Glycemic Index Simplified

GLYCEMIC INDEX SIMPLIFED

 

Picture an old-fashioned roller coaster with plenty of ups and downs. That’s what your blood sugar and insulin levels look like over the course of a day. The highs that follow meals and snacks drop to lows later on. Learning to eat in a way that makes your blood sugar levels look more like a kiddie coaster with gentle ups and downs than a hang-on-tight ride with steep climbs and breathtaking drops can make a difference to your health. How can you do this? A tool called the glycemic index (GI) can help. It rates carbohydrate-containing foods by how much they boost blood sugar (blood glucose). The glycemic index, or GI, measures how a carbohydrate-containing food raises blood glucose. Foods are ranked based on how they compare to a reference food — either glucose or white bread. Different carbohydrate foods are given a number and this number indicates if the food causes a certain peak and decline in sugar levels. (1)

Someone with diabetes for instance, can use the glycemic index as one strategy to keep their blood sugar under control. And there may be other benefits since low glycemic index diets have been linked to reduced risks for cancer, heart disease, and other conditions.(2). The purpose to create a table with the food based on glycemic index is to provide a useful guide for meal planning for athletes and diabetics. However, it should not be used in isolation as it does have its limitations.

 

GLYCEMIC INDEX AND BLOOD GLUCOSE LEVELS

All carbohydrates are digested and absorbed at different rates. The effect that carbohydrates will have on your blood sugar levels will differ according to the type of carbohydrate you eat. This effect is known as the glycemic effect, term commonly known as glycemic index. All carbohydrate foods have an effect on blood glucose and the GI table was developed to reflect this. Simple carbohydrates are digested and absorbed quicker than complex carbohydrates which cause a subsequent peak and a quick decline in blood glucose levels which is undesirable. (2)

Classification of glycemic index
Classification of glycemic index

According to the chart, if a food has a GI of 70 or above, it is a high glycemic food and you would try to avoid these as they would rapidly increase the blood sugar levels. If the food is in the moderate category it is better but you wouldn’t be basing your diet on these foods. You would consume them with caution. Low glycemic foods are the category you should be basing your diet on since those foods gives a slow release of sugar in the blood without overburdening the body.

Glycemic index classification
Glycemic index classification

The graph indicates the blood sugar release in the body of high GI foods versus low GI foods. As you can see we get a surge of energy with high GI foods with a high amount of sugar in the blood and a quick decline. That is when you will feel tired, exhausted and you will be looking for that sugar rush again. With low GI foods the release of sugar in the blood is slower and last longer without any adverse effect on the body which is what we are aiming in a healthy diet.

Fiber is what decreases the GI of a food. The more fiber a food contain the less the GI, the more refined the food the more the GI. Fiber can be differentiated into soluble and insoluble fibers.  

Fiber
Fiber
  • Insoluble fiber includes cellulose, hemic celluloses and lignin, which make up the structural parts of plant cell walls. A major role of insoluble fiber is to add bulk to stools and to prevent constipation and associated problems such as hemorrhoids. Good sources include wheat bran, corn bran, rice bran, the skins of fruits and vegetables, nuts, seeds, dried beans and wholegrain foods.
  • Soluble fiber includes pectin, gums and mucilage, which are found mainly in plant cells. One of its major roles is to lower LDL (bad) cholesterol levels. Good sources of soluble fiber include fruits, vegetables, oat bran, barley, seed husks, flaxseed, psyllium, dried beans, lentils, peas, soy milk and soy products. Soluble fiber can also help with constipation.

 

As you can see from the chart above there are some fruits and vegetables that are low, medium and high GI. Just because of them high GI does not mean you want to avoid the food. What can we do to help reduce the glycemic effect of these foods? You can add them with foods that are hard to digest to balance the effect for example with any protein or high fiber food or a good fat containing food. You can also match the high GI foods with the low GI foods to balance the effect out.

 

GLYCEMIC INDEX – WHY BOTHER?

Low GI foods
Low GI foods

Low GI foods:

  • Provides a more sustained release of carbohydrates energy throughout exercise and activity.
  • Creates a reduced insulin response
  • Ensure that energy stores are not depleted overnight.
  • Theoretically should prove beneficial during long-term, moderate intensity exercise and for overall diet as well

 

 

 

FACTORS THAT INFLUENCE GLYCEMIC INDEX

 

  • RIPENESS – the more ripe the fruit or vegetable the higher the GI will be. The riper they get the more enzyme in the food will break down the starch producing sugar. Hence making the food easier to break down.
    Riper the fruit the higher the GI
    Riper the fruit the higher the GI
  • STORAGE TIME – the longer you store your fruits and vegetables, the more time the enzymes, naturally found in those foods, have to break down the complex carbohydrates to simpler carbohydrates.
Processed wheat
Processed wheat
  • PROCESSING – the more refined the food the higher the GI value of the food. For instance whole grain bread has a lower GI compared to white bread. Juice has a higher GI than whole fruit.
  • COOKING METHOD – the more you cook food the easier it is for the starch to swell and break down. So always try to go for an al dente having more of a crunch to vegetables and they lose fewer nutrients during the process. For instance, mashed potato has a higher GI than a whole baked potato.
    Cooking food
    Cooking food
  • VARIETY – if you mixing low GI and high GI foods together, that will reduce the overall GI of the meal and you will still get the benefits of both foods in your diet. for instance, long-grain white rice has a lower GI than brown rice but short-grain white rice has a higher GI than brown rice.
  • PROTEIN CONTENT – if protein is added to the meal that will automatically reduce the GI of the food since protein food take longer to digest. Hence decreasing the GI value of the food.
    Adding protein source to cereal
    Adding protein source to cereal

Once you have understood these basic concepts of GI, plan out your diet sensibly. Speak to a dietician, tell them what food you like and what you don’t and they would help you with a diet plan for losing weight. For diabetics, it is essential to understand these concepts to control their ‘sugar’ or rather glucose level in the blood. Moreover, athletes would need a better understanding to know how to use GI during exercise as it would vary compared to the general public.

REFERENCES

  1. Use glycemic index to help control blood sugar. Harvard Medical School. https://www.health.harvard.edu/blog/use-glycemic-index-to-help-control-blood-sugar-201208135154.
  2. Glycemic index and Diabetes. American Diabetes Association. http://www.diabetes.org/food-and-fitness/food/what-can-i-eat/understanding-carbohydrates/glycemic-index-and-diabetes.html.

 

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