Carbohydrate and lipid composition of vegetables, and bioavalability assessed in a rat model: Impact different cultivation systems

Environmental as well as cultivation factors may greatly influence the chemical composition of plants. The main factors affecting chemical composition of foodstuff is level and type of fertilizer (conventional and organic cultivation systems), location or soiltype and year of harvest. Organic foods are defined as products which are produced under controlled cultivation conditions characterized by the absence of synthetic fertilizers and very restricted use of pesticides. Dietary carbohydrates constitute a major fraction of most feedstuffs and can be divided according to glycosidic linkage into sugars (mono- and disaccharides), oligosaccharides, starch and non-starch polysaccharides (NSP). The bulk of disaccharides and starch will be broken down by the action of pancreatic and mucosal enzymes in the small intestine, while there are no enzymes capable of cleaving some types of oligosaccharides and NSP. A fraction of starch (resistant starch) may also pass the small intestine undegraded either because the starch is physically inaccessible, the starch has a structure that resist amylolysis or the starch is retrograded after heat treatment. Lignin is not a carbohydrate but is tightly associated to cell wall polysaccharides. The term dietary fibre (DF) is used for cell wall and storage NSP and lignin. Adequate intake of dietary fibre are generally accepted as linked to health benefit into a protective role in large bowel cancer, diabetes, coronary heart disease and the issue of faecal bulking. Linoleic (C18:2 n-6) and α-linolenic (C18:3 n-3) are essential fatty acids, which cannot be synthesized in the mammalian organism, and therefore must be supplied in the diet of animals and man. These fatty acids are precursors for the important longer chain higher polyunsaturated fatty acids of the n-6 and n-3 families. Although fats are essential part of the diet, but if consumed in excess, they may exert negative effects on human weight change. Potatoes, carrots, peas, green kale, apple, and rapeseed were grown by three different cultivation strategies, i.e. organic (ORG), conventional (CON), or semi-organic (ORG+) farming system. Each ingredient was treated as for application for human consumption: potatoes, mature, soaked peas and kale were boiled and raw carrots and apples were shredded, and the food was then freeze-dried and packed into airtight bags. Rapeseed oil was produced from the air-dried rapeseeds of the three cultivation treatments, and the residual was discarded. The carbohydrate fraction of the ingredients except rapeseed oil was analysed into: starch, sugars, oligosaccharides and all its constituents and lignin. Likewise the dietary lipids of all ingredients were extracted and the long-chain fatty acids determined by GLC. The ingredients were mixed with a standard synthetic mixture and were formulated to meet the NRC requirements for rats and used in a balance experiments for measuring the bioavalability of the ingredients. Carbohydrate and lignin were predominant dietary constituents with value from 584 g/kg DM in kale to 910 g/kg DM in potatoes. Triacylglycerol was the major lipid class in pea with 82 % of total fatty acids in contrast to apple with only 35 % of fatty acids of the ether extract

Risk of selection bias due to non-participation in a cohort study on pubertal timing.

BackgroundNon-participation in aetiologic studies of pubertal timing is frequent. However, little effort has been given to explore the risk and potential impact of selection bias in studies of pubertal timing.ObjectiveWe aimed to explore the risk of selection bias due to non-participation in a newly established puberty cohort.MethodsWe evaluated whether three maternal exposures chosen a priori (pre-pregnancy obesity, smoking, and alcohol drinking during pregnancy) were associated with participation, whether pubertal timing was associated with participation, and whether selection bias influenced the associations between these exposures and pubertal timing. In total, 22 439 children from the Danish National Birth Cohort born 2000-2003 were invited to the Puberty Cohort and 15 819 (70%) participated. Exposures were self-reported during pregnancy. Pubertal timing was measured using a previously validated marker, "the height difference in standard deviations" (HD:SDS), which is the difference between pubertal height and adult height, both in standard deviations. For this study, pubertal height at around 13 years in sons and around 11 years in daughters was obtained from an external database, and adult height was predicted based on parental height reported by mothers.ResultsParticipation was associated with most exposures but not with pubertal timing, measured by HD:SDS. The associations between exposures and HD:SDS were comparable for participants only and all invited for participation.ConclusionIn conclusion, the risk of selection bias in aetiologic studies on pubertal timing in the Puberty Cohort appears minimal

Organic Food and Health: A new project to study the effects of plant cultivation methods (organic and conventional) on nutritional value, health and reproduction in an animal experiment

Many consumers believe that food from plants grown under certain conditions, such as organic agriculture, will benefit health more than conventional food. This cannot be determined simply by analysing the material, since our understanding of the connections between food components and health is still to imprecise for such a purpose. Rather than waiting until basic research provides the knowledge needed for this approach, in the spring of 2001 we have initiated a project to study physiological effects of plant quality directly, in an animal experiment. The following cultivation treatments are used to grow plants that are typical ingredients for a human diet (potato, mature peas, kale, spring wheat, oilseed rape, carrots and apples): 1. A model of a distinct conventional cultivation system, with high input of mineral nutrients and use of as much pesticides as is allowed. 2. A model of a distinct organic cultivation system, with low input of organic plant nutrients and no use of pesticides. 3. A combination of model 1 and 2, with low input of nutrients and use of pesticides. The materials from each cultivation treatment will be thoroughly characterised, by measuring contents of nutrients (protein, minerals, energy content, vitamins), the biological value of major protein sources of feed plants will be assessed, selected secondary metabolites including known anti-nutrients will be measured and other quality indicators will be assessed including biocrystallization. Based on these results, 3 feed mixtures will be prepared, either based on defined weight percentages of each material from each treatment, or, if large variation in biological value is found, one or two feed mixtures can be adjusted to provide the same availability of protein and energy as the reference treatment (model 1). Potato, mature peas and kale will be cooked and freeze-dried, wheat is ground and baked to biscuits, oil is produced from the rapeseed, and raw carrots and apples are shredded and freeze dried, before feed pellets with the desired composition are prepared from the material. Three groups of rats are each provided one of the dietary treatments during 2.5 generation, and reproductive characteristics and performance are recorded. Subgroups of the last generation are selected for an intensive study in which uptake and excretion of energy and protein and selected micronutrients are determined. Respiration trials are performed to assess the energy metabolism, and simultaneous measurements of the activity levels of the rats are performed. In addition, blood and tissue samples of the rats will be obtained to study the effect of the dietary treatments on the immunological and antioxidant status of the rats. Data from the experiments are assembled and analysed using relevant statistical models, and the relationship to the nutritional characteristics of the plant material is described. Funding for the core project for a 4-year period is secured from the Danish Research Centre for Organic Farming (DARCOF). However, the intention is to provide a platform for international collaboration, since the well-documented material of plants and animals can provide multiple opportunities for associated projects. To investigate other aspects of plant composition or health than what is foreseen in the present project, or to follow up on it with additional experiments