All diets have their evangelists, and the glycaemic index (GI) is no exception. The scientists love it, doctors are raving about it and the UK's largest supermarket chain is 110% behind it.
The issue food manufacturers must address, however, is whether consumers have the faintest inkling of what GI is all about, and whether it is worth pouring hard earned cash into something that might end up in the dustbin of dieting history before the decade is out.
While the science behind the diet is complex and consumer awareness remains low, its basic premise is simple, insists Jeya Henry, professor of human nutrition at Oxford Brookes University. That is, high-GI foods like sugary snacks rapidly raise blood sugar and release energy quickly but soon leave you feeling hungry again, while low-GI foods like porridge oats release energy more slowly, staving off hunger pangs and making you "feel fuller for longer"
And food manufacturers, he contends, have a "tapestry of opportunities" to cash in, both by altering manufacturing processes or reformulating products to reduce their GI.
For a start, there is already a host of low-calorie, low-carb products on the market using ingredients like inulin or fructose to replace easily digestible carbohydrates that could simply be repositioned as low-GI.
If you're not already using these ingredients, reformulate, he says. But this doesn't necessarily mean reaching for the artificial sweeteners. "There is a multitude of ways to reduce GI. Add more tuna to your pasta ready meal; use fruit or oat fibre in your snacks, or change your processes. If the manufacturing process builds a structure that hinders gelatinisation [swelling of starch granules] and enzyme access through using less water, lower temperatures or less pressure, GI will be lower." However, a straight swop replacing sugars and starches with low GI ingredients is not always possible, he warns.
For example, replacing 100% of the sugar in a dessert may not be advisable as sugar has properties such as moisture retention, shelf-life enhancement, texture and bulk. Remove it altogether, and products taste and feel very different to the original.
To retain the original texture and flavour of ice cream for example, Danisco Sweeteners has had to replace sucrose with a mixture of polyols, dextrose and fructose for customers keen to develop low-GI varieties.
Dutch ingredients giant Sensus, which has replaced glucose syrups in cereal bars and other products with inulin to reduce their GI rating, says ingredients companies are still learning. "Flour replacements for cookie dough and cake batter are different," says scientific and regulatory affairs manager Diederick Meyer. "Sometimes you can't just use inulin, you have to use Hi-maize as well. We've used combinations of vital wheat glutens, sodium caseinate, resistant starch and inulin in cookies and cakes."
While the reformulated product may have a lower GI, he adds, it may also have an ingredients list as long as your arm. Likewise, the industry won't do itself any favours if it manipulates GI ratings by adding fat or protein, he warns. "Carbs should not simply be replaced by using a higher fat or protein content, which lowers GI but may have negative health repercussions. It is important to select ingredients that lead to overall well being."
This is particularly important if GI is to retain credibility, adds Dr Gary Frost, director at Hammersmith Food Research , who points out that chips have a lower GI-rating than baked potatoes, but are clearly not the healthier option: "Manufacturers must not send out mixed messages."
Not surprisingly, given that potatoes have a high GI-rating, the British Potato Council is concerned that consumers will spurn them if the low-GI diet catches on. Chief executive Helen Priestley says: "Media over-simplification is a real danger with foods being classed as good or bad without the necessary context. Just taking a GI approach to the choice between potatoes, rice and pasta gives a very different outcome than when other nutritional qualities are considered."
Cooking also increases GI ratings by destroying the native structure of starch, so that customers selecting a product on the basis that it is low-GI may find it has a very different rating after they cook it, she says.
Undeterred, however, Tesco is pressing on with plans to label 1,000 products by the year end, says head of brands, diet and health, Hamish Renton: "GI is moving into the mainstream. People are really buying into this."
Encouragingly for manufacturers, Tesco has also seen sales uplifts of products with low-GI labels and is keen to engage with 'pro-active suppliers' looking at ways to reformulate products to reduce their GI-rating, he says. Warburtons, which recently introduced a new low-GI white loaf with added wheatgerm, also claims the extra sales have more than justified its investment.
So what does the future hold?
While the Australians and South Africans have been using GI for years to stave off the hunger pangs, the Brits are coming round to the concept rather more gradually.
However, Tesco's endorsement, and growing interest from Sainsbury and Marks & Spencer should ensure that GI fits neatly into the gap that Atkins left behind, says Professor Henry, who remains convinced that GI is the biggest commercial opportunity to present itself to the industry for decades.
High-GI foods are increasingly linked to spiralling obesity, heart disease and type two diabetes, he says. "Just look at the south Asian community in the UK and Europe. They have a five-fold risk of diabetes compared with the local population. This is an enormous market when you also include people that are predisposed to diabetes. That's 10-12% of the population. This is going to change the face of our approach to weight control and to an array of diseases from diabetes to obesity."
National Starch market development manager Mike Croghan is more circumspect, however. "We've had a lot of interest in Hi-maize from bakery and cereals manufacturers in the UK, Japan, South Africa and Australia. We also have other low-GI ingredients in the pipeline. However, the challenge is getting consumers to buy into it.
"GI doesn't mean anything to most people. Phrases like 'sustained energy release' or graphs plotting energy release are more useful, but a lot depends on what claims we will be allowed to make [under new European legislation]. This is a massive commercial opportunity, but it won't explode overnight." FM
LOW GI INGREDIENTS ON THE MARKET
Polyols like sorbitol and isomalt can be used to reduce GI ratings in products like jams, biscuits, baked goods and ice cream.
Palatinit, a subsidiary of German sugar manufacturer Südzucker, has been using isomalt (produced from beet sugar) in a range of well-known brands including Wrigley's Extra, Strepsils and Sulá sugar-free sweets for years. Manufacturers can replace sugar with isomalt on a one-to-one basis, with "usually no, or only minor modifications in recipes or production parameters", claims a spokesman.
Separately, Cargill has recently acquired European authorisation to place isomaltulose on the market for use in food. Present in honey and cane juice, it is suitable for use in sports drinks, meal replacement drinks, bars, and cereals, says marketing director Mark Wastijn.
Litesse, a polydextrose from Danisco, serves as a low-GI fat replacer and bulking agent in frozen desserts, cereal clusters, biscuits, confectionery and beverages.
Sugar replacement D-Tagatose from Arla Ingredients is a low-calorie monosaccharide suitable for use in dairy, beverages and confectionery. If it is approved as a novel food ingredient by the Food Standards Agency, it will be actively marketed as a low-GI ingredient, says spokesman Mads Vigh.
Process tolerant resistant starches such as National Starch's Hi-maize have been shown to reduce the glycaemic response of foods. A premium white bread with 20% of its flour replaced by Hi-maize delivered a 25% reduction in carbohydrate, a 20% reduction in calories, a 45% reduction in glycaemic response and six times more dietary fibre than the standard equivalent.
Gums and beta-glucans (the main component of oat soluble fibre), can be used to replace thickening and moisture retention properties of traditional carbs in products like pasta. Cargill's Barley Betafiber can also be used in bread, extruded snacks, soups and yoghurts.
Inulin and oligofructose:
Dutch ingredients supplier Sensus has produced chicory-based inulin ingredients, Frutalose and Frutafit, which have been used in combination with maltitol to replace sugar and flour in cakes. They have also been used in cereal bars to remove digestible carbs such as sugar and glucose syrup.
As it is not possible to ascribe a GI-rating to a product by analysing it in a lab, testing must be done on humans. This involves taking blood from 12-15 people that have consumed a product in controlled conditions, immediately after consumption and at regular intervals thereafter. Analysis then determines how quickly carbohydrates are broken down into glucose in the blood. Products are given GI ratings out of 100. High is 70+, medium is 56-69, and low is less than 55.