Study Casts Doubt on Glycemic Index

By JOHN C. DRAKE, Associated Press Writer

Wednesday, March 1, 2006


COLUMBIA, S.C. - Diets that distinguish between "good carbs" and "bad carbs," are not an effective way of controlling blood sugar levels, a new study suggests.

Although made popular by the South Beach Diet and others, the glycemic index has never been fully embraced by most dietitians and remains a point of debate among scientists.

Now, diabetes researcher Elizabeth Mayer-Davis of the University of South Carolina says the use of the index should be ended altogether in favor of more traditional methods of losing weight and reducing the risk of diabetes — eating less and exercising more.

"The glycemic index is sufficiently flawed as an index that it is not helpful for scientists or people trying to create a healthy diet," Mayer-Davis said.

The glycemic index is a 100-point scale, with white bread at 100 points, that measures how quickly carbohydrates enter the bloodstream as sugar.

According to index supporters, people should avoid high-glycemic foods such as white bread and potatoes because they will quickly raise a person's blood-sugar level. Meanwhile, low-glycemic foods such as carrots and apples are absorbed more slowly, making a person feel full longer and reducing cravings, which helps with weight loss.

Promoters of the diet also say that eating low-glycemic foods will result in less fluctuation in their blood sugar levels.

Both the Atkins and South Beach diets have raised interest in the theory, and an entire series, "The Glucose Revolution," guides consumers through a diet based on it.

Beth Kunkel, a professor of food science and human nutrition at Clemson University and president of the South Carolina Dietetic Association, said that while there is debate among dietitians about its validity, it would be a mistake to reject the concept altogether. Kunkel was not involved in the University of South Carolina study.

"To just reject it out of hand and quit working on it would be a mistake," Kunkel said. "I just think we're five to 10 years away from really understanding it from a research viewpoint."

Previous studies have shown conflicting results. One small study showed that people on a low-glycemic diet were less hungry later in the day than a group fed a high-glycemic diet. Another study, involving 39 overweight people, showed that those on a low-glycemic diet lowered their risk of heart disease. Both studies were conducted by Dr. David Ludwig of Boston's Children's Hospital.

However, American Heart Association officials have disputed the significance of those findings.

The new study, published in the February issue of the British Journal of Nutrition, relied on food questionnaires from more than 1,000 people over five years and assessed their consumption of high- and low-glycemic foods. Researchers tested their blood sugar levels twice during the study period and found no significant correlation between the glycemic index of foods and the blood-sugar levels of participants.

Mayer-Davis said that researchers should develop a new measure of how different carbohydrates can affect health. She said a better index would be based on the physical characteristics of foods, such as fat content and calories, because numerous factors influence a food's effect on blood-sugar levels.

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On the Net:

University of South Carolina's Arnold School of Public Health:

http://www.sph.sc.edu


http://news.yahoo.com/s/ap/20060301..._glycemic_index


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Atkins may have "raised interest" in the theory, but he never promoted it. In fact, he made it clear that he believed the glycemic index on its own was flawed, and that people still need to consider the total carb content in food. This has been the same view as other low-carb authors, including the Eadeses of Protein Power, and Dr. Richard Bernstein in Diabetes Solution.

The glycemic index is an incomplete science, in my opinion, and I'm amazed at how quickly it's been fashioned into a complete lifestyle, and promoted as the be-all and end-all way to eat . As a tool for determining which carbs are "good", it's really only useful for selecting single-ingredient plant foods. Once foods are combined, results become less reliable.

Milk and dairy products are a great enigma for GI diet promoters. Milk has a very low glycemic index, ie. it produces only a small rise in blood sugar. Yet it's very insulinogenic .. causing an insulin spike nearly 6 times what one would expect for its GI-rating. In addition, milk, when combined with a starchy plant food such as bread or pasta, will cause the combined food to have a higher insulinemic effect than the starchy food alone.

Some time ago, I listened to a CBC-radio interview with Dr. David Jenkins, the creator of the glycemic index, from the University of Toronto. Jenkins is a staunch vegan, and he stated that his goal all along has been to prove that diabetics can control their blood sugars with a high carb, low-GI, plant-based diet .. that there's no need to consume animal products. I can still hear his silent "eeeuuuwwww" when he spat out the words "animal products".

The glycemic index may be a useful tool, but as I said, it's an incomplete science and still too many variables. Think I'll stick with low carb, which is low-glycemic by default .


Doreen

Here is a flaw in their argument. There is no such thing as "different carbohydrates." To our bodies, they are merely simple sugars. There are merely foods containing different amounts of carbohydrates that may also be packeged differently with other nutrients. But 100 gms of carbohydrates from white bread will stimulate the same amount of insulin as 100 grams of carbohydrates from apples in a particular individual. The curve of the insulin spike may be higher and narrower with the white bread, but the areas under the curves will be the same. One type of curve may produce hunger pangs faster than the other, but the contribution to insulin resistance will be the same.

Controlling innsulin resistance is a key to good health. The glycemic index is not a good tool for that job.

'carrots and apples' - funny, one of the arguments against glycemic index was that carrots rated very high on the index, but only contain a few carbs. The logical conclusion was to calculate glycemic load: amount of carbs x glycemic index.

This study seems to ignore that important point - what a waste of research funding!!

Eating less works quite well in bringing down insulin and glucose regardless of the type of diet. But i'm not going to start eating white bread from today

I read a study done by DR Fontanna not too long ago where he got a few obese subjects and restricted their food and only making minor modifications to diet, but basically were still eating SAD. All tests improved, regardless of their still HI GI Index Diet, even some got their diabetes under control and become glucose tolerent. It was noted that they could have done much better if a complete rather than a minor change it diet was done, like vegetables and fruit, grains, olive oil etc...

let's see them try to convince the millions of people that tried to "eat less and exercise more" to only get worse -- but tried low glycemic and it was the easiest diet ever.

I'll bet that these "experts" have never been severly obese and had to lose weight.

Just because I've never had cancer does not make me an expert on how to avoid cancer. What makes these people weight loss experts?

"The New Glucose Revolution" is probably the poorest diet book ever written.

More info about the Glycemic Index....

http://www.glycemicindex.com/

Atkins actually described it as a "beautiful tool" and a "highly effective system" and while he did go on to warn that you also needed to address total carbs (which leads you to GL) - I think it is fair to say he promoted it - and the GL system is obviously tainted by the flaws in the GI concept.

OTOH the Eades describe the GI as containing so many flaws as to render it "useless as a helpful tool", and while its been a while since I read Bernstein, I can't imagine he failed to mention its many failings. Apart from anything else it does not produce consistent results across different test subjects eating the same food prepared the same way (check out the non-sanitised listing of tests done in different laboratories around the world on Mendosa's site) That alone tells you it is not good science. And of course the GI does nothing to measure the impact of carb sources like fructose (particularly concentrated forms like HCFS) which may have a lower glycemic impact, but are more, not less damaging than foods higher on the GI list.

Guess what?, I'm doing the Atkins diet and I only monitor total carbs.

Regardless of what you say and what journalists say, it's got nothing to do with the Atkins Diet!

Everyone loves to bash to the Atkins diet, expecially Protein Power folks! Even though Mike Eades doesn't critizise it!

I'm hardly bashing the Atkins diet.

I'm just pointing out that the good doctor did go to some lengths to 'promote' and explain the 'usefulness' of the GI index (a pointless diversion from a controlled carb WOL in my view), and if you want to ignore that part of his book ... I would applaud your decision to do so!

I think some of the confusion re GI numbers comes from a misunderstanding of what lowering the overall GI of your diet can actually accomplish. Using lower GI foods, such as whole grains and vegetables, as opposed to sugars and high-GI stuff, is unqueastionably healthier. It will help avoid the big insulin/blood sugar spikes which, if repeated over and over, are believed to help cause insulin resistance and TII diabetes. OK, that's kind of a "duh!" statement - we all know that.

But just because lower GI foods help avoid development of IR doesn't mean that a diet full of them will lower blood sugar levels sufficiently once elevated blood sugar levels and TII diabetes has developed. Once you body stops handling carbs effectively, the obvious thing to do is to cut back on the total amount of carbs, not just play with the quality of carbs. The more impaired insulin function (or amount) is, the more important this becomes, because it takes approximately the same amount of insulin to deal with a given quantity of carbohydrate, whether it comes from pasta, potatoes, sugar, or green beans.

Yes, cutting back on high-GI foods *does* sometimes help bg levels, but usually only in early-stage diabetes, and only when the person is cutting back on food generally and losing weight. Avoiding big bg spikes allows impaired insulin function to keep ahead of things, and lowered insulin levels also may lower hunger and total CHO consumption. But that method is iffy and won't work for many people, especially those whose IR is more established and insulin function more impaired.

Dr. Atkins felt that choosing lower-GI carbs was a good idea, and I agree. It's another "duh!" thing. He recommended that as a tool to be used *within* the framework of a controlled carb quantity paradigm, of course. And most of us would agree with him. 50 g CHO from white bread 'n strawberry jam is going to affect your body differently than 50 g CHO from black beans, say.

So it's not so much that the GI is a worthless concept - though it does have its limitations. It's that using GI alone, without also controlling the quantity of CHO, is not going to be effective in controlling bg levels in a lot of TII's, probably most.

Karen

Thanks for this!!

I have to say that I thnk that there will always be some study somewhere that will try to poke holes into anything that has caught on....and effects an industry that has lobbies. I'd be very interested to know who exactly funded this study?

This has been the only plan that I've been able to work for me. Is is the fact that its the GI that has worked or was it just that I was ready for this...I don't know. But I'm not going stop eating this way because of a study!!!

The GI theory may have flaws, but at least it encourages people to choose foods with nutrients. Alternatives like counting WW points or using Deal-a-Meal cards often don't work because many dieters who are allowed few calories and only X servings of carbohydrates will use their last points/cards for bread or desert, not broccoli, if they are all considered to be "the same", which is how they got fat in the first place. And then the sugars cause cravings and they get even fatter.

If you have a spare half an hour, here's a link to a BBC radio program on GI:

http://www.bbc.co.uk/radio4/factual..._20050213.shtml

Direct link to the radio stream:

http://www.bbc.co.uk/radio4/factual...og_20050213.ram

(You need the Real Player for listening)