The Food Standards Agency (FSA) in the UK has been campaigning to persuade people to switch to one per cent fat milk. This sits between semi-skimmed at 1.7 per cent fat and skimmed at 0.1 to 0.3 per cent.
Because milk is so widely and regularly drunk in the country, a widespread shift towards lower fat milk would make a big difference to overall fat intake.
For someone drinking two litres of milk a week, the FSA says switching from semi skimmed to one per cent milk would result in a reduction in fat consumption of 20g a week.
But some argue that this is not the best way to improve the fat composition of dairy products or even the best strategy for reducing fat in the diet.
Dr Adam Lock, assistant professor at Michigan State University, accused the FSA of going for the easy option of targeting one food group rather trying to improve dietary habits.
Lock said dairy contains the most diverse range of lipids found in nature, some of which have been shown to be beneficial to human health.
Fats certainly have a high calorific load and reducing them in the diet could play a key role in tackling obesity and poor health. But not all fats are the same and studies suggest that some shorter chain fatty acids in dairy such as conjugated linoleic acid (CLA) may offer significant nutritional benefits.
Back to the farm
Simply cutting the fat out of dairy products may therefore not be the best way to make them healthier and improve public health. Manipulating the fat profile of dairy by reducing unhealthy saturated fat content and keeping or even upping the beneficial fat content could be a better strategy.
Geoff Talbot, an independent fat consultant, told this publication that this is hard to achieve at a processing level. He said it is possible to blend milk fat with unsaturated vegetable fats but then you could end up with dairy analogues that cannot be called dairy products.
Instead the fat expert said the most promising approach is to go back to the farmyard and try and control the fatty acid content of milk by changing what cows eat.
There is significant research going on in this area. Lock has published a study suggesting that changing cows' diets could significantly increase the CLA content of milk but cast doubt on whether significant increases in omega-3 content were achievable (Lipids, Vol. 39, no. 12 (2004)).
Meanwhile, Professor Ian Givens from the University of Reading is currently working on a project to explore the potential of feeding cows with oilseeds and novel fat types to reduce the saturated fat content of milk and increase monounsaturated fat levels.
The focus is not on polyunsaturated fats for the same reason Lock was cautious about the potential to increase omega-3 content in milk. Neither omega-3 or polyunsaturated fats are found in substantial quantities in milk, making them harder to promote.
As well as looking at how novel fats and linseed oil can change the fat composition of dairy, researchers are also looking at the influence of organic and conventional farming practices. A very recent study suggested that the higher content of grass and conserved grass in the diet of organic cows increased the CLA and omega-3 content of the milk (Journal of Dairy Science Vol 94, Issue 1, 2011).
So the solution to better reduced fat dairy products could be found at the farm. But there may be a political and economic barrier to progress.
Increasingly dairy farmers are not being paid by the litre of milk produced but on a component based approach – according to the quantity of fat and protein in the milk. A higher fat content in the farmyard milk can help the farmer get more money per litre of milk produced.
While this remains the case, there may be little incentive for farmers to make potentially costly changes to feeding practices in order to improve the nutritional credentials of their milk.