Top Crop Manager

Features Agronomy Seeding/Planting
Glycemic index complicated but coming

Another consumer trend for growers to grasp.

February 16, 2008  By Ralph Pearce

First there was counting calories. Then it was finding foods with lower cholesterol, followed by the anti-carbohydrates diets which has since led to the trans fat revolution.

Now comes glycemic index.

For growers, the task of planting, harvesting and marketing is hard enough with new varieties and hybrids, changes in technology and worrying about the inconsistencies of weather. Yet for some, keeping up to speed with consumer trends is very important, and glycemic index has been getting mentions in food trade publications and the mainstream media.


Other agri-food products and their producer organizations are recognizing glycemic index, as well. Potatoes have a high GI ranking according to some web sites while Pulse Canada has raised the issue as one of significance for Canadian diets, since edible beans have a lower glycemic index, relative to other foods. It is important to note that a food item does not really have a set glycemic index; this is established by both the nature of the item’s carbohydrate biological structure, and how it is prepared for consumption.

Bread may be basic, yet research is now showing how it is made is at least as important as its ingredients.

Glycemic index is a summary of the blood sugar response to eating different types of foods containing
carbohydrates. From a wheat grower’s perspective, glycemic index may be of interest as it relates to bread making. In June 2006, Peter Ilnyckij of the Ontario Ministry of Agriculture, Food and Rural Affairs gave a presentation at a seed company’s grower day about the many changes in the wheat industry. At the time, he was working within the Cereal, Milling, Bakery and Pasta division with the Food Industry Competitiveness Branch, and among the topics he mentioned that day was glycemic index in breads. In particular, he stated the method of preparation of bread may be more important than the ingredients, especially where the glycemic index is concerned.

Relevance can be confusing
Creating awareness of glycemic index has not come without its challenges. First coined in the 1980s from work at the University of Toronto, the index has been the subject of some controversy. It has received varying responses from health care agencies and in some countries, it is permissible, if not required to be listed on a food product’s label. Australia, considered by some to be a pioneer in acceptance and recognition of glycemic index, and the UK allow this practice. In Canada, GI is not allowed to be listed on product labels.

“Some of the ways it becomes controversial is perhaps over-interpretation,” explains Dr. Terry Graham, a researcher with Human Health and Nutritional Science at the University of Guelph. Two pastas with a glycemic index of 75 and 79, respectively, would have no physiological difference. “If it was 40 and 79, it does have a meaning. But how you prepare it and what you put on it will influence the glycemic response considerably.”

Graham suggests the number can be misleading, especially since the index is determined under very specific preparation methods. As soon as a person puts a meat or thick cheese sauce on pasta, its glycemic index is altered. “You could be fooling yourself by purchasing a low glycemic index item but then preparing it to result in a high glycemic index meal,” says Graham, drawing a parallel to adding Omega-3 fatty acids to a doughnut, which does not result in a healthy donut.

This tendency is seen in many facets of food production and marketing. Frozen french fries or oat-based cereals are widely marketed as ‘zero cholesterol’, a somewhat meaningless statement since they are both derived from plants and plants have no cholesterol. The same is true for the term ‘artisan bread’. Loosely defined, artisan breads are sourdough-based and made using more traditional, less processed methods, including a lengthier fermentation process. So the notion that a grocery chain or a fast food outlet is selling artisan bread products is debatable at best, and Graham maintains the inaccurate use of many of these terms is likely to continue.

Sourdough breads show best results
Interestingly, it is the sourdough breads which have tested lowest in glycemic index in some of Graham’s work. With the help of a four year grant from OMAFRA, he has tested white bread, whole wheat bread, whole wheat with barley and sourdough bread on a number of individuals. The research measured various factors, including blood sugar response, the glycemic index, insulin response and the reaction of special gut or intestinal hormones.

“To our complete amazement, our whole wheat bread was inferior or certainly no better than white bread,” says Graham. “When we tested sourdough white bread, it was superior. So the fact that the leavening process was different altered some aspect of that bread so that the insulin and blood
glucose responses were quite different.”

The thing to remember with this research was that each person ingested 50 grams of carbohydrates as bread, rather than a set number of slices, which is not indicative of a normal person’s eating habits. Depending on the bread, a person might have to eat more or less to reach 50 grams of carbohydrates. Graham is currently involved in work that would measure responses based on eating the same amount of bread across the various types being tested. The breads include true ‘artisan’, whole grain breads.

Room for improvement, understanding
Glycemic index of a food is still a valuable measuring tool, provided its meaning, determination – and limitations – are understood.

John Michaelides, director of Technical Services with the Guelph Food Technology Centre, agrees there is a place for helping consumers understand food properties like glycemic index. “I think consumers are becoming more aware of it and there’s obviously a trend towards healthy foods,” states Michaelides. “But the challenge with the glycemic index is that it is a very expensive test to do, so in order to adopt that and have it on the labels is very costly. And you have to take into account that it is specific to a product, so if you change the formulation of the product, or the process of production, you have to redo the test. I’m sure some of the large companies will get a jump on it, if it becomes legal to be put on the label.”

Michaelides points out that one Canadian supermarket chain, with its regular consumer newsletter, offers information about glycemic index, as well as other health related aspects, and it is endorsed by some researchers at the Faculty of Medicine at the University of Toronto. The road to widespread awareness and acceptance, however, is still a long one. “All that consumers need to know is this product provides a better control of the blood glucose and it is healthier,” says Michaelides. -end-


Stories continue below