New approaches to providing nutritional information J. A Monro, New Zealand Institute for Crop Food Research 7.1 Introduction Both food processors and consumers have a basic need for valid and relevant nutritional information; on the one hand to guide production and marketing of genuinely functional products, and on the other to allow selection of products according to efficacy. Data on product efficacy that are relevant, in the sense of being easily communicated, understood and appropriately applied are, however often unavailable. There is little to guide evidence-based food choice to meet such widespread health challenges as control of blood glucose levels, and maintenance of large bowel function, two examples that will be considered in detail in this o New approaches to nutritional information must, therefore, focus not only on ata that validly represent physiological changes linked to health, but also on transforming the data to show meaningfully the relative efficacy with which prod ucts can bring about change. This chapter focuses on new approaches to nutri- tional information that attempt to link food choice to health end-points through effective communication 7.2 Why food processors need new types of nutritional information Food processing has been shown to have large effects on a range of nutritional properties. Changes in macronutrients, such as starch and protein, 3and the destruction of vitamins during food processing, have been well documented and are updated in this book. Most studies have been constrained by
7 New approaches to providing nutritional information J. A. Monro, New Zealand Institute for Crop & Food Research 7.1 Introduction Both food processors and consumers have a basic need for valid and relevant nutritional information; on the one hand to guide production and marketing of genuinely functional products, and on the other to allow selection of products according to efficacy. Data on product efficacy that are relevant, in the sense of being easily communicated, understood and appropriately applied are, however, often unavailable. There is little to guide evidence-based food choice to meet such widespread health challenges as control of blood glucose levels, and maintenance of large bowel function, two examples that will be considered in detail in this chapter. New approaches to nutritional information must, therefore, focus not only on data that validly represent physiological changes linked to health, but also on transforming the data to show meaningfully the relative efficacy with which products can bring about change. This chapter focuses on new approaches to nutritional information that attempt to link food choice to health end-points through effective communication. 7.2 Why food processors need new types of nutritional information Food processing has been shown to have large effects on a range of nutritional properties.1 Changes in macronutrients, such as starch and protein,2,3 and the destruction of vitamins during food processing,4 have been well documented, and are updated in this book. Most studies have been constrained by
166 The nutrition handbook for food processors experimental design to a few foods and conditions, and apart from effects on nutrient levels measured in standard food analyses, nutritional information that reflects the effects of processing does not generally reach consumers in a form in which it can be widely used to choose foods. Similarly, food processors often do not have available means to apply, either accurately or practically, relevant nutritional criteria to select prototype products during development. Below are listed several reasons for the need for new nutritional information 7.2.1 Showing effects of food properties on nutritional qualities Much of the impact of processing on nutritional quality comes about through changes in physicochemical properties of food polymers, such as dietary fibre, hat cannot be represented by food composition values. Changes in structure asso- ciated with such processes as starch hydration and gelatinisation, milling, and extrusion,can have an large impact on the rate and extent of digestion, and onsequently on a range of physiological markers linked to disease end-points For example, the impact of cereals on blood glucose and insulin responses is increased markedly as particle size is reduced by milling, or as starch is 7.2.2 Tracking changes in nutritional quality Information from rapid, valid, but relevant tests is needed to guide processing to healthy products. Because of the expense, time, ethics, compliance and other issues involved in clinical trials, human subjects are not usually suitable for mon- oring effects of processing until potential products have been identified Food processing for improved nutrition may require pragmatic choice of dif- ferent tests at different stages in product development, to maintain momentum in product development. Active ingredients and formulations may be identified with screening tests, using indirect predictors of health effects, such as ingredient prop- erties. Responses in animal models may guide food processing further, and most promising products then taken into clinical trials, in which effects on biomarkers with established links to health end-points are measured, before a claim of efficacy is made. Increasing rigour in nutritional evaluation of functional prop. erties during the course of product development is illustrated in Table 7.1 As a general principle, the properties of foods that affect physiology should be measured under conditions as close as is reasonable to those in which the food property acts in vivo. Developing a soluble fibre-enriched product to lower blood cholesterol is an example. Ingredients of high soluble fibre content could be iden tified using soluble fibre analysis under simulated gastrointestinal conditions. 12 As hypocholesterolaemic effects of soluble dietary fibres result from increased intestinal viscosity, fibre viscosity should be measured, followed by in vitro digestion of products containing selections of viscous fibre sources, with mea surement of digesta viscosity. Promising products could be subjected to animal trials to establish that predicted gut viscosity and blood lipid changes occur
experimental design to a few foods and conditions, and apart from effects on nutrient levels measured in standard food analyses, nutritional information that reflects the effects of processing does not generally reach consumers in a form in which it can be widely used to choose foods. Similarly, food processors often do not have available means to apply, either accurately or practically, relevant nutritional criteria to select prototype products during development. Below are listed several reasons for the need for new nutritional information. 7.2.1 Showing effects of food properties on nutritional qualities Much of the impact of processing on nutritional quality comes about through changes in physicochemical properties of food polymers, such as dietary fibre,5 that cannot be represented by food composition values. Changes in structure associated with such processes as starch hydration and gelatinisation,6 milling,7 and extrusion,8 can have an large impact on the rate and extent of digestion, and consequently on a range of physiological markers linked to disease end-points. For example, the impact of cereals on blood glucose and insulin responses is increased markedly as particle size is reduced by milling,7 or as starch is gelatinised.6,9 7.2.2 Tracking changes in nutritional quality Information from rapid, valid, but relevant tests is needed to guide processing to healthy products. Because of the expense, time, ethics, compliance and other issues involved in clinical trials, human subjects are not usually suitable for monitoring effects of processing until potential products have been identified. Food processing for improved nutrition may require pragmatic choice of different tests at different stages in product development, to maintain momentum in product development. Active ingredients and formulations may be identified with screening tests, using indirect predictors of health effects, such as ingredient properties. Responses in animal models may guide food processing further, and most promising products then taken into clinical trials, in which effects on biomarkers with established links to health end-points are measured,10,11 before a claim of efficacy is made. Increasing rigour in nutritional evaluation of functional properties during the course of product development is illustrated in Table 7.1. As a general principle, the properties of foods that affect physiology should be measured under conditions as close as is reasonable to those in which the food property acts in vivo. Developing a soluble fibre-enriched product to lower blood cholesterol is an example. Ingredients of high soluble fibre content could be identified using soluble fibre analysis under simulated gastrointestinal conditions.12 As hypocholesterolaemic effects of soluble dietary fibres result from increased intestinal viscosity,13 fibre viscosity should be measured, followed by in vitro digestion of products containing selections of viscous fibre sources, with measurement of digesta viscosity. Promising products could be subjected to animal trials to establish that predicted gut viscosity and blood lipid changes occur 166 The nutrition handbook for food processors
New approaches to providing nutritional information 167 Table 7.1 Types of nutritional tests that may be used in food processing at different stages of product development Level of se in food processing Comments Ingredient Identifying ingredients May change in processing. Affected by with desired properties food matrix and gut milieu. Cheap Food De ent retention es physiochemical properties, composition Meeting labeling ailability, and bioactivity, but relatively cheap In vitro Predicting responses to gut May give an indication of effects of digestion on food properties, but not take other important food-host interaction Animal Predicting effects in the May be physiologically different to models whole body context humans Require validation. Compliance studie u le lly limited application Costly, slow, ethically difficult, study earing final product. population variable, compliance may be poor. Intermediate endpoints required Epidemiology Identifies possible health- Associations identified, but not cause relevant food factors effect relationship(uncertain) Ecologically valid. Not suitable for Case-control Identifying possible f Less controlled than experimental factors in health b methods leaving room for doubt about cause-effect Experimental Provides basis for a health Most rigorous, but findings apply to the claim experimental conditions -may lack external validity. in vivo. Final selections could then be clinically evaluated, to establish firmly their potential as functional foods for humans. 7. 2.3 Avoiding unjustified extrapolation between products The complexity of processing effects on food matrices makes nutritional proper ties susceptible to processing conditions, and extrapolation of function between different products uncertain. Nonetheless, it is a common cost-cutting measure for marketers to use a functional effect of a bioactive in one product, to promote other foods containing the bioactive, but with a different processing history. To reduce unjustified extrapolation, information is required from tests that are prac tical and inexpensive enough to use for detecting nutritional effects of different processing conditions in large numbers of samples
in vivo. Final selections could then be clinically evaluated, to establish firmly their potential as functional foods for humans. 7.2.3 Avoiding unjustified extrapolation between products The complexity of processing effects on food matrices makes nutritional properties susceptible to processing conditions, and extrapolation of function between different products uncertain.14 Nonetheless, it is a common cost-cutting measure for marketers to use a functional effect of a bioactive in one product, to promote other foods containing the bioactive, but with a different processing history. To reduce unjustified extrapolation, information is required from tests that are practical and inexpensive enough to use for detecting nutritional effects of different processing conditions in large numbers of samples. New approaches to providing nutritional information 167 Table 7.1 Types of nutritional tests that may be used in food processing at different stages of product development Level of Use in food processing Comments evidence Ingredient Identifying ingredients May change in processing. Affected by properties with desired properties. food matrix and gut milieu. Cheap and quick. Food Defining nutrient retention. Ignores physiochemical properties, composition Meeting labeling bioavailability, and bioactivity, but requirements. relatively cheap. In vitro Predicting responses to gut May give an indication of effects of digestion conditions. digestion on food properties, but not take other important food-host interactions into account. Animal Predicting effects in the May be physiologically different to models whole body context. humans. Require validation. Compliance good. Human Usually limited application Costly, slow, ethically difficult, study studies95 until nearing final product. population variable, compliance may be poor. Intermediate endpoints required. Epidemiology Identifies possible health- Associations identified, but not causerelevant food factors. effect relationship (uncertain). Ecologically valid. Not suitable for product testing. Case-control Identifying possible food Less controlled than experimental factors in health by methods leaving room for doubt about association. cause-effect. Experimental Provides basis for a health Most rigorous, but findings apply to the claim. experimental conditions – may lack external validity
168 The nutrition handbook for food processors 7. 2.4 Helping consumers choose foods for health Food properties can be used to select foods for health only if supported by useable efficacy data. Information from tests of the nutritional and functional propertie of foods needs to be easily used by both processors and consumers, to discrimi nate between products. Without scientific but communicable efficacy data, food processors cannot develop or ethically promote foods, and consumers cannot choose foods for real health effects 7.2.5 Gaining consumer confidence Consumer confidence in a product or company requires that claimed benefits are delivered Distrust is associated with perceptions of deliberate distortion of infor- mation, and having been proven wrong in the past. Therefore, the more that the benefits of a food product are exaggerated and overextrapolated, while scrutiny by food regulators and nutritionists continues, the greater the likelihood of gen- erating mistrust. Investment in tests to demonstrate real differences in efficacy of oducts is, therefore, a prudent strategy. 7.3 Limitations of food composition data in food processing A number of related reasons why simple direct relationships between constituent levels in foods and effects on health cannot be assumed are outlined below 7.3.1 People eating foods are complex systems consuming complex systems Food composition data are obtained from standardised analyses of discrete nutri ents, whereas the nutritional effects of food components are modulated by mul tiple interactions within the food matrix, within the gut, and within the body after absorption. Effects of nutrients in foods are, therefore, seldom the same when consumed in a food, as they would be if consumed as a pure nutrient. Yet, food composition is often used as a measure of ' nutritional quality', and nutrient formation panels have been the consumers' main guide to healthy food selec- tion. The ability to make informed food choices for health has therefore been quite restricted 7.3.2 Analytical data may not reflect bioactivit Bioactivity is determined by response of the body to food. Several metabolic steps may converge to contribute more to a response than might be expected from amounts of a single active component in a food. For instance, vitamin A acti- vity may be obtained not only from vitamin A as retinal, but also from a range of provitamin A carotenoid precursors. Therefore, analytical methods must
7.2.4 Helping consumers choose foods for health Food properties can be used to select foods for health only if supported by useable efficacy data.15 Information from tests of the nutritional and functional properties of foods needs to be easily used by both processors and consumers, to discriminate between products. Without scientific but communicable efficacy data, food processors cannot develop or ethically promote foods, and consumers cannot choose foods for real health effects. 7.2.5 Gaining consumer confidence Consumer confidence in a product or company requires that claimed benefits are delivered. Distrust is associated with perceptions of deliberate distortion of information, and having been proven wrong in the past.16 Therefore, the more that the benefits of a food product are exaggerated and overextrapolated, while scrutiny by food regulators and nutritionists continues, the greater the likelihood of generating mistrust. Investment in tests to demonstrate real differences in efficacy of products is, therefore, a prudent strategy. 7.3 Limitations of food composition data in food processing A number of related reasons why simple direct relationships between constituent levels in foods and effects on health cannot be assumed are outlined below. 7.3.1 People eating foods are complex systems consuming complex systems Food composition data are obtained from standardised analyses of discrete nutrients, whereas the nutritional effects of food components are modulated by multiple interactions within the food matrix,17 within the gut,18 and within the body after absorption.19 Effects of nutrients in foods are, therefore, seldom the same when consumed in a food, as they would be if consumed as a pure nutrient. Yet, food composition is often used as a measure of ‘nutritional quality’, and nutrient information panels have been the consumers’ main guide to healthy food selection. The ability to make informed food choices for health has therefore been quite restricted. 7.3.2 Analytical data may not reflect bioactivity20 Bioactivity is determined by response of the body to food. Several metabolic steps may converge to contribute more to a response than might be expected from amounts of a single active component in a food. For instance, vitamin A activity may be obtained not only from vitamin A as retinal, but also from a range of provitamin A carotenoid precursors.21 Therefore, analytical methods must 168 The nutrition handbook for food processors
New approaches to providing nutritional information 169 measure not only vitamin A in a food, but also carotenoids with the potential for conversion to active vitamin A, as vitamin A equivalents. Similarly, blood lipid is a biomarker that depends on more than dietary lipids as lipid type and carbo- hydrate intake, for instance, may also affect blood lipids 7.3.3 Availability or extraction in analytical systems may not equate with bioavailability Analyses are usually designed to measure all of a component of interest in a food, rather than the bioavailable fraction. Most samples are finely ground to facilitate complete extraction with an effective solvent. As a result, food components may be much more soluble during food analysis than during digestion in the gut Soluble dietary fibre is a good example; as prescribed in the American Associa- tion of Analytical Chemists method for soluble fibre analysis, food samples must be finely ground and extracted in hot buffer at 100C, whereas in the gut extrac tion is normally at 364C, from a mixture of particles. Soluble fibre extraction in gut conditions may therefore be much less than in fibre analysis 7.3.4 Physiological effects of food constituents depend on prior physiological state The effects of food constituents are emergent consequences of the interaction between food and body, and subject to the existing physiological state. A viscous polysaccharide may, for instance, lower blood cholesterol in subjects with hyper cholesterolemia, with much less effect in normals. Similarly, the impact of a food carbohydrate on blood glucose levels is affected by the capacity of the bodys cells to absorb glucose, which may be affected by insulin release, by sensitivity to insulin, and by the state of muscle glycogen reserves as a result of exercise The body may modulate uptake and utilisation of a nutrient in response to nutrient status; iron uptake is increased in states of iron deficiency,and vitamin C is excreted when uptake exceeds requirements. 0 7.3.5 A single analytical value may represent a group of compounds differing in nutritional properties Physiological effects often depend on physicochemical properties that vary within a food constituent class that is represented by a single analytical value. Total dietary fibre as a single value in a food table is a family of compounds of diverse form, physicochemical properties, and physiological effects. Dietary fibres exist as insoluble faecal bulking materials, such as wheat bran, that have little impact on blood cholesterol, or as viscous, fermentable, cholesterol-lowering polysaccharides, such as guar gum, that have relatively little impact on faecal bulk
measure not only vitamin A in a food, but also carotenoids with the potential for conversion to active vitamin A, as vitamin A equivalents. Similarly, blood lipid is a biomarker that depends on more than dietary lipids as lipid type and carbohydrate intake, for instance, may also affect blood lipids.22 7.3.3 Availability or extraction in analytical systems may not equate with bioavailability23 Analyses are usually designed to measure all of a component of interest in a food, rather than the bioavailable fraction. Most samples are finely ground to facilitate complete extraction with an effective solvent.24 As a result, food components may be much more soluble during food analysis than during digestion in the gut. Soluble dietary fibre is a good example; as prescribed in the American Association of Analytical Chemists method for soluble fibre analysis,25 food samples must be finely ground and extracted in hot buffer at 100 °C, whereas in the gut extraction is normally at 36.4 °C, from a mixture of particles. Soluble fibre extraction in gut conditions may therefore be much less than in fibre analysis.26 7.3.4 Physiological effects of food constituents depend on prior physiological state The effects of food constituents are emergent consequences of the interaction between food and body, and subject to the existing physiological state. A viscous polysaccharide may, for instance, lower blood cholesterol in subjects with hypercholesterolaemia, with much less effect in normals.27 Similarly, the impact of a food carbohydrate on blood glucose levels is affected by the capacity of the body’s cells to absorb glucose, which may be affected by insulin release, by sensitivity to insulin, and by the state of muscle glycogen reserves as a result of exercise.28 The body may modulate uptake and utilisation of a nutrient in response to nutrient status; iron uptake is increased in states of iron deficiency,29 and vitamin C is excreted when uptake exceeds requirements.30 7.3.5 A single analytical value may represent a group of compounds differing in nutritional properties Physiological effects often depend on physicochemical properties that vary within a food constituent class that is represented by a single analytical value. Total dietary fibre as a single value in a food table is a family of compounds of diverse form, physicochemical properties, and physiological effects.31 Dietary fibres exist as insoluble faecal bulking materials, such as wheat bran, that have little impact on blood cholesterol,32 or as viscous, fermentable, cholesterol-lowering polysaccharides, such as guar gum,33 that have relatively little impact on faecal bulk.34 New approaches to providing nutritional information 169
170 The nutrition handbook for food processors 7.3.6 Food matrix properties may strongly modulate nutritional effects 5 Food processing may give products of the same composition, with markedly different physiological effects, because of differences in structure and physico- chemical properties. For instance, digestion in a porous starch-protein matrix in the form of bread takes place much more rapidly than in a solid, non-porous matrix of similar composition, in the form of pasta or whole kernels, which con- sequently have less impact on blood glucose levels. 7.4 Foundations for practical nutritional information Several characteristics of nutritional information for evidence-based food choices for health are summarized below and will be illustrated with reference to data sets for managing blood glucose (Table 7.2)and large bowel function respec tively (Table 7.3). In a nutshell, health end-points need to be selected, markers Table 7.2 Developing nutritional data sets related to health end-points associated with elevated blood glucose Consideration Relevance to blood glucose End-points Disorders from glycation and glycaemia, including vascular disease of retina, kidneys, nerves. Heart disease. Polyuria. Intermediate Postprandial glycaemic response: blood glucose elevation underlies point or many long term complications of diabetes mellitus, involving marker of hyperinsulinaemia and glycation. Currentl Sugars and available carbohydrate: not dependable indicators of blood sed indic ucose response, which depends on digestion rate of available carbohydrates and on their monosaccharide composition Glycaemic index(GI): A percentage based on glycaemic response to food carbohydrate compared with response to glucose. Use restricted to equicarbohydrate comparisons and does not respond to food intake. Not useful for accurate blood glucose control Relevant Relative glycaemic potency(RGP):A percentage based on index comparison of food with glucose. RGP ranks whole foods by ycaemic impact on an equal weight basis, but does not re food intake. Suitable for food comparisons on an equal wei Practical Glycaemic glucose equivalents(GGE): Derived from RGP.A units measure of glycaemic impact based on foods. Responsive to food quantity. Useful for communicating efficacy Can be applied to food items of any weight. Validation Clinical measurements have shown that GGE intake predicts and intake a sponse to foods of different GL, carbohydrate content, carbohydrate doses consumed in most meals
7.3.6 Food matrix properties may strongly modulate nutritional effects35 Food processing may give products of the same composition, with markedly different physiological effects, because of differences in structure and physicochemical properties. For instance, digestion in a porous starch-protein matrix in the form of bread takes place much more rapidly than in a solid, non-porous matrix of similar composition, in the form of pasta or whole kernels, which consequently have less impact on blood glucose levels.36,37 7.4 Foundations for practical nutritional information Several characteristics of nutritional information for evidence-based food choices for health, are summarized below and will be illustrated with reference to data sets for managing blood glucose (Table 7.2) and large bowel function respectively (Table 7.3). In a nutshell, health end-points need to be selected, markers 170 The nutrition handbook for food processors Table 7.2 Developing nutritional data sets related to health end-points associated with elevated blood glucose Consideration Relevance to blood glucose End-points Disorders from glycation and glycaemia, including vascular disease of retina, kidneys, nerves. Heart disease. Polyuria. Intermediate Postprandial glycaemic response: blood glucose elevation underlies end-point or many long term complications of diabetes mellitus, involving marker of hyperinsulinaemia and glycation. effect Currently Sugars and available carbohydrate: not dependable indicators of blood used indices glucose response, which depends on digestion rate of available carbohydrates and on their monosaccharide composition. Glycaemic index (GI): A percentage based on glycaemic response to food carbohydrate compared with response to glucose. Use restricted to equicarbohydrate comparisons and does not respond to food intake. Not useful for accurate blood glucose control. Relevant Relative glycaemic potency (RGP):58 A percentage based on index comparison of food with glucose. RGP ranks whole foods by their glycaemic impact on an equal weight basis, but does not respond to food intake. Suitable for food comparisons on an equal weight basis. Practical Glycaemic glucose equivalents (GGE):44 Derived from RGP. A units measure of glycaemic impact based on foods. Responsive to food quantity. Useful for communicating efficacy. Can be applied to food items of any weight. Validation Clinical measurements have shown that GGE intake predicts glycaemic response to foods of different GI, carbohydrate content, and intake at carbohydrate doses consumed in most meals.61
New approaches to providing nutritional information 171 identified that can be causally linked to the end-points, valid indicator variables that predict changes in markers identified for practical tests, and measurements icated so they can be easily understood 7.4.1 End-points that are important to well-being A number of health and disease end-points, affecting a large proportion of the population, need to be addressed in developing healthy foods. Some, such as car diovascular disease, colorectal cancer, osteoporosis, and constipation are associ- ated with a combination of ageing and unhealthy dietary patterns. Others, such as obesity, are largely the result of food processors and marketers successfully providing foods that appeal to the basic human preferences for sweetness and fats, in all age groups. It would be best to design foods with a number of end- points in mind, and evaluate them with a battery of tests to demonstrate nutri- tional balance. Producing foods for specific functions or using foods as medicines risks unbalanced nutrient intake 7.4.2 Biomarkers that are relevant s To be health-relevant and useable, food information needs to relate to practically measurable but valid markers linked to health end-points, such as blood cho- lesterol in relation to cardiovascular disease, or alterations in faecal components Table 7.3 Developing nutritional data sets related to health end-points associated with insufficient faecal bulk Consideration Relevance to faecal bulk Various large bowel disorders including constipation, diverticulosis, colorectal cancer Intermediate Faecal mass, repres distal colonic bulk. biomarker Currently used fibre: does not reliably predict faecal bulk because bulking depend on fermentability, water holding capacity and bacterial Relevant index Faecal bulking index(FBI): The impact of a whole food on faecal bulk as a percentage of the effect of an equal weight of wheat bran. Usable for measuring efficacy on an equal weight basis Practical units Wheat bran equivalents(WBEab): Expressed as a content in foods. lay be used to communicate relative efficacy. Applicable to food items of any weight. Validation aecal bulking response measured as mass of rat faecal pellets after hydration closely reflects response in humans
identified that can be causally linked to the end-points, valid indicator variables that predict changes in markers identified for practical tests, and measurements communicated so they can be easily understood. 7.4.1 End-points that are important to well-being A number of health and disease end-points, affecting a large proportion of the population, need to be addressed in developing healthy foods. Some, such as cardiovascular disease, colorectal cancer, osteoporosis, and constipation are associated with a combination of ageing and unhealthy dietary patterns. Others, such as obesity, are largely the result of food processors and marketers successfully providing foods that appeal to the basic human preferences for sweetness and fats, in all age groups. It would be best to design foods with a number of endpoints in mind, and evaluate them with a battery of tests to demonstrate nutritional balance. Producing foods for specific functions or using foods as medicines risks unbalanced nutrient intake. 7.4.2 Biomarkers that are relevant38 To be health-relevant and useable, food information needs to relate to practically measurable but valid markers linked to health end-points,10,38 such as blood cholesterol in relation to cardiovascular disease,39 or alterations in faecal components New approaches to providing nutritional information 171 Table 7.3 Developing nutritional data sets related to health end-points associated with insufficient faecal bulk Consideration Relevance to faecal bulk End-points Various large bowel disorders including constipation, diverticulosis, colorectal cancer. Intermediate Faecal mass, representing distal colonic bulk. end-point or biomarker Currently used Dietary fibre: does not reliably predict faecal bulk because bulking index effects depend on fermentability, water holding capacity and bacterial growth. Relevant index Faecal bulking index (FBI):34 The impact of a whole food on faecal bulk as a percentage of the effect of an equal weight of wheat bran. Usable for measuring efficacy on an equal weight basis. Practical units Wheat bran equivalents (WBEfb):42 Expressed as a content in foods. May be used to communicate relative efficacy. Applicable to food items of any weight. Validation Faecal bulking response measured as mass of rat faecal pellets after hydration closely reflects response in humans.85
172 The nutrition handbook for food processors in relation to colon cancer, and to be obtained with standardised procedures that can be applied to a wide enough range of foods for comparisons to be made Biomarkers are required because human death, disease and sub-optimal health are not permissible dependent variables, and many are the result of cumulative changes over long periods. Instead, intermediate biomarker 'end-points', markers of exposure to a food component, and food properties that research has already established as causal in disease and health must be used to assess health effects of food processing. Intermediate end-points must be either causal factors or correlated with changes that lead to end-points. For instance, hyperlipidaemia is an intermediate biomarker that is causally related to a true end-point atherosclerosis. However, as many factors are involved, evidence for the benefit of a product would be more convincing if several relevant biomarkers were measured. At present most biomarkers require clinical or laboratory mea- urement and are not widely used to monitor nutritional changes in the course of product development. A good deal of further work is required to develop tests hat are useful to industry 7.4.3 Validity that is balanced with practicality Validation is a crucial step in selecting variables that indicate effects of foods and food processes on biochemical precursors of health end-points. Because most foods are complex systems, ideal experimental trials in which one food factor is varied while all other variables are kept constant are not often possible, and there is a need to balance practical requirements of food processing with degree of nutritional validation. Given that final products should be comprehensively eval- uated, progress in food processing will often best be maintained by being pre- pared to sacrifice some degree of validity for expediency by appropriate choice of tests. as discussed in section 7.2.3 and illustrated in Table 7.1 7.4.4 Nutrition information that is up-to-date Nutrition s is constantly advancing, and as hard data throws new light on the relationship between a food property or component and a health end-point, indices of food effects on health are likely to change. For instance, heart disease is now considered to be infuenced less by intake of fat than by intake of specifi fatty acids such as saturated and trans-fatty acids. Such changes are not a sign that nutrition science cannot be relied on but that continuing research leads to A food company that had not kept abreast of nutritional knowledge recently formulated a new ' diabetic muesli bar, replacing all sucrose sources with dex- trins, in the belief that ' replacement would improve blood glucose control However, such wisdom was obsolete, because sucrose, being half fructose, induces a much lower blood glucose response than dextrins, which are rapidly digested glucose polymers. The new 'diabetic bar had a greater glycaemic impact than the unmodified version
in relation to colon cancer,40 and to be obtained with standardised procedures that can be applied to a wide enough range of foods for comparisons to be made. Biomarkers are required because human death, disease and sub-optimal health are not permissible dependent variables, and many are the result of cumulative changes over long periods. Instead, intermediate biomarker ‘end-points’, markers of exposure to a food component, and food properties that research has already established as causal in disease and health must be used to assess health effects of food processing. Intermediate end-points must be either causal factors or correlated with changes that lead to end-points. For instance, hyperlipidaemia is an intermediate biomarker that is causally related to a true end-point – atherosclerosis.39 However, as many factors are involved, evidence for the benefit of a product would be more convincing if several relevant biomarkers were measured. At present most biomarkers require clinical or laboratory measurement and are not widely used to monitor nutritional changes in the course of product development. A good deal of further work is required to develop tests that are useful to industry. 7.4.3 Validity that is balanced with practicality Validation is a crucial step in selecting variables that indicate effects of foods and food processes on biochemical precursors of health end-points. Because most foods are complex systems, ideal experimental trials in which one food factor is varied while all other variables are kept constant are not often possible, and there is a need to balance practical requirements of food processing with degree of nutritional validation. Given that final products should be comprehensively evaluated, progress in food processing will often best be maintained by being prepared to sacrifice some degree of validity for expediency by appropriate choice of tests, as discussed in section 7.2.3 and illustrated in Table 7.1. 7.4.4 Nutrition information that is up-to-date Nutrition science is constantly advancing, and as hard data throws new light on the relationship between a food property or component and a health end-point, indices of food effects on health are likely to change. For instance, heart disease is now considered to be influenced less by intake of fat than by intake of specific fatty acids such as saturated and trans-fatty acids.41 Such changes are not a sign that nutrition science cannot be relied on but that continuing research leads to clarification. A food company that had not kept abreast of nutritional knowledge recently formulated a new ‘diabetic muesli bar’, replacing all sucrose sources with dextrins, in the belief that ‘sugar’ replacement would improve blood glucose control. However, such wisdom was obsolete, because sucrose, being half fructose, induces a much lower blood glucose response than dextrins, which are rapidly digested glucose polymers. The new ‘diabetic’ bar had a greater glycaemic impact than the unmodified version. 172 The nutrition handbook for food processors
New approaches to providing nutritional information 173 7. 4.5 Relevant indices that are based on factors that confer relevance on food data The relevance of food information is determined by validity, sufficiency, practi cality, and communicability. Is an index a true reflection of a change in a bio- marker or end-point, is it sufficient on its own to predict a change in the end-point, is it a variable that can be measured easily, and expressed in terms that users understand well enough to use in food choice? 7.4.6 Food data that is easily understood Food data is not relevant if it cannot accurately link consumer behaviour to health end-points, in other words, if it cannot guide food choice for health. To do so it should be easily used. The relative efficacy of foods may, for instance, be expressed in terms of equivalents to a familiar reference that exhibits a specifie effect to a known degree, as in wheat bran equivalents and faecal bulking. Gly chemic index(GD), on the other hand, is an example of a number that is supposed to represent the glycaemic potency of a food. However, unlike intake of a nutri- ent, GI does not change with the composition, serving size, or intake of food, so it makes little sense to consumers, and cannot be used accurately to modify eating patterns that affect blood glucose. 4 7.5 Limitations of food composition data: the case of carbohydrates The above framework for building practical, evidence-based data sets linked to health end-points is illustrated below by reference to two physiological effects of food carbohydrates: postprandial glycaemia(post-meal elevation of blood glucose), and faecal bulking. Postprandial glycaemia is determined largely by carbohydrate digestibility, and faecal bulk largely by non-digestible, non- fermentable polysaccharides. 7.5.1 Limitations of carbohydrate composition data Standard food analyses do not account for the large effects of the structure of car- bohydrate molecules and foods in the carbohydrate nutrition. Monosaccharide composition and order, glycosidic bonds, degree of polymerisation, chain con figurations, non-covalent interactions between chains, and crosslinks that carbo- hydrates readily form may all greatly affect physicochemical properties, 4and the physiological effects that depend on such properties. Furthermore, food struc ture, such as particle size, may considerably modulate the ability of food carbo- hydrates to express their potential properties, by limiting solubility, extraction, and access of dis enzymes. Beyond effects on extraction, interactions between carbohydrates and other food components in the intestine are multiple nd complex. The amounts of carbohydrate fractions in foods are therefore not usually reliable guides to their physiological effectiveness
7.4.5 Relevant indices that are based on factors that confer relevance on food data The relevance of food information is determined by validity, sufficiency, practicality, and communicability. Is an index a true reflection of a change in a biomarker or end-point, is it sufficient on its own to predict a change in the end-point, is it a variable that can be measured easily, and expressed in terms that users understand well enough to use in food choice? 7.4.6 Food data that is easily understood Food data is not relevant if it cannot accurately link consumer behaviour to health end-points, in other words, if it cannot guide food choice for health. To do so it should be easily used. The relative efficacy of foods may, for instance, be expressed in terms of equivalents to a familiar reference that exhibits a specified effect to a known degree, as in wheat bran equivalents and faecal bulking.42 Glycaemic index (GI), on the other hand, is an example of a number that is supposed to represent the glycaemic potency of a food.43 However, unlike intake of a nutrient, GI does not change with the composition, serving size, or intake of food, so it makes little sense to consumers, and cannot be used accurately to modify eating patterns that affect blood glucose.44 7.5 Limitations of food composition data: the case of carbohydrates The above framework for building practical, evidence-based data sets linked to health end-points is illustrated below by reference to two physiological effects of food carbohydrates: postprandial glycaemia (post-meal elevation of blood glucose), and faecal bulking. Postprandial glycaemia is determined largely by carbohydrate digestibility,45 and faecal bulk largely by non-digestible, nonfermentable polysaccharides.46 7.5.1 Limitations of carbohydrate composition data Standard food analyses do not account for the large effects of the structure of carbohydrate molecules and foods in the carbohydrate nutrition. Monosaccharide composition and order, glycosidic bonds, degree of polymerisation, chain con- figurations, non-covalent interactions between chains, and crosslinks that carbohydrates readily form may all greatly affect physicochemical properties,6,47 and the physiological effects that depend on such properties. Furthermore, food structure, such as particle size, may considerably modulate the ability of food carbohydrates to express their potential properties,35 by limiting solubility, extraction, and access of digestive enzymes. Beyond effects on extraction, interactions between carbohydrates and other food components in the intestine are multiple and complex.18 The amounts of carbohydrate fractions in foods are therefore not usually reliable guides to their physiological effectiveness.33,48 New approaches to providing nutritional information 173
174 The nutrition handbook for food processors Postprandial glycaemia and distal colonic bulk are both physiological markers hat are strongly influenced by the effects of food properties on carbohydrate availability, but which cannot be reliably predicted from food composition data New nutritional information is required for control of postprandial glycaemia (Table 7. 2)and distal colonic bulk (Table 7.3), taking into account end-points biomarkers of exposure, current indices, relevant indices, their validation, and communication discussed above 7.6 Relative glycaemic potency and glycaemic-glucose Control of postprandial glycaemia-the blood glucose response to food intake is an increasingly important health issue. Diabetes mellitus, marked by an inabil ty to control blood glucose levels, is increasing rapidly in many developed countries, in which an over-supply of high energy and highly digestible carbo- hydrate foods is coupled with predisposing factors, including physical inactivity. obesity, and inheritance. Many consumers need to be able to manage postpran- caemla by selecting foods and food combinations according to glycaemic impact, but food labels at present give them little assistance 7.6.1 End-point Health consequences of hyperglycaemia are multiple and most evident in the diabetes mellitus syndrome. Persistently raised blood glucose causes protein glycation throughout the body, leading to cumulative, diffuse damage, emerging as pathology in a number of organ systems. Basal membrane damage is com- monly an underlying factor in changes to micro-vessels involving the eyes, kidneys and nerves. Intense insulin production in response to diabetic hyper- glycaemia, or to repeated acute glucose loading from large intakes of highly digestible carbohydrate, is thought to contribute to the progression of glucose intolerance, through B-cell toxicity, leading to loss of the capacity of the pancreas to produce insulin. Hyperinsulinaemia as a response to elevated blood glucose favours elevated blood lipids, obesity and hypertension, all risk factors in heart disease 49, 50,51 Post-prandial glycaemia may also lead to a number of acute and sometimes serious disorders, as the body attempts to counter the osmotic effects of high blood sugar levels. The excretion of sugar by the kidneys leads to water loss, excessive thirst, and in extreme cases, to fatal electrolyte imbalances 7.6.2 Markers As blood glucose response is causal in glycation, insulin response, osmotic effects and other aspects of diabetic pathology, it is a highly relevant marker of the fluence of foods and carbohydrates on progression towards disease end-points
Postprandial glycaemia and distal colonic bulk are both physiological markers that are strongly influenced by the effects of food properties on carbohydrate availability, but which cannot be reliably predicted from food composition data. New nutritional information is required for control of postprandial glycaemia (Table 7.2) and distal colonic bulk (Table 7.3), taking into account end-points, biomarkers of exposure, current indices, relevant indices, their validation, and communication discussed above. 7.6 Relative glycaemic potency and glycaemic-glucose equivalents Control of postprandial glycaemia – the blood glucose response to food intake – is an increasingly important health issue. Diabetes mellitus, marked by an inability to control blood glucose levels, is increasing rapidly in many developed countries, in which an over-supply of high energy and highly digestible carbohydrate foods is coupled with predisposing factors, including physical inactivity, obesity, and inheritance.28 Many consumers need to be able to manage postprandial glycaemia by selecting foods and food combinations according to glycaemic impact, but food labels at present give them little assistance. 7.6.1 End-point Health consequences of hyperglycaemia are multiple and most evident in the diabetes mellitus syndrome.28,49,50 Persistently raised blood glucose causes protein glycation throughout the body, leading to cumulative, diffuse damage, emerging as pathology in a number of organ systems. Basal membrane damage is commonly an underlying factor in changes to micro-vessels involving the eyes, kidneys and nerves.51 Intense insulin production in response to diabetic hyperglycaemia, or to repeated acute glucose loading from large intakes of highly digestible carbohydrate, is thought to contribute to the progression of glucose intolerance, through b-cell toxicity, leading to loss of the capacity of the pancreas to produce insulin.52 Hyperinsulinaemia as a response to elevated blood glucose favours elevated blood lipids, obesity and hypertension, all risk factors in heart disease.49,50,51 Post-prandial glycaemia may also lead to a number of acute and sometimes serious disorders, as the body attempts to counter the osmotic effects of high blood sugar levels. The excretion of sugar by the kidneys leads to water loss, excessive thirst, and in extreme cases, to fatal electrolyte imbalances.53 7.6.2 Markers As blood glucose response is causal in glycation, insulin response, osmotic effects and other aspects of diabetic pathology, it is a highly relevant marker of the influence of foods and carbohydrates on progression towards disease end-points 174 The nutrition handbook for food processors
