The GI Factor & the GI Symbol

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Jennie Brand-Miller PhD discusses with us "The GI Factor & the New GI Symbol". This interview took place on DiabetesStation.com on 10th September 2002.

KATE GILBERT - Dr. Jennie Brand-Miller is a co-developer of the Glycemic Index, a dietary system used by many people with diabetes as well as athletes and others needing to closely monitor their eating. As a researcher in dietetics at the University of Sydney, Dr. Brand-Miller has published widely on this theory.

Recently, a program has been introduced into Australia where symbols appear on some food products in supermarkets to indicate whether they are "High GI" ie raise the blood glucose levels quickly or "Low GI" provide a slow and steady rise to the blood glucose levels. The GI is being used in Canada, Britain, Sweden, Italy, Germany, South Africa, New Zealand but I think the Aussies are ahead!

DJ - WHAT'S GI anyway?

JENNIE BRAND-MILLER, PHD - What's GI? This is a number that tells you how fast the carbohydrate in foods is absorbed into the bloodstream. It's a scale from 0 to 100.

HEIDYN - Is the GI factor different for different people? And is there a way to test what foods would be higher? Diabetes is often so unique per individual.

JENNIE BRAND-MILLER, PHD - Yes, people are unique in their glycemic response, but the relative differences to foods are the same. Potatoes will give higher glycemic responses in everyone, while barley will always be low.

KATE - How long would it take a person to learn to use the GI Factor effectively in the management of their diabetes?

JENNIE BRAND-MILLER, PHD - Kate, it doesn't take long. People don't need to know the GI of every food. What they need to know is the best substitutions to make within the food groups that they are already eating. Say instead of Coke it would be better to have sparkling apple juice and instead of Cornflakes to have rolled oats.

BEN - If I understand GI, it's the rate that the carbs are digested (calories converted to energy). The faster the absorption, the higher the index? It's not only the carbs but the rate of conversion. The higher the index the more rapidly it raises a diabetic's blood glucose?

JENNIE BRAND-MILLER, PHD - Ben, yes you are right. The GI reflects how fast the carbohydrate in a food is converted to sugars and absorbed.

KATE - What would you say to someone (as many have said to me) that feels the GI Factor is all too complicated and they're doing fine counting portions or exchanges like they were taught at diagnosis 15 years ago?

JENNIE BRAND-MILLER, PHD - Kate, if they are doing fine - I assume that means their glycated hemoglobin is below 8, then I wouldn't change anything. But the GI isn't complicated - that's my experience. In our study in ~100 children, those who had experienced both carbohydrate exchanges and flexible low GI diets, voted to continue with the GI diet, not exchanges.

KATE - What would be the greatest benefit to a young, active person with Type 1 Diabetes who incorporated the GI Factor into their diabetes management? Does it allow more flexibility, for example?

JENNIE BRAND-MILLER, PHD - I think the GI approach is good for the young active person because it allows greater flexibility AND no food is off limits.

CAROLYN - I know that for 10g of carb I need 1 unit of insulin. Can you work out a similar thing for GI level or is it not that easy?

JENNIE BRAND-MILLER, PHD - Carolyn, if you know you need 1 unit of insulin for 10g carbs, then you could multiply the 10g by the GI (expressed as a percentage). A food like Coca Cola with a GI of 60 will give you a value of 6. Then I'd see if injecting 6 units of insulin for this particular food gives you better control.

ELLEN - Do you find people have less hypos with it?

JENNIE BRAND-MILLER, PHD - A low GI food is digested and absorbed slowly so the chance of hypoglycemia is reduced, yes. Some carbohydrate is still being absorbed hours after the meal.

KATE - Many people with Type 1 diabetes have reported to me that the combination of a low GI meal and very fast acting insulins creates a situation where they are hypoing after a meal. Can you explain why this is happening and how it might be avoided?

JENNIE BRAND-MILLER, PHD - Kate, I would imagine that if you used your normal insulin: carb ratio, yes, you might see a hypo after the meal. That's why I say multiply by the GI (and divide by 100) to estimate the insulin dose. The lower the GI, the lower the amount of insulin needed.

KATE GILBERT - Fast-acting insulin will have little to no action after a couple of hours though a low GI meal may still be releasing glucose into our system. Would that cause delayed rises in blood glucose levels?

JENNIE BRAND-MILLER, PHD - Kate, I don't think so because the rate at which it comes in is so slow that the cells can take it up without the need for insulin.

KATE GILBERT - So, a completely insulin-deficient diabetic's body can uptake some glucose into its cells without insulin?

JENNIE BRAND-MILLER, PHD - Kate, yes, even in a person with complete insulin deficiency, glucose can enter the cells under its own steam - a process of mass action. This is also what happens during exercise.

DAMIAN - During exercise, glucose is taken up through contraction stimulated translocation of the receptors responsible for glucose transport: a direct result of muscle contraction.

CAROLYN - What about alcohol and the GI factor? How does it vary with different drinks?

JENNIE BRAND-MILLER, PHD - Alcoholic drinks like wine and spirits don't contain carbohydrates so you can't test their GI. But we have found that the glycemic response to a meal that includes wine is reduced compared with a meal with water. This can be explained by the fact that alcohol depresses gluconeogenesis.

KATE - The GI Symbol concept is great. Food products in Australia can now apply to have their GI Factor officially tested and be labelled as such. How many products are bearing the symbol currently?

JENNIE BRAND-MILLER, PHD - The GI symbol has only just been launched but we have 4 companies signed up. They include the makers of Performax bread, the makers of Burgen breads, Norco icecreams and the makers of a range of juices called Wild about Fruit. Their juices have nothing taken out and nothing added in.

ELLEN - Do you have a trademark in the US for this symbol?

JENNIE BRAND-MILLER, PHD - We have begun the registration process in the US and UK. You will see it there soon. About $250,000 has been spent so far to bring the symbol onto the market around the world.

ELLEN - Jennie, why do you think the Americans do not embrace the GI? Your honesty is appreciated.

JENNIE BRAND-MILLER, PHD - Ellen, I think because no major long term study using the concept has been carried out in the US. Very early, three studies were published in the US that concluded that the GI didn't work in mixed meals. This effectively poured cold water on the whole concept from the point of view of Americans. But around the world, another dozen studies showed that it did work in mixed meals. I think the Americans are beginning to embrace it now.

BEN - The other part of the GI resistance is both an information overload AND not fixing something if it isn't broken. Some of us have had to learn through personal experience what works and what doesn't. And after 48 years of proving success and failures to myself, it's difficult to take on another challenge and calculation to incorporate into my diabetes control.

JENNIE BRAND-MILLER, PHD - Ben, yes I agree with you. But for those who are starting the long road now, we hope the trial and error process will be a lot shorter and less frustrating. The advice is based on scientific evidence, not dogma.

BEN - Dr. Brand-Miller, don't give up on your research or us. Good science will always win out. It's just that some of us have had experiences over the years that don't always fall in line with the textbooks.

ELLEN - Even if I don't fully understand the GI, I appreciate that you are making every effort to improve the lives of people living with diabetes.

So, in summary, for the person who wants to just do the bare minimum the GI can help you know some easy choices to make re what kind of bread for example. But then the next step up, GI can be used to give you an extremely precise tool for pretty much perfectly matching insulin to food - if you like numbers!

You can read much more about the Glycemic Index at www.glycemicindex.com
A brand new edition of The Glucose Revolution, Dr. Brand-Miller's book about the GI Factor, has just hit the streets too.

ELLEN - How does one use the Glycemic Index of a can of coca cola to determine how much insulin to take and whether or not they should take the bolus several minutes before consuming it when using Humalog or Novolog?

JENNIE BRAND-MILLER, PHD - Ellen, you can work out the glycemic load of any serving of food by multiplying the grams of carbohydrate in that food by the GI. Say it's Coke and it contains 25g carbs in 250ml, we know it's GI so the glycemic load is 25 x 60% = ~14. This number gives you a better idea of how this drink will affect blood sugars than the carbohydrate content alone!

ELLEN - What do they do with that number exactly? Is it recommended that they take the fast acting insulin a bit ahead of time to the insulin get working before the bg climbs?

JENNIE BRAND-MILLER, PHD - Ellen, I presume you normally work out the amount of insulin you need by counting carbs. Yes? If so, then don't count carbs, count glycemic load. The lower the number, the less insulin you need.

ELLEN - I guess it would be easier to use if it's in some PDA software etc. Seems it's just one more factor to add to the equation when calculating how much insulin to take.

CAROLYN - I have always counted carbs and never really had a problem. Why should I now look at GI level?

JENNIE BRAND-MILLER, PHD - Carolyn, if you don't have a problem, then there's no need to fix anything. But if someone is overweight or has sub-optimal glucose control (lots of hyper and hypos), then GI is worth a try.

DAMIAN - What about the research that shows people on a lower GI diet are generally more glycogen depleted than those on a higher GI diet? This will have far reaching implications for athletes that are trying to maintain a low GI approach to their diet and perform optimally.

JENNIE BRAND-MILLER, PHD - Damian, glycogen depleted is not the right word. They might have somewhat lower glycogen levels but that won't worry anybody except the most elite athletes.

ELLEN - So they still store sufficient glycogen for their counter-regulatory system to kick in with hypos?

JENNIE BRAND-MILLER, PHD - Ellen, of course.

ELLEN - Who funds your research Jennie?

JENNIE BRAND-MILLER, PHD - Hi Ellen, our work in children with type 1 diabetes was funded by Diabetes Australia. Our work in animal models was funded by NHMRC (ie the Australian government). We are doing some work on high protein diets now and that's funded by Meat and Livestock Australia. Nowadays, I make enough profits from commercial GI testing that I can fund my own research.

KATE GILBERT - What happens to the revenue raised through licensing the GI Symbol to companies for use on their products?

JENNIE BRAND-MILLER, PHD - The revenue raised by the GI symbol will be poured back into communication and education programs aimed at young and old, diabetic and non-diabetic, health professionals and the food industry. We want to make sure that the messages are correct and not confusing. If we ever end up with funds to spare, it will be distributed among the three partners: the University, Diabetes Australia and JDRF.

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