The Glycemic Index has passed its use-by date

The glycemic index (GI) is not just bad science, it has a dangerous loophole big enough to drive an ice-cream truck through. Its time it went to the place where old (and wrong) public health messages go to die.

Wendy’s Chocollo (with waffle cone), Bulla Light vanilla ice-creamNestle MiloUncle Toby’s Choc Chip Crunchy Muesli Bar and CSR LoGiCane Sugar all have something in common. Yes, they’d all look pretty good on the dessert menu, but they also share something else. The owners of each of these products (and almost a hundred others like them) have paid for the right to display a GI Symbol.

Much like its more famous cousin (the Heart Foundation tick), the GI Symbol is designed to guide confused consumers towards “healthier choices” in the supermarket.

The symbol alerts us to foods which have a low glycemic index. The GI is a measure of the amount that a food affects our blood sugar levels. Our body converts most of the carbohydrates in our food to blood glucose. This causes a spike and then a decline in the amount of glucose we have in circulation.

But not all foods are equal. Some (like glucose) spike our blood sugar levels more quickly than others (like potatoes). This is because the carbohydrates in some foods are more quickly converted to blood sugar than others.

The glycemic index of a food is measured by comparing the way a healthy person’s blood sugar level responds (over a 2 hour period) to 50g of glucose and how they respond to 50g of carbohydrate in the food being tested (let’s say boiled potatoes). If the tested food produces an effect which is 70% of the one measured for the glucose then it is said to have a GI of 70. A low GI food is one which has a GI of 55 or less (meaning that the blood sugar response is 55% of that of pure glucose over a two hour period).

The theory goes that if we could make sure we were eating just the foods which have a low impact on our blood sugar, then we would keep our blood sugar levels more even (and presumably somehow be more healthy as a result). I say presumably because there is a real scarcity of credible evidence that the GI of a food has any measurable (positive) health impact.

GI may be a pointless academic exercise but it is not a harmless one. It has a hidden danger in that the carbohydrate it assigns the lowest (and therefore the best) rating is fructose (it has a GI of 19). Fructose is a very sweet tasting (almost twice as sweet as sugar) carbohydrate that does not produce a significant blood sugar response.

When this little quirk of fructose was first discovered (in the early 1980’s) it was pronounced a miracle sugar for people with diabetes. They could have sweets just like everyone else and their blood sugar would never spike as long as the sweets were made with fructose. Even some sugar was ok too (because, being half fructose, it also has a low(ish) GI).

Diabetes organisations the world over happily advised diabetics they could eat sugar or, even better, pure fructose. Unfortunately for sweet tooths everywhere, by about 2001, it was becoming abundantly clear that the ‘no free lunch’ rule applied (or was it no free pudding?). Fructose was even more dangerous for diabetics than sugar.

It turned out that the reason fructose didn’t have a big glycemic index was because it is converted to fat (by our liver) and not circulating blood sugar (like just about every other carbohydrate). Telling diabetics (or anyone else, but particularly diabetics) to consume a substance that was immediately converted to fat was a very bad idea (verging on the culpably negligent).

The American Diabetes Association quietly withdrew its recommendation in 2002, but the message never got through to Australia. The Australian Diabetes Council tell us they “want to end the myth that sugar causes diabetes”, apparently because sugar-free diets aren’t “much fun.”

And the folks selling the Low-GI stickers (the GI Foundation – a collaboration of University of Sydney, Diabetes Australia and the Juvenile Diabetes Research Foundation) still tell us it is “best to ignore the sugar content of a food and instead focus on the food’s GI.” A director of the GI Foundation (Sydney University nutritionist Jennie Brand-Miller) even went so far as to say recently that “Unlike saturated fats, trans fats, salt and alcohol, sugar doesn’t actually do any direct harm to the human body.

For the last decade (at least), the research on fructose (and sugar) has shown again and again that exactly the opposite is true. Fructose consumption is a causal factor in obesity, heart disease, hypertension and Type II Diabetes. It is implicated strongly in cancer growth and it is highly likely to be behind the explosion in the number of cases of chronic kidney disease and fatty liver disease.

That all sounds pretty harmful to me. So perhaps that is why the American Heart Association recommended (after reviewing all the evidence in 2009) that Americans needed to dramatically reduce their sugar consumption. Men should consume no more than 9 teaspoons of sugar a day (about a can of soft drink’s worth). That’s less than half the current (vague) Australian recommendation (of about 23 teaspoons a day).

Just like skinny leather ties and big hair, the glycemic Index seemed like a good idea in the eighties. It held out hope (for a dessert filled future) to millions of diabetics everywhere. But science eventually found out what was really going on (as it usually does) and the world moved on.

In Australia we got stuck on the notion that GI should work (and to this day stubbornly refuse to acknowledge the fructose loophole). The food industry leapt on the marketing power of a ‘healthy label’ that meant they could still use as much sugar as they wanted. Positions became entrenched. Reputations were built. And as a result we now have folks like the GI Foundation and the Australian Diabetes Council telling us there’s nothing wrong with eating sugar.

This would all be mildly entertaining if we weren’t talking about real people with very real (and very life-threatening) problems. Every day in Australia nine people lose a limb to Type II diabetes (and 275 more people develop the disease). Every day the number of obese children grows like never before in human history. Every day the number of new cases of chronic kidney disease sets a new benchmark.

The science says all of this misery (and lots more) can be traced back to eating sugar. So how about we stop playing ducks and drakes with quaint scientific notions (that protect the processed food industry from having to face reality). How about we start caring about the people who follow the advice they see on a packet of food. How about we face the truth about sugar and demand that those we pay to care – do.

Join the discussion 16 Comments

  • Paul says:

    Excellent article David.

    The position of the GI foundation on sugar/sucrose (and its super sweet active ingredient fructose) is mystifying.

    Even if they haven’t kept up with the news/research regarding fructose they should still be very skeptical of foods that use fructose for the simple reason that the intense sweetness of fructose is used to lace many of the high GI foods that the GI foundation frowns upon – sweet refined flour products and cereals, juices etc.

    If they were serious about encouraging people to avoid high GI foods the simplest recommendation would be that people should avoid all foods containing concentrated fructose with the exception of modest amounts of fruit in its natural packaging.

    Certainly, warning people explicitly about the dangers of consuming intensely sweet fructose is a buzz kill to the sweet tooths amongst us but considering the consequences of diabetes that seems a small price to pay.

    If Diabetes Australia wish to be taken seriously they need to rethink their position on fructose (and its primary delivery system – refined sugar/sucrose)

  • Dale says:

    Challenging the “establishment” is gutsy. Go you.

    “Positions became entrenched. Reputations were built.” So true. It makes it very difficult (but not impossoble) to change course.

    The Heart Foundation and Diabetes Australia Qld are the two charities that benefit from the Brisbane to the Gold Coast Bike ride. Now there’s an ethical dilemma.

  • Darren Spies says:

    HI All, have a look at this You tube link….this guy puts what David G is saying in a short 5 min technically correct way…it is excellent.

  • Darren Spies says:

    This comment has been removed by the author.

  • AMars says:

    It’s about time the GI system was questioned.
    Personally, I find it irritating and confusing. I’m fortunate not to have diabetes, but my partner does and he has just about given up. His doctor gave him a GI chart, and that lasted two months.
    I’ve basically advised him to watch all sugars and have taught him to read the labelling on all food products, and avoid imported products without labels.

  • The best guide to what food actually is and what we SHOULD be eating is through the Weston A. Price Foundation. Their DVD called the Oiling of America is excellent and the lecture is delivered by Dr Sally Fallon. This DVD is about GI specifically but it’s all part and parcel of our food and a must view.

  • I should have said that it ISN’T about GI specifically!

  • David Wren says:

    Dr Karl taught me not to just believe what I hear, but to look to peer reviewed scientific studies.

    I read David G’s book and not wishing to be fooled or influenced by an author’s bias, I’ve now read many scientifically researched and peer reviewed articles which all back up what David G. has said in his book.

    We better start using sugar cane for ethanol production because it’s killing plenty of Australian’s in its sucrose form.

  • Dette says:

    I am hypoglycemic and have been on a low GI diet for some 15 years. I am also 20 kilos heavier than when I started. Although my original dietician had me sugar free for 3 years and I was never so slim or fit as I was in those 3 years. But he retired and the next dietician said just go “low GI” and you’ll be right mate. Now I’m obese and my hypoglycemia is out of control.

    My husband read your book last year and went fructose free and has so far lost 10 kilos. I have just read the book and now the whole family as of yesterday is fructose free.

    I’ve started a blog – to document our journey over the next 365 days.

    You might also like this – This American doctor uses the same word as you – “POISON”.

    Thank you for opening our eyes. My 6 year old is hypoglycemic too and I’m looking forward to giving him a better life with food then what I have had.

  • John Doyle says:

    This should be taken up like Asbestos was.
    These touts for sugar need to be held accountable for their work. By denying they are acting like Big Tobacco, who still deny culpability. If they had said in the beginning that it may be harmful but it’s not illegal so smoke at your own risk, they would have saved a lot of trouble for themselves. The asbestos industry ran a similar campaign and now we see it with seed oils and sugar.
    We learn slowly don’t we?

  • Eli Goodman says:

    This is ridiculous nonsense. Fructose simply takes longer to be utilised due to its molecular structure, and it is no more likely to be converted into fat than any other sugar… Raised blood glucose levels causes the body to produce a protein which directly damages blood vessels, contributing to cardiovascular diseases… Low GI is the best choice – just make sure the food is healthy in other ways too.
    Please use credible sources such as peer reviewed scientific articles. Put some effort in. Don’t state your opinion as fact.

  • David Gillespie says:

    Eli there is nothing controversial about what I say about fructose metabolism. It is so well settled it appears in most biochemistry text books. They usually say something like – Unlike glucose, which is metabolized widely in the body, fructose is metabolized almost completely in the liver in humans, where it is directed toward replenishment of liver glycogen and triglyceride synthesis. Here’s quite a readable online summary of the sort of thing you’ll find in those textbooks –

    But please feel free to post evidence of your assertion that “Fructose simply takes longer to be utilised due to its molecular structure”

  • Elinor says:

    This is sensationalism. In your article you take no care to clarify information and you ommit information, intentionally misleading the reader.
    Wikipedia page on fructolysis states: “Under one percent of ingested fructose is directly converted to plasma triglyceride.[2] 29% – 54% of fructose is converted in liver to glucose, and about quarter of fructose is converted to lactate. 15% – 18% is converted to glycogen.[3] Glucose and lactate are then used normally as energy to fuel cells all over the body.[2]”
    Stop cherry picking to suit your agenda – selling a book.
    Everyone needs carbohydrates. Low glycemic index carbohydrates are the healthiest. If someone is consuming fructose syrup and other refined/processed foods, then their diet is the issue – not that they’re choosing low GI versions of those foods.

  • Linda says:

    Did she just quote Wikipedia?

  • Linda says:

    “Everyone needs carbohydrates”. According to whom?

  • Elinor says:

    Yes, Linda. Wikipedia publishes well established knowledge. All the more reason to think this book is either intentionally deceptive or the author can’t see past his own biases.

    Carbohydrates are required. It’s a fact. What makes you think it’s up for debate.

    Additionally, most natural foods containing carbohydrate are low GI, fewer are moderate GI: Most fruit, most vegetables, dairy, legumes, nuts, and some grains such as oats and brown rice(moderate). Would it make sense to cut them out because of their GI status? No. Are they less healthy than their higher GI counterparts? No. That’s because low GI isn’t the problem; it’s the intake of highly processed “food” that is the problem. But logic on this matter makes for a very short book.

    Glycemic index of foods can be searched for here:

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