Business Times - 20 Jun 2009
Lowdown on sugars
The buzzwords are glycemic index (GI) and glycemic load (GL), which are the latest and best ways to track your diet. By Cheah Ui-Hoon
FORGET about counting calories, it's so 80s. These days, it's all about finding out about the quality of those calories, and not just doing the math to make sure that you don't go over 2,000 or 2,500 calories a day.
The buzzword is now glycemic index (GI) and glycemic load (GL) - which is the latest - and best (so far anyway) - way to track how healthy your diet is. 'The drawback about calories is that it tells you nothing about the quality of the food you're eating,' says Pooja Vig of The Nutrition Clinic.
'GI as a concept is catching on fast, especially in markets like Australia, where they've launched a GI symbol programme (for food products),' says Made Astawan, lecturer and researcher at the Department of Food Science and Technology in Indonesia's Bogor Agricultural University.
Although it had initially started out as a dietary strategy to help diabetics gain better control over their blood sugar levels, the GI is now being seen as a way to treat obesity, cardiovascular disease, and various other health problems, as well, says Ms Vig.
Already there's more research being carried out on the GI and how they affect other aspects of health. Those who eat a high-fibre, low-GI breakfast burned more fat when they exercised, the findings from a small study by the University of Nottingham in the UK suggest, which was published in the May edition of The Journal of Nutrition.
The low-GI breakfast contained muesli and milk, yoghurt and canned peaches, and a small amount of apple juice, totalling 3.5g of fibre, while the high-glycemic index breakfast provided 1.5 grams of fibre from cornflakes and milk, white bread and jam, and a carbonated glucose drink.
In the same month, in the US journal Ophthalmology, a study noted that eating a diet rich in leafy vegetables, nuts and fish and low in starchy carbohydrates (which fits the low GI profile) appears to lower risk for age-related macular degeneration, the leading cause of severe vision loss in people over 50.
The findings is the first to calculate the combined effect of certain dietary nutrients and eating habits on a person's risk for age-related macular degeneration. The data was collected from 4,003 participants in the ongoing Age-Related Eye Disease Study led by researchers at the Tufts University Jean Mayer USDA Human Nutrition Research Center on Aging.
What is GI
So how does the GI work? Dr Astawan explains that, in the past, diabetic patients were always told to avoid simple carbohydrates such as sugar, which were thought to cause blood glucose spikes.
They were unconcerned about complex carbohydrates such as starches, as they were not believed to interfere with blood glucose control. 'However, such a diet did not always result in steady blood glucose levels. So in 1994, David Jenkins, MD, PhD, a professor of nutrition at the University of Toronto, Canada, decided to find out why,' he explains.
Dr Jenkins investigated the effect that carbohydrates have on the body in the most logical way he could think of. He fed a predetermined amount of some common carbohydrates to his subjects, and recorded their blood glucose levels before and after eating. The study showed that all carbohydrates have different effects on the body, and that finding evolved into the development of the Glycemic Index - a ranking on a scale of 0 to 100 of the effect that carbohydrates have on blood sugar levels.
There are three categories of GI: low (< 55), medium (56-69) and high (> 70). The GI diet helps to control blood sugar levels which limit the storage of fat through control of insulin spikes.
'Many low GI or natural foods tend to contain fewer calories anyway, thus also resulting in weight loss,' says Dr Astawan. 'Calorie counting is related mainly to weight loss - the fewer calories ingested, the more weight lost. However, not all this weight loss will come from fat loss, but also from muscle and water loss,' he adds in explaining the difference between a low-calorie diet and a low GI one.
'More recent studies have shown that low GI foods, through their regulation of blood sugar and insulin, actually limit and prevent the accumulation of fat. Therefore, being aware of GI of foods will benefit everyone and anyone aspiring to lead a healthy lifestyle and manage their weight,' says Yulia Kusumawardani, who works in the Scientific and Consumer Care Section of nutrition snack company Soyjoy.
Increasingly, companies are beginning to conduct tests for the GI values of their products and Soyjoy is among the first few companies to do this, she says. 'Our packaging clearly states that we are a low GI food,' says Ms Kusumawardani.
Now that we're up to speed on the GI, here's another new-ish concept to understand. To further apply what we know about GI foods, the future of weight loss programmes looks set to be based on a thing called the Glycemic Load, or GL, which takes into account the GI of a food, and how much of it comprises carbohydrates. 'GL is more accurate in stabilising blood sugar,' says The Nutrition Clinic's Ms Vig.
'The carbohydrate in carrots, for example, has a high GI. But carrots are pretty low in carbohydrates compared to other foods like potatoes, bread, and sweets, so carrots' GL is relatively low,' she explains.
The bottom line is that if a food has a high GI but very little carbohydrate, it will not have much adverse impact on blood sugar and insulin levels.
On the other hand, if a food has both a high GI and a high carbohydrate content, it should be limited, she says.
An advocate of the GL diet, British nutritionist Patrick Holford, notes that GL literally means the quantity of carbohydrates (the Atkins factor) multiplied by the quality (the GI factor).
For example, watermelon has fast-releasing sugar (GI of 72), but a big slice has only 6g of carbs. So you multiply the quantity (6g) by the quality (.72) equalling 4.3 GLs. 'The GL value of a food is real. It defines what that food will do to your blood sugar level and hence, your appetite, energy and weight,' says Mr Holford, in a previous article about GL.
He calculates that by consuming 45 GLs a day - spaced out in three meals and two snacks, combining protein with carbohydrate - this strategy will further even out blood sugar and maximise weight loss. He recommends low GI carbs and a moderate protein diet, rather than a low-carb, high-protein diet (the Atkins).
Ms Vig says however that the trick is in getting portion sizes right. 'It's difficult because there are no GL labels to tell you if you're getting the right 'load'.' So after she advises clients about the GI and GL, she shows them how to get the portions right by simple 'eye-balling' of their plate.
'You don't want to get into too much calculations because people don't eat like that, or it becomes too much like calorie-counting, which isn't a long-term solution,' she says, adding however that she's stricter with diabetics.
Most people eat 15 to 20 kinds of food regularly, so she goes through the GI and GL of those foods with her clients.
In general, she advocates a combination of the Mediterranean type diet and a low carb diet at her clinic, with an emphasis on both good quality meat and vegetarian sources of protein, to mitigate the increased cancer risks associated with a high meat, high dairy diet, plus the potential stress on the kidneys and loss of bone mass.
'A meal that has fibre, protein and some fat in it reduces the sugar surge that is experienced by the body,' she adds.
As Dr Astawan points out, he expects more food companies to follow in Soyjoy's footsteps and come up with GI labels, besides the calorie count (which tend to also confuse you with their readings per 100g serving, or portion serving).
'For the future, GI values are very important information that should be clearly indicated on all food packaging. With that information, people can choose food easily based on their GI values, in addition to other nutritional information.
'Since people with diabetes mellitus, with obesity issues and also dieters are recommended to consume low GI foods, this labelling would make it more convenient (to know what's the quality of calories they're consuming),' he says.
Understanding the glycemic index
The GI is a ranking between 0-100 of carbohydrates, measuring the effect they have on blood sugar levels.
Low GI <55
Medium GI 56-69
High GI >70
High GI foods result in a 'sugar rush', followed by lethargy and hunger pangs. Low GI foods prevent such fluctuations, resulting in one feeling fuller for longer.
GI is a ranking of individual foods only, not whole meals, but the main idea is that including low GI foods in your meal will result in a lower GI value overall.
For more information on the Glycemic Index, go to ww.glycemicindex.com
For list of GI values of common foods, visit www.the-gi-diet.org/lowgifoods
For more on Glycemic Load, go to http://www.holforddiet.com