Study says organic milk more uniform than other types
Scientists at the University of Newcastle in the UK have found that organic milk generally contained less saturated fat and more good fatty acids than milk produced at intensive commercial dairy farms. Its health giving properties were also much less likely to be affected by changes in the weather, the report in the Journal of Dairy Science says. The study also found non-organic milk collected during a particularly poor UK summer and the following winter had significantly higher saturated fat content and far less beneficial fatty acids than in a more “normal” year. The researchers discovered the link between milk quality and a changing climate while undertaking research into the differences between organic and conventional milk.
By contrast, organic supermarket milk showed higher levels of nutritionally beneficial fatty acids compared with “ordinary” milk regardless of the time of year or weather conditions. “The results suggest greater uniformity of feeding practice on farms supplying organic milk since there were no brands which differed consistently in fat composition,” notes Gillian Butler, leader of the study. “This implies a fairly uniform approach to feeding practised across these suppliers.”
Overall, organic milk had higher concentrations of beneficial polyunsaturated fats than conventional milk, although there was no significant difference in the total fat or protein content. Organic milk had 24% higher total polyunsaturated fatty acids. Of the two types of milk, organic milk had significantly higher levels of several PUFAs that have been associated with health benefits in other research. These included vaccenic acid, conjugated linoleic acid, alpha-linoleic acid and eicosapentaenoic acid. Organic milk also had a more desirable n-3:n-6 ratio. The differences between the compositions of the two milks was smaller in winter than in summer, although they remained statistically significant for both seasons.
Between organic and conventional milk, there was no difference in the total amount of saturated fatty acids, but there were differences in the mixture of individual saturated fatty acids that made up this total. This included significantly more myristic acid in organic milk, which is thought to carry a high risk of coronary heart disease, although this was only significant in the summer of the second year of sampling.
They also note that the year of the sampling had an effect on the milk composition, suggesting that different climatic conditions and food availability for cows may affect overall milk quality. The results suggest that if wetter, cooler summers continue in the UK, then farmers may have to rethink current dairy practices.
The researchers, who are part of the University’s Nafferton Ecological Farming Group and its Human Nutrition Centre, looked at the quality of 88 different milks of 22 brands, in supermarkets across North East England at varying times of year over a two-year period.
