Their blood sugar response is fast and high. Carbohydrates that break down slowly, releasing glucose gradually into the bloodstream, have low glycaemic indices (GIs of less than 55).

Up until recently, it was believed that carbohydrates could be divided into two main categories simple and complex. Simple carbohydrates consisted of sweet, sugary foods, such as cakes, biscuits, sweets, chocolate, jam and honey. Complex carbohydrates consisted of the more starchy foods, such as bread, potatoes, rice, pasta and cereals. It was commonly thought that the sweet, simple carbohydrates caused our blood sugar levels to rise far more rapidly and give us a quicker energy burst than the starchy, complex ones. Now however, thanks to the creation of the glycemic index, we know this not to be the case and foods such as baked potatoes and some types of bread tend to have a far higher GI and cause a far greater surge in blood sugar levels than many sweeter, more sugary foods.

What is the problem with eating high-GI food?

The sugars in high-GI foods are broken down quickly so they do not supply a sustained source of energy. Instead, they cause our blood sugar levels to rise rapidly. The body has to respond to this by making large quantities of the blood sugar-lowering hormone, insulin, and releasing it into the blood. Unfortunately, insulin is often too good at its job and instead of just reducing blood sugar levels to a desirable level, it sends them plummeting to levels lower than they were originally. This sets up a yo-yo effect as the body then responds by making us crave fatty, sugary foods in an attempt to make our blood sugar levels rise once more. so the disadvantages of eating high-GI diet are:

1) The rush of energy given by high GI foods does not last and is soon followed by an energy lull. So you get hungry and want to eat more.

2) After eating high GI foods you will have a lot of readily available energy in your blood. Your body will use this energy first rather then other stores of energy like body fat. This makes it harder to loose weight.

The health benefits of low GI eating

Lowering the GI of your diet may help prevent and manage overweight and obesity – the underlying cause of type 2 diabetes, heart disease and some cancers. We know from research around the world over the past 25 years the many benefits of eating healthy low GI foods, they:

• 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.
• Reduce your triglycerides, total and ‘bad’ (LDL) cholesterol.
• Increase your levels of ‘good’ (HDL) cholesterol.
• Reduce your risk of developing type 2 diabetes.
• Reduce your risk of developing cardiovascular disease.
• Help to manage your blood glucose levels and reduce your risk of developing diabetes complications.
• Sustain your energy levels longer.

Low GI eating really is for everybody, every day, every meal.

source: Home of the Glycemic Index

Why it’s not healthy to eat high-GI food?

1. Food cravings and lethargy
Many of us experience this yo-yo effect as the ‘mid-afternoon lull’. We eat a high-GI lunch – sandwiches or a baked potato, for example – and by 3.30pm we are not only feeling tired, lethargic and lacking in concentration, but we are positively craving something sweet to give us that much needed energy boost. This often happens again after the evening meal when we find ourselves heading back to the kitchen for a dessert, some chocolate biscuits or a glass of wine just a short while after having eaten.

2. Weight gain
A diet rich in high-GI foods can cause you to eat more calories (and therefore gain weight) for two reasons. The first is that high-GI foods are quick to break down. The quicker a food breaks down, the sooner you will become hungry and the more likely you will be to want to eat again. Secondly, high-GI foods will cause your blood sugar levels to rapidly rise and then fall, which in turn will result in strong urges to eat fatty, sugary foods shortly after a meal. Both points are compounded by the fact that another of insulin’s main roles is to promote fat storage, so the more insulin you have in your blood the more likely you are to store any excess calories you eat as fat.

3. Lack of concentration and mood swings
The brain is entirely fuelled by blood sugar. Therefore when levels drop as a result of the excessive production of insulin, it becomes more difficult to concentrate. Research has also found that low blood sugar levels are often linked to mood swings, reduced reaction times and even depression.

4. Diabetes
Diabetes is one of the most common health problems in the world, It is thought that the stress that high-GI foods place on the body to keep blood sugar levels constant can result in either the insulin not working properly or the pancreas, the manufacturing site of insulin, becoming less efficient at producing it, sometimes giving up altogether.

5. Heart disease
As we have already seen, a diet rich in high-GI foods can result in people becoming overweight or developing diabetes. Obesity and diabetes are two of the principal risk factors that can lead to heart disease. In addition, high levels of insulin, which are brought about as a result of eating high-GI foods, are strongly linked to increased blood pressure and cholesterol (along with other blood fats), both of which are also major contributing factors to heart disease.

5 ways to lower your GI food

1. Mix high-GI foods with low-GI foods – research shows that a high-GI food combined with a low-GI food of the same carbohydrate quantity will result in an intermediate GI for the overall meal.
2. Eat protein with your carbohydrates – high-protein foods, such as lean meat, chicken and fish, tend to slow the rate at which a meal is digested and therefore lower the GI of the overall meal.
3. Choose vegetables first – all too often we base our meals around the carbohydrate-rich food, such as pasta, potatoes or rice. Instead, first plan your meal around the vegetables you hope to use, then around the protein-rich foods, such as meat, fish or pulses, and then the carbohydrate-rich food. This will automatically help to lower the GI of a meal.
4. Use beans and pulses as often as possible – try puréeing them to make sauces, cooking them in stews, serving them with fresh herbs as side dishes, adding them to salads, making them into dips or using mashed beans or lentils instead of mashed potatoes.
5. Keep cooking times to a minimum – cooked foods often have a higher GI than uncooked foods, so make sure your pasta is al dente and your vegetables are cooked for the shortest time possible. This will also help to retain more of their vitamins and minerals.

10 tips for reducing the GI of your diet

1. 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 colours.

2. Cut back on most potatoes

If you are a big potato eater and can’t bear the thought of giving them up, you don’t have to. Just cut back on the quantity. Choose a lower GI potato such as Almera, 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. And try other starchy vegetables occasionally like sweet potato, yams or taro – steamed, roasted or mashed.

3. 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 GI 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 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 chilli, 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. The trick is to combine them with those low GI tricklers to achieve a moderate overall GI. How? Lentils with rice (think of that delicious classic Italian soup), rice with beans and chilli (go Mexican), tabbouli tucked into pita bread (with falafels of course and a dash of hummous), baked beans on toast or piled on a jacket-baked potato for classic comfort food.

8. Incorporate a lean protein source with every meal

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 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.

source: Home of Glycemic Index

To see the glycemic index of some popular food please click here