Tuesday, February 2, 2010

Understanding GI prt 2: GI's are high for most common food

Yesterday the background to GI's were explained. Today we look at the GI ranges for common foods. Have a good look at the figure below. I would draw your attention to what GI sugar (sucrose) has. This GI has been highlighted with a red line.

Staggering that nearly all starches have a higher GI than sugar. That means your blood sugar levels get messed up more by a tablespoon of potato than they do with a tablespoon of sugar. As our culture eats a lot of starch eg bread, rice, potaotes, etc that our blood sugars are all messed up.

I might point out that starches combined in your stomach with protein and vegetables would have a lower GI as the stomach and intestine process these things as well as the starch. Therefore the blood sugar rise would be less and more sustained.

Intriguingly enough pulses eg beans, peas etc have the lowest GI index. This means as a food source they are very healthy (they also have lots of fiber which is great for your health).

Milk products have a low GI, they have a sugar lactose in low concentrations 4-5%. Interestingly enough lactose is also made from two glucose molecules like maltose which has the maximum GI. At the moment I am at a loss for why this is. One reason could be that adults have reduced ability to digest lactose as they get older if they haven't had a constant milk intake over their lives. The other effect could be due to the protein in milk coagulating in the stomachs low pH, this could cause the sugars to be trapped into this solid mass and be up taken slowly.

Sweet fruits such as grapes and bananas have a higher GI than sugar, no real surprise here. However most fruits in their native form have quite a low GI. I was amazed that a few years back a customer talked to me about how her doctor told her not to eat fruit as it was a high GI product. At the time I thought this is wrong but couldn't put my finger on it. Now here is the evidence that I was right. Even sugary fruit such as an apple has one of the lowest GI.

Breakfast cereals (these are American?!) have higher GI than sugar. I find this totally amazing it in theory states that i would be better to have a tablespoon of sugar rather than a table spoon of breakfast cereal.I think I am going to make the move to non instant rolled oats this year. The GI's for breakfast cerals are shocking. I will read the labels closely when I am in the supermarket. I'm sure I have seen low GI advertised on a ceral box.
    You may ask where are the vegetables in this list? That is a really good question. Vegetables have an GI of effectively zero. That is right they don't causes rises in your blood sugars. Yet another good reason to have heaps of vegetables each day.

    So in conclusions I am left with the feeling that GI has not been well explained. For someone who prides himself on understanding most nutritional concpets I have learned a huge amounts in writting these two posts. At least another two posts will follow as we unpack the implications of this GI information

    Reference:  S. W. Rizkalla, F. Bellisle and G. Slama Health benefits of low glycaemic index foods, such as pulses, in diabetic patients and healthy individuals British Journal of Nutrition, Volume 88, Supplement S3, December 2002, pp 255-262 

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