Organic meat and milk could offer more health benefits than conventionally delivered products, according to a new study by scientists from the UK, Poland, Norway, Italy, Denmark, Switzerland, Greece and Turkey.
Both organic meat and milk provide 50% more of the omega-3 fatty acids that are important in human nutrition. Organic meat has slightly lower concentrations of two saturated fats that are linked to greater risk of cardiovascular disease.
And organic milk contains 40% more linoleic acid, and carries slightly higher concentrations of iron, vitamin E and some carotenoids.
But conventional milk contains 74% more iodine and slightly more selenium, two minerals essential for healthy development.
The comparison is delivered in two studies in the British Journal of Nutrition, both led by Professor Carlo Leifert of the Nafferton Ecological Farming Group at the University of Newcastle.
Neither study is based on new laboratory work: both are what are called meta-analyses. The researchers looked at data from around the world, and reviewed 196 research studies of milk and 67 papers on meat to identify clear differences between organic and conventional milk and meat, in terms of fatty acid composition, and in the concentrations of certain minerals and anti-oxidants. The logic behind meta-analysis is that any single study could be skewed, or deliver an arguable conclusion, but a review of all the studies might give a surer guide. The reviews included several studies of mothers and children and the consequences of organic milk and dairy consumption.
“People choose organic milk and meat for three main reasons: improved animal welfare, the positive impacts of organic farming and the perceived health benefits. But much less is known about the impacts on nutritional quality, hence the need for this study,” said Leifert.
“Several of these differences stem from organic livestock production and are brought about by differences in production intensity, with outdoor-reared, grass-fed animals producing milk and meat that is consistently higher in desirable fatty acids such as the omega-3s, and lower in fatty acids that can promote heart disease and other chronic diseases.”
His co-author and colleague Chris Seal, professor of food and human nutrition at Newcastle said “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 recommends we should double our intake. But getting enough in our diet is difficult. Our study suggests that switching to organic could go some way towards improving intakes of these important nutrients.”
But other scientists questioned the significance of some of the conclusions. Ian Givens, professor of food chain nutrition at the University of Reading, argued that though the higher fatty acid content of organic milk was not disputed, a switch from conventional to organic milk would increase intake by only a tiny amount overall: an increase of 1.5% in the total diet.
“Organic produce isn’t more nutrient-packed in every regard, either,” he said. “The lower iodine and selenium content of organic milk has been recognised before, and since milk is the greatest single source of dietary iodine, the lower value in organic milk needs to be recognised. This is especially true for pregnant women, for whom iodine is a critical nutrient to ensure the healthy development of their baby.”
Tom Sanders, professor emeritus of nutrition and dietetics at Kings College said that differences in fatty acid composition might be more related to production systems than to organic or conventional content.
“Generally, cows that eat grass produced milk and meat that contained up to 50% more omega-3 fatty acids than those fed on grains. In countries where there is a lot of rain such as the UK, Ireland, Brittany and New Zealand most milk and cheese comes from cows fed on grass and you can tell this from the bright yellow colour derived from the carotene present in grass,” he said.
Researchers led by Leifert in 2014 found that organic crops and the foods prepared from them were up to 60% in key anti-oxidants, and lower in levels of the toxic metal cadmium, than conventionally produced crops.
He said “We have shown without doubt that there are composition differences between organic and conventional food. Taken together, the three studies on crops, meat and milk suggest that a switch to organic fruit, vegetables, meat and dairy products would provide significantly higher amounts of dietary antioxidants and omega-3 fatty acids.”
