Developing food strategies for the prevention of diabetes

Developing food strategies for the prevention of diabetes

Crafting foods with a healthier balance of carbohydrates, fats and proteins, as well as fortifying them with fibre and other micronutrients, can help prevent the progression of this disease. Manon Khazrai, PhD, investigates.


Various risk factors conspire in the development of type 2 diabetes. One of the primary ones is obesity — defined by a body mass index of over 30. Other risk factors include increased age, a family history of diabetes, prior history of gestational diabetes, impaired glucose tolerance, physical inactivity and race/ethnicity. In recent years there has been an increase in type 2 diabetes related to changes in lifestyle such as inactivity and diets rich in saturated fats.

The association between abdominal obesity (waist circumference >102cm in men, >88cm in women),1 high levels of low-density lipoprotein (LDL) cholesterol, low amounts of high-density lipoprotein (HDL) cholesterol, hypertriglyceridaemia, high blood pressure, high fasting glucose, and insulin resistance is highly predictive of type 2 diabetes.

Recently, a large clinical trial, the Diabetes Prevention Program (DPP),2 investigated whether diet and physical activity were more effective than the pharmaceutical metformin in preventing or delaying the onset of type 2 diabetes in subjects with impaired glucose tolerance and a family history of type 2 diabetes. The results of this study showed that the group that underwent lifestyle changes, intensive nutrition and exercise counselling (150 minutes a week), and behaviour modification lost seven per cent of their body weight, with a 58 per cent reduction in the incidence of diabetes vs. 31 per cent in the metformin group.

The clear message is that a realistic weight loss programme together with increased physical activity contributes to a reduction in weight and its maintenance with related positive health benefits. 3

A small caloric deficit of 500-800kcal/day is sufficient to achieve a weight loss of about one or two pounds per week.4 Total fat intake, particularly saturated fat, should be reduced as recent studies have reported the negative effect of dietary fat, especially saturated fats on insulin sensitivity. Moreover, reduction in fatty foods helps to lower the incidence of cardiovascular risk factors independent of weight reduction. A higher intake of dietary fibre has also been related to a decrease in the risk for type 2 diabetes.

The right mix

According to the American Diabetes Association, the goals of medical nutritional therapy for diabetes are to prevent and treat complications such as cardiovascular disease, hypertension, nephropathy, obesity and dislipidaemia, and include:

  • Achievement and maintenance of safe and near-to-normal or normal blood glucose levels
  • A normal lipoprotein profile
  • A change or improvement of health through food choices and physical activity
  • Careful consideration of personal and cultural choices.

A healthy and balanced diet should provide enough calories for the daily energy requirement to maintain or achieve reasonable body weight, to provide for the needs of pregnant or lactating women, to allow for normal growth in children and adolescents, and to satisfy the needs of ageing patients.

In general, a healthy diet should provide 55 per cent of calories from carbohydrates, 10-20 per cent from protein and 30 per cent or less from fat.

Carbohydrates are the body's main energy source.5 It is important that people with diabetes consume the right amount of carbohydrates, as they are the primary energy source for the central nervous system, which depends on blood glucose. Carbohydrates also have the role of 'protein sparer,' preventing the use of proteins for energy purposes, allowing them to perform their real role in tissue building and as metabolic primers for fat metabolism.

From a biochemical point of view, carbohydrates are divided into three groups: sugars, oligosaccharides and polysaccharides.

Simple sugars are thought to be absorbed quickly, thus rapidly increasing the level of blood sugars. Sugars should be restricted in the diet, as a high intake usually increases triglyceride levels in the blood and may also contribute to the development of dental caries. Moreover, sugars usually are associated with high-calorie foods, which should be limited in order to maintain a healthy body weight. Their amount should not be more than 10 per cent of the daily total energy intake. Polysaccharides are preferred, especially those containing fibre, because the more fibre food contains, the more slowly it is digested, raising blood-sugar levels at a slower rate.

A system for classifying carbohydrates, known as the glycaemic index, measures the effect that a food has on blood-sugar levels.6 Foods that have a high glycaemic index cause a rapid and strong rise in blood-sugar levels; diets filled with these foods have been linked to an increased risk for both diabetes and heart disease. Various factors, including the degree of processing, physical form and fibre content, determine a food's glycaemic index.

Foods that contain simple carbohydrates, such as potatoes, quickly raise blood-sugar levels, whereas foods that contain complex carbohydrates, such as whole fruit, raise blood-sugar levels more slowly. However, the glycaemic index relates to the quality and not the quantity of carbohydrates consumed — hence the glycaemic load concept was originated, which takes into account not just the quality of carbohydrate, but also the quantity.

Lipids: Because people with diabetes have an increased risk of heart and blood-vessel disease, a normal to low-fat diet is advisable in order to reach and maintain a desirable weight. As part of a healthy diet, 30 per cent of daily calories should come from fat, and of this, less than 10 per cent should be saturated fat, less than 10 per cent polyunsaturated fat and 10-15 per cent mono-unsaturated fat. However, a diet with a low intake of fat can be dangerous because not only is fat a major source of energy for the body, as it supplies 9kcal/g, it is also the source of essential fatty acids (EFAs), such as linoleic, linolenic and arachidonic acids. These are called 'essential' because the body cannot synthesize them and they are needed for a number of key functions such as transport and metabolism of cholesterol, precursors of prostaglandins and others.

Among the EFAs, omega-3 fatty acids found in fish, especially salmon, mackerel and herring, have been shown to lower plasma triglyceride levels in patients with type 2 diabetes. Moreover, fat is important because it helps the absorption of the fat-soluble vitamins A, D, E and K.

Mono-unsaturated fat is a type of unsaturated fat that lowers blood LDL cholesterol levels without altering those of HDL cholesterol.7 It is also resistant to oxidation. This is important because oxidation enables cells in arteries to absorb fats and cholesterol and helps accelerate the formation of plaques. This type of fat is found in olive oil, avocados, canola oil, etc. In people with diabetes, a diet higher in mono-unsaturated fats and lower in carbohydrates has been shown to reduce postprandial glycaemia and triglyceridaemia, but it is not recommended for someone with type 2 diabetes as it may cause weight gain. Mono-unsaturated fats and carbohydrate intake should be based on dietary goals and metabolic profile of each individual.

The effects of polyunsaturated fat on subjects with diabetes have not been well studied. Compared with mono-unsaturated fat, this vegetable fat lowers total blood cholesterol but is susceptible to oxidation, which ultimately may lead to coronary artery disease. Polyunsaturated fats are found in cottonseed, soybean, sunflower and safflower oils.

Saturated fat is an animal fat that raises total blood cholesterol and increases the risk for coronary artery disease.8 It is found in hydrogenated vegetable fats, coconut and palm oils, cocoa butter, meat fat, whole milk, butter cream, and fatty cheeses.

Protein should account for 15-20 per cent of total caloric intake, and should increase during pregnancy, breast feeding, infancy and childhood, illness, and disease.9

Proteins, unlike fats and carbohydrates, contain nitrogen. They are usually large molecules composed of amino acid, nine of which are 'essential' as they cannot be synthesized and must be supplied by the diet. Foods that have all nine essential amino acids present are considered complete. These foods are of animal origin — meat, eggs, fish and poultry.

Amino acids are the basic building blocks of the body and thus proteins are needed to build and maintain specific tissues. Proteins are normally not energy suppliers, but in cases of stress, diseases or fasting, when there is either an increased need for energy or the caloric intake is not sufficient to cover the body's needs, they are used to provide energy. Thus, a diet with the right amount of carbohydrates has a protein-sparing effect. However, dietary-protein intake must be balanced, as large amounts can cause gout or kidney stones in some individuals, as purine breaks down to uric acid, and high concentrations can crystallize in the kidneys and joints. Moreover, excess nitrogen is a burden for the kidneys and animal food proteins are also rich in fat, especially saturated types, which cause cardiovascular disease and obesity.

Fibre is the indigestible part of plant foods.10 There are two types of fibre: soluble and insoluble. Soluble fibres, such as gums and mucilages, form gels with pectin or gums in the intestine and thus slow the rate of nutrient absorption, helping to reduce postprandial glucose levels. Insoluble fibres, such as lignins, celluloses and hemicelluloses, increase bulk and decrease transit time. Both types are useful as they prolong gastric emptying, shorten intestinal transit time, prevent constipation and bind cholesterol, thus limiting its absorption. Foods rich in fibre include vegetables, fruits, whole wheat, bran, cereals and legumes. An adequate diet should provide 30g/day fibre.

Vitamins and minerals are certainly required in illness, stress or pregnancy. High doses of dietary antioxidants such as vitamins C and E, selenium, beta-carotene, and other carotenoids have been prescribed to people with diabetes.11 Antioxidants are substances that neutralize the action of free radicals, which are molecules that damage cells, and increase the risk of cancer and heart disease. In this case they are thought to protect LDL particles from oxidation. The role of micro-elements zinc and chromium in glycaemic control is difficult to determine, as they are present in minute amounts and their deficiency is not easily assessed. Although a number of studies show that chromium can help manage blood-sugar levels.

Sodium in the diet should be limited, according to the ADA, because it helps reduce blood pressure and the tendency to retain fluids. The main source of sodium in the diet is common table salt. However, as natural foods contain the right amount for the body's need, the general consumption of salt is too high and the recommended goal is to reduce sodium intake to 2,400mg or sodium chloride (salt) to 6,000mg/day. Snacks, pickles, bacon, sauces, olives, chips and processed foods in general contain too much salt and should be cut down.

Future trends

Prevention is the key to addressing diabetes. The International Diabetes Federation (IDF) and other diabetes associations, with the aid of the World Health Organization, should join forces to put pressure on governments to pay more attention to diabetes. As subjects at high risk for type 2 diabetes are easily identifiable, in the future governments should collaborate in changing population behaviours, for example with advertisements and campaigns against junk food, inactivity and obesity. The IDF states that as good metabolic control can prevent the complications of diabetes, it will ask governments to push for better treatment as well.

1. Kelley DE, Goodpaster BH. Skeletal muscle triglyceride. An aspect of regional adiposity and insulin resistance. Diabetes Care 2001;24:933-41.
2. Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002;346:393-403.
3. Bosello O, et al. The benefits of modest weight loss in type 2 diabetes. Int J Obes Relat Metab Disord 1997;21(Suppl 1):S10-13.
4. American Dietetic Association. Position statement. Weight management — position of ADA. J Am Diet Assoc 2002;102:1145-55.
5. American Diabetes Association. Evidence-based nutrition principles and recommendations for the treatment and prevention of diabetes and related complications. Diabetes Care 2002;25 (Suppl 1):S50-S60.
6. Jenkins DJ, et al. Starchy foods and glycemic index. Diabetes Care 1988;11:149-59.
7. Berry EM, et al. Effects of diets rich in monounsaturated fatty acids on plasma lipoproteins — the Jerusalem Nutrition study: high MUFAs vs high PUFAs. Am J Clin Nutr 1991;53:899-907.
8. Expert panel on detection, evaluation and treatment of high blood cholesterol in adults. Executive summary of the third report of the national cholesterol education program (NCEP). Adult treatment panel III. JAMA 2001;285:2486-97.
9. Franz MJ. Protein and diabetes: much advice, little research. Curr Diab Rep 2002;2:457-64.
10. Nuttall FQ. Dietary fiber in the management of diabetes. Diabetes 1993;42:503-8.
11. Ylonen K, et al. Dietary intakes and plasma concentrations of carotenoids and tocopherols in relation to glucose metabolism in subjects at high risk of type 2 diabetes: the Botnia Dietary Study. Am J Clin Nutr 2003;77:1434-41.

Formulator options: sweeteners and sugar alternatives for diabetes products

As options for sugar replacement continue to increase, one of the major concerns for product developers is formulating the correct sweetening and bulking system. Expert knowledge of ingredients and their properties allows for the making of products that not only taste and perform comparably to the standard product, but could also offer, for instance, caloric and dental benefits to the end consumer. Additional, more specialised end-consumer benefits also become achievable, including suitability for diabetics (through reduced glycaemic response) and gut-health benefits (due to the prebiotic effect of a number of bulk alternative sweeteners and bulking agents).

A number of classifications can be used to describe alternative ingredients to sugar, the major two being high-potency sweeteners and sugar alcohols. However, also worth mentioning are bulking agents. In general, bulking agents will provide body and texture to the final product and are usually low in sweetness and low in calories. An example of a commonly used bulking agent is a randomly bonded melt condensation polymer of dextrose branded as Litesse. It is non crystalline, but its high viscosity in solution makes it a valuable ingredient for providing bulk and mouthfeel. Litesse has only 1kcal/g and is a prebiotic fibre source.

Sugar alcohols, or polyols, are produced by the catalytic hydrogenation of the corresponding saccharide. For example, lactitol is produced from lactose, and xylitol from xylose. Many can be found in nature in plants and fruits, although extraction from these sources is not economically viable. The hydrogenation process greatly modifies the physico-chemical properties of the sugar alcohol compared to that of the corresponding precursor sugar. The hydrogenated nature of the sugar alcohols also causes them to be less prone to microbiological fermentation and more difficult for mammals to digest and absorb. It is for this reason that sugar alcohols have a reduced caloric value, can be used in tooth-friendly products and are suitable for diabetics.

The right choice of carbohydrate in a food product can make an important contribution to the organoleptic quality of the product, but also has a great influence on our physiology and general health. These speciality carbohydrates all have low-glycaemic responses and are ideally suited for use in the development of better-for-you products that may be fat- or sugar reduced, sugar free, calorie controlled, or low GI.

Helen Mitchell, PhD, is director of applications at Danisco Sweeteners, which offers full technical and application assistance in all areas of food product development globally.

Select suppliers: ingredients for diabetic-friendly products

Acatris: FenuLife is an odourless and tasteless fenugreek extract for supplements and foods to curb appetite, reduce the glycaemic index, and balance blood sugar. It is high in dietary fibre (50 per cent), of which 15-20 per cent is galactomannan.

Cargill: Oliggo-Fiber inulin is a non-digestible soluble fibre extracted from chicory root. Inulin does not significantly affect blood-sugar levels. Ascend brand trehalose is a sugar replacer that elicits a lower insulin response than glucose before or during continuous exercise. Its mildly sweet taste makes it ideal for sports drinks and nutrition bars. Xtend isomaltulose is a novel slowly digestible sweetener made from sucrose and maltose to reduce the glycaemic and insulinemic response in foods.

Cevena: Viscofiber is the only viscous oat and barley beta-glucan concentrate commercially available for the dietary-supplements and functional-foods market. Its high concentration of beta-glucan gives it its health benefits for bars, cereals, soups, beverages, baked goods, yoghurt, ice cream, pasta and more.

Danisco Sweeteners: Litesse is a speciality carbohydrate with only 1 kcal per gram. Originally developed as a sugar replacer while providing bulk and mouthfeel, more recently it has been discovered that the prebiotic fibre source can also act as a partial fat replacer in shortcrust pastry.

GTC: Natureal oat bran contains a minimum of 15 per cent oat beta-glucan as dry substance, a natural, soluble fibre suitable for blood-glucose control in nutrition bars, cereals, meal-replacement products and more.

Gum Technology has much experience in weight-loss and weight-control products. Guar and locust bean gum have been shown to be useful in controlling diabetes.

Integrity Nutraceuticals: Cinnulin PF is a water extract of cinnamon that contains active compounds to help control glucose levels without the harmful toxins found in whole cinnamon or fat-soluble extracts.

InterHealth: ChromeMate niacin-bound chromium nicotinate increases the safety and effectiveness of chromium, an essential trace mineral required for normal insulin function.

Jungbunzlauer: Erythritol is a low-calorie, non-cariogenic bulk sweetener qualified for use in sugar-free, reduced sugar or low-calorie foods such as ice cream, chocolates, bakery and confectionery. European approval of erythritol is expected soon.

Matsutani/ADM: Fibersol-2 is a unique digestion-resistant maltodextrin soluble dietary fibre and a low-calorie bulking and bodying agent that's been shown to reduce the post-meal rise in blood-glucose levels. It has low viscosity, bland taste, low hygroscopicity and high stability. ADM is the exclusive North American distributor.

National Starch: Hi-Maize resistant starch reduces the glycaemic response compared to carbohydrate foods such as bread without added Hi-maize.

Nutrinova: Sunett brand ace-K is a high-intensity sweetener used to replace sugar in beverages, confectionery, baked goods, dairy products and more.

Nutrition 21: Chromax brand chromium picolinate has an FDA-qualified health claim as a supplemental ingredient that may reduce the risk of insulin resistance and possibly type 2 diabetes.

Orafti: Beneo inulin and oligofructose non digestible dietary fibres both have a glycaemic index of virtually zero, which means they break down slowly in the digestive system, causing slow and steady rises rather than sudden spikes in blood sugar and insulin levels.

Sabinsa: Selenium SeLECT mimics the action of insulin by stimulating glucose uptake and regulating metabolic processes. Highly bioavailable, only for supplements.

Tate & Lyle: Splenda brand sucralose is the hottest high-intensity sweetener on the market, rapidly gaining ground on aspartame for the sugar-alternative market share.

TIC Gums: TICorganic Certified Organic Inulin is a source of soluble dietary fibre in beverages and functional foods. Part of the company's full range of hydrocolloids, TICorganic Inulin has a low viscosity even at levels as high as 15 per cent.

Z Sweet: With no calories and no glycaemic effect, Z Sweet is ideal for diabetic-food and beverage-sweetener applications. The GRAS ingredient is a proprietary blend of erythritol and natural flavours.


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