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Scientists have been studying what makes one food high and another low for more than fifteen years. There is a wealth of information that can easily confuse. We have summarised the results of their research in the following table which looks at the factors which influence the G.I. factor of a food.
The key message is that the physical state of the starch in the food is by far the most important factor influencing the G.I. value. That’s why the advances in food processing over the past two hundred years have had such a profound effect on the overall G.I. factor of the food we eat.
Particle size. Another factor that influences starch gelatinisation is the particle size of the food. Grinding or milling of cereals reduces the particle size and makes it easier for water to be absorbed and enzymes to attack. That is why cereal foods made from fine flours tend to have high G.I. factors. One of the most significant alterations to our food supply came with the introduction of steel roller mills in the mid-nineteenth century. Not only did they make it easier to remove the fibre from cereal grains, the particle size of the starch was smaller than ever before. Prior to the nineteenth century, stone grinding produced quite coarse flours that resulted in lower rates of digestion and absorption.
When starch is consumed in its natural packaging—whole intact grains that have been softened by soaking and cooking—the food will have a low G.I. factor. For example, cooked barley has a G.I. factor of only 25. Most cooked legumes have a G.I. factor between 30 and 40. Cooked whole wheat has a G.I. factor of 41.
The only whole (intact) grain food with a high G.I. factor is rice, specifically low amylose rice, such as Calrose rice at 83. These varieties of rice have starch which is very easily gelatinised during cooking and therefore easily broken down by digestive enzymes. This may help explain why we sometimes feel hungry not long after rice-based meals. However, some varieties of rice (Basmati, a long grain fragrant rice, and Doongara, a new Australian variety of rice) have lower G.I. factors because they have a higher amylose content than normal rice. Their G.I. factors are in the range of 54 to 64.
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I have read some alarming things about diabetes. Are these true?
Books can be misleading. Sometimes they have been written many years ago and not been properly brought up to date. This means that they do not contain recent knowledge and there is no doubt that we know a lot more about diabetes than we did in earlier days. Many of the problems which used to be encountered can now be helped and are no longer such a worry. If you do read something which seems alarming, you should discuss it with your doctor.
I have heard that diabetes can have ‘complications’. What are these?
A. These are seldom a worry in childhood, but it is true that some people, as they grow older, develop other problems of health due to their diabetes. Some of these could have been prevented, or would have been less troublesome, if the diabetes had been more carefully looked after. On the other hand, some problems may develop despite every care. Not everyone has these complications, and it is probable that as a result of the enormous amount of research in progress, we may one day be able to prevent them completely. The important complications that you may hear about are as follows:
1. Poor circulation in the legs with slow healing sores
You may also have heard of old people developing ‘gangrene’ of the feet. This can be a problem in old age but trouble can be avoided by proper care of the feet. This means keeping feet clean and dry and treating minor cuts and sores promptly and properly.
It is important to cut toe-nails correctly and have ingrowing toe-nails looked after properly. Always be sure shoes are a good fit. With these measures, and careful control of the diabetes, there is no reason why gangrene should ever develop.
2. Impaired vision or blindness
It is true that some persons with diabetes develop poor vision as they get older. We think that good diabetic control may help minimize this, and only a small number of people are likely to be seriously affected. There are some forms of treatment available for those with diabetes who show signs of eye complications, and sometimes these are very effective in preventing blindness. There is a lot of research work being done at present to study the way the blood vessels of the eye are affected by diabetes and how we can maintain good vision. The very early signs of eye problems can be detected by tests that photograph the back of the eye.
3. Kidney trouble
Once again, as with visual disorders, some people do get kidney disorders later in life as a result of diabetes. It would be surprising if modern research does not point the way in the next few years to the prevention of this.
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