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