Managing Dietary Glucose

Could carbohydrate consciousness be coming back? It is, but with a more-responsible approach than the low-carb fad that includes how carbs impact blood glucose levels. The greatest obstacles appear to be lack of legislation coupled with the inability of experts to agree on terminology and procedure for qualifying and quantifying select carbs.

The healthy carb landscape

Consumers jumped into the low-carb craze without any education. They thought all carbs were bad for them, says Don Montuori, publisher of the new Packaged Facts report Low Glycemic Foods and Beverages in the United States, MarketResearch.com, Rockville, MD. This, of course, is not true. Our bodies need carbs ... just more of the right ones and fewer of the not-so-right ones. This is why an understanding of glycemic impact has a real potential to improve the way Americans eat.

Packaged Facts projects that U.S. sales of foods and beverages labeled as low glycemic totaled a mere $350 million in 2006. However, the market is projected to reach $1.8 billion in 2011. Whats driving this growth is the current obesity and diabetes epidemics, along with increased consumer awareness of the impact carb choice has on general health and wellness, says Montuori. Furthermore, suppliers are recognizing this business opportunity and assisting with product development efforts by offering low-glycemic, carbohydrate-based ingredients. Their investment in technology and clinical studies eases the burden for marketers to offer consumers products designed to assist with glucose management.

Rhonda Witwer, business development manager, National Starch Food Innovation, Bridgewater, NJ, says: If we deliver the benefits that make carbs healthier to eat, we believe the industry can expect a very healthy annual growth rate. Consumers are certainly looking for a healthier way to include carbohydrate- based foods into the diet.

Words of sorts 

When it comes to differentiating carbs by their impact on blood glucose levels, the food, nutritional and medical industries have yet to reach agreement on appropriate terminology. They do agree that not all carbs are created equal.

Even FDA agrees, as illustrated by requirements for carb listings on Nutrition Facts panels. Certain carbs must be quantified (total carbohydrate, dietary fiber and sugars), while listing others is voluntary (soluble fiber, insoluble fiber, sugar alcohol and other carbohydrates).

Diabetics know that different carbs impact their blood glucose levelsand how having blood glucose levels go too high or too low can result in a variety of short- and long-term health consequences.

This carbohydrate-blood glucose relationship and its potential impact on health has been, and continues to be, studied in nondiabetics. Research suggests a possible correlation to sustainable weight loss, as well as reducing the risk of developing diabetes and other diet-related ailments, including heart disease.

The term glycemic index (GI) was one of the first to describe this relationship. About 25 years ago, scientists in Canada and Australia began classifying carbohydrate- containing foods based on their potential to increase blood glucose. GI ranks carbs on a scale from 0 to 100, reflecting the extent they raise blood sugar levels after eating. High-GI foods are rapidly digested and absorbed, creating marked fluctuations in blood sugar levels. Low-GI foods, with their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels.

Critics of GI say that glucose response inherently varies from person to person and according to the context in which the food is consumed. It also only quantifies the impact of individual foods and does not consider the amount eaten. The usefulness of this term is being debated by academics, nutritionists and food manufacturers around the world, says Helen Mitchell, director of applications, Danisco Sweeteners Ltd., Redhill, England. Nevertheless, a growing number of consumers have expressed interest in products that assist them with monitoring glucose intake.

Coni Francis, scientific affairs manager, GTC Nutrition, Golden, CO, says: The low-glycemic trend has gained momentum in part as an alternative to the low-carb trend, and as a result of heightened consumer understanding that eating foods that provide a smaller rise in blood glucose levels after meals helps to maintain weight and improves the bodys sensitivity to insulin.

The concept is emerging as a viable tool that food manufacturers can use to bring healthier products to consumers looking to improve and maintain their well-being, Francis continues. This concept is rapidly gaining acceptance as consumers increasingly understand how the specialty ingredients in their functional foods affect glycemic response.

Another term often used is glycemic load (GL), which some believe measures glycemic response to specific foods in a morepractical way. GL is derived by multiplying GI by the grams of carb in a serving and quantifies foods potential glycemic impact.

At present, the trend in Australia is clearly to list the GI on the label of foods, and not the GL, says Jennie Brand-Miller, professor of human nutrition, University of Sydney, Australia. While all low-GL foods will have less of an impact on blood glucose levels, low-carb, high-GI foods with a low-GL may have detrimental effects on other aspects of health, such as blood lipid profiles and insulin resistance, as compared to high-carb, low-GI foods that also have a low-GL.

According to Brand-Miller, international interest in Australias GI Tested certification trademark is booming, with a significant proportion of North American food companies expressing interest. The number of foods with the logo is expected to increase by several hundred percent over the next three years in Australia.

U.S. marketers currently reference both GI and GL; however, neither has gained widespread use. Most nutritionists would agree that some form of glycemic labeling can help consumers choose a better diet, says Ron Deis, vice president, technology, SPI Polyols, Inc., New Castle, DE. We just need a scientifically sound and agreeable way to present this information to the consumer.

In September, AACC International, St. Paul, MN, approved a variety of definitions associated with glycemic carbohydrates, the carbohydrates in food that elicit a measurable glycemic response change in blood glucose concentration after ingestion. The only carbohydrates that can do this are classified as available carbohydrates or net carbohydrates.

Available carbohydrates are absorbed as components such as glucose and fructose. These may have occurred in the food as such, or as more-complex molecules that were digested, such as starch, maltodextrin, sucrose, etc. However, some carbohydrates are only partially available, due to the nature of the food matrix, degree of cooking or the nature of the carbohydrate itself.

AACC also adopted a definition for glycemic impact, the weight of glucose that induces a glycemic response equivalent to that induced by a given amount of food. So, in the near future, the term glycemic impact likely will be used by marketers to promote foods for glucose management. Or, maybe not.

Consumers in the United States do not understand the term glycemic, says Witwer. Our research suggests consumers are more likely to recognize blood sugar levels in the same way most people recognize blood cholesterol today. When consumers were asked about a label claim stating helps to maintain healthy blood sugar levels, they responded strongly in favor of this concept. An impressive 66% of Americans thought that it was an important label claim, even though they had never seen it on food labels.

Proceed with caution 

In addition to determining the preferred language to communicate to Americans about carbs, issues arise regarding reproducible study findings. Some studies have shown that a low-GI diet did not reduce the risk of diabetes, while other studies correlate with reduced risk, says Witwer. Were not sure where the scientific studies will balance out over the long run, but we are concerned about the lack of consistency in the data at this point in time.

Julian Stowell, science director, Danisco Sweeteners, adds: A growing number of studies suggest that reducing the glycemic impact of the diet can help consumers to eat less calories. However, again, not all investigators have reached the same conclusion.

Another concern about GI is the lack of consistency regarding healthy foods: carrots have a high GI, while foods such as chocolate end up with a significantly lower GI. This sends a mixed message that is difficult for consumers to understand. Deis adds, Glycemic response is a good thing to note, but GI disregards the benefits associated with consuming low-digestible carbohydrates, and this is definitely an issue.

For example, a recent study demonstrated that insulin resistance has been increasing in the American population at alarming ratesrates that reflect the increasing incidence of obesity. We have already seen that dietary fiber has a correlation to increased insulin sensitivity, says Witwer. Natural resistant starch has been shown in two clinical trials to actually increase insulin sensitivity.

Stowell adds: Groups such as the International Life Sciences Institute (ILSI) have a major effort underway to evaluate the level of scientific substantiation associated with the various claims relating to glycemic response and health. ILSI has also undertaken an expert consultation on methodology, which is now providing clear guidelines for those involved in measurements.

Conceptual formulating 

So many unknowns, yet many manufacturers are actively involved in developing products that induce controlled, healthier glycemic responses when consumed. The evidence suggests that we need to lower the average GI of the diet by around 10 to 15 units to achieve significant health benefits, says Alan Barclay, researcher, University of Sydney. In order to achieve this, we need to focus on those foods that contribute the most available carbs to the daily food intake. This means lowering the GI of all of the commonly consumed grain-based foods, such as breads, breakfast cereals, rice and noodles.

Barclay points out that research shows that people do not look at GI alone. Therefore, making sure that a food is not too high in calories, total and saturated fat, sodium, etc., is also an important factor, he adds.

Deis says: What could be helpful is for consumers to know what foods are high-, medium- or low-GI, so that they can balance the foods eaten throughout the day. High-GI foods are not bad, but should be eaten with more moderation than low-GI foods.

Many things affect the GI of an individual food: processing; heating and hydrating; what was eaten previously; exercise; stress; etc. Thus, it is difficult to say with real certainly whether the stated GI of a product will actually be reflective of how the body will respond to that product under a certain set of conditions, adds Mitch Kanter, research fellow, North America director of health and nutrition, Cargill, Inc., Minneapolis. For example, if I ran shortly before I ate my bowl of oatmeal, the impact of the oatmeal on my blood glucose and insulin levels may be different than it would be on a day when I did not run. With that said, I do believe there is real value in attempting to eat foods and meals with an overall low GI.  The question, then, is: How is this determined?

Varying variables 

Currently, to consider all the ingredients and manufacturing process of prepared foods, clinical testing is necessary for glycemic labeling, since it takes into consideration variables that impact GI, including a foods acidity. Increased acidity slows gastric emptying, and thus the rate of starch digestion. Fat, too, slows the rate of gastric emptying, potentially decreasing GI.

With starch ingredients, the level of gelatinization must be considered, Deis says. If the food is cooked so that the starch in the food is gelatinized, the starch becomes more available to digestion, increasing the GI of the food. Also, amylose is more resistant to absorption of water and digestion, so higher amylose means lower GI.

Witwer adds: Resistant starch is an example of how various factors affect the glycemic impact of foods. Unripe bananas contain a lot of resistant starch, but as the fruit ripens, the starch turns to digestible sugar. Thus, a slightly green banana may deliver 8 to 10 grams of resistant starch, but a fully ripe banana would deliver none. Thus, a slightly green banana would have a significantly lower-glycemic impact than a fully ripe banana.

The story is even more dramatic with potatoes. A raw potato is 100% resistant starch. When it is cooked, that resistant starch turns to rapidly digested starch. Thus, a hot baked potato has a very high-glycemic impact. However, if the potato is allowed to cool the starch retrogrades and a portion becomes resistant to digestion, says Witwer. The resistant starch in a cooked and cooled potato has been found to be approximately 10% to 12%.

Formulators must also consider physical barriers. Unprocessed whole grains deliver a significant amount of resistant starch. Processing into flour, or into wholegrain flour, destroys the protective coating of the seed and all of the resistant starch is lost. Furthermore, the smaller the particle size, the more easily the particle is digested, and the higher the GI.

When it comes to fiber ingredients, higher-viscosity fibers slow the rate of digestion, decreasing GI. In general, soluble fibers increase viscosity in the small intestine; insoluble fibers often do not have the same effect.

Scientific studies have shown that the fermentation of specific fibers will make your body more efficient in managing glucose, says Witwer. Hi-maize resistant starch is a low glycemic starch that has been shown to assist in the control of appetite and satiety. It also impacts insulin sensitivity, and increases lipid oxidation. Himaize easily replaces flour and easily reduces the glycemic impact of carbohydrate-based foods without changing the taste or texture.

Our OatVantage oat bran concentrate has been shown to assist the body in maintaining healthy blood sugar levels, Francis says. It is rich in beta-glucan and has the added advantage of helping reduce low-density lipoprotein cholesterol.

Because low-GI foods are more slowly digested and absorbed by the body, providing a sustained release of energy, low-GI foods can be described as being more satiating, says Joseph ONeill, vice president sales and marketing, Orafti Active Food Ingredients, Malvern, PA. Foods with high GIs are digested more rapidly and provoke large fluctuations in blood glucose and insulin secretion, causing a person to be hungry again sooner. Ingredients that lower GI have the potential to make one feel full, and subsequently eat less.

As nondigestible dietary fibers, Beneo inulin and oligofructose each have GIs of virtually zero, continues ONeill. For example, Beneo P95 is a short-chain inulin that has almost identical functionality to sugar, with one-third of the sweetness of sucrose. It works well in combination with high-intensity sweeteners, helping to round out the sweetness profile to make recipes taste more like traditional sugar formulations. The clinically proven health benefits associated with Beneo include all those of traditional forms of dietary fiber. Additional benefits include enhanced calcium absorption, improved digestive health, function and immune enhancement through the fibers prebiotic effects.

Mitchell says: Specialty dietary fibers such as Litesse polydextrose gain from the ability to mimic sugar, and in some cases fat, by recreating the full-bodied sensory experience. Polydextrose has a low relative glycemic response and is not sweet, making it ideal for use in combination with intense sweeteners. Because of its clean taste, polydextrose can be used in high proportions for up to a 50% calorie reduction, even in products with sensitive flavor systems.

How sweet it is 

There are a plethora of ingredients to choose from when replacing high-glycemic carbs, such as sugar, in products. To keep GI low, product designers often turn to high- and medium-intensity sweeteners, such as acesulfame-K, aspartame and sucralose, as well as lower-calorie sugars, such as tagatose and trehalose, as well as some polyols. Another sweetening option is fructose, which is naturally occurring and has an extremely low GI, but a high sweetness level, says Mitchell.

All polyols are low-GI ingredients, and many contribute a desirable sweetness, notes Deis. Polyols can be used in combination with fiber to lower the added sugar content and decrease overall GI in foods, he says. Maltitol can be used to replace sugar and lower GIboth through limited availability in the gastrointestinal tract, as well as use of its solubility to limit starch gelatinization. Maltitol syrups replace the entire range of corn syrups used in the food industry, replacing added sugars and cutting the GI by half.

Ron Perko, director of sales, Cargill Sweetness Solutions, adds: Erythritol is an all-natural, zerocalorie polyol that is 70% as sweet as sugar. Erythritol is not metabolized in the body and makes no contribution to the GL of a food product. Erythritol has also been show to work in synergy with sucralose. It improves smoothness and body, while reducing any astringent aftertaste.

Only time will tell if some form of glycemic labeling will help Americans shape up. But its safe to say, if products designers develop foods with more of the right carbs, and fewer of the not-so-right carbs, Americans might just feel better and look more slender. 

Donna Berry, president of Chicago-based Dairy & Food Communications, Inc., a network of professionals in business-to-business technical and trade communications, has been writing about product development and marketing for years. Prior to that, she worked for Kraft Foods in the natural-cheese division. She has a B.S. in Food Science from the University of Illinois in Urbana- Champaign. She can be reached at [email protected]. 

Complicating Calculations

The final formulation and interaction of ingredients will impact the finished products GI and GL, says Anne Mollerus, global product line manager, Cargill Sweetness Solutions, Minneapolis. Clinical testing of the finished product is important to ensure that the low-GI benefits of ingredients have carried through processing and formulating.

The GI of a food is determined by feeding a portion containing 50 grams of digestible (or available) carbohydrate to 10 healthy fasting subjects, then measuring blood glucose at predetermined intervals over a two-hour period. On a separate occasion, the same 10 subjects are fed an equal carb portion of glucose as a reference standard. The area under the curve (AUC) is measured for both. The GI value is calculated for each person by dividing their glucose AUC for the test food by their glucose AUC for the reference food. The final GI value for the food is the average GI value for the 10 people.

Only about 10 facilities in the world conduct such in vivo testing, including the commercial clinical testing facility at the University of Sydney. A new Australian standard on the in vivo measurement of GI has just been developed, Barclay says. It has been submitted to the International Organization for Standardization. GI testing at a laboratory that follows the Australian standard will help ensure that the GI has been measured accurately and reliably. We do not recommend in vitro testing for food-labeling purposes.

However, in vivo testing has its drawbacks. For starters, theres human variability. Furthermore, it is expensive for the routine food analysis necessary for nutrition labeling.

AACC recommends that a concerted effort be made to develop validated in vitro methodology that accurately mimics in vivo behaviora similar issue was addressed for dietary fiber in the past. This is the major portion of nondigestible or unavailable carbohydrate. An in vitro assay was developed to support food labeling, because an in vivo assay would be impractical.