Controlling Blood Glucose

Controlling Blood Glucose

By Angela M. Miraglio, R.D.
Contributing Editor

People with diabetes know all too well the importance of a normal blood glucose level. For them, excursions into a high or low range result in both short- and long-term health consequences. In recent years, scientists began to question whether fluctuating blood glucose led to other chronic diseases such as cardiovascular disease and obesity. Not all medical authorities in the United States agree on the value of dietary measures of glycemic impact for disease prevention. However, some researchers, health authorities abroad and numerous popular diet books promote the health benefits of diets designed to lower glycemic response and keep blood glucose levels from reaching extreme highs and lows.

In theory, erratic blood glucose levels trigger a multitude of hormonal reactions that lead to hunger and increased food consumption, resulting in obesity, diabetes and heart disease. Consuming less sugar-laden, sweetened products would appear to be an obvious first step toward control of blood glucose. However, complex hormonal responses involving insulin to lower blood glucose level and glucagon to raise them, along with other hormones, regulate blood glucose levels. Thus, the simple act of ingesting sugar and other carbohydrate-containing foods does not correlate directly with subsequent blood glucose level.

Measuring glycemic response

Originally a clinical tool, glycemic index (GI) ranks the effect of carbohydrate- containing foods on blood glucose compared to a standard high-glycemic reference food on a gram-for-gram basis. It is determined by measuring the blood glucose values over two to three hours after eating 50 grams of a food and after 50 grams of either glucose or white bread. The value for the test food is then expressed as a percentage of the reference food, which is given a value of 100. High-GI foods, those with a value of 70 or higher, are quickly digested and absorbed, creating a higher spike in blood glucose, while low-GI foods, those having a value of 55 or less, are slowly digested and absorbed, resulting in a lower, prolonged glycemic response.

Critics say that GI has little relation to the way people eat, because it is not based on typical portions and measures glycemic response from individual foods versus complete meals. Additionally, several variables affect digestion and, therefore, GI: cooking method (gelatinized starch is more easily digested); processing method (reduced particle size and fiber removal make digestion easier); type of starch (amylose is harder to digest than amylopectin); fiber (viscous, soluble- fiber foods slow digestion); fat (slows digestion and, consequently, absorption of food components) and acidity (also slows stomach emptying and, therefore, the digestion rate).

Glycemic load (GL) measures glycemic response to specific foods in a more practical way. Derived by multiplying the GI by the grams of carbohydrate in a serving, GL quantifies the potential glycemic impact of foods. High-GL foods score 20 or more, and low-GL foods are 10 or less. Overall, GL is more relevant for meal planning and dietary management. However, it still attributes more glycemic impact to single foods than complete meals. Neither GI nor GL measure the effect of foods on insulin sensitivityan important factor in glycemic response.

Other dietary factors also influence insulin levels and, ultimately, blood glucose levels. For example, postprandial amino-acid levels stimulate insulin secretion, resulting not only in increased blood insulin levels but also lowered blood glucose. An excess of insulin release after meals is considered responsible for starting the roller coaster ride of blood glucose levels that dip into hypoglycemia and then rise to a hyperglycemic peak, leading to increased hunger and eating. Thus, while a high-protein food does not create the elevated blood glucose levels associated with high-GI foods, it could nonetheless initiate the same hormonal cascade.

Despite all the scientific debate and inability to define an accurate measure of glycemic response, consumers seem to recognize that they need to control blood glucose levels. Consumers dont understand the glycemic word, says Rhonda Witwer, business development manager of nutrition, National Starch Food Innovation, Bridgewater, NJ. But when we tested the structure-function claim, helps maintain healthy blood sugar levels, two-thirds said it was important. For consumers, GI and GL are out and out wrong. They do not adequately represent the impact of fiber. So, while glycemic management is valuable, other tools, such as measures of insulin sensitivity, offer meaningful benefits to consumers over the long term and are less likely to become the next passing fad.

Sweet alternatives

Product developers already know how to design low- and no-sugaradded products for the diabetic and weight-loss markets. Typically, these products incorporate ingredients such as sugar substitutes and other alternative sweeteners with bulking agents to mimic the sweetness and texture of sugar-laden products with some degree of success. Typical bulking agents include xylitol, polydextrose, lactitol and erythritol. Alternative sweeteners range from the noncaloric, such as aspartame and sucralose, to lower-calorie sugars such as Dtagatose and trehalose. Certainly, this approach lowers the potential glycemic response of these foods and beverages, and now many ingredient suppliers supply such data on their products.

Isomalt, a disaccharide polyol that is totally sugar-free, and isomaltulose, a disaccharide derived from sucrose, work well in low-glycemic foods, according to Debra Bryant, director of business development and technical, Palatinit of America, Morris Plains, NJ. Replacing sugar with an isomalt variant can significantly reduce the glycemic value of many food products, including confectionery, baked goods, ice cream, cereal, fruit bars and jam, she says. The very low glycemic response of isomalt has been verified in multiple tests at the Sydney University Glycemic Index Research Service (SUGIRS). It stems from the stability of its molecular bonds.

Isomaltulose, a disaccharide derived from sucrose and a natural constituent of honey and sugar cane molasses, with a mild sweet taste, can be used in both foods and beverages. She adds, Although isomaltulose has the same caloric value as regular sugar, it is digested much more slowly, which stems from the stability of its molecular bonds. This results in a low-glycemic and low-insulinemic response, as well as a prolonged energy supply in the form of glucose. Besides tests to establish the GI value for isomalt and isomaltulose, numerous studies demonstrate the very low effect on blood glucose and insulin levels of these ingredients. Byrant reports that a number of low-GI candies use isomalt as part of their formulation, and that both isomalt and isomaltulose can reduce the GI of confectionery, baked goods, ice cream, cereal, nutrition bars and jam.

Whole-grain fiber options

The limited digestion of dietary fiber results in a generally lower glycemic impact, no matter what the source. Recently, several studies associated whole grains with reduced risk for heart disease and diabetes, adding support to dietary recommendations to increase whole grains. According to FDA, whole grains consist of intact, ground, cracked or flaked fruits of grains with the starchy endosperm, germ and bran in relatively the same proportion as they exist in the intact grain. The cereal grains that could qualify as whole grains include barley, buckwheat, bulgur, corn, millet, rice, rye, oats, sorghum, wheat and wild rice.

This news breathes new life into foods commonly eaten years ago but which, for one reason or another, do not make the hit list for todays consumers. Elizabeth Ardnt, manager product development, ConAgra Foods, Omaha, NE, says: Our Sustagrain barley is the first wholegrain product thats both naturally high in dietary fiber and low in starch, making it one of the lowest-glycemic-index grains commercially available. This variety of waxy barley has a macronutrient composition unlike any other, with more than 30% total dietary fiber (TDF). Nearly 50% of this fiber is cholesterol- lowering beta-glucan, giving Sustagrain roughly three times the TDF and soluble fiber of conventional whole oats, with less than half the starch of other cereals. She adds that it also has 18% to 20% protein and is high in lysine, one of the limiting amino acids in grains.

Arndt compares the composition of the ConAgra Mills barley product to other whole grains to illustrate its advantages: wheat has only 12% TDF, mostly insoluble; oats are 10% to 12% TDF with 4% to 6% betaglucan; and different barleys vary considerably in TDF and beta-glucan. She states that although this product is slightly higher priced than other barley, it does not need to be used at the 100% level to achieve improved glycemic response, due to its nutritional profile.

Several published clinical studies looked at this barely in a number of different food formats and processing conditions. The results show a significantly lower glycemic response. The glycemic index for Sustagrain barley is 25 in testing done through the University of Sydney, Arndt says. Available in flour, whole kernel, flaked, steel-cut, and quick-cooking rolled forms, it can add enough fiber in breads and breakfast cereals, soups, energy bars, rice side dishes, and pastas to rate nutrient-content claims. She notes Inclusion rates at 25% in baked goods and pasta respectively qualify as good or, excellent sources of dietary fiber. When used at 100% in hot cereals, Sustagrain provides nearly 50% of the daily value for fiber. In terms of taste, she states it has a mild grain flavor, with slight malty notes.

Resisting glycemic climbs

Another naturally occurring component of carbohydrate foods appears to also help in decreasing glycemic response. As a nondigestible, nonviscous carbohydrate, resistant starch technically qualifies as an insoluble dietary fiber. However, unlike other insoluble fibers, microflora in the large intestine ferment it completely. Most people are surprised to discover natural resistant starch is already in their diets, says Witwer. A growing body of work shows natural resistant starch delivers some of the health benefits of fiber, plus offers some unique advantages of its own. And, like fiber, we are not consuming enough resistant starch to get the benefits.

Witwer goes on to explain that two recently published studies found improved insulin sensitivity in healthy subjects after supplementation with their natural high-amylose maize resistant starch. One study using a high dose (60 grams) demonstrated improvement within 24 hours; the other study, with half that amount consumed over 30 days, demonstrated a 33% increase in insulin sensitivity at a dose that was well-tolerated. In the longer-term study, observations of elevated ghrelin, a stomach hormone involved in appetite stimulation and other metabolic activity, and short-chain fatty acids accompanied changes in both adipose tissue and skeletal muscle metabolism deemed responsible for the increased insulin sensitivity. Further studies with larger numbers and insulin- resistant subjects are needed to confirm the value of resistant starch in controlling the glycemic response. It is important to note, however, that resistant starches are not a homogeneous category of ingredients, and the impact of chemically modified resistant starches (both soluble and insoluble) is generally unknown.

In addition to numerous physiological benefits, resistant starch works well in a number of applications, without affecting taste, texture or appearance. A small particle size, white color, bland flavor and low water-holding capacity make it easy to use as a one-for-one replacement for flour, but actual inclusion levels vary according to the particular starch being used, the actual application and its need for gluten, the desired fiber level, and processing conditions. Because these starches generally will not swell or contribute viscosity during most processing, a higher use level compared to traditional starches is possible in low-moisture systems. Pasta and bakery goods, some snacks and beverages are among the consumer products using our Hi-maize 5-in-1 Fiber, Witwer says. We even have a customer selling it on the Internet in 5- lb. bags for home use.

Fiber, sweetness and low GI

Another dietary fiber known for its beneficial gastrointestinal attributes as a prebiotic appears to also lower glycemic response when used for sugar replacement. Naturally-occurring soluble fibers are extracted from chicory root, inulin and shorter-chain fructooligosaccharides (FOS), or oligofructose. As such, it makes sense that their limited digestion in the colon and the resulting lower-caloric contribution would mean less effect on blood glucose levels.

Sensus America LLC, Monmouth, NJ, produces a number of inulin and FOS products for use in a wide range of applications in place of sugar and sugar alcohols. Sally Romano, vice president of sales and marketing, describes one of the companys inulin/FOS products as sweet liquid fiber. She says, this product is a natural, prebiotic fiber with a sweetness 50% that of sucrose. It is convenient, as it comes in a liquid form, and it can provide humectancy and shelf life in a range of products, from nutritional bars, dairy products, etc. With only 15% lower sugars and 85% inulin/FOS, it allows sugar reduction and the addition of dietary fiber in products such as cereal bars, yogurts, smoothie beverages, fruit preparations and jams, confections, sweet baked goods and cereals. Additional functional attributes include ease of handling in manufacturing process; synergy with high-intensity sweeteners, resulting in their reduced usage levels; masking of off-flavors from high intensity sweeteners; and enhancement of fruit flavors.

Both the liquid and powder inulin/ FOS products from Sensus America lay claim to a low GI rating. This makes it possible to create products with a low GI and GL by replacing both liquid glucose syrups and sugar, which is advantageous for diabetic and other low-GI diet strategies. A GRAS ingredient with no limits on usage levels, it also allows manufacturers the opportunity to produce products that boast about fiber content, reduced sugar and calories.

Some research demonstrates the potential value of inulin and FOS in lowering glycemic response and related symptoms. Last October, Orafti reported on the results of a new study from the scientists at Leatherhead Food International on the glycemic response of ice creams. In this industry-funded study, 12 healthy volunteers ate ice creams made with 15% of the companys oligofructose or different types of sugar replacers, or sucrose.

Measurements of blood glucose levels over a two-hour period showed that the glycemic response from oligofructose-containing ice cream at 14 was 70% lower when compared to traditional, sucrose-containing ice cream at 44. More recently, a pilot study in humans showed that supplementation with oligofructose confirmed results from animal studies that it can enhance satiety and lower energy and food intake, possibly through the effects on gut hormones.

Increasing options

A water extract of white kidney beans, already in use as a dietary supplement, recently was successfully tested for use in white bread to lower its GI. Previously shown to delay digestion and absorption of carbohydrates, the addition of 3,000 mg to commercially available white bread resulted in almost a 40% reduction in GI when compared to the same product without the extract, in studies conducted by Pacific West Research, Northridge, CA, a private clinical-trials facility. The manufacturer, Pharmachem Laboratories, Kearny, NJ, claims that the bean extract has no effect on taste or texture and can be incorporated into flour or baked goods at different production stages. Currently, this ingredient is in use in some low-carb breads and pastas in the United States, and in yogurt in Korea. The company hopes to receive GRAS status by April 2006.

For those trying to implement a low-GI diet strategy, white potatoes frequently end up on the list of foods to avoid. However, research reported in the April 2005 issue of the Journal of the American Dietetic Association demonstrated that the variety and method of preparation greatly influenced the GI. Additionally, precooking and reheating, or consuming potatoes cold, also resulted in a reduced GI, presumably from the formation of resistant starch. Thus, convenience foods and meals with precooked, frozen and then reheated potatoes offer glycemic advantages over fresh prepared and consumed potatoes.

Vivaldi, an Israeli-grown potato variety, offers a buttery taste with fewer carbohydrates and calories than traditional potatoes. Naturally Best, based in Lincolnshire, UK, bred this potato for its taste but recently determined that it contains 26% fewer carbohydrates and 33% fewer calories than typical potatoes, leading to expectations of a lower-GI value. This may represent yet another choice for potato lovers following a low-glycemic diet strategy.

Other common foods may help lower postprandial glycemia of high- GL meals. A study in the Dec. 2005 issue of the Journal of the American Dietetic Association examined the effect of adding vinegar or peanuts to a high-GL meal in healthy, nondiabetic subjects. This single intervention with a small number of subjects indicated that adding 20 grams cider vinegar with 5% acetic acid or 25 grams peanut butter may be an alternative way to lower the glycemic effect of a high-GL meal. If additional studies with larger numbers of healthy and diabetic subjects confirm this finding, then new opportunities to lower GL in foods and beverages consumed at mealtime or in convenience meals open up.

Available in a variety of unrefined foods, chromium works with insulin in regulating blood glucose levels. But since many Americans eat mostly refined and processed foods, an estimated 90% do not consume the recommended minimum intake of 50 micrograms a day. For this reason, many in the dietary- supplement world have long advocated the use of chromium picolinate for glucose-related health problems. With GRAS status for use in nutritional bars and beverages since 2002, it offers another option for formulating products aimed at glycemic control. In August 2005, FDA ruled on a qualified health claim petition from Nutrition 21, Inc., Purchase, NY, the manufacturers of a chromium picolinate supplement. Although FDA denied many of the requested claims related to cardiovascular and kidney diseases caused by insulin resistance or elevated blood sugar levels, they did allow one claim:

One small study suggests that chromium picolinate may reduce the risk of insulin resistance, and therefore possibly may reduce the risk of type 2 diabetes. FDA concludes, however, that the existence of such a relationship between chromium picolinate and either insulin resistance or type 2 diabetes is highly uncertain. While not a strong endorsement for chromium picolinates health benefits, its likely that those who already use it as a dietary supplement would welcome its addition to a tasty, nutritional food or beverage product.

From a marketing perspective, slow-carb or low-GI foods replaced the no/low carb fad. Many major manufacturers now formulate products with an eye toward their glycemic impact for consumers who need, or want, to control their blood glucose levels. But to achieve long-term success in this arena, food scientists will need to continually update products to reflect the latest in nutrition science on the effect of food, beverages and meals on blood glucose and related diseases.

Angela M. Miraglio, M.S., R.D., is a Fellow of the American Dietetic Association from Des Plaines, IL. Her firm, AMM Food & Nutrition Consulting, provides communications and technical support to the food and beverage industry. She can be reached at

[email protected].