Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Cater with Care : impact of protein-enriched foods and drinks for elderly people
    Beelen, J. - \ 2016
    Wageningen University. Promotor(en): Lisette de Groot; Frans Kok, co-promotor(en): Nicole de Roos. - Wageningen : Wageningen University - ISBN 9789462578814 - 142
    undernutrition - hospital catering - hospitals - protein - elderly - protein intake - food - beverages - diet studies - dietetics - dietitians - randomized controlled trials - ondervoeding - ziekenhuiscatering - ziekenhuizen - eiwit - ouderen - eiwitinname - voedsel - dranken - dieetstudies - diëtetiek - diëtisten - gestuurd experiment met verloting

    Protein undernutrition is a major health concern for older adults, especially for those who are ill. There is growing consensus for a protein intake target of 1.2 - 1.5 gram per kg bodyweight per day (g/kg/d) for these older adults. However, this target is not reached by the majority of older adults. Therefore, more effective and novel strategies to increase protein intake are warranted, including the use of protein-enriched foods and drinks. This thesis evaluated the impact of the developed protein-enriched foods and drinks on protein intake and physical performance among older adults. The studies in this thesis were done as part of the Cater with Care® project; a collaboration between the university, care organizations, and partners from the food industry. The industrial partners developed the products, focusing each on different product categories: Carezzo Nutrition developed bread, pastry, and fresh juices and soups; The Kraft Heinz Company focused on long shelf-life and convenience foods; and the Veal Promotion Foundation produced veal meat.

    To fit the products to the needs of the target group, interviews with undernourished older adults (at home or hospitalized) and with dietitians were conducted (chapter 2). These interviews showed that undernutrition awareness is low among older adults. To treat undernutrition by changing their eating habits, older adults need to be aware of their health problem, they need to be willing to change, and they need to be able to understand and implement the dietitian’s advices. This process takes time while undernutrition should be treated immediately. For immediate treatment, enriched products could be used, without first creating awareness. According to the interviewees, enriched products should fit within older adults’ eating habits, and have small portion sizes.

    To gain insights in food choices of hospitalized older adults (65 years and older) an observational study was conducted. In this study, energy and protein intakes of 80 hospitalized older patients at low and high risk of undernutrition were assessed (chapter 3). Patients who received an energy- and protein-rich menu, because of their risk of undernutrition, were better able to reach the protein and energy targets than patients with a low risk of undernutrition receiving a standard menu. Based on these results we proposed that all hospitalized older adults – both at low and high risk of undernutrition – should receive an energy- and protein-rich menu.

    Subsequently, a pilot study was done in a care home and a rehabilitation center with the aim to explore the potential of the developed protein-enriched products to increase protein intake (chapter 4). Participants did not compensate their consumption of regular protein-rich foods (e.g. dairy, cheese) upon the introduction of protein-enriched foods and drinks. The 22 institutionalized elderly (mean age 83 years) consumed 12 gram protein per day more than they did before the intervention. Consequently, more people met the protein target of 1.2 g/kg/d than before the intervention. We concluded that protein-enriched products enabled institutionalized elderly to reach protein intake targets. Furthermore, we gained valuable feedback to improve the assortment of protein-enriched products for the effectiveness study.

    In the final study, effects of the protein-enriched products on protein intake and physical performance were studied in a randomized controlled trial during hospitalization and subsequent recovery at home. During the hospital period in which 147 older patients participated, patients that received protein-enriched products increased their protein intake compared to the control group that already received a protein-rich hospital menu (chapter 5). As a result, 79% of the intervention group reached a protein intake of 1.2 g/kg/d, compared to 48% of the control group. Finally, effects of the protein-enriched products were tested at home, for a longer period (chapter 6). Half of the hospital phase participants (n = 75) continued the intervention at home for 12 weeks. The protein-enriched products were successfully implemented in the daily menu of the older adults: the intervention group had a higher average protein intake (1.5 ± 0.6 g/kg/d) than the control group (1.0 ± 0.4 g/kg/d) during the 12-week intervention period. Seventy-two percent of the intervention group reached a protein intake of 1.2 g/kg/d during the 12-week intervention, compared to 31% of the control group. Protein intake of the intervention group was mainly increased by the following protein-enriched products: bread, dairy drinks, dairy desserts, soups, and fruit juices. However, despite the successful improvement of protein intake, we found no added value on physical performance in the first 6 months after hospitalization.

    It was concluded that with the protein-enriched familiar foods and drinks, we have a feasible, acceptable, and appetizing long-term strategy to increase protein intake of older adults in various settings. We envisage a beneficial role of these protein-enriched products in combination with physical activity in older adults with lower protein intakes.

    Het ontwikkelen van evidence-based richtlijnen voor diëtistisch handelen: een stappenplan uitgewerkt voor patiënten met een gynaecologische tumor in het UMC Utrecht
    Vries, J.H.M. de; Groot, S.D.W. de; Runia, S. ; Remijnse, T.A.W. ; Staveren, W.A. van - \ 2003
    Nederlands Tijdschrift voor Dietisten 58 (2003)2. - ISSN 0166-7203 - p. 33 - 39.
    dieetadvisering - ziekenhuizen - richtlijnen (guidelines) - gynaecologie - Cancer - diëtetiek - diet counseling - hospitals - guidelines - gynaecology - Cancer - dietetics
    Beschrijving van een methode gehanteerd in het UMC voor het ontwikkelen van lokale richtlijnen binnen de diëtetiek. Er worden voorbeelden gegeven uit een project dat is uitgevoerd bij patiënten met een gynaecologische tumor die worden behandeld met chemotherapie
    Assessment of vegetable, fruit, and antioxidant vitamin intake in cancer epidemiology
    Ocké, M.C. - \ 1996
    Agricultural University. Promotor(en): D. Kromhout; W.A. van Staveren; H.B. Bueno de Mesquita. - S.l. : Ocke - ISBN 9789054855064 - 164
    carcinoom - neoplasma's - epidemieën - epidemiologie - groenten - fruitgewassen - dieet - diëtetiek - carcinoma - neoplasms - epidemics - epidemiology - vegetables - fruit crops - diet - dietetics

    Inverse associations are consistently observed in epidemiological studies on the relations between the consumption of vegetables and fruits and different types of cancer. The strength of these associations is, however, unknown amongst others because of measurement error in data on vegetable and fruit intake. The antioxidant (pro)vitamins β-carotene, vitamin C, and vitamin E, are three of many substances in vegetables and fruits which may be responsible for the anticarcinogenic effect. This thesis is focused on the problem of intake assessment of vegetables, fruits, and antioxidant (pro)vitamins.

    In the first part of the thesis, two studies on the relationships between the consumption of vegetables, fruits, and antioxidant (pro)vitamins and the occurrence of cancer are described. In the Seven Countries Study intake of vitamin C was inversely related to stomach cancer mortality at ecological level. Subjects with low intakes of vegetables, fruits, and β-carotene that were stable over time experienced more than two-fold increased risks of lung cancer in the Zutphen Study than subjects with high stable intakes. A lack of information on the extent of measurement error in the dietary data in both studies hampered the correct interpretation of the results.

    The second part of the thesis includes several studies on the estimation of measurement error in data on vegetable, fruit, and antioxidant (pro)vitamin intake and biochemical markers. In a study on the effects of frozen storage at -20°C it was shown that vitamin E concentrations in EDTA-plasma decreased dramatically between 6 and 12 months, whereas for β-carotene this took place after 1 year. The use of such plasma in nested case-control or case-cohort studies would result in highly attenuated odds ratios for β-carotene and vitamin E.

    Reproducibility and relative validity for food group and nutrient intake assessed with an extensive semi-quantitative food frequency questionnaire was also investigated. The questionnaire seemed adequate for ranking subjects according to intake of most nutrients and food groups including fruits, but it did not yield such good results for vegetables, β-carotene, vitamin C for men, and vitamin E for women. The observed correlation coefficients between questionnaire and repeated 24-h recall data may be either over- or underestimates of the true validity coefficients, because of unknown error structure in both types of data. Validity coefficients estimated by a triangular comparison between questionnaire, 24-h recall, and biomarker measurements will probably be overestimates of true validity coefficients.

    From these studies it is concluded that measurement error in assessing vegetable, fruit, and antioxidant (pro)vitamin intake may be large, which is a handicap for epidemiological studies. Further progress lies in improvement of dietary assessment methods, and probably even more in understanding error structures and the development of analytical methods to recognize and cope with those structures.

    Efficiency aspects of design and analysis of prospective cohort studies on diet, nutrition and cancer
    Kaaks, R.J. - \ 1994
    Agricultural University. Promotor(en): W.A. van Staveren; J.G.A.J. Hautvast; E. Riboli. - S.l. : Kaaks - ISBN 9789054853145 - 173
    carcinoom - neoplasma's - epidemieën - epidemiologie - therapeutische diëten - voeding - patiënten - voedselhygiëne - voedingstoestand - consumptiepatronen - dieet - diëtetiek - efficiëntie - carcinoma - neoplasms - epidemics - epidemiology - therapeutic diets - nutrition - patients - food hygiene - nutritional state - consumption patterns - diet - dietetics - efficiency

    This thesis presents and analyzes methodological approaches to improve the design and analysis of prospective cohort studies on the relations between diet, nutritional status and cancer. The first chapters discuss methods to optimize the measurement of the individuals' habitual dietary intakes, focussing on the use and design of sub-studies for the "validation" or "calibration" of baseline dietary questionnaire assessments. The power of prospective studies can be improved by maximizing the variation in true dietary intake levels actually distinguished - or "predicted" - by questionnaire assessments. This can be achieved by designing an optimal questionnaire method, using a preliminary validity study to evaluate its performance. An additional possibility is to broaden the range of dietary exposures by conducting multiple cohort studies in populations with different dietary habits. A main objective is to precisely estimate the magnitude of the predicted variation of intake levels, to account for the effect of measurement error as well as of the real variation in exposure, in the evaluation of the power or sample size requirements of a cohort study, and in the estimation of relative risks describing diet-disease relations. The predicted variation is estimated most efficiently by means of a "calibration" sub-study, which differs from validity studies in that it requires only a single (unbiased) reference measurement per person (e.g., based on a 24-hour recall), in a representative sub-sample of cohort members. In multi-cohort projects, calibration studies are essential to improve the between-cohort comparability of relative risk estimates, and to increase the power of a statistical test for the presence of a diet-disease association based on a pooled summary estimate. A simplified method is proposed for the estimation of sample size requirements of dietary calibration studies. When the exposure assessments are based on a biochemical marker, a most efficient design is to store biological specimens in a biobank, and to postpone laboratory analyses until cases with disease have been identified. Nevertheless, the number of scientific hypotheses potentially of interest is usually much larger than can be tested with limited amounts of biological specimens available. The last chapter of this thesis discusses the use of a sequential study design, to allow the evaluation of a maximum number of different hypotheses at the expense of as little biological material as possible.

    Diabetes and diet : food choices
    Niewind, A.C. - \ 1989
    Agricultural University. Promotor(en): J.G.A.J. Hautvast; N.G. Röling. - S.l. : Niewind - 92
    diabetes mellitus - suikerziekte - dieet - diëtetiek - voedselhygiëne - voedingstoestand - consumptiepatronen - diabetes mellitus - diabetes - diet - dietetics - food hygiene - nutritional state - consumption patterns
    This thesis reports on the food choices of diabetic patients. Two studies were undertaken considering the barriers these patients experience with the diabetic diet. Furthermore, the changes in food choices during the first years after the diagnosis of insulin-dependent diabetes as well as patients, food choice motives were investigated. It is concluded that despite thebarriers diabetic patients experience with their diets, they are motivated to change food choices for health-related reasons on a short-term and a more long-term basis. However, the actual changes in food use patients make after being diagnosed as diabetics are only partly in agreement with the principles of the diabetic diet. Many of the changes in food use are not necessary and the barrierssome are even undesirable from a nutritional perspective. It is advised that patients' understanding of the diabetic diet as well as nutrition education programmes for diabetic patients need to be improved.

    Diabetes and diet : managing dietary barriers
    Friele, R.D. - \ 1989
    Agricultural University. Promotor(en): J.G.A.J. Hautvast; A.T.J. Nooij. - S.l. : Friele - 108
    diabetes mellitus - suikerziekte - voedselbereiding - kookkunst - diëten - diëtetiek - dieetvoedsel - dieet - voedselhygiëne - voedingstoestand - consumptiepatronen - diabetes mellitus - diabetes - food preparation - cookery - diets - dietetics - dietetic foods - diet - food hygiene - nutritional state - consumption patterns

    This thesis reports on the barriers diabetic patients experience with their diet, and the ways they cope with these barriers. A dietary barrier is a hinderance to a person's well-being, induced by being advised a diet. First inventories were made of possible dietary barriers and ways of coping with them. Secondly the prevalence of these barriers and ways of coping with them were assessed among different diabetic populations. Most prevalent were barriers expressing physical discomfort and restrictions in food-use. Barriers with the highest prevalence were most often dealt with by non-compliance.

    The prevalence of barriers among recently diagnosed diabetics did not differ from prevalences after a follow-up period of one year. It was concluded that dietary barriers are not easily overcome by diabetic patients. Hardly any differences were found in barrier prevalence when comparing insulin- treated and non insulin-treated diabetic patients. Prevalence of barriers among diabetics with conventional insulin therapy was higher when compared to diabetics with continuous subcutaneous insulin infusion and a liberalized diet.

    It is concluded that diets allowing for variability in energy-intake and meal-times will decrease prevalence of dietary barriers among diabetics. Also barrier prevalence could decrease when the diet is not perceived as consisting of forbidden foods. Diets leading to less dietary barriers are not only more pleasurable to live with, such diets also are more likely to be adhered to.

    Substituenten voor keukenzout in de voeding
    Veer, O. van der - \ 1983
    Wageningen : L.H. - 21
    dieet - diëtetiek - voedsel - voedselhygiëne - voedingsmiddelen - mineralen - zouten - literatuuroverzichten - diet - dietetics - food - food hygiene - foods - minerals - salts - literature reviews
    comparison of various cholesterol lowering diets in young healthy volunteers : effects on serum lipoproteins and on other risk indicators for cardiovascular diseases
    Brussaard, J.H. - \ 1981
    Landbouwhogeschool Wageningen. Promotor(en): J.G.A.J. Hautvast, co-promotor(en): M.B. Katan. - Wageningen : Brussaard - 109
    voeding - cholesterol - voedselhygiëne - voedingstoestand - consumptiepatronen - vaatziekten - bloedstoornissen - hart- en vaatziekten - hart- en vaatstoornissen - dieet - diëtetiek - nutrition - cholesterol - food hygiene - nutritional state - consumption patterns - vascular diseases - blood disorders - cardiovascular diseases - cardiovascular disorders - diet - dietetics
    This thesis deals with the effect of type and amount of dietary fat on the concentration and composition of serum lipoproteins, colonic function, plasma glucose and serum insulin levels and blood pressure in healthy human volunteers.

    Two experiments were carried out. In the first experiment with 60 volunteers a moderate fat diet with a high proportion of polyunsaturated fatty acids (as recommended by several advisory bodies), was compared with three other diets during a test period of 5 weeks. One diet was low in total fat with a low proportion of polyunsaturated fatty acids, one diet was high in total fat with a high proportion of polyunsaturated fatty acids and one was high in total fat with a low proportion of polyunsaturated fatty acids. In the second experiment with 35 volunteers the moderate fat diet rich in polyunsaturated fatty acids and the low fat, low polyunsaturated fatty acid diet were compared again, but this time the test period lasted 13 weeks. The diets were composed of regular foodstuffs and differed in carbohydrate and fat content or fatty acid composition only. There were only minor differences in intake of dietary fiber and other nutrients known to affect cholesterol metabolism. Subjects in both studies were under strict dietary control. All foodstuffs, except for 100 kcal (0,4 MJ) per day were supplied individually according to each person's energy need. Actual food intake was measured by food records and analysis of double portions. The fatty acid composition of cholesterol esters in serum was analysed in the second experiment in order to check adherence to the diets.

    The serum lipoprotein composition and concentration observed during the experiments are given in Chapters 2 and 3. In serum, total cholesterol , triglycerides, apolipoprotein-A I and -B were measured; in high-density-lipoprotein (HDL), cholesterol was measured; in low-density-lipoprotein (LDL), cholesterol and triglycerides were measured and in very-low-density-lipoprotein (VLDL), triglycerides, apolipoprotein-B and the apolipoprotein-C II /C III ratio were measured. From these experiments two conclusions can be drawn. Firstly, that both a low fat diet, low in polyunsaturated fatty acids and a moderate fat diet, high in polyunsaturated fatty acids lower total serum cholesterol levels when compared with the habitual diet of affluent communities. Secondly, that a low fat diet causes lower HDL-cholesterol and higher fasting VLDL-triglyceride levels than a moderate-fat diet, high in polyunsaturated fat.

    It is by no means certain that changes in the concentration of HDL and VLDL really result in changes in the risk of death from cardiovascular diseases. In long-term intervention trials, such a hypothesis has not been tested; only the effect of changes in serum total cholesterol has been studied in intervention trials.

    Chapter 4 deals with effects on colonic function. No changes in mean transit time through the gut, fecal wet and dry weight, frequency of stools and concentration of fecal steroids were found. This shows that the intake of dietary fiber had been roughly equal in all diet groups within each experiment. Because there were no consistent short- or long-term changes in fecal bile acid or neutral steroid excretion, it is concluded that changes at the intestinal level do not explain the changes in total serum cholesterol concentration.

    Chapter 5 gives the results of measurements of fasting and postprandial serum insulin and glucose concentrations. The results show, that neither the amount nor the type of dietary fat had a strong influence on these variables in healthy subjects.

    Chapter 6 describes the effect of type and amount of dietary fat on blood pressure as well as the effect of dietary fiber from various sources and type of protein. None of these dietary components had a demonstrable effect on blood pressure in young normotensive subjects.

    The results of these experiments do not call for changes in the dietary recommendations of the Netherlands Nutrition Council, as far as the risk of death from cardiovascular diseases is concerned.

    Rationalisering van de dietetiek
    Swieringa, J. - \ 1980
    Landbouwhogeschool Wageningen. Promotor(en): J.G.A.J. Hautvast, co-promotor(en): W.C. Veeger. - S.l. : S.n. - 190
    kookkunst - dieet - dieetvoedsel - diëtetiek - diëten - vasten - voedselbereiding - slechte voeding - vermageringsdiëten - cookery - diet - dietetic foods - dietetics - diets - fasting - food preparation - malnutrition - weight loss diets
    Until recently the majority of therapeutic diets prescribed were based almost exclusively on empirism and aimed at symptomatic treatment of certain diseases. This situation has been changing radically in the last few decades. Under the influence of increased knowledge in the field of nutrition on the one hand, the greater insight into the patho- physiology of digestion and the rapid extension of the knowledge of metabolic disorders on the other hand, diet therapy is rapidly developing into a scientifically valid and often causal method of treating diseases.

    In spite of these developments little attention has so far been paid to definition of terms. The terminology used in the naming and prescribing of diets is extremely confusing and there is no adeauate classification of therapeutic diets. Sometimes the diets are named according to their purpose (cholesterol lowering diet, etc.); in other cases the diet carries the names of the disease (diabetes diet, hepatitis diet, etc.) or of the diseased organ (gastric diet, kidney diet, etc.); in still other cases the (deviating) composition determines the designation (low-protein diet, salt- free diet, fruit diet, etc.) or the diet is named after its "inventor" (Sippy-cure, Meulengracht diet, etc.). Quantity specifications too, are often extremely vague (moderate, limited, low, strict, ascending) and in some cases completely incorrect (e.g. salt-free). Even the definition of the term (therapeutic) diet as such is still a subject of wide-spread disagreement.

    In practice this confusing nomenclature causes every physician and dietitian to form his own idea of a particular therapeutic diet, based on his personal insight and experience. The contents af a therapeutic diet can therefore vary according to the physician or dietitian and hospital concerned.

    Whether or to what extent these differences actually rest on medical grounds remains unclear. Directly consequent on this an often unnecessarily large diversity of therapeutic diet meals is prepared, notably in hospitals. Lack of clearity and discrepancies with regard to the procedure and the delimination of physicians' and dietitians' duties can also be traced back to this. The confusing terminology prevents the realization of satisfactory regulations on labelling of foodstuffs (esp. diet products) and compensation for the costs of a therapeutic diet.

    The original occasion for the research was an experiment carried out in 1972-1973 in two hospitals, in which the production of meals was entirely contracted out to an industry of foodstuffs. This experiment concerned the industrial production of separate, individual mealcomponents, from which the hospital patients, including the dietpatients, could compose their meals as they choose. This necessitated a clear and unambiguous formulation of the medical requirements these therapeutic diet meals had to fulifii. Soon, however, the investigation began to lead a life of its own and was therefore entirely dissociated from the afore mentioned experiment.

    The research was primarily directed at logical analysing and ordening of therapeutic diets and the procedure followed by physicians and dietitians in prescribing a diet. The main issue was: What is a therapeutic diet? In this way a clearly consistent and coherent stock of concepts was developed (Chapter 2 and 3) on the basis of which rules regarding the prescription and composition of therapeutic diets were drawn up.

    Besides the respective duties and responsibilities of physicians and dietitians were delimited and a sound model for paramedical delegation was developed (Chapter 4).

    It is essential that physicians and dietitians employ uniform units and specifications of foodstuffs in prescribing and composing therapeutic diets. National agreements have been reached on this head, which can also constitute the basis of a simple system of labelling and declaration of nutritional values (Chapter 5).

    About half of all hospital patients are prescribed a therapeutic diet. In Chapter 6 an organization model has been developed for catering in hospitals, applying the results of the preceding chapters. A model according to which diet patients, too, can compose a meal as they choose from the supply of foodstuffs and dishes.

    By rationalization - the title of the research - we mean the formalization (Chapter 4), normalization (Chapter 5) and organization (Chapter 6) of the prescribing and composing of therapeutic diets, both intramurally and extramurally, by way of logical analysis, definition and ordening (Chapter 2 and 3).

    The investigation is a composition of basic scientific research (analysis, ordening and definition) and applied scientific research (formalization, normalization and organization). It was carried out in close co-operation with those concerned, notably physicians and dietitians. As regards set-up the investigation can best be described as an action-research. Twenty-eight hospitals took part in the last phase of the research: the diffusion and adoption.

    We have defined a therapeutic diet as a diet which deviates from a normal diet for medical reasons. By a normal diet we understand an optimal diet; a diet which under physiological conditions contributes towards the best health to be achieved. A normal diet is synonymous with a healthy diet. In this definition Met is the genus proximum. A therapeutic diet differs from a normal diet in two respects (differentiae specificae):
    - it is a deviating diet
    - the deviation rests on medical (patho-physioiogical) grounds.

    Only if both conditions have simultaneously been complied with we can speak of a therapeutic diet or modified diet.

    (There is no completely correct English equivalent for the Dutch word "dieet". Instead of therapeutic diet a better translation would be modified diet).

    As in theoretical nutrition we define a diet as a set of nutrients. A therapeutic or modified diet is a diet in which the amount of one more nutrients deviates - for medical reasons - from what would be a normal quantity for the patient in question under physiological conditions.

    Proceeding from this definition the therapeutic (modified) diets have been divided into four categories:
    1. nutrient-limited diets: diets in which the quantity of one or more nu trients is less than normal
    2. nutrient-enriched diets: diets in which the quantity of one or more nutrients is more than normal
    3. nutrient-eliminated (or-free) diets: diets in which one or more nutrients do not occur at all
    4. nutrient-substituted diets: diets in which one or more macro-nutrients are replaced by an equivalent set of micro-nutrients. Substitution is always a combination of limitation or elimination and enrichment.

    If the quantity of only one nutrient diverges from the normal amount we speak of single modified diets. If the quantity of two or more nutrients deviates from the normal we speak of multiple modified diets or combina tion-diets. A multiple modified Met is a combination of two or more single modified diets.

    This classification constitutes the basis of a clear, unambiguous and consistent method of naming and prescribing therapeutic diets. In order to keep classification and terminology as simple as possible a distinction has been made between the main characteristics of a modified diet and the derived characteristics. By a main characteristic we mean a modification directly proceeding from the clinial picture of the patient in question. A derived characteristic is a characteristic which is a consequence of a main characteristic and as such is related only indirectly to the patient's disease.

    A therapeutic diet is named - exclusively - after its main characteristic(s).

    A diet-prescription is correct and complete if it states:
    a. the main characteristic(s) of a diet; i.e. the name;
    b. the degree in which the quantity ties of nutrients should deviate from the normal: i.e. the quantities of nutrients permitted or required per 24 hours. (Energy and proteins are indicated preferably in quantities per kg body weight and fats and carbohydrates in per cent of energy).

    Drawing up such a diet-prescription is part of the duties and responsibili ties of the physician. To promote uniformity and clarity in the method of prescribing (not: the contents) we have developed a modelform on which physicians can, in a simple manner, record the diet-prescription. This diet-prescriptionform at the same time serves as a means of delegation, when patients are referred to a dietitian by the physician.

    Theoretical nutrition and dietetics are concerned with diet as a set of nutrients. Applied nutrition and dietetics concern diet as a set of foodstuffs. Foodstuffs are (consumable) products containing one or more nutrients. The diet prescription specifies the limiting conditions with which the diet as a set of foodstuffs should comply. Theoretically the problem of composing a therapeutic diet can be completely solved if the nutritional values of all foodstuffs are known, in particular the content of nutrients relevant to that therapeutic diet. In that respect there is no essential difference between composing normal and therapeutic (modified) diets. In both cases the foodstuffs should be selected in such a way that the daily diet complies with the required content of nutrients, on the understanding that in the case of therapeutic diets the quantity of one or more nutrients should be more or less than the normal quantity. Most modified diets too leave a lot of room for combination and variation.

    But in practice dietitians follow another procedure, taking into account the eating habits (the meal- and menu-pattern) of the patient in question. The patient's customary diet is correced and adapted to the diet prescription by
    a. prohibiting (in nutrient-limited and -eliminated diets) or requiring (in nutrient-enriched and -substituted diets) the use of particular kinds of foodstuffs per component of the menu:
    and/or by
    b. prescribing the use of a maximum quantity (in nutrient-limited diets) or minumum quantity (in nutrient-enriched diets) of particular kinds of foodstuffs per component of the menu.

    By quantities we understand the number of consumption-units, i.e. the number of slices, spoonfuls, cups, etc. The determining factor with respect to the kind of foodstuff is the quantity of one ore more nutrient(s) the food stuff contains per consumption unit. Similar foodstuffs are foodstuffs containing approximately, i.e. within certain limits, the same amount of a particular, relevant nutrient.

    The instructions drawn up by a dietitian in this way for a specific patient are called: dietetic-advice. Dietetic-advice is the translation in terms of foodstuffs of the diet- prescription, expressed in terms of nutrients.

    Dietetic-advice is also the nature of a prescription with regard to the patient, but it is attuned to the requirements and eating habits of the individual patient. Dietetic-advice can be continually adapted even when the prescription remains the same, and its contents can be entirely different for two different patients, even though the diet prescription is identical in both cases.

    To promote uniformity and clarity with respect to the dietetic advice the foodstuffs are divided into 14 menu groups, on the basis of the meal- and menu-pattern customary in the Netherlands. Each group corresponds with a fixed component of a meal. All foodstuffs belonging to a particular menu group have the same function in the composing of a meal or daily diet. In addition all foodstuffs have been divided into (at most) five kinds per nutrient: nutrient-free, nutrient-limited, nutrient-average, high-nutrient and nutrient-extreme.

    The classification-matrix, obtained in this way, serves as the basis for drawing up by far the greater proportion of all dietetic advices. With the dietitians and catering managers of the 28 hospitals taking part in our investigation agreements were made about:
    a. the size of the composition units of the most frequently occurring food stuffs (i.e. the number of grams),
    b. the limits (i.e. the amount of nutrients per consumption unit) within which foodstuffs are of the same kind (e.g. low-, high-, etc.)
    That is what we called: normalization.

    All practical problems, with respect to the prescribing, advising and composing of therapeutic diets, are all indirectly caused wholly or to a considerable extent by the fact that so far little attention has been paid to definition and terminology. Problems accordingly, which have all become wholly solvable thanks to the research.

    Nevertheless the investigation is first and foremost a basic scientific research. Definition is the basis of every science. The terminology and classification, of therapeutic diets which we have developed serve as a paradigm; a terminological model, for structuring a professional language by means of which implicit skill can be transformed into explicit - and thus verifiable and transmissible - knowledge. A paradigm which, at the same time, serves as a hypothesis for discerning gaps in existing scientific dietetic knowledge.

    The definition of a therapeutic modified diets constitutes the foundation of the entire research. A definition by wich modified diets have been restricted to the field of medicine in the pure sense of the word. This is not merely a question of definition, but is theoretically fundamental. Dietetics concerns itself with the relation disease -->diet; a relation which is of an entirely different nature and order from the relation diet --->health, with which nutrition concerns itself.

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