Glycemic Index

By Greg Glassman

In Nutrition, Reference

November 01, 2002

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For several decades now, bad science and bad politics have joined hands to produce what is arguably the most costly error in the history of science - the low fat diet. This fad diet has cost millions unnecessary death and suffering from heart disease, diabetes and, it increasingly seems, a host of cancers and other chronic and debilitating illnesses.

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12 Comments on “Glycemic Index”


adguig wrote …

Sweet potato is a bad, high-GI food? I don't think so, it is in fact the complete opposite.


wrote …

It's not a matter of whether you like them or not but their measure. With glucose as the reference load and measuring 100, Sweet Potato measures 54. The dividing line for good and bad was chosen at 50. That makes them bad and you wrong.


Bill wrote …

A sweet potato is bad? You've got to be kidding! A sweet potato is loaded with antioxidants, vitamins, minerals and fiber. A recent study has shown that sweet potatoes helped stabilize blood sugar levels and improve insulin response in animals. Also, a food's glycemic effect depends on whether it is eaten alone or with other foods. Judging a food solely by its glycemic index is bad advice.


JD wrote …

perhaps considering only the glucose level of a food to determine its "badness" is a bit too simple ...


Anonymous wrote …

I read that a 3 oz. sweet potato's GI is 48 - making it on the high end of having a low GI.
I willing to believe this is wrong, but...


wrote …

I read some literature about 'Glycemic Load' a while back, which seemed a more sensible way of going about things.

In testing GI, a portion of the food is usually used that contains 50g of carbohydrate, rather than 50g of the food.

To get the Glycemic Load, you divide the GI figure by 100 (to get a percentage) and multiply by the amount of carbohydrate in the portion - giving you the 'payload' that will effect your blood sugar.

For example: a 100g slice serving of Watermelon with a GI of 72 (above 50, so a 'bad food') and a carbohydrate content of 5g (it contains a lot of water) makes the calculation 0.72x5=3.6, so the GL is 3.6.

As I recall: A GL of 20 or more is high, a GL of 11 to 19 inclusive is medium, and a GL of 10 or less is low.

In this way, a lot of foods that weren't on the list get back on, and some that were on are sensibly removed.

This is very similar to how I understand the recomendations in the book 'Protein Power' that each meal is restricted to 10g of Effective Carbohydrate Content (ECC) per meal - which is the carbohydrate content of the food minus the fibre content(?).

Just some thoughts from an interested non-expert. Best to read around the subjects to get more clarity/accuracy on these concepts.


Anonymous wrote …

The dividing line for "low-GI" tends to be 55, putting sweet potato at the upper end of low. Besides which, it's not the GI of any particular food that is important, but the overall GI of the meal - which means you can mix a little medium/high-GI food with a larger amount of low-GI foods with impunity.


wrote …

I can understand where you are coming from in this article, but your view is very close minded. You can't decide whether a food is good or bad for you based solely on it's GI number. Sure it is good to try and keep a balanced insulin level, but that doesn't mean you should only eat the foods that are "low-GI". If you do that it can lead to health problems as well, such as, a lack of certain essential minerals that many of the "high-GI" foods are loaded with. Also, eating too much protein can be very detrimental to your health. I know this is an old article, but just the fact that you cited the Atkin's diet makes this a very hard article to take seriously. Eating healthy is all about eating a balanced diet, this means you can and should eat anything you want, but you have to make sure you eat a variety, any food is alright in moderation, and any food can be harmful if eaten too much. Fish is great for you yet if eaten too often it can increase your mercury to unsafe levels which can lead to poisoning, neurological disorders, and just poor overall health. Eating healthy means eating variety. Besides, if I was to follow your advise then I could never eat pasta or a sandwich?


wrote …

I agree with Spencer on the Atkins Diet. Atkins died of heart disease, so how well did his diet help him? Also, many people would VERY MUCH APPRECIATE if these statements and claims have cited sources. It may be "boring" to have a list of sources on the bottom of the page but it will make others feel MORE SECURE in the knowledge their diet and exercise program is backed by sound research.


replied to comment from Max Willey

Max, Atkins died of a severe head injury a week after falling on an icy pavement. Here is the cited source for my statement/claim...


replied to comment from Matt Marshall


You're right and I apologize for not reading MY source clearly. Thank you for correcting me.


wrote …

I'm slightly confused. Squash and sweet potatoes are both said to be allowed on the paleo diet due to their low impact on blood sugar levels. Why, then, are they listed on the bad side of the glycemic index? In addition, oatmeal is typically off the list for the paleo diet, yet it is on the good side? If the Crossfit prescription is to eat meat, veggies, nuts, seeds, some fruit, little starch, and no sugar, why is there this discrepancy? If Coach Glassman sees this comment, what type of diet do you follow?

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