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

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 You can contact him directly here.

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Keith you could apply the same logic and references of myths to A2 milk and get the same answer , your bias is perfectly clear

Grass-fed and A2 are separate issues, although milk can have both attributes. Debates move forward when people stick to the evidence and make corrections as new evidence emerges or errors become apparent. In relation to grass-fed, where the issues are indeed complex, then present your facts if you think I am in error. In relation to A2, that is the topic for other threads. Non specific assertions as to bias are simply playing the man rather than the ball. In essence they are a form of venting.
Keith W

"Non specific assertions as to bias are simply playing the man rather than the ball. In essence they are a form of venting."
This is applicable for so many comments on this website and many others.
So good, very good. Applause.

If grass-fed is a marketing tool (like organic) then so be it. People believe all sorts of nonsense and make purchasing decisions based on it.

Exactly my point Doris just look at A2


A great deal of hot air comes from the Westminster parliament-so you are well named. This article,written by someone who I strongly suspect knows a great deal more about the subject than you do,has nothing to do with A2 milk-so,put up or shut up.

I wonder if in the future we will be able to load vegetative material into a digester and produce various foods?
What happened to the artificial milk?

The most important factor in eating animals, or animal products, is the health of the animal. Animals know what they need in their diet, so an animal that has been free to choose what it needs to eat is always going to be a better food source. Conversely, if you eat products from an unhealthy animal then you will be unhealthy. The oldest source of this wisdom I have found comes from Vitruvius.

It isn't just animal products either. If you eat from sick land, or an animal grazing on sick land, then you will be sick also.

Umm.. there's one animal which doesn't seem to know what they need in their diet... (us) so there could be others...

Keith : I think your faith in the findings of the American Heart Association is badly misdirected ; the AHA has a long and repeated history of spouting whatever their primary funders ( the big US food manufacturers ) tell it to say ....

... Inuit ( formerly " eskimos " ) used to eat a diet consisting of 80 % + saturated fat ( seal and whale blubber ) , and had no history of heart disease .... not until white man brought them up to speed with our westernized diet , and hooked them on sugar and refined white flour ....

The benefit from grass fed cows and beef , is that the omega 3 levels in the milk/meat are in perfect proportion to the omega 6 levels , for the human body to digest .... grain fed bovine produce milk/meat with a much higher omega 6 to omega 3 ratio : and this is a serious health issue ...

... as is the widespread use of seed oils ( canola / sunflower / grapeseed / etc ) .... they're seriously bad news to the healthy functioning of our bodies .... margarine is a disastrous product for our gut and digestive system ...

Get back to the simple , natural things , Keith : full fat milk , cheeses , butters and yoghurts are good for us ; they're nutritionally dense foods that we're evolved to consume , and immensely beneficial to our gut biome ...on the other hand , margarine , cakes , sugar and coke are not . : kick them to the curb ...

Gummy Bear Hero
I have not seen any evidence that the American Heart Association is funded by the big food manufacturers. In fact I am confident that it is not. But if you have evidence to the contrary, then I would like to see it.
Keith W

According to this site they pay to have the heart healthy tick.

"For each of the approximately 630 "heart healthy" logos on cereal boxes or other food products, the AHA gets a cool $7500 a year.

Well actually, the Center for Science in the Public Interest (CSPI) reports that the AHA charges companies on a per product basis: $7,500 for 1-9 products, $6,750 for 10-24 products and $5,940 for 25-99 products in their first year.

To renew in subsequent years, the prices are $4,500, $4,050, and $3,570 respectively."

And here are all the details outlining processes one of which states certification fees must be paid.

There is this article in Forbes - dated back in 2012. They say it is not a pay to play system....but have a read and follow some of the links.

Keith : the AHA has always been a not-for-profit organization ... they reached a nadir in the 1940's , until Proctor & Gamble gifted a lot of money to get their " patronage " ...

... since then , any company with $US 5490 to 7500 to spare , can buy a heart tick from them , to place on their product , providing the product is low in fat overall , and low in saturated fats particularly ...

Kelloggs and their ilk can get AHA heart ticks for breakfast cereals which whilst they're low in fat , are horrendously high in sugar ,,,

.. over the years , the US rate of overweight and obesity has risen to epidemic proportions ... diabetes type 2 is through the roof , and escalating ... all in spite of the AHA ..

In fact , I contend , because of the AHA ... they believe that fat is the problem in our diet ... yet , despite Americans eating less and less meat and fatty products , the obesity rate continues to rise ... coincidently at the same time as sugar consumption has risen .... oh !

Gummy Bear Hero
Thanks for coming back on ths.
I have no argument that the medical fraternity was slow to undestand the negative impact of excess sugar. It is now evident that replacing fat with sugar was not a smart move.
The argument for non saturated fats (mono and poly) over saturated fats has been around for a long time but somehow it got lost.
Also, the use of processing technologies to create trans fats from vegetable oils was not a smart move. That has largely been solved in developed countries.
I think it s unfair to think that the heart tick could be 'bought'. I think the criteria were explicit and companies could for a set fee use the tick for products that met the criteria. Yes, I agree that the criteria were flawed.
Right now, the 'fat is back' story is probably part of the reason that butter is doing so well over the last year or so. It will be interesting to see how that story now develops over the next few years as the public health folk try and fine tune their messages. One of the points I have been tryng to make is that marketers who push for saturated fats may face some headwinds from these medical folk.
As for the Inuit, I sometimes wonder what they did die of. I don't think they lived to a particularly old age, but I have no reliable data on that. I also need to check on the blubber of the sea mammals they lived on to see what I can find as to its fatty acid profile.My guess is that it would have been high in both omega-3 and omega-6. And they also would probably have eaten lots of oily fish. Incidentally, it is likely that we could breed cattle with a different and more desirable fatty acid profile but that research has been buried deep and embargoed.
Keith W

Keith perhaps the question of whether the AHA survive financially without selling the heart healthy logo is needed first. It appears if they didn't have this concept their funding would be surely dimished from current levels.

"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."
Could this not be turned into a plus for NZ milk powder and other products, with a "no added sugar" message? Charge a premium for it. I'm sure consumers would want dairy options with a lower sugar content.

Yes, the option of a lower lactose milk raher than lactose-free is indeed an interesting option.
Both cheese and yoghurt are lower in lactose than milk.
In the case of cheeses much of the lactose stays with the whey ('sweet whey') and hence is removed in the cheese-making process..
In the case of yoghurt, much of the lactose is gobbled up by the yoghurt bacteria.
But then, of couese, the manufacturers go and add sugar back into the yoghurt mix to saisfy the consumer 'sweet tooths'!
Keith W

The opening of this piece is astonishing. "'Here in New Zealand, we live the notion that milk from grass-fed cows is superior to milk from cows fed other rations.." etc.

Here in New Zealand? Really? Any interest in nutritional reports internationally, any five minutes on google, will show that informed discussions and reports of grass-fed dairy benefits are far more prevalent beyond New Zealand than they are here.

And why is this discussion so rare here? At least partly it's because New Zealand's commodity dairy thinking has been satisfied with becoming the world's largest importer of palm kernel extract for feed. Added to this, the same thinking is now hell-bent on expanding the use of dairying barns - further degrading any remaining provenance value.

No, it is not New Zealand that 'lives in the notion' of grass-fed benefits. Far from it. New Zealand has other notions altogether. We, apparently, prefer the nutritional wisdom and price benefits derived from commodity WMP auctions to the wisdom and pricing available internationally.

Added to this, the same thinking is now hell-bent on expanding the use of dairying barns - further degrading any remaining provenance value. I would beg to differ on the first part of your statement workingman. A lot of the drive to barns is coming from the environmental lobby or NZ consumers that mistakenly believe that barns are the only solution to environmental issues. I know a farmer who has a large barn system. He said he can make it work for him, but not everyone could as it requires very different skills to grass farming. He also said that he doesn't know who could afford to buy his farm now either if he or his family should want to sell it as it is no longer your typical NZ dairy farm. I don't know of any farmers who believe it is the right direction for the industry to take, but many feel the pressure they are under from public perception of environmental footprints they believe they will be forced to do it. Fonterra has their 'Trusted Goodness' labeling and it relies on outdoor farming not barns being the norm.
The processors and DairyNZ are well aware of losing the provenance opportunity if the industry converted to barns.

Thank you, Casual Observer. I am more familiar with the argument (as previously asserted, for example, on this site by Professor Woodford) for the expansion of dairying barns being based in the opportunity for year-round dairy supply, than by agitation from either the environmental lobby or New Zealand consumers.

As to the perceived value in New Zealand provenance - not merely in dairy products - the gap between actual local conditions and claimed authenticity is becoming stretched to extremes. And when this elastic snaps, as it will do, New Zealand origin or the New Zealand experience will count for very little indeed.