A few years ago, low-GI foods were all the rage. What happened? Most of us remember the low-GI craze that hit supermarket shelves a few years ago. However, since then, the emergence of other diet and detox fads has left the low-GI phenomenon largely ignored. But is low-GI still the best way to go, or are there now other, more effective means of making healthy food choices?
Meet the Healthy Food Guide GI expert: Professor Jennie Brand-Miller. A professor at the University of Sydney, Professor Brand-Miller is one of the world’s key GI researchers, and a member of the Healthy Food Guide Editorial Advisory Board. Her belief in the benefits of the GI system, and her perseverance despite many critics, is a major reason for much of our knowledge. Professor Brand-Miller is a little more modest: “The main reason we lead the world [in GI knowledge] is that Australian dietitians have researched the GI, put it into practice and gently encouraged the food industry to develop products with a low GI,” she says.
What is the glycaemic index?
Most of us have heard of the term ‘blood glucose levels’ (also known as ‘blood sugar levels’). Our blood glucose levels are directly impacted by the foods we eat, particularly carbohydrates (proteins and fats have no impact on blood glucose levels). As carbohydrates are digested, they are broken down into sugars that enter the bloodstream and give us energy. But they don’t all act the same way: some are quickly digested and absorbed, while others break down slowly.
The Glycemic Index (GI) is the scientific way of describing how carbohydrates affect our blood glucose levels. Different carbohydrate foods are given different numerical ratings between 0 and 100, depending on how quickly they are digested by our bodies. Those foods that break down slowly, gradually releasing glucose into the bloodstream, have a lower GI (55 and below), while those quickly digested and absorbed having a higher GI rating. A GI of 70 and above is considered high.
Why is GI important?
Foods high on the index are broken down into sugars very quickly, causing a ‘spike’ in blood glucose levels – which is not good for your health. Research has shown that having these glucose spikes is damaging to arteries and various blood vessels. High-GI diets have been linked to insulin resistance, a higher incidence of metabolic syndrome risk factors and the metabolic syndrome, the progression of blood vessel disease (atherosclerosis) and a higher risk of prostate cancer, fatty liver disease and age-related macular degeneration. High-GI foods are also not good for weight control, as the significant blood glucose level peaks we experience are followed by big drops, which stimulate hunger and often send us in search of more ‘quick fix’, high-GI foods.
Low GI foods, however, release their sugars more slowly, providing a more sustained source of energy. A growing body of evidence also suggests that following a low-GI diet provides a number of significant health benefits, including:
improving blood fats, blood glucose and insulin levels,
a reduced risk of cardiovascular disease and type 2 diabetes,
a reduced risk of certain cancers, including endometrial, breast, colon and ovarian cancer,
a reduction in ‘bad’ LDL cholesterol in people with diabetes,
higher rates of fat-burning during exercise; and
a reduced risk of haemorrhagic stroke in women.
Unlike many other diets, there appears to be no down-side to eating the low-GI way. In fact, a low-GI diet fits in very well with the general healthy eating recommendations we know can help with weight management and reducing disease risk, including eating more fruit, vegetables and wholegrain breads and cereals, as well as low-fat dairy and lean meats.
Is it the best approach for weight-loss?
Since the early 1980s, when the concept of GI was introduced, research findings have maintained that the low-GI approach to weight loss and fat loss holds up. In a Sydney University study comparing four different diets aimed at weight loss, a high carbohydrate, low-GI diet achieved the best outcomes. Subjects following this diet lost weight, body fat and lowered their levels of LDL (‘bad’) cholesterol, while those following a high protein diet had similar weight and fat loss, but increased their cholesterol levels. So while the low-GI phenomenon might not seem as exciting or as sexy as other diets, it actually is the one that delivers results you can feel and maintain.
Low-GI foods for…
Type 2 diabetes – eat nuts
People with diabetes are two to four times more likely to develop heart disease than people without diabetes, but eating a small handful (30g) of raw, unsalted nuts four to fives times a week may help prevent heart disease by reducing the risk between 18–51 per cent. One study found that following a nut-rich Mediterranean diet meant greater weight loss and going longer without blood-sugar-lowering medication, all without causing weight gain.
Weight loss – eat legumes
Research shows people who regularly consume low-GI legumes, such as chickpeas or beans, typically weigh 2.5kg less and have smaller waists, even though they eat around 835kJ more each day. Why? You’re eating less fat but more fibre, say researchers. And since legumes have such a low GI, they are great for reducing the overall GI of meals when you add them to meals. Turn to p48 for low-KJ weight loss meals with low-GI ingredients.
More energy – eat bran
You’ve heard all the benefits of eating a healthy breakfast, but choosing something low-GI, like bran, at breakfast time actually reduces the GI of your lunch, as well. This benefit, called ‘the second meal effect’, means you will experience a longer, slower, more sustained energy release after lunch, as well as after breakfast – helping you sail through your day with more energy.
Growing kids – eat bananas
Bananas are the perfect snack food, especially for kids. They are a great source of B vitamins, which help with the release of energy from food and they are also low-GI, providing a sustained and substantial energy boost for growing, active kids. For a sweet, creamy summer treat, peel a banana, insert a wooden stick in one end and pop in the freezer. Dip it in melted choc first, for extra decadence.
Should I only eat low-GI foods?
Looking at the GI of a food can help us to make healthier food choices, but it’s not the only thing to consider, because:
The GI of food isn’t the only thing that causes our blood glucose levels to fluctuate – portion size also has an effect. For example, many lollies have a relatively high GI. But eat a single lolly, and your blood glucose levels won’t rise very much. On the other hand, pasta has a low GI, but a big bowl of pasta can still raise your blood glucose and insulin levels significantly. Scientists call this the Glycemic Load (GL).
Some low-GI foods are high in saturated fat (like chocolate, pizza and potato chips) and really shouldn’t make up a large percentage of your diet, while some high-GI foods contain important nutrients and don’t need to be avoided (such as watermelon and pumpkin).
The GI of a food can change when you combine it with another food. For example, wholemeal bread has quite a high GI, but a smear of peanut butter lowers the overall GI.
The GI of a food is definitely worth considering – but there’s no need to avoid nutrient-dense foods with a high GI; nor is it a good idea to eat as much of a food as you like, just because it has a low GI rating – particularly if you are watching your weight, or if you’re concerned about your blood glucose or insulin levels. Overall, low-GI foods should be used to supplement other healthy eating guidelines, including eating plenty of fruit, vegetables, wholegrain breads and cereals, and limiting foods high in saturated fats and added sugar.
A small portion of high-GI food, or a large amount of low-GI?
The Glycemic Load (GL) is a rating system that looks at both the GI and the portion size of a food, to determine what kind of effect that food will have on your blood glucose levels. Like GI, GL has a scale: 0 – 10 is low, 11–19 is medium and anything 20 or more is considered high. You can calculate the GL by multiplying the GI of the food by the amount of carbohydrates per serve, then dividing that number by 100. Or, if maths isn’t your strong suit, go to www.glycemicindex.com for updated lists of the GI and GL of more than 2,500 individual food items.
How do I know if it's low-GI?
GI is measured using scientific methods on human subjects. It can’t be estimated by looking at the composition of the food, nor can it be tested in a test-tube, which explains why we don’t see GI on all food labels like we do with fat and sugar. While GI claims on foods are increasing, the Glycemic Index Foundation’s Low GI symbol is the only one you can really rely on. As well as certifying that a food is low-GI (as tested by approved methods), it must also be an overall healthy choice within its category, having to meet criteria for energy, total and saturated fat, sodium levels and, where appropriate, the fibre and calcium content. “Because it’s not always easy to make the best carbohydrate choices, the GI Foundation has done all the hard work for you – making healthy choices, easy choices,” says Professor Brand-Miller.
Healthy Food Guide GI expert
Professor Jennie Brand-Miller from the University of Sydney is one of the world's key GI researchers, and a member of the Healthy Food Guide Editorial Advisory Board.
Her belief in the benefits of the GI system, and her perseverance despite many critics, is a major reason for much of our knowledge. Professor Brand-Miller is a little more modest: “The main reason we lead the world [in GI knowledge] is that Australian dietitians have researched the GI, put it into practice and gently encouraged the food industry to develop products with a l ow GI,” she says.
Did you know? Boiling pasta for 15 minutes instead of 10 increases the GI of the pasta. Why? Any processing that makes food quicker and easier to digest, such as mashing, processing, grinding or cooking, will generally increase the GI of a food.