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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    Temporary undernutrition during early gestation, corpora lutea morphometrics, ovarian progesterone secretion and embryo survival in gilts
    Langendijk, P. ; Bouwman, E.G. ; Chen, T. ; Koopmanschap, R.E. ; Soede, N.M. - \ 2017
    Reproduction Fertility and Development 29 (2017)7. - ISSN 1031-3613 - p. 1349 - 1355.
    fasting - LH - pigs - pregnancy
    The present study reports effects of severe undernutrition on luteal function and pregnancy in pigs. Gilts were inseminated and either fasted on Day 10 and 11 after conception (n = 11) or fully fed throughout (n = 10). Fasting did not affect LH or progesterone pulsatile secretion pattern on Day 11 in samples taken from blood vessels draining an ovary. Ultrasonographic measurements of the size of the corpora lutea did not show any effect of fasting either. However, fasted gilts had 10 to 30 % lower systemic progesterone from Day 12 through Day 15 after conception (P < 0.05). All gilts farrowed, but fasted gilts had fewer born piglets than fully fed gilts (8.8 ± 0.8 vs 10.9 ± 0.5 respectively; P < 0.05). In conclusion, fasting during embryo elongation can compromise embryonic survival by affecting ovarian function in the days after fasting, without having an immediate effect on LH secretion and progesterone output by the ovaries.
    An apple a day... : de rol van voeding in transmurale zorg
    Witteman, Ben J.M. - \ 2015
    Wageningen : Wageningen University - ISBN 9789462571990 - 32
    ziekenhuiszorg - voedsel - chronische darmontstekingen - darmziekten - prikkelbaar colon - coeliakie - narcose - ondervoeding - vasten - darmen - hospital care - food - inflammatory bowel diseases - intestinal diseases - irritable colon - coeliac syndrome - narcosis - undernutrition - fasting - intestines
    'De gemiddelde levensverwachting stijgt in Nederland. Nochtans worden we op jongere leeftijd met chronische aandoeningen geconfronteerd. De kans hierop neemt de komende jaren sterk toe: van 1 miljoen nu naar 1,5 miljoen in 2020. Hierdoor zullen we geconfronteerd worden met voedingsproblemen waarbij een chronische ziekte een rol speelt. Aangepaste voeding, op grond van de onderliggende pathofysiologie, kan naast preventie van progressie van ziekte ook leiden tot een eerder klinisch herstel. De darm als gate-keeper van het lichaam speelt hierbij een belangrijke rol. Voedingsonderzoek bij deze doelgroep, gericht op verbetering van de darmgezondheid kan de patiënt een beter welzijn geven en de gezondheidszorg mogelijk goedkoper maken.'
    Functional characterization of Angptl4 protein
    Lichtenstein, L.L. - \ 2009
    Wageningen University. Promotor(en): Michael Muller, co-promotor(en): Sander Kersten. - [S.l. : S.n. - ISBN 9789085855033 - 118
    vetzuren - genexpressie - lipidenmetabolisme - vasten - nutrigenomica - fatty acids - gene expression - lipid metabolism - fasting - nutrigenomics
    Background: Elevated plasma triglycerides (TG) are increasingly recognized as a risk factor for atherosclerosis. A new adipocytokine was discovered by several groups which is referred to as Angptl4 (Angiopoietin-like protein 4). Angptl4 was recently identified as a major determinant of plasma TG levels in mice. Angptl4 is a 50 KDa secreted protein belonging to the family of fibrinogen/angiopoietin-like proteins.

    Objective/Design: In order to characterize the metabolic function of Angptl4, we explored dietary modulation effects on transgenic mice overexpressing Angptl4.

    Results: Taking advantage of the induction of Angptl4 by fasting, we showed that Angptl4 strongly inhibits LPL and HL activities. Later, we reported the development, validation and utilization of an ELISA assay to quantitatively assess Angptl4 levels in human plasma. Within an individual, Angptl4 levels rise in response to elevation of plasma free fatty acids. Furthermore, we address the function of Angptl4 in the heart. Dietary unsaturated fatty acids have a major impact on human health, which is likely achieved via changes in gene expression. Fatty acids regulate gene expression mainly via nuclear receptors, including the PPARs. Angptl4 appears to be regulated by dietary fat in a PPARb/d dependent, but in a PPARa independent way. Upregulation of Angptl4 resulted in decreased cardiac uptake of plasma TG-derived fatty acids and decreased fatty acid-induced oxidative stress and lipid peroxidation. Finally we investigated the function of Angptl4 in the intestine. Elevated saturated fat consumption is associated with increased risk for numerous chronic diseases, including inflammatory bowel disease, and obesity. Besides carrying out nutrient digestion and absorption, the GI-tract also produces a variety of hormones that play pivotal roles in nutrient handling and energy homeostasis. We report that Angptl4 is fat sensitive hormone produced by enteroendocrines cells. Noticeably, chronic saturated fat feeding led to complex and dramatic phenotype in Angptl4-/- mice. Angptl4-/- fed saturated fat developed a severe pathology leading to death. This lethal phenotype is preceded by excessive inflammation as shown by a dramatic hepatic acute phase response.

    Conclusion: The data show that Angptl4 protects against the pro-inflammatory and ultimately lethal effects of chronic overconsumption of saturated fat.

    Characterization of the two PPAR target genes FIAF (Fasting-Induced Adipose Factor) and G0S2 (G0/G1 switch gene 2)
    Zandbergen, F.J. - \ 2006
    Wageningen University. Promotor(en): Michael Muller, co-promotor(en): Sander Kersten. - s.l. : S.n. - ISBN 9789085043928 - 136
    lipidenmetabolisme - obesitas - vetweefsel - genexpressie - vasten - hormonen - lipid metabolism - obesity - adipose tissue - gene expression - fasting - hormones
    The prevalence of obesity has increased dramatically over the last decades. Obesity, defined as excess body fat, develops if energy expenditure is lower than its intake and if the surplus energy is stored in adipose tissue as fat. Excess adipose tissue, especially around the waist, is associated with an increased risk for diseases such as type 2 diabetes and atherosclerosis.These disorders aremajor causes of death from cardiovascular disease in the Western world.

    Common features of obesity, atherosclerosis and diabetes are insulin resistance and elevated plasma levels of triglycerides (TG) and low-density lipoprotein (LDL) cholesterol, whereas high-density lipoprotein (HDL) cholesterol is decreased.

    A number of the pharmacological interventions to treat early stages of atherosclerosis and type 2 diabetes target the peroxisome proliferator-activated receptors (PPARs). Activation of these transcription factors results in the expression of a variety of target genes, many of which play important roles in lipid metabolism. There are three PPAR isoforms: PPARa, PPARbor PPARd,and PPARg. Synthetic ligands for PPARaand forPPARgdecrease plasma TG levels and lower the concentration of LDL-cholesterol in blood whereas they elevate plasma HDL-cholesterol levels. Linked to their hypolipidaemic effect, they may also have hypoglycaemic effects, reducing chronically elevated insulin signalling and associated insulin resistance, which predisposes to the development of type 2 diabetes.

    In an effort to gain more insight into the relationship between PPAR target gene expression and its beneficial effect on lipid metabolism with regard to atherosclerosis and type 2 diabetes, the expression of genes in liver of wild-type mice and mice that lack functional PPARα was compared during fasting. Amongthe genes that were found to be differentially regulated in the wild-type and the PPARα mice, wereboththefasting-induced adipose factor (FIAF) and the G 0 /G 1 switch gene 2 (G0S2) strongly up-regulated in the wild-type mice during fasting.

    The research described in this thesis focuses on the characterization and elucidation of the function of these two genes and their protein products. FIAF belongs tothe family of fibrinogen/angiopoietin-like proteins and was previously found to be highly expressed in adipose tissue and to be up-regulated in response to fasting, hence its name. For G0S2, which was also highly expressed in adipose tissue and which we found to be localized to the endoplasmic reticulum (ER), no homologous genes could be found. During adipogenesis, the differentiation of pre-adipocytes into fully differentiated adipocytes, the levels of mRNA and protein for FIAF and G0S2 were greatly up-regulated.Subsequent experiments indicated that G0S2 is a direct PPARγ and probable PPARα target gene with a functional PPRE (PPAR-responsive element) in its promoter. Using the same approach, a functional PPRE was found within intron 3 of the FIAF gene, establishing FIAF as being a direct PPAR target gene too.

    The up-regulation of G0S2 mRNA during the differentiation of adipocytes seemed to be specific for adipogenesis, no up-regulation of G0S2 mRNA was observed during osteogenesis or myogenesis.Furthermore, G0S2 expression was associated with cell cycle arrest in3T3-L1pre-adipocytes, which is required for the differentiation of these cells into adipocytes.This indicates that G0S2 may be involved in adipocyte differentiation.

    Further investigation showed thatFIAF was present as the native protein and in truncated forms in bothmouse and human blood plasma. Interestingly,truncated FIAF was produced by human liver and treatment with PPARα agonist markedly increased plasma levels of truncated FIAF, but not native FIAF, in humans. The levels of both truncated and native FIAF showed marked inter-individual variation but were not associated with body mass index and were not influenced by prolonged semistarvation.

    To determine the physiological role of FIAF, we studied the effect of FIAF overexpression in a transgenic mouse model (FIAF-tg mice). Thetransgenic mice had markedly reduced adipose tissue stores compared to their wild-type littermates, despite similar food intake. The FIAF-tg mice also had elevated plasma levels of TG, glycerol, free fatty acids (FFA), and HDL as well as very low-density (VLDL) cholesterol. The increase of plasma TG levels was attributable to elevated VLDL levels. Oral lipid loading showed that the FIAF-tg mice had severely impaired plasma TG clearance. The effects on plasma TG levels are most likely the result of FIAF-mediated inhibition of the activity of lipoprotein lipase (LPL), a key regulator of plasma TG clearance. The elevated levels of FFA and glycerol are indicative of increased lipolysis, a notion supported by theincreased expression level of adipose triglyceride lipase (ATGL) in the adipose tissue of FIAF-tg mice. Additional genes that were differentially expressed are involved in oxidative metabolism and uncoupling, which might explain the decreased weight of the FIAF-tg mice while their food intake was similar to that of their wild-type littermates.The elevated HDL levels might be the result of FIAF-mediated inhibition of other lipases in addition to LPL, e.g.endothelial and hepatic lipase (EL/HL).

    Interestingly, after fractionation of mouse plasma by FPLC, the full length form of FIAF was present specifically in the HDL-containing fractions, whereas the truncated form of FIAF was specifically present in the LDL-containing fractions.In human plasma, both full length and truncated FIAF were only present in the HDL-containing fractions. In addition, the levels of truncated FIAF and HDL-cholesterol in human plasma correlated positively. Combined with our earlier finding that treatment with synthetic PPARaligandincreased the plasma levels of truncated FIAF in humans, this raises the possibility that FIAF might be involved in the mechanism by which PPARaligand treatment increases HDL-cholesterol levels in humans, resulting in a protective effect on atherosclerosis.

    The up-regulation of FIAF during fasting and the ability to inhibit plasma TG clearance indicate that FIAF might play an important role in repartitioning TG from adipose tissue to other tissues under circumstances of energy shortage. In addition, alterations in FIAF signalling might be involved in dyslipidemia, the presence of abnormal lipid levels in the blood. FIAF thus forms an interesting candidate for therapeutic targeting of dyslipidemia.

    Gewichtsverlies van biggen tijdens vasten en daaropvolgend transport
    Swinkels, H. ; Huiskes, J. ; Heetkamp, M. ; Schrama, J. - \ 1995
    Praktijkonderzoek varkenshouderij 9 (1995)1. - ISSN 1382-0346 - p. 4 - 4.
    diervoedering - vasten - slechte voeding - massa - biggen - veevervoer - gewicht - vermageringsdiëten - jonge dieren - animal feeding - fasting - malnutrition - mass - piglets - transport of animals - weight - weight loss diets - young animals
    In een samenwerkingsproject tussen het Praktijkonderzoek Varkenshouderij en de Landbouwuniversiteit Wageningen hebben vijf transporten (60 km) met elk 40 biggen plaatsgevonden. Voor aanvang van het transport kregen de biggen gedurende een periode van 16 uur geen voer verstrekt
    Household food security and nutritional status of vulnerable groups in Kenya : a seasonal study among low income smallholder rural households
    Kigutha, H.N. - \ 1994
    Agricultural University. Promotor(en): J.G.A.J. Hautvast; W.A. van Staveren. - S.l. : Kigutha - ISBN 9789054852940 - 161
    voedselhygiëne - voedingstoestand - consumptiepatronen - slechte voeding - vasten - vermageringsdiëten - voedingsfysiologie - huishoudens - gezinsinkomen - hulpbronnen - seizoenen - kenya - food hygiene - nutritional state - consumption patterns - malnutrition - fasting - weight loss diets - nutrition physiology - households - household income - resources - seasons - kenya

    Climatic seasonality is now recognized as being a constraint to agricultural production and to household food security in many countries within the tropical regions of the world. This study investigated the extent to which a unimodal climatic pattern affects food production and food availability of smallholder rural households, with special emphasis on households with limited landholdings and low cash incomes. Further investigations involved looking at the effect of fluctuating levels of food availability on dietary intakes and the nutritional status of three vulnerable groups namely: preschool children, lactating women and the elderly. The study was carried out in Nakuru district within the Rift Valley province in Kenya between April 1992 and June 1993. Foods coming into the household from own production, purchases, and gifts were recorded on monthly basis from recalls. Body weight of all the subjects was measured once every month. Height was measured once at baseline for the adults, while length for preschool children was measured three times. Food consumption was determined by 24-hour recall method on monthly basis, and by 3-day weighed records at three points during the lean and the harvest seasons. A unimodal climatic pattern was found to influence food production and hence household food availability during most months within the production cycle. This subsequently influenced food consumption and the nutritional status of the vulnerable groups in the study. Lactating women lost up to 9 percent, elderly men 7 percent, and elderly women 3 percent of their body weight. While no weight losses were observed in the children, weight gains were minimal during the lean season but improved slightly during the postharvest period. It was observed that the energy and nutrient intakes of the children depended more on diet quality rather than on household food availability per se.

    Micronutrient deficiencies in Ethiopia and their inter-relationships
    Wolde - Gebriel, Z. - \ 1992
    Agricultural University. Promotor(en): J.G.A.J. Hautvast, co-promotor(en): C.E. West. - S.l. : Wolde-Gebriel - ISBN 9789054850038 - 168
    voedingsstoornissen - voedselbereiding - eten koken - voedsel - voedingsmiddelen - maaltijden - borden - slechte voeding - vasten - vermageringsdiëten - ethiopië - nutritional disorders - food preparation - cooking - food - foods - meals - dishes - malnutrition - fasting - weight loss diets - ethiopia

    A nationwide study on the prevalence of xerophthalmia was carried out in 6,636 children aged 6 months to 6 years in all the Regions of Ethiopia except Eritrea and Tigrai which were excluded for security reasons. Bitot's spots were observed in 1.0% of all children with higher prevalence in the pastoral (1.6%) and cropping (1.1%) agro-ecological zones than in the cash- crop (0.4%) and ensete ('false banana', Ensete ventricosum (Welw.) Cheesman) (0.0%) zones. Conjunctival xerosis and Bitot's spots were twice as common in boys than in girls and this was seen in all age groups. One case of corneal xerosis and two cases of corneal scar (0.03%) were also found. Serum retinol levels were deficient (<0.35 μmol/l) in 16% and low (0.35-0.69 μmol/l) in 44% of children. Results of the present survey indicate that the problem is, according to WHO criteria, of public health significance. More stunting than wasting was observed, with peak prevalence of these signs of malnutrition being observed in the second year of life.

    It is estimated that there are three quarters of a million blind persons in Ethiopia. Results of a study of the 721 pupils in the six schools for the blind showed that 70% of the blindness was due to corneal opacity or shrinkage of the eye ball. Measles was implicated as a cause of blindness in 40% of the children while a further 13% regarded "mitch" as the predisposing factor. Mitch is an Amharic term used to describe a wide range of vague illness with fever and measles possibly comprising a large proportion of these cases.

    A nationwide study on 35,635 school children and 19,158 household members showed that the prevalence of gross goitre was 30.6% and 18.7% respectively while that of visible goitre was 1.6% and 3.2% respectively. Prevalence was significantly higher in females than in males and increased with age more in females than in males. Prevalence increased with increasing altitude. Based on an epidemiological model, the numbers of people suffering from various iodine deficiency disorders have been estimated.

    In Melkaye village of Hararge Region, a high prevalence of symptoms of vitamin A deficiency were found in 240 children examined: night blindness, 28.7%; Bitot's spots 6.7%; corneal xerosis 0.83%; corneal ulceration/keratornalacia 6.3%; and corneal scars 5.8%. Of the children studied, 30.2% had deficient serum retinol levels (< 0.35 μmol/l) while 58.0% had low levels (0.35-0.69 μmol/l). Thus both the clinical and biochemical parameters indicate that the problem of vitamin A deficiency was probably the most severe ever reported. The reason for the very severe deficiency of vitamin A in this area was the total dependence of the inhabitants for six years on supplies of relief foods which were devoid of vitamin A. About 55% of the children were malnourished with more wasting than stunting. Seventy children were reported to have died two years prior to the survey.

    In a study of 14,740 children in Shoa Region of Central Ethiopia, goitre, xerophthalmia (Bitot's spots) and clinical anaemia were observed in 34.2%, 0.91% and 18.6% respectively of the children. Based on a sample of 344 children, the median of most biochemical parameters was within the normal range except for haemoglobin, mean corpuscular haemoglobin concentration (MCHC) and urinary iodine excretion where the median was lower, and mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), and immunoglobulins G and M where it was higher. Many significant correlations were observed and these were used as the basis for the formulation of hypothethes. The anaemia found was not nutritional in origin but due to the effect of infestation with intestinal parasites and malaria.

    The effect of vitamin A supplementation on the treatment of goitre with iodized oil was assessed in a series of studies in Shoa Region. Iodized oil supplementation significantly reduced goitre size in those who had grade IB goitre (observable when neck extended). After 4 and 7/8 weeks post-treatment, concentrations of thyroxin and that of urinary iodine excretion increased significantly, while those of total triiodothyronine and thyrotropin decreased significantly. Vitamin A supplementation increased serum levels of retinol and retinol-binding protein at weeks 4 and 7/8 but had no effect on goitre size or parameters of iodine metabolism.

    In a similar study on anaemia, supplementation with iron and folic acid significantly increased levels of haemoglobin, haematocrit, red blood cell count, serum iron, transferrin saturation, ferritin and mean corpuscular haemoglobin concentration and significantly decreased levels of total iron binding capacity and transferrin at 4 and 7/8 weeks posttreatment. Only the increase in red blood cell count and decrease in mean corpuscular volume were significantly greater in those supplemented with vitamin A than those who were not supplemented.

    In the Gurage area in Central Ethiopia, cultivation, harvesting, yield and processing of ensete were studied in 60 households in six villages. Ensete was propagated vegetatively and has a six-year growing cycle in which it was transplanted three or four times. The yield of ensete food ("ko'cho") was 9.5 tons/yr/ha (6.1 MJ/m 2/yr). Except for cassava, the energy yield of ensete was higher than that from all other crops grown in Ethiopia while the protein yield (11.4 g/m 2/yr) was higher than that of all crops except banana and Irish potato although the protein density is very low (12 g/kg). The pseudostem and corm provide a starchy pulp which is fermented and can be stored for up to 5-7 years in an earthen pit. It can then be prepared for consumption in a variety of ways which have been studied in detail. The mean intake of ensete was 0.55 kg/day and provided 68% of total energy intake, 20% of protein, 28% of iron but no vitamin A. Energy intake from all food consumed was extremely low in Gurage, being only 60% of requirements.

    Energy metabolism of overweight women before, during and after weight reduction, assessed by indirect calorimetry
    Groot, C.P.G.M. de - \ 1988
    Agricultural University. Promotor(en): A.J.H. van Es; J.G.A.J. Hautvast. - S.l. : De Groot - 122
    energetische waarde - slechte voeding - vasten - vermageringsdiëten - overvoeding - obesitas - voedingsfysiologie - vrouwen - energy value - malnutrition - fasting - weight loss diets - overfeeding - obesity - nutrition physiology - women
    Previous studies had suggested that periods of low energy intake evoke compensatory adaptations in energy metabolism, which retard weight loss, and promote weight regain when energy intake returns to normal. The aim of this thesis was to investigate whether a slimming (low-energy) diet based on alternating energy intake could counteract this decrease in energy requirement. The persistance of the reduction of energy metabolism was studied 1 month and approximately 1 year after weight reduction.

    The effects of three slimming diets were compared pairwise in three separate studies. To this end, a cross-over design was used (fig. 2). Two alternating diets (diet AB/100: one day solely bread, water. coffee and tea, the other day providing 100 % (normal diet) the daily energy need and diet A50/100: one day providing 50 % of the daily energy need, the other day 100 %) and one continuous diet (C50: providing 50 % of daily energy need every day) were prescribed or supplied. Ten women participated in each study. First each subject lived on a weight-maintenance diet (S100) for 8 days, then two periods of low energy intake, of 4 weeks each, followed immediately afterwards. Energy balances were determined during the final 8 days of each diet period. The 24 hour energy expenditure was measured in a respiration chamber for 2 or 3 successive days. The activity pattern in the respiration chamber was standardized. Dopplermeters and actometers were used to record physical activity.

    Follow-up measurements of energy balance were made on ten subjects 1 month after slimming and on eight subjects energy balance was determined approximately 1 year after slimming. Weight-maintenance diets, adjusted for weight loss, were supplied during the follow-up measurement periods.

    Over the first 4 weeks of slimming body weights decreased by averages of 5.8 kg (C50), 4.5 kg (AB/100) and 3.9 kg (A50/100). The average weight losses over 8 weeks were 6.9 to 9.0 kg. After 8 weeks at a low energy intake 24 hour energy expenditure had declined by 12 - 15 %. This decline was partly (50 %) accounted for by the reductions in body weight and partly (30 %) by reduced dietary induced thermogenesis. The remaining part (20 %) of the decline was probably due to the reduced cost and amount of physical activity which was indicated by Dopplermeter counts and actometer counts.
    Sleeping energy expenditure also decreased during slimming by 6 - 13 %, but this was no more than could be expected from weight loss.
    Weight reduction by alternating (low with normal) low energy intakes resulted in a reduction of energy expenditure which, when weight loss and energy intake were taken into account, was similar to the reduction by continuous low energy intake, thus alternating low energy intake did not prevent energy expenditure rates from declining.
    Subjects participating in the follow-up studies maintained their reduced body weights successfully. Their 24 hour energy expenditure rates in the follow-up studies were still below the rates measured before slimming. When body weight and energy intake were taken into account, both the 24 hour energy expenditure values and the sleeping energy expenditure values were the same before slimming, and 1 month or 1 year after slimming.
    The changes of energy metabolism were determined by alterations in body weight and energy intake and probably in physical activity as well. It remains to be investigated whether other adaptive mechanisms are evoked when energy intake is restricted more severely or for longer periods.

    European collaborative study on the role of diet and other factors in the aetiology of atrophic gastritis: a pre-cancerous lesion of gastric cancer
    West, C.E. - \ 1984
    Wageningen : Stichting Nederlands Instituut voor de Voeding - ISBN 9789070840082 - 118
    vasten - slechte voeding - maagziekten - vermageringsdiëten - fasting - malnutrition - stomach diseases - weight loss diets
    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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