Nutritional Differences Between Organic and Conventional Meat
The main concept behind organic farming was put to paper by English agriculturalist Lord Northbourne. he wrote about the farm as having a “biological completeness” with a “balanced organic life” with the plants, soil and microorganisms forming an “organic whole” in his book Look to the Land written in 1940. The farm was seen as a complete living organism, rather than merely a location where a product was made. The ideas presented in his book eventually led to the various forms of organic food production, which are exemplified by no pesticide use, “no till” farming practices that improve soil structure and prevent soil erosion, and use of mulches and crop rotation instead of chemical fertilizers. Key concepts involve recycling nutrients throughout the farm, and only producing what the land can support.
Seventy years later, the organic market is booming, and organic food is seen as being more healthy than conventionally produced. A common theme that I see, which has been addressed by Średnicka-Tober in a recent publication on the differences between organic and conventionally-produced meat, is that organic food is more nutritious than conventional. When I see claims like this, I ask myself what the mechanism could be that organic food contains more of the good stuff (essential nutrients) and less of the bad stuff (pesticides, toxic heavy metals, saturated fat) compared to conventionally grown foods? Some reasons given seem to make sense: lower pesticide use in organic crops means lower pesticide residues on foods, and this seems to be partly supported by evidence showing that only 7% of organic foods contained any detectable pesticide residue compared to 38% of conventionally grown foods (statistic from an article by Holzman). However, when we talk about greater nutrient levels, I am skeptical of an across-the-board improvement in organic food compared to conventionally grown.
Using beef cattle as the example, the main difference between organically-raised and conventional meat animals is that animals raised under the organic system must be allowed to graze on pastures, whilst conventionally-raised cattle often spend their last few months in a feedlot, where their diet is gradually changed from hay to a more energy-dense diet that also contains grain to improve weight gain. However, non-organic grass-fed beef is also produced. And organic farmers may use grain feed to help organically-raised animals gain weight, as long as it is organic grain, which makes the issue less black-and-white than it first appears. This means that animals raised according to organic principles are more likely to be fed grass rather than grain, and tend to gain weight more slowly as their food is poorer and requires more effort to obtain.
However, the effect of grass feeding on meat quality depends on the nutrient in question. For example, the iron content of beef is not likely to be different between conventionally raised and organically raised animals as iron is a nutrient that the body needs to regulate within a certain range. Likewise, vitamin A is stored in the liver and the body regulates the amount in circulation, and thus the flesh. As vitamin A is an essential nutrient for cattle, it is added to cattle diets, whilst cattle grazing on pasture can produce their own from the beta-carotene that is found in grasses. The iodine content of meat depends on the iodine content of the soil that cattle feed is grown on, and is also not related to the farming method used. As iodine deficiency also affects cattle, both organic farmers and conventional farmers with animals that eat food grown on iodine deficient soils must supplement with iodine to avoid deficiency disease. On the other hand, animals allowed to range for food may be leaner, and the fatty acid profile is likely to be diverse due to the greater content of omega-3 polyunsaturated fatty acids in grasses and other plants in the pasture.
And that is exactly what the Średnicka-Tober publication found. They conducted a meta-analysis of publications that compared the nutrient content of various meats (beef, sheep, poultry, goat) from organic versus conventional farming methods. Concentrations of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) were similar between both farming methods, while polyunsaturated fatty acids (PUFA: particularly omega-3) were greater in organically farmed meat. In total, intakes of omega-3 PUFA from meat were around 135 mg higher per day if organic meat is eaten rather than conventionally farmed. Conventionally farmed meats contribute 613 mg omega-3 PUFA compared to 748 mg from organically farmed meats, however it seems that most of this difference is alpha-linolenic acid, which has a less relevant role in the diet than the longer chain omega-3 PUFAs docosahexaneoic acid and eicosapentaenoic acid. To place this in perspective, the long chain omega-3 PUFA content of oily fish such as salmon, mackerel and anchovies exceeds 1700 mg per serving, and these omega-3s are longer chain. Fish makes a much more important contribution to omega-3 PUFA intake than choosing organic over conventional. There was also a trend to lower copper concentrations and higher iron concentrations in organic meat from a small number of studies.
So it seems that organically farmed meat contains more omega-3 PUFA, due to the higher omega-3 PUFA content of their diet. Levels of MUFA and SFA were similar. Due to the paucity of data for other nutrients, it is more difficult to say whether organic meat is healthier than conventional meat. Why hasn’t this been researched more? Perhaps because one would not expect to see a difference, and it is hard to justify spending resources on research where there is no effect expected.
Dominika Średnicka-Tober, Marcin Barański, Chris Seal, Roy Sanderson, Charles Benbrook, Håvard Steinshamn, Joanna Gromadzka-Ostrowska, Ewa Rembiałkowska, Krystyna Skwarło-Sońta, Mick Eyre, Giulio Cozzi, Mette Krogh Larsen, Teresa Jordon, Urs Niggli, Tomasz Sakowski, Philip C. Calder, Graham C. Burdge, Smaragda Sotiraki, Alexandros Stefanakis, Halil Yolcu, Sokratis Stergiadis, Eleni Chatzidimitriou, Gillian Butler, Gavin Stewart and Carlo Leifert. Composition differences between organic and conventional meat: a systematic literature review and meta-analysis. British Journal of Nutrition, available on CJO2016. doi:10.1017/S0007114515005073.
Blanco-Penedo I, López-Alonso M, Miranda M, Hernández J, Prieto F, Shore RF. Non-essential and essential trace element concentrations in meat from cattle reared under organic, intensive or conventional production systems. Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2010 Jan;27(1):36-42. doi: 10.1080/02652030903161598. http://www.ncbi.nlm.nih.gov/pubmed/19750401
Susanne Padel, Carolyn Foster (2005) "Exploring the gap between attitudes and behaviour: Understanding why consumers buy or do not buy organic food", British Food Journal, Vol. 107 Iss: 8, pp.606 - 625. http://dx.doi.org/10.1108/00070700510611002