Targeting the Glycemic Index

Foods with low glycemic index (GI) are poised to be a blockbuster trend to keep an eye on this year.

"GI foods have become more popular since the demise of the low-carb Atkins diet. There has basically been a move from ‘low-carb’ to ‘slow carb,’" observes S.L. "Sam" Wright IV, President and CEO, the Wright Group, Crowley, La. "With the rising obesity crisis and related increases in the incidence of type 2 diabetes (18 million U.S. patients), pre-diabetes (16 million), and metabolic syndrome (60–90 million), consumers are looking for answers. In Australia, a logo has been in use since 2002 to denote when a food is considered low glycemic. We can see that happening in the U.S. and other countries at some point in the near future."

The GI is a ranking of carbohydrates on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating, according to the University of Sydney, Australia. "Foods with a high GI are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels. Low-GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels." The glycemic load (GL), a measure of the total glycemic response to a food or meal, is calculated by multiplying the GI by the amount of carbohydrate in grams and dividing by 100.

Conflicting Opinions
Supporters of GI believe that low-GI foods can help control weight and reduce the risk of diabetes and related conditions by raising blood sugar more steadily. Ebbeling et al. (2005) indicated that a low-GL diet could be more efficacious than a conventional, energy-restricted, low-fat diet in reducing cardiovascular disease risk in obese young adults. In the 12-mo study of 23 obese young adults, plasma triacylglycerols of those on the low-GI diet decreased by 37.2%, compared to 19.1% in the conventional group. Plasma triacylglycerols are fatty acid molecules associated with ischemic heart disease.

Pereira et al. (2004) supported the belief that a reduction in GL may aid in the prevention or treatment of obesity, cardiovascular disease, and type 2 diabetes. In the study of 39 overweight or obese young adults, those on the low-GL diet reported less hunger than those on the low-fat diet. Insulin resistance, serum triglycerides, C-reactive protein, and blood pressure also improved more with the low-GL diet.

While research supporting GI benefits exists, there are still conflicting opinions, particularly over its benefit in weight loss. For example, Raatz et al. (2005) confirmed the benefit of lowering GI on insulin sensitivity of obese adults, but lowering the GL and GI of weight-reduction diets did not provide any added benefit to energy restriction in promoting weight loss.

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Mayer-Davis et al. (2006) found that the GI of the diet was not related to any of the measures of blood glucose. Results from the study of 813 volunteers "call into question the utility of GI and GL to reflect glycemic response to food adequately, when used in the context of usual diet," the researchers said. Another concern related to the GI is a lack of evidence to support it as a dietary plan.

In addition, some feel that the GI is too complicated for consumers to understand. To address this, AACC International is working to develop definitions that will enable determination of available and glycemic carbohydrate in grams per serving (or per 100 g) of food and help consumers better understand how a given food will affect blood sugar levels.

Solo GI Nutrition, Inc., Alberta, Canada, has introduced a new low-glycemic snack bar, Solo GI™. The bars are said to be "digested slowly, minimizing blood sugar swings (preventing the peak, crash and craving cycle) so you feel full and satisfied longer." UK-based Warburtons has developed a low-GI All in One white bread that is said to provide a source of longer-lasting energy.

"Taste, mouthfeel, and other sensory issues are common problems when formulating these types of specialized foods," observes Wright. His company offers value-added and microencapsulated nutrients and bakery ingredients that have proven very useful in creating low-GI foods. Several other companies are offering ingredients for use in development of low-GI foods.

Fiber-Related Ingredients
Among the ingredients are those related to fiber.
• Oat bran concentrate, Natureal GI from GTC Nutrition, Golden, Colo., is high in beta-glucan and said to slow the uptake and release of energy from a meal and exert positive control over healthy blood glucose levels and subsequent insulin response. Tappy et al. (1996) found that 5 g of beta-glucan reduced glycemic response by 50% in a 35-g carbohydrate meal. "The soluble fiber in Natureal oat bran concentrate has been associated with benefits for blood sugar control and satiety, and with weight management," says Coni Francis, the company’s Scientific Affairs Manager.

She explains that the ingredient’s effectiveness for glycemic control is attributed to the viscous nature of beta-glucan. "Viscosity is critical to slowing stomach emptying and regulating the uptake of energy from a meal. This effect is important to controlling glycemic response and blunting the after-meal insulin surge, which is thought to have positive effects for healthy weight maintenance." Additionally, in the category of prebiotic fibers, the GI of another GTC ingredient, NutraFlora® scFOS® is virtually zero, and does not increase glycemic response.

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• Oligofructose is a prebiotic known for its immune and gastrointestinal health benefits. Work at Leatherhead Food International showed that Beneo™ oligofructose from Orafti, Malvern, Pa., lowered the GI of ice cream. According to Orafti, 12 healthy volunteers ate ice cream containing 15% Beneo or different types of sugar replacers and traditional ice cream containing 15% sucrose. Blood glucose levels were measured over a 2-hr period and used to calculate the glycemic response. The oligofructose ice cream gave a glycemic response of 13, compared to 44 for the traditional ice cream.

• Inulin, another prebiotic, was shown in the same Leatherhead study to lower the GI of dark chocolate. Chocolate containing Frutafit® inulin from Sensus America LLC, Monmouth Junction, N.J., and other carbohydrates had a significantly lower glycemic response, 4–26, compared to 44 for the control chocolate.

• Resistant starch, Hi-maize™ from National Starch Food Innovation, Finderne, N.J., has been shown to help maintain healthy blood sugar levels in healthy individuals. The company said that seven published studies have shown beneficial effects of the resistant starch on glucose and insulin response and suggested that the fermentation by-products of the starch may be responsible for the increase in insulin sensitivity.

• Fenugreek extract, FenuLife® Concentrate from Acatris Inc., Minneapolis, Minn., is a standardized source of fenugreek galactomannans. According to the company, the galactomannans form a viscous gel in the stomach and intestinal tract that slows down the absorption of sugar into the bloodstream, helping to prevent sharp spikes in blood sugar and insulin normally found with carbohydrate intake.

Sweeteners
Nutritive sweeteners are also being promoted for use in low-glycemic products.
• Isomalt^TM bulk sugar replacer from Palatinit of America, Morris Plains, N.J., boasts low-glycemic response. Similar to sugar in sweetness, taste, and technological properties, it has half the calories and is sugar-free. "The very low glycemic response of Isomalt has been verified in multiple tests (SUGIRS, 2002a). It stems from the stability of its molecular bonds," says Debra Bryant, Palatinit’s Director of Technical Services and Business Development.

The sweetener was tested against glucose and given a GI of 2, indicating a minimal effect on the blood glucose level. It is manufactured from pure beet sugar in a two-stage process, which rearranges and stabilizes its molecular bonds, Bryant says. "As a result, neither plaque in the mouth nor digestion in the small intestine is able to break down Isomalt completely. This means that teeth are protected and calories are cut back, with the blood glucose level remaining virtually constant."

• Isomaltulose, a disaccharide derived from sucrose, marketed by Palatinit as Palatinose™, has a low GI of 32 (SUGiRS, 2002b). "The key physiological characteristic of Palatinose is the combination of a low blood glucose response and the fact that it is fully digested and absorbed in the small intestine as glucose and fructose," explains Bryant. "Most interesting is that although hydrolysis and absorption are complete, they are much slower in comparison to sucrose. This leads to a lower increase in blood glucose and insulin levels compared to glucose and sucrose. This means a constant stream of energy over a longer period of time, compared to quickly absorbed carbohydrates."

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• Sucromalt, derived from sucrose and maltose, was introduced in the Xtend™ line of slowly digestible sweeteners by Cargill, Minneapolis, Minn. The fully digestible, slow-release carbohydrate delivers the full energy of sugar but is digested more slowly. The Xtend family also includes isomaltulose.

• Tagatose, marketed under the Gaio® name by Arla Foods Ingredients Inc., Basking Ridge, N.J., was shown to have little to no glycemic response. Oral intake of 75 g of tagatose resulted in no increase in blood glucose or insulin in healthy persons or type 2 diabetics (Donner et al., 1999). The sweetener was utilized in chocolate products made by Miada Sports Nutrition of New Zealand, and a study commissioned by Miada showed that Miada® ChocoLite® had a low GL of 1 and estimated relative GI of 8.

Chromium
Chromium (Cr) is an essential trace mineral that has been shown to enhance impaired glycemic function and help regulate blood glucose metabolism. "In essence, Cr helps improve insulin binding at different sites in the body, including in muscle, liver, and adipocytes (fat cells). Increased insulin binding will enhance glucose uptake," explains Philip Domenico, Assistant Director, Technical Services, Nutrition 21, Inc., Purchase, N.Y. "Cr is on the list of micronutrients that influence the blood glucose response to foods. However, it does so differently than nutrients like fiber. By enhancing insulin action, it helps to quickly reduce sugars from the blood. Cr content may also contribute to the lower GI of fruit juices and whole grains, compared to refined or processed foods."

Chromium picolinate (CrPic), marketed as Chromax® by Nutrition 21, is a stable and highly bioavailable form of nutritional Cr. Several studies showed that CrPic can moderate the glycemic response of high-carbohydrate foods. Frauchiger et al. (2004) measured the acute effects of CrPic supplementation immediately after intake of 400 or 800 mcg of Cr as CrPic. Ten of the 13 subjects responded favorably with an average reduction of 33% in glycemic impact of white bread. Donaldson (2001) studied the effects of one week on 200 mcg of Cr as CrPic. Four of six subjects responded favorably, with an average reduction of 38.3% in the GI of carrots.

"The data support the utility of supplemental Cr as an essential co-factor for insulin function," says Domenico. "There is mounting evidence that the need for CrPic supplementation is related to the degree of impaired glucose tolerance and insulin resistance. Indeed, our strongest data on the benefits of CrPic on glycemic control come from clinical studies in people with diabetes."

He adds that even in normal (non-diabetic or obese) subjects, Cr helps transport glucose to cells after ingestion, thus reducing high levels of blood glucose. "Whether from the front end (fiber inhibiting glucose absorption) or back end (Cr enhancing glucose disposal), if high peaks in blood glucose levels are moderated, that is usually a good thing. More studies are warranted on the additive or synergistic effects of Cr supplementation with other nutrients to help work out the variables that affect the GI."

by Linda Milo Ohr,
Contributing Editor, Denver, Colo. 
[email protected]

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