Comparison of nutritional quality between conventional and organic dairy products: A meta-analysis

Department of Organic Food Quality and Food Culture, University of Kassel, 37213 Witzenhausen, Germany.
Journal of the Science of Food and Agriculture (Impact Factor: 1.71). 11/2012; 92(14):2774-81. DOI: 10.1002/jsfa.5639
Source: PubMed


As a contribution to the debate on the comparison of nutritional quality between conventional versus organic products, the present study would like to provide new results on this issue specifically on dairy products by integrating the last 3 years' studies using a meta-analysis approach with Hedges' d effect size method. The current meta-analysis shows that organic dairy products contain significantly higher protein, ALA, total omega-3 fatty acid, cis-9,trans-11 conjugated linoleic acid, trans-11 vaccenic acid, eicosapentanoic acid, and docosapentanoic acid than those of conventional types, with cumulative effect size ( ± 95% confidence interval) of 0.56 ± 0.24, 1.74 ± 0.16, 0.84 ± 0.14, 0.68 ± 0.13, 0.51 ± 0.16, 0.42 ± 0.23, and 0.71 ± 0.3, respectively. It is also observed that organic dairy products have significantly (P < 0.001) higher omega-3 to -6 ratio (0.42 vs. 0.23) and Δ9-desaturase index (0.28 vs. 0.27) than the conventional types. The current regulation on organic farming indeed drives organic farms to production of organic dairy products with different nutritional qualities from conventional ones. The differences in feeding regime between conventional and organic dairy production is suspected as the reason behind this evidence. Further identical meta-analysis may be best applicable for summarizing a comparison between conventional and organic foodstuffs for other aspects and food categories. Copyright © 2012 Society of Chemical Industry.

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    • "Consequently, the presented results are most likely related to the effect of the differences in diet, rather than to the fact that cows consumed organic or conventionally produced feed. On the contrary, studies that identify specific production differences for organic and conventional milk (e.g., higher amount of pasture in the diet of organic cows) fail to consider the influence of the farming system (organic or conventional) on their results (Palupi et al., 2012 ). Additionally, comparisons among studies are problematic because it is difficult to account for any number of variables, including sampling conditions (e.g., frequency of sampling, time of sampling, samples taken from individual cows vs. bulk milk vs. multiple farms), inherent differences in farming systems between regions, levels of input, and even regulatory differences in conventional and organic production between nations. "
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    ABSTRACT: Consumer perception of organic cow milk is associated with the assumption that organic milk differs from conventionally produced milk. The value associated with this difference justifies the premium retail price for organic milk. It includes the perceptions that organic dairy farming is kinder to the environment, animals, and people; that organic milk products are produced without the use of antibiotics, added hormones, synthetic chemicals, and genetic modification; and that they may have potential benefits for human health. Controlled studies investigating the differences between organic and conventionally produced milk have so far fallen short of a conclusion as to whether or not these differences exist. Controlled studies investigating whether differences exist between organic and conventionally produced milk have so far been largely equivocal due principally to the complexity of the research question and the number of factors that can influence milk composition. A main complication is that farming practices and their effects differ depending on country, region, year, and season between and within organic and conventional systems. Factors influencing milk composition (e.g., diet, breed, and stage of lactation) have been studied individually, whereas interactions between multiple factors have been largely ignored. Studies that fail to consider that factors other than the farming system (organic vs. conventional) could have caused or contributed to the reported differences in milk composition make it impossible to determine whether a system-related difference exists between organic and conventional milk. Milk fatty acid composition has been a central research area when comparing organic and conventional milk. Milk fatty acid composition has been a central research area when comparing organic and conventional milk largely because milk fatty acid profile responds rapidly and is very sensitive to changes in diet. Consequently, the effect of farming practices (high input vs. low input) rather than farming system (organic vs. conventional) determines milk fatty acid profile, and similar results are seen between low-input organic and low-input conventional milks. This confounds our ability to develop an analytical method to distinguish organic from conventionally produced milk and provide product verification. Lack of research on interactions between several influential factors and differences in trial complexity and consistency between studies (e.g., sampling period, sample size, reporting of experimental conditions) complicate data interpretation and prevent us from making unequivocal conclusions. The first part of this review provides a detailed summary of individual factors known to influence milk composition. The second part presents an overview of studies that have compared organic and conventional milk and discusses their findings within the framework of the various factors presented in part one. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
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    • "Nonetheless, both studies found that organic food had significantly lower levels of pesticide contamination. While this finding may support the hypothesis that organic food has health benefits, no evidence for this has been presented so far [4], [7], [24]. "
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