After 25 years of research, Australian food scientist and nutritionist Jennie Brand-Miller deserves her title as ?queen of the Glycaemic Index.? With the blood sugar-centric diet exploding onto the world stage, Shane Starling spoke to her to sort the wheat from the watermelon
FF&N: Why is the Glycaemic Index attracting so much attention right now?
JB: GI is not the be all and end all, but we think it is a big part of the obesity/diabetes story. Carbs have been pushed and pushed, and this is proving to be bad advice. The emphasis was to keep the fat out but that meant high carbs. That made people fat. Even I used to advocate carb consumption but carbs make people hungry — they spike and trough sugar levels — and that has been proven in both animal and human studies.
We need to get smarter about carbs and not see all starch as holy. We need the food industry to come on board and develop healthy low-GI breakfast cereals, breads and rice — those three categories are vital.
FF&N: How does the GI diet differ from low-carb diets?
JB: A lot of these diets are about carbohydrates, but they have different ideologies. Atkins is about strictly avoiding carbs. South Beach is more about higher protein and good fat choices. Mine is about moderate- to high-carb intake and being selective about carbs. The difference is that we say carbs are good. The others try and cut carbs out altogether, in which case the chances are you will eat more saturated fats than you ought to. GI works because you don?t have to avoid bread, rice, etc. We are trying to encourage changes that are sustainable and that cultivate good dietary habits. No food groups are cut out. It is flexible. It fits in better with people?s eating habits. And it has scientific backing no other diet can claim. People have to take responsibility for what they put in their bodies, and the GI diet can assist that process.
FF&N: How did your ideas develop?
JB: Initially, I thought only diabetics needed to control blood sugars. Gradually, blood sugars became an issue in cardiovascular disease and only recently has GI broken through to weight control. For five years I have been advocating GI as helpful for weight control because it is satiating. There are lots of short-term studies that show low-GI foods are more satiating than high-GI foods. I thought that must be helpful for weight loss. There are 10 studies that back this up, including one of my own, so I am scientifically justified when I say that the GI has implications for weight loss. GI is taking off right now because everybody is concerned with weight control, only a fraction with diabetes or heart disease.
FF&N: How does the GI diet affect bodily function?
JB: When your blood glucose levels go up, they come down again. If the levels are too low you go into a coma; too high you destroy a range of bodily cells such as those in your eyes, your kidneys, heart and blood vessels. The agent that keeps it within that narrow window is insulin. So when your blood glucose goes up after a meal it is insulin that brings it down again. If you have insulin resistance, the body is less responsive to insulin?s messages. More is produced to bring down the blood glucose levels. This is common among people with diabetes and people who are overweight. Indeed, many health experts are calling insulin resistance the common soil for all lifestyle diseases.
High-GI foods exaggerate insulin resistance and make it worse than it ought to be. The beta cells that produce insulin get damaged because they are very sensitive and so when next the body needs insulin, the cells under-produce because they are damaged. This can lead to the onset of pre-diabetes or diabetes. A low-GI diet works by reducing stress on the beta cells, reducing the demand for insulin secretion and assisting the body to remain more insulin-sensitive.
A study published in The Lancet last year showed rats on a high-GI diet had a complete disruption of their beta cells whereas the low-GI rats were healthy. They were the same weight after 18 weeks, but the low-GI rats had more muscle and less fat.
FF&N: In a way the low-carb dieting boom has been beneficial because it has educated people about carbohydrates and how they are not all created equal.
JB: It has made people realize that ditching carbs altogether is not a good thing. I take my hat off to Atkins for recognizing the link between carb intake and weight loss. He was ostracized and attacked by the mainstream health profession because he had an idea they didn?t like. Yet when they tested it, he was right. Studies have shown that when you adopt an Atkins diet, you lose weight faster and your cardiovascular risk factors are better than on a traditional low-fat diet. But at the same time, that doesn?t necessarily make it a good or sustainable diet. Also, long-term health risk factors are much higher because of the saturated fat content of the diet through dairy and meat products.
People have had enough of Atkins, and so they are moving back to what I think is a happy compromise. Atkins is low-carb, conventional diets are carb heavy — in the middle are diets like the GI diet.
FF&N: Are all sugary foods bad?
Sugars are good for us because they maintain our insulin sensitivity, but they have to come in at a rate at which we can cope with their GI potential. We want them trickling rather than gushing. They also displace saturated fats.
FF&N: Ingredients companies are releasing ingredients that seek to lower the GI value of traditional high-GI foods like white bread and breakfast cereals. Do you see this as a good thing?
JB: If they can do it, I am interested. But I suspect many of these products are in fact low carb and not low GI, and therefore I would doubt their goodness. Technologically, I know it is difficult to have complex carbs in white bread. In Australia, a low-GI wheat is being trialled in breads, and we are surprised how good the breads are. It is going back to the way nature intended wheat to be in the first place. Conventional breeding has driven a higher and higher GI, but if you look back a few thousand years there were many low-GI grains.
I would like to think that such foods are not just healthy from the point of view of starches, but in their full nutrient profile. I don?t like the idea of foods being generated that are low-GI and nothing else. GI is only one wheel on the cart and there are many other wheels that are just as important. The ingredients industry is going to make me cranky if all they want to do is take out sugar and put in a polyol — that is low carb, not slow carb. With your indulgence foods like chocolate, you may as well have the real thing. There is a place for indulgence foods.
FF&N: What factors fed the rise of GI in Australia?
JB: Dietitians and other health professionals got behind it. They questioned the starch versus sucrose distinction. The Australian character was important too — being willing to give anything a go. The media was very friendly from the start, too. There was also a GI labelling scheme that had government approval that was established between the University of Sydney and two diabetes groups. The symbol only goes on foods that are healthy and have been properly GI tested. We have registered the symbol in Canada, in the US, in New Zealand and the UK.
The objective of the symbol is to make it an internationally recognised symbol of creditable information about the GI. It was needed because in Australia at least, there was a flurry of claims about GI that were made without adequate justification. Those kinds of products can ruin the GI?s credibility.
FF&N: Do you find it difficult to separate your commercial and scientific interests?
JB: I?m not trying to sell books, I am trying to sell a low-tech solution to what is a diabetes and obesity epidemic. I don?t want health budgets crippled by drugs and the need to do kidney transplants.
FF&N: Do you worry the GI message will be blurred as more parties try to exploit its growing popularity?
JB: There have been some GI diet books that list red meats like bacon and salami as high-GI foods when they do not even rate as GI foods because they have no carbs. So these dumbed-down versions can confuse the issue, and although the authors may mean well, they could be inadvertently causing some damage, maybe in the longer term.
FF&N: Some people say the glycaemic load (GL) is a better measure of a food?s ability to alter blood sugar levels. Do you agree?
JB: People like GL because there are a few examples of foods like watermelon, beetroot and a few others that have high GI but are considered healthy foods. We say forget about the GI of fruits and vegetables except potatoes because they are all good for you and can be eaten in abundance. For that handful of examples GL may be a better measure, but for most foods it is not. If you concentrate on GL, you play into the hands of the low-carb camp because if you have a scale of foods based on GL, the foods at the bottom of the scale will be the foods with the lowest carb content, not the lowest GI. We don?t want to push people away from carbs. GL will be a massive distraction if it gains popularity. It will destroy the credibility of GI.