GLYCAEMIC INDEX and the Goal of Smoothing Your BLOOD SUGAR LEVEL
The glycaemic index (G.I.) is a ranking of foods on a scale from 0 to 100 according to the extent to which the particular food raises blood sugar levels after eating (Table 1, below, shows examples). The marker for this index is taken from the ingestion and absorption rate for glucose. This was given an index value of 100 ~ being the purest form of carbohydrate product as it can be absorbed directly from the gut without modification to become glucose in the blood (blood sugar). Some foods on the Australian market already show their G.I. rating on the nutrition information panel ~ but these are currently the exceptions. Foods with a high-G.I. are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels. Low-G.I. foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels, and have proven benefits for health. 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 G.I. of the overall diet.
The World Health Organisation (W.H.O.) recently recommended that people in industrialised countries should base the majority of their diets on low-G.I. to medium-G.I. foods in order to prevent the most common diseases of affluence, such as coronary heart disease, diabetes and obesity.
The G.I. of foods has important implications for the food industry, but it is not a straightforward matter to adopt for food labelling, nor is the index in relation to carbohydrate content unaffected by other nutrients present in the food!
Terms such as complex carbohydrates and sugars, which commonly appear on food labels, are now recognised as having little nutritional or physiological significance. The WHO recommends that these terms be removed and replaced with the total carbohydrate content of the food and its G.I. value (2). However, for this to happen for all foods the G.I. rating of the foods must be tested physiologically and only a few nutrition research groups around the world currently provide a legitimate testing service.
Upon looking at a complete table of G.I. indices, you will note some anomalies ~ i.e. chocolate appears to have a very low-G.I.. This is because the fat content of the product influences the speed of absorption as well. Hence, matters are not as straightforward as a simple analysis of the carbohydrate type(s) present! For this reason, a (healthier) plain baked potato has a much higher G.I. index than, say Potato Crisps! Before you rush out to the corner shop for a supply of Gary Lineker’s favourite … or disregard the idea of such an index completely ~ this is a guide and can still be used to assess healthier COMBINATIONS of foods generally. Thus, I would suggest that it is a valid reference point to have in mind when planning menus.
If you frequently feel drowsy after eating, it would be worth keeping a food diary for a while to see if a pattern emerges. Do you feel drowsy when you have eaten foods with a high-G.I. ?
Other anomalies : The G.I. of wheat will change depending on how it is processed, yet that of oats remains about the same whether it is in form of porridge oats, oatcakes or oatmeal.
What is the significance of Glycaemic Index?
· Low-G.I. means a smaller rise in blood sugar and can help control established diabetes
· Low-G.I. diets can help people lose weight and lower blood lipids
· Low-G.I. diets can improve the body's sensitivity to insulin
· High-G.I. foods can help re-fuel carbohydrate stores after exercise
How to switch to a low(er) G.I. diet
· Breakfast cereals based on barley, oats and/or wheat bran (I sound a note of caution in respect of wheat bran products, so nothing is straightforward : not too heavy-handed with wheat bran, as many people are intolerant of wheat generally; and wheat bran in particular being a course fibre can be very aggressive on the lining of the gut, and can reduce absorption of some important minerals due to a high phytate content)
· "Grainy" breads made with whole seeds (wholemeal bread being the purest example)
· Use more whole seeds as snacks either raw, ground up or in proprietary products
· Pasta and rice in place of potatoes
· Select fruit and vegetables that generally give you a low to medium index in the majority.
I would caution against getting too fixated on the index figures, but it does serve as a useful guide.
Sucrose (refined table sugar) 59
Fructose (fruit sugar ~ from the fruit
Grains and Cereals ~ incl breads and biscuits
French baguette 95
Baked beans 48
Dairy (heavily influenced by fat content)
Ice cream (low fat) 50
Parsnips (cooked) 97
Snacks and Drinks
Generally, foods below 50 are great to include in your diet, while those above 70 should generally be avoided, or reduced and mixed with a low scoring food to even out the release of glucose to your bloodstream. Those between 50 and 70 should be considered as “infrequent” and again taken with a low-scoring food.
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