Organic diets and physical activity: Research experience using a rat model

Total energy expenditure or heat production is comprised of basal metabolic rate, thermic effect of food, and physical activity. Physical activity is the most variable and easily altered component of total heat production. Physical activity is influenced by a number of biological parameters i.e. diet, genetics, age, and gender. The diet components of the macro as well as micronutrients and other components (secondary metabolites) associated with a diet could contribute to the well being of the animal and cause variation in physical activity. In order to investigate physical activity as a parameter to differentiate diets based on conventional or organic grown carrots the total heat production and physical activity was measured in a rat model. The experimental diets were formulated to meet the NRC requirements for rats by mixing 40% of freeze dried carrots with an Altromin chow diet. The carrots were from a 2-year field study. The carrots were grown by three different cultivation strategies: one conventional (C) and two organic systems (OA, organic using animal manure; and OB, organic using cover crops). The diets were given to weaned female GKMol rats, in groups of five rats per diet and given their assigned diet, for approx. 2.5 months. Throughout the experimental period the rats were monitored and weighed each week. The rat’s heat production and physical activity was measured with two open-air circuit respiration chambers, and measurement was done on a group of 5 rats. In the chamber the rats were placed in individual cages. The activity was measured using both passive infrared detectors and with video recording. There was not surprisingly lower physical activity level of rats during the day. Being night-active animals, rats are usually resting during the day-time

Preference of organic grown carrorts in a rat model

Food preference tests represent an approach in food quality research, taking advantage of the instinctive feeding behavior of animals by allowing them to choose between food samples. A great number of investigations using laboratory rats concerning essential and/or dangerous contents are based on this method and have shown its effectiveness. The selection of food is influenced to some degree by smell and taste, but mostly by wholesomeness and need. In the present study a preference test was used in order to test eventual selective differences among rats with regard to same composition, but cultivated in three different systems. The experimental diets were formulated to meet the NRC requirements for rats by mixing 40% of freeze dried carrots with an Altromin chow diet. The carrots were from a 2-year field study. The carrots were grown by three different cultivation strategies: one conventional (C) and two organic systems (OA, organic using animal manure; and OB, organic using cover crops). Wistar female rats (N=30, 15 per year) weighing 230 g, were kept individually in cages, and were arranged in a block design with three blocks of 5 rats. For 5 days, each rat had free access to each of the three kinds of diets (C, OA, OB), and consumption of feed from each of the diet-troughs was measured every day. Thereafter, the rats were offered an ordinary rat chow until the preference test was repeated 2 weeks later. Preferences expressed by daily food-intake were analyzed statistically taking into account the correlations of the choices of a rat per experimental day, and over the course of the experiment. The overall conclusion of the study is that rats show individual preference for the test diets, and that no clear difference among the dietary treatments could be obtained

Rats show individual preference for short-term choice of three human diets

A preference test was conducted to investigate whether rats could distinguish among three iso-energetic and iso-nitrogeneous human diets prepared with ingredients cultivated by each of three different farming strategies: LIminusP: low input of feritlizer without pesticides, LIplusP: lowinput of fertilicer and high input of pesticides and LHplusP: high input of fertilizer and high input of pesticides. The experimental diets were formulated to meet the NRC requirements for growing rats by mixing potatoes, carrots, peas, green kales, apples, and rapeseed oil. For five days, rats (N=27) had free access to each of the three diets, and consumption of each of the diets was recorded daily. Thereafter, rats were offered a standard laboratory chow until the test was repeated. The results indicated that the majority of the rats showed individual preference for the diets and behaved similarly on different experimental days (ρ = 0.63 in repetition 1 and ρ = 0.73 in repetition 2) and in the two repetitions (τ = 0.79). However, no clear difference among the dietary treatments could be obtained

The R Package geepack for Generalized Estimating Equations

This paper describes the core features of the R package geepack, which implements the generalized estimating equations (GEE) approach for fitting marginal generalized linear models to clustered data. Clustered data arise in many applications such as longitudinal data and repeated measures. The GEE approach focuses on models for the mean of the correlated observations within clusters without fully specifying the joint distribution of the observations. It has been widely used in statistical practice. This paper illustrates the application of the GEE approach with geepack through an example of clustered binary data.

USE OF A RAT MODEL TO ELUDICATE IMPACT OF ORGANIC FOOD ON HEALTH

Ingredients (potatoes, carrots, peas, green kale, apples, and rapeseed oil) were grown according to three different cultivation systems (“Organic”, low input of fertilizer without pesticides; “Minimally fertil-ised”, low input of fertilizer and high input of pesti-cides, “Conventional”, high input of fertilizer and high input of pesticides). Three iso-energetic and iso-nitrogeneous diets were composed of equal propor-tions of the ingredients originating from each of the cultivation systems, and the diets were investigated with respect to several physiological responses and biomarkers of health using a rat model. In addition, the diets were tested in a food preference test using the same type of rats, but another generation. In both experiments, the diets were optimized according to the nutritional requirements of reproducing rats, except for a high content of fat. Most of the measured variables (biomarkers of health) showed no differ-ences between the experimental diets, however, some differences between dietary treatments were obtained, which were in favour of the “organic” diet contrasted with the “conventional” diet. The prefer-ence test showed a significant interaction between diet choice and mother’s diet. However, the results obtained from the present study cannot be extrapo-lated to all organic and conventional cropping sys-tems, mainly because crops were grown only in one replication. Thus, it is of outmost importance that future investigations on the effect of organic food in relation to human health and well-being should be based on well-defined and controlled food produce system with replication

OrgTrace – No Difference in Levels of Bioactive Compounds found in Crops from Selected Organic and Conventional Cultivation Systems

The objective of the present study was to compare the content of selected bioactive compounds in organically and conventionally grown crops, and to evaluate if the ability of the crops to synthesize selected secondary metabolites was systematically affected by growth systems across different growth years as well as soil types. The results showed that contents of neither polyacetylenes and carotenoids in carrots, flavonoids in onions, nor phenolic acids in carrots and potatoes were significantly influenced by growth system. Thus it could not be concluded that the organically grown crops had higher contents of bioactive compounds than the conventionally grown. This indicates that giving preference to organic products because they contain more bioactive components is doubtfull. However, there are many other reasons for the consumer to choose organic food products, including: no pesticide residues in foods, animal welfare, and environmental protection

Organic food and health - status and perspectives

In a recent study it was investigated, through a well-controlled animal feeding experiment, whether conventional and organic food products showed differences in animal physiology of a type and magnitude that could indicate that organic products would affect humans differently. The primary, but still tentative conclusion from this study was that the most significant effects on rats was observed on health aspects that have rarely been assessed in prior studies: Immune status, sleep/activity pattern, accumulation of adipose tissue, liver function, and vitamin E status, while a large numbers of markers of “traditional” nutritional value showed no differences. Although the results of the present study could not directly be applied to organic and conventional production systems the observed differences were all in favour of the organic treatment, and thus pointed in the direction of potential health benefits when eating organically grown rather than conventionally grown food. However, this study like other studies related to the issue suffers from the fact that only one replication per food produce was used in the animal studies. Therefore the size of the effects could not be evaluated with respect to replication variation, which could have been determined by establishment of field trials. In addition, it was not possible to correlate the responses of the animals to the analysed diet composition due to the limited number of replicates, whereby the explanations of the effects were limited. Thus, it is of outmost concern that future investigations on the effect of organic food in relation to human health and well-being should be based on well-defined and controlled food produce system with replications

Heredity of interocular similarities in components of refraction : a population-based twin study among 66-to 79-year-old female twins

Purpose To examine genetic influences on interocular similarities in ocular refraction and components of refraction among elderly female twins. Methods Refraction was assessed in 94 monozygotic (MZ) and 74 dizygotic (DZ) female twins aged 66-78 years. Absolute values of interocular differences (Aniso variables) in spherical refraction (SR), refractive astigmatism (AST), spherical equivalent (SE), corneal refractive power (CR), corneal astigmatism (CAST), anterior chamber depth (ACD) and axial length (AL) were calculated. The differences between sisters in each of the Aniso variables were calculated and graded into two categories, best differentiating the groups, here isometropic and anisometropic values. The cut-offs for grading as isometropic were AnisoSR <0.75 D, AnisoAST <0.5 D, AnisoSE <1.0 D, AnisoCR <0.5 D, AnisoCAST <0.50 D, AnisoACD AL MZ and DZ pairs in the Aniso variables and the interrelationships between the Aniso variables. Results When the Aniso variables were treated as continuous, no significant differences were found between the MZ and DZ subjects. When the proportions of isometropic intratwinpair interocular differences in the Aniso variables in the MZ and DZ cotwins were compared, the prevalences (MZ/DZ) were AnisoSR: 68%/60%; AnisoAST: 66%/57%; AnisoSE: 87%/68%; AnisoCR: 83%/78%; AnisoCAST: 69%/35%; AnisoACD: 77%/63%; and AnisoAL: 76%/60%. The differences were statistically significant for Aniso SE (p = 0.035, Fisher's exact test) and CAST (p = 0.007). The greater homogeneity in the interocular differences between the MZ sisters supports the assumption that isometropia of different elements of refraction is genetically influenced and tending to continue up to older ages. In cases where AnisoSE was = 1 D, no similar influence on emmetropization was observed. The difference between sisters in AnisoSE was associated with the intratwinpair difference in Aniso AL, but not with the intratwinpair differences in AnisoCR, irrespective of zygosity. Conclusion The higher prevalence of similarities in isometropia of the spherical equivalent and corneal astigmatism between the MZ pairs compared to DZ pairs is consistent with the view that genetic influences on the refractive elements of the eye, tending to isometropia, continue into older age. The interrelation between CR and AL tends to maintain isometropia of SE irrespective of zygosity.Peer reviewe