Organic MILK Quality

Source Information: Srednicka-Tober et al. (2016) Higher PUFA and omega-3 PUFA, CLA, a-tocopherol and iron, but lower iodine and selenium concentrations in organic milk: A Systematic Literature Review and Meta- and Redundancy Analyses. British Journal of Nutrition. 115, 1043-1060.

New study finds significant differences between organic and non-organic MILK and DAIRY products

In the largest study of its kind, an international team of experts led by Newcastle University, UK, reports that organic milk contains substantially more omega-3 fatty acids including in excess of 50% more nutritionally desirable very long chain omega-3 fatty acids EPA, DPA and DHA.

Analysing 196 studies into compositional differences between organic and conventional milk and dairy products, the team found a switch to organic milk and dairy products would substantially increase omega-3 fatty acid intakes, as recommended by the European Food Safety Authority (EFSA).

The study, published in the British Journal of Nutrition also showed significantly higher levels of polyunsaturated fat (PUFA), conjugated linoleic acid (CLA), vitamin E (a-tocopherol) and iron in organic milk, but a lower ratio of omega-6/omega-3 fat lower levels of selenium and iodine in organic milk.

Chris Seal, Professor of Food and Human Nutrition at Newcastle University explains:

"Omega-3s are linked to reductions in cardiovascular disease, improved neurological development and function, and better immune function."

"Western European diets are recognised as being too low in these fatty acids and the European Food Safety Authority (EFSA) recommends we should double our intake."

"But getting enough in our diet is difficult. Our study suggests that switching to organic would go some way towards improving intakes of these important nutrients."

New Methods used to analyse the data

This is the most extensive review of the nutrient content in organic vs conventionally produced milk and dairy products and used ground-breaking methods of meta- and redundancy analysis. This approach not only allowed nutrient profiles to be compared accurately, but also identified the main reasons for composition differences.

The study showed the more desirable fat profiles in organic milk were closely linked to outdoor grazing and low concentrate feeding in dairy diets, as prescribed by organic farming standards. Interestingly some of the studies reviewed showed that the use of traditional breeds and low milking frequency also contributes to milk quality differences.

Gordon Tweddle from Acorn Organic Dairy a participant in a cross European survey on milk quality (included in the analysis) commented: "So you showed that keeping cows outdoors eating natural foods - grass and clover - improves milk and meat quality. We were confident that was so, but it is reassuring that science has finally confirmed it!"

The findings contradict those of a UK Food Standard Agency (FSA) commissioned study which concluded there were no substantial differences between organic and non-organic livestock products. This FSA study, however, based its conclusions on only 12 comparative papers on milk and combined data from meat and milk composition in the analysis.

Interestingly, Dangour et al. reported a trend towards significantly higher levels of polyunsaturated and omega-3 fatty acids in organic livestock products (meat and milk) in their report to the FSA, but this was not mentioned in the published paper or press release.

Dr Gavin Stewart, a Lecturer in Evidence Synthesis and the meta-analysis expert in the Newcastle team, added: "The much larger evidence base available in this synthesis allowed us to use more appropriate, powerful statistical methods to draw more definitive conclusions regarding the differences between organic and conventional milk and dairy products"

What the findings mean

Organic milk has more omega-3s and a more desirable fat composition

The systematic literature review analysed data from around the world and found organic milk has a more desirable fat profile.

A range of poly-unsaturated fatty acids (PUFA) have been linked to a reduced risk of cardiovascular disease in scientific studies. These include (a) linoleic acid (LA, the main omega-6 fatty acid in milk), (b) a-linoleic acid (ALA, the main omega-3 fatty acid in milk) and the very long chain (VLC) omega-3 fatty acids (c) eicosapentaenoic acid (EPA), (d) docosapentaenoic acid (DPA), and (e) docosahexaenoic acid (DHA). EPA, DPA and DHA have also been linked to other health benefits including improved foetal brain development, delayed decline in cognitive function in elderly men and reduced risk of dementia (especially Alzheimer's disease). The European Food Safety Authority (EFSA) has estimated that average dietary intakes of VLC omega-3 fatty acids account for less than half of what we need for optimum health. To reduce cardiovascular disease risk, European and North American agencies therefore currently advise consumers to increase fish, and especially oily fish, consumption to increase their VLC omega-3 intake. Unfortunately implementing these recommendations widely across the human population is neither possible nor sustainable, since most of the world's fish stocks are already fully or overexploited.

A switch from conventional to organic would raise omega-3 fat intake without increasing calories and undesirable saturated fat. For example, half a litre of organic full fat milk (or equivalent fat intakes from other dairy products like butter and cheese) provides an estimated 16% (39 mg) of the recommended, daily intake of very long-chain omega-3, while conventional milk provides 11% (25 mg).

Other positive changes included (a) higher levels of fat soluble vitamins such as vitamin E and carotenoids, and (b) a lower omega-6/omega-3 ratio in organic milk and (c) 40% more CLA in organic milk.

The ratio of omega-6 fatty acids relative to omega-3 fatty acids in typical Western diets is thought to be too high, driven by the widespread use of vegetable oils. Consequently, reductions in omega-6 especially linoleic acid (LA) intakes have been recommended, since high LA intakes were linked to an increased risk of obesity, neurodevelopmental deficits in young children and chronic diseases such as certain cancers, autoimmune and cardiovascular diseases.

CLA is a polyunsaturated fatty acid (PUFA) produced as a result of microbial activity in the rumen. It is therefore only found in milk and meat fat from ruminant livestock (cattle, sheep and goats) and milk and dairy products account for 60% of total dietary CLA intake. Increased intakes of CLA have been linked to a range of health benefits including reduced risk for obesity, cancer, diabetes and cancer development, although most evidence is from cell culture and animal studies (Lawson et al. 2001). As a result, there is still debate about health benefits from increasing CLA intake in humans, but a recent analysis of 18 human studies concluded that CLA supplements produce a modest weight loss in humans. However, CLA supplements, marketed as having a range of health benefits, are mainly made synthetically from vegetable oils and are chemically different compared to CLA found naturally in milk and meat.

Avoiding iodine over- and under-supply from milk is a challenge

The study also found 74% more iodine in conventional milk which is important information, especially for UK consumers, where iodized table salt is not widely available and dairy products are an important source.

Iodine is low in most foods, except seafood, and the World Health Organisation (WHO) recommends Iodine fortification of table salt to address this. Fortification of cattle feeds is also widely used to increase iodine concentrations in both organic and conventional milk.

For iodine the UK Scientific Advisory Committee on Nutrition in 2014 concluded "The prevalence of iodine deficiency has been reduced by the use of iodised salt and oral or parenteral iodised oil. The former approach was used in Europe either as a mandatory or, as in the UK, a discretionary measure. However, little iodised salt is now consumed in the UK and some other European countries, and a resultant concern is that there is an increasing risk of iodine deficiency in Western Europe."

Gillian Butler, co-author of the paper and senior lecturer in animal nutrition at Newcastle University, explains:

"There is a relatively narrow margin between dietary Iodine deficiency (<140 µg/day) and excessive intakes (> 500 µg/day) from our diet which can lead to thyrotoxicoxis."

"Optimising iodine intake is therefore challenging, since globally there seems to be as much concern about excessive rather than inadequate intake."

In the USA, China, Brazil and many European countries, where Iodine fortified salt is widely used, elevated levels of iodine in milk may increase the risk of excessive intake for individuals with high dairy consumption. For this reason the European Food Safety Authority (EFSA) has proposed a reduction in the permitted level of iodine in cattle feed from 5 to 2 mg iodine per kg of feed.

However, in the UK, where iodized salt is not widely available, the population relies more on milk and dairy products for adequate iodine supply. National Diet and Nutrition Survey data (NDNS) suggest that milk and dairy products supply between 31-52% of iodine in the UK diet.

The daily recommended intake of iodine in the UK is 140 µg/day and just over half comes from dietary sources other than milk/dairy products. Based on the results from the study, half a litre of milk would provide 53% and 88% of the daily recommended intake from organic and conventional milk respectively. However, pregnant and breastfeeding women have a higher iodine requirement (250 µg/day) and are therefore more at risk of iodine deficiency, which could affect neurological development in babies.

Further evidence of the health benefits of organic milk

The systematic literature review also describes recently published results from several mother and child cohort studies linking organic milk, dairy products and vegetable consumption to a reduced risk of certain diseases. This included reduced risks of eczema and hypospadias in babies and pre-eclampsia in mothers.

Three of these publications reported results from Dutch, Danish and Norwegian Cohort studies linked the consumption of organic milk/dairy products with a reduced risk of (a) eczema in infants, and (b) boys being borne with hypospadia (a male genital deformation). For more information please see:

Kummeling I, Thijs C, Huber M et al. (2008) Consumption of organic foods and risk of atopic disease during the first 2 years of life in the Netherlands. British Journal of Nutrition 99, 598-605

Christensen, J.S. et al. (2013) Association between organic dietary choice during pregnancy and Hypospadias in offspring: A study of 306 boys operated for hypospadias. The Journal of Urology 189, 1077-1082

Brantsaeter, A.L. et al. (2015) Organic Food Consumption during Pregnancy and Hypospadias and Cryptorchidism at Birth: The Norwegian Mother and Child Cohort Study (MoBa). Environmental Health Perspectives on line, doi 10.1289/ehp.1409518

Media Contacts

Professor Carlo Leifert, Professor of Ecological Agriculture, School of Agriculture, Food and Rural Development, Newcastle University. Tel: 01661-830222/830444; E-mail: teresa.jordon@newcastle.ac.uk

Louella Houldcroft, Senior Communications Manager, Faculty of Science, Agriculture and Engineering, Newcastle University; Tel: +44 (0) 191 208 5108; Mob: 07989 850511; Email: louella.houldcroft@newcastle.ac.uk