Abstract
Demand for organic milk is partially driven by consumer perceptions that it is more nutritious. However, there is still considerable uncertainty over whether the use of organic production standards affects milk quality. Here we report results of meta-analyses based on 170 published studies comparing the nutrient content of organic and conventional bovine milk. There were no significant differences in total SFA and MUFA concentrations between organic and conventional milk. However, concentrations of total PUFA and n-3 PUFA were significantly higher in organic milk, by an estimated 7 (95 % CI -1, 15) % and 56 (95 % CI 38, 74) %, respectively. Concentrations of α-linolenic acid (ALA), very long-chain n-3 fatty acids (EPA+DPA+DHA) and conjugated linoleic acid were also significantly higher in organic milk, by an 69 (95 % CI 53, 84) %, 57 (95 % CI 27, 87) % and 41 (95 % CI 14, 68) %, respectively. As there were no significant differences in total n-6 PUFA and linoleic acid (LA) concentrations, the n-6:n-3 and LA:ALA ratios were lower in organic milk, by an estimated 71 (95 % CI -122, -20) % and 93 (95 % CI -116, -70) %. It is concluded that organic bovine milk has a more desirable fatty acid composition than conventional milk. Meta-analyses also showed that organic milk has significantly higher α-tocopherol and Fe, but lower I and Se concentrations. Redundancy analysis of data from a large cross-European milk quality survey indicates that the higher grazing/conserved forage intakes in organic systems were the main reason for milk composition differences.
Highlights
Long-chain n-3 fatty acids (EPA + DPA + DHA) and conjugated linoleic acid were significantly higher in organic milk, by an 69 %, 57 % and 41 %, respectively
The main objectives of the present study were to [1] carry out a systematic literature review of all available studies published before March 2014 that focused on quantifying composition differences between organic and conventional milk and dairy products; [2] conduct weighted and unweighted meta-analyses (WM and unweighted meta-analysis (UM)) of the published data; [3] carry out sensitivity analyses focused on identifying to what extent meta-analysis results are affected by data extraction
The meta-analysis results showing that milk yields per cow were on average 20 % lower in organic compared with conventional systems confirms results from a previous metaanalysis[13], which linked lower yields per cow to the use of high grazing/conserved forage diets used in organic dairy systems
Summary
Long-chain n-3 fatty acids (EPA + DPA + DHA) and conjugated linoleic acid were significantly higher in organic milk, by an 69 (95 % CI 53, 84) %, 57 (95 % CI 27, 87) % and 41 (95 % CI 14, 68) %, respectively. As there were no significant differences in total n-6 PUFA and linoleic acid (LA) concentrations, the n-6:n-3 and LA:ALA ratios were lower in organic milk, by an estimated 71 (95 % CI −122, −20) % and 93 (95 % CI −116, −70) %. A main driver for the increase in demand has been the consumer perception that organic milk and dairy products typically contain higher concentrations of nutritionally desirable compounds, making them ‘healthier’(4,5). Over the past 20 years, a large number of scientific studies have compared concentrations of nutritionally relevant compounds in milk from organic and conventional dairy production systems. LDL production and enhance its clearance, whereas EPA and DHA reduce arrhythmia, blood pressure, platelet sensitivity, inflammation and serum TAG levels[19]
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