Keith Woodford says the evidence in support of grass-fed milk is complex and liable to great distortion

By Keith Woodford*

Here in New Zealand, we live the notion that milk from grass-fed cows is superior to milk from cows fed other rations. Supposedly it is better for health. And supposedly the cows are happier if they can dance around in the sunshine doing what comes naturally. And supposedly it makes us more cost-efficient than our international competitors.

There is an element of truth to all of the above notions. But more often than not there is lots of myth intertwined with truth. Here, I want to tease out what is truth, what is myth, what depends on specific context, and some things that are still unknown.

The argument that grass-fed milk has better health attributes than milk produced from other rations relates primarily to the fatty-acid composition. There is indeed evidence that grass-fed milk contains less saturated fat, at least in some situations, and more Omega-3 fatty acids. The Omega-3 fatty acids are a specific form of polyunsaturated fats, with these polyunsaturated known in shorthand as PUFAs.

The science of Omega-3 fatty acids is complex and controversial. There is agreement that a diet rich in oily fish will be high in Omega-3 fatty acids, and there is also agreement that these fatty acids are important, particularly in children, for optimal brain development. 

There is also some agreement that Omega-3 fatty acids are relevant to heart health. But note that I used weak terms such as ‘some’ and ‘relevant’.  The heart health evidence is far from conclusive.

 The Omega-3 problem with grass-fed milk is that the increased quantities are unlikely to be enough to make any difference in a practical setting. Several years back, I discussed this over dinner in London with Dr Alex Richardson from Oxford University.

 Alex Richardson has spent much of her career studying health effects of Omega-3 fatty acids, and knows as much as anyone on this topic. I am always cautious about claiming anyone is an expert on any topic - it often seems to imply that there is nothing more to learn. But Alex certainly knows a great deal about Omega-3 fatty acids. She is passionate about their importance but was dismissive in response to my question as to whether the amounts in grass-fed milk would actually make a difference. Alex’s advice to me was to keep eating fish.

Focusing on the reduced saturated fatty acid content of grass-fed milk is also a two-edged sword. Yes, grass-fed milk and butter is somewhat lower in saturated fat than milk and butter from cows fed a high concentrate diet, but it is still very high in saturated fat – much higher than most of the vegetable oils that are butter alternatives. 

The broader community struggles to make sense of all the contradictory nutritional messages that are communicated by the media, fuelled in many cases by industry advocates. One of the myths of the last few years is that it is now ‘okay’ to be eating lots of saturated fat.  Somehow, this has become the fellow-travelling corollary to the message that sugar is bad when eaten in excess.

In June 2017, the American Heart Association published a ‘Presidential Advisory’ in the medical journal Circulation.  It had nothing to do with President Trump, but it did say “we conclude strongly that lowering intake of saturated fat and replacing it with unsaturated fats, especially polyunsaturated fats, will lower the incidence of CVD [coronary vascular disease]”.  It was written to counter misinformation.  

In essence, this statement is now the considered position at the highest level of the American medical research establishment. It is where the scientific evidence lies. For those who want to read the full paper – some 25 pages – it is open access and can be down-loaded here.

In understanding the health evidence, a key issue is to recognise that modern human diets are much higher both in sugar and saturated fat than the traditional diets of our evolutionary past. Those diets were much higher in complex carbohydrates and non-saturated fats.  We do need some sugar and we do need some saturated fats; it is the excess quantity that causes the issue.

The key element of this message, which many people struggle with, is that it is not arguing for low fat; it is arguing for limiting the amount of saturated fat and replacing it with non-saturated fat.

The relevance of this to the grass-fed milk debate is that butter made from grass-fed milk is still going to be very high in saturated fat. So, if the latest messages from the American Heart Association are correct – and they also align with the messages from public health experts at Auckland University here in New Zealand, and the well-respected Harvard School of Public Health in the USA - then arguing for grass-fed butter on health grounds is like travelling a slippery path.

There is lots more to be learned about milk from grass-fed cows. One of the surprising things about this milk is that it contains higher trans fats than other milk. Now trans fats are actually one of the things we don’t want, either in our milk or anything else.

Most people will recall that trans fats are the reason that inferior brands of margarine and other processed foods became a health hazard, with the trans fats being formed in the processing stage. Trans fats are now strongly regulated against within food processing, but the ruminant bacteria in cows beat to their own drum and so they do still produce trans fat. It is probably the largest remaining source of trans fat in modern human diets.

There is a further twist in New Zealand to the grass-fed story, and that relates to PKE (from palm kernel). Fonterra is now restricting its farmers to 3kg of PKE per cow per day. This is because, according to Fonterra, more than 3kg per cow per day affects the milkfat composition.

Fonterra has not been explicit as to what are the effects of PKE on milkfat, and there is no informative published literature which can be drawn upon. Fonterra has referred to a Massey University thesis, but I have read that thesis and it is not enlightening on the specific effects of PKE.

Despite the lack of information, it is likely that the issue is that butter made from milk produced by PKE-fed cows has an even higher saturated fat content than milkfat from cows on other feeds. The likely product composition effect is that it is further raising the already-high melting temperature of butter and other fat-based dairy products, which in turn affects product workability.

As a general rule, products high in saturated fats are solids at room temperatures, while products high in unsaturated fats are often liquids. Hence, butter is solid and olive oil is a liquid. In contrast, it is the remaining unsaturated fat in butter that leads to rancidity if it is left out of the fridge.

None of the fatty acids in PKE are unique to PKE. However, PKE is particularly high in lauric acid which is a saturated fat. This bypasses the rumen and is absorbed in the intestines. The cow can then either send this straight to the milk, or convert it in the liver to other fatty acids for use in both body maintenance and milk.

In some parts of the world, there is a move to promote grass-fed milk as a marketing tool rather than a health tool. For example, in the Netherlands, farmers get a price premium of about five percent if the cows are out on pasture for at least 120 days for six hours per day. This is actually less than 10% of the total time over a year, and will have minimal effect on milk-product composition, but it does allow the marketing companies to put nice pictures of gazing cows on their packaging. And that is what consumers want to see.

In the United States, some producers living close to urban centres differentiate their milk as being grass-fed, which is then direct-sold to consumers at premium prices. However, this is very much a niche market.

I see no evidence of grass-fed milk premiums in American supermarkets, although there are definitely premiums for organic milk.

For New Zealand to get substantial grass-fed premiums, it will need to work out how it is going to get premiums for its mainly commodity products.  Most of New Zealand’s milk loses its identity long before it gets anywhere near the consumer. This includes food service ingredients which Fonterra classes as ‘value-add’, and is very good at.

The ingredient purchasers are looking primarily for product consistency and product safety using objective measures. They do not care about pretty pictures.

Another vulnerability for New Zealand is that its major product of whole milk powder (WMP) includes imported lactose. In general, those cows will not be grass-fed.

In recent years, New Zealand has been importing between 70,000 and 100,000 tonnes of lactose to add to its milk powders.   This is because the ratio of lactose to other components in NZ-bred cows on grass-fed diets does not meet the international composition standards for WMP.

Independent of health and marketing issues, the other big issue for grass-based systems is the extent to which grass forms the basis of production efficiency here in New Zealand. That too is a big topic, where elements of truth and myth get intertwined. But it is too big a topic for this article; it will have to wait for another time.

If there is one core message in all of the above, it is that simple answers are usually wrong. These matters are complex. 

*Keith Woodford is an independent consultant who holds honorary positions as Professor of Agri-Food Systems at Lincoln University and Senior Research Fellow at the Contemporary China Research Centre at Victoria University.  His articles are archived at http://keithwoodford.wordpress.com. You can contact him directly here.