Wetter, cooler summers can have a detrimental effect on the milk
we drink, according to new research published by Newcastle
University.
Researchers found 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.
But they also discovered that switching to organic milk could
help overcome these problems. 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 study, which is published in this month's Journal of
Dairy Science (January 2011), leads on from previous research
undertaken nearly three years ago which looked at the difference
between organic and conventional milk at its source - on the
farms.
"We wanted to check if what we found on farms also applies to
milk available in the shops," said Gillian Butler, who led the
study. "Surprisingly, the differences between organic and
conventional milk were even more marked. Whereas on the farms the
benefits of organic milk were proven in the summer but not the
winter, in the supermarkets it is significantly better quality year
round."
There was also greater consistency between organic suppliers,
where the conventional milk brands were of variable quality.
"We were surprised to see obvious differences between the
conventional brands, with the more expensive ones not necessarily
better," said Mrs Butler. "Some brands - which promote their
suppliers as wholesome and grazing on fresh pastures - actually
sold milk that appeared to be from very intensive farms."
Low levels of omega-3 and polyunsaturated fatty acids were
discovered in some of these brands, which are indicative of a diet
low in fresh grass. These samples also showed evidence of the cows
being supplemented with a saturated fat product derived from palm
oil.
Mrs Butler puts the differences down to a lower reliance on
grazing and fertiliser suppressing clover on conventional farms.
"The results suggest greater uniformity of feeding practice on
farms supplying organic milk since there were no brands which
differed consistently in fat composition," she said. "This implies
a fairly uniform approach to feeding practised across these
suppliers."
Organic dairying standards prescribe a reliance on forage,
especially grazing, and, in the absence of nitrogen fertiliser,
tend to encourage swards of red and white clover, which have been
shown to alter the fatty acid intake and composition of milk.
While protein, antioxidants, vitamins, minerals and some mono
and polyunsaturated fatty acids in milk are considered beneficial,
saturated fatty acids are believed to have a negative effect on
human health.
"We're always being told to cut down on the saturated fat we
consume and switching to organic milk and dairy products provides a
natural way to increase our intake of nutritionally desirable fatty
acids, vitamins and antioxidants without increasing our intake of
less desirable fatty acids," said Mrs Butler.
"By choosing organic milk you can cut saturated fats by 30-50
percent and still get the same intake of beneficial fatty acids, as
the omega-3 levels are higher but omega-6 is not, which helps to
improve the crucial ratio between the two."
While undertaking their research into the differences between
organic and conventional milk, the researchers discovered the
surprising link between milk quality and our changing climate.
Their results suggest that if we continue to have wetter, cooler
summers then farmers may have to rethink their current dairy
practices.
There was a considerable difference between the milk bought in
the first sampling period (July 2006 and January 2007) and
corresponding times a year later. The second set of samples,
following a particularly wet summer in 2007, was higher in
saturated fat and lower in beneficial fatty acids.
"We didn't expect to find differences between the sampling
periods," said Mrs Butler. "But this is likely to be down to the
impact of the weather on availability and quality of forage."
In North East England, for example, the summer of 2007 was
particularly wet, with approximately 30 per cent higher recorded
rainfall and 12 per cent lower temperatures compared with 2006.
"These conditions may affect the cows' behaviour, reducing
grazing intake and milk output," said Mrs Butler. "Farmers also
often increase supplementation with concentrated feeds or conserved
forage to maintain milk yields in these conditions."
During the region's main silage making period (late May until
the end of July) rainfall in 2007 was three times higher than the
previous year, which also made for poorer quality silage and
therefore the need for greater supplementation to compensate in
winter diets.
"If these weather patterns continue, both forage and dairy
management will have to adapt to maintain current milk quality,"
said Mrs Butler. "The higher levels of beneficial fats in organic
milk would more than compensate for the depression brought about by
relatively poor weather conditions in the wet year."
The researchers, who are part of the University's Nafferton
Ecological Farming Group and its Human Nutrition Centre, looked at
the quality of milk in supermarkets across North East England at
varying times of year over a two-year period.
They concluded that organic brands of milk available in
supermarkets are higher in beneficial fatty acids such as CLA and
omega-3 fatty acids in summer (as in their previous research) and
winter (where previous research showed that the difference in the
winter was not as noticeable).
Emma Hockridge, head of policy at the Soil Association, said:
"This groundbreaking research proves for the first time that people
buying organic milk will be benefitting from the higher levels of
beneficial fatty acids in organic milk through the whole year."
SOURCE