The mysteries of grass-fed milk

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 developed-country 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.

About Keith Woodford

Keith Woodford is an independent consultant, based in New Zealand, who works internationally on agri-food systems and rural development projects. He holds honorary positions as Professor of Agri-Food Systems at Lincoln University, New Zealand, and as Senior Research Fellow at the Contemporary China Research Centre at Victoria University, Wellington.
This entry was posted in Agribusiness, Dairy, Fonterra. Bookmark the permalink.

25 Responses to The mysteries of grass-fed milk

  1. Honora Renwick says:

    Indeed these matters are complex. Regarding the trans fats found in grassfed dairy (trans-rumenic and trans-vaccenic acid via biohydrogenation of polyunsaturated fats) …
    “While there have been very few highly controlled clinical trials studying the effects of CLA and VA on heart disease and atherosclerosis, the few that exist also support the conclusion that these natural trans fats may actually reduce the risk of heart disease. In animal studies, CLA has demonstrated potent anti-atherogenic effects, preventing fatty streak and plaque formation in the arteries of rodents by changing macrophage lipid metabolism. (6, 7) While more research in humans is needed, it seems that grass-fed dairy and meat products, high in both CLA and vitamin K2, are some of the best foods you can eat if you’re looking to prevent a heart attack.”

    The links to the 23 studies cited in this topic can be found in this post:

    • Keith Woodford says:

      Thanks Honora,
      I am somewhat cautious in regard to Chris Kesser’s writings, and I think here he may have added 2 plus 2 to get 5. I think the jury is still out as to the differences in effects between natural trans fats from those produced during food processing. Certainly the dairy industry was very energetic and successful in getting natural trans fats exlcuded from other trans fats in American regulations. And of course the whole topic of CLA is complex given that it is omega-6. I think we have more to learn here.
      Keith W

      • victorcozzetto says:

        Love your book Keith, but this article broke my heart. Honora is absolutely right, as are some of the other commenters. To state it simply – cows evolved to eat grass, not grain, and no other diet will ever produce healthier milk and meat. We will never top what nature has evolved to produce over millions of years.

        I am not a fan of Chris Kresser either, but you can look to the work of Sally Fallon, Chris Masterjohn, the Weston A. Price Foundation, and many other scientists for the truth about grass-fed milk. You certainly will not find the truth coming from the AHA, as big business has too much influence on such policies and ‘findings.’ Saturated fat from naturally raised animals is essential for optimal human health. Raw grass-fed A2 milk is far superior in nutrition to any milk product that is not grass-fed, pasteurized, homogenized, or otherwise adulterated.

        I hope that you, and NZ in general, will not be swayed by American policies, and instead notice that raw grass-fed milk from small farms is on the rise. It is so sad to see that NZ has such difficulties in getting raw grass-fed milk.

  2. Honora Renwick says:

    Oops, make that 23 citations, not 23 studies!

  3. Ken Rabas says:

    In the United States we have 2 fluid milk brands that are 100% grassfed and certified organic. Organic Valley brand is labeled GRASSMILK. Maple Hill Organic has been marketing its 100% grassfed organic Yogurt for several years and is now also marketing 100% grassfed organic fluid milk. Both may be available nation wide.Both appear to be growing faster than the rest of the organic dairy industry, also the 100% grassfed beef market has made significant in roads, I believe it up to over 5% of all beef sales.

    • Keith Woodford says:

      Thanks Ken.
      Do you have any information as to the proportion of the Organic Valley milk which is ‘GRASSMILK” as compared to their standard pasture-grazed organic milk, where animals are also fed grain?
      I did a quick online search for store locations in San Francisco and Los Angeles and my impression was – open to correction – that it was sold in specialty stores rather than general supermarkets. Is it sold outside California?
      And do you have any prices informaton for GRASSMILK versus ‘ordinary organic’ versus standard milk?
      Keith W

  4. Tom Walker says:

    Good title to your article Keith,”the mysteries of grass fed milk”..reminds me of the ”mysterious” grass fed premium that Fonterra used to justify bringing in PKE ”guidelines” in their first email they sent to talk of fats in this correspondence!

    Speaking of which in my discussions with OCD they say they have no problems processing milk with a high PKE component and as long as it is a licenced animal feed will not be telling their suppliers what they can or cannot feed their cows.

    • Keith Woodford says:

      Thanks Tom
      In relation to OCD that is helpful to know.
      There is a fair chance that if NZ wanted to produe milk with less saturated fat then we could breed accordingly. There is definitely research highly relevant to fat issues (but not specific to PKE) that is buried deep within the bowels of Fonterra and its predecessor Dairy Research Institute from manay eyars ago. It remains embargoed. The difficulty is that commercial institutions have difficulty in facing up to isssues which take a long time to breed out. But chickens do eventually return home to roost.
      Keith W

  5. David Thomas says:

    Another interesting blog, this time on grass-fed milk. However your blog supported the view that saturated fats in dairy products are a health risk for cardiovascular disease. You cited the recent statement by the American Heart Association that that ‘lowering intake of saturated fat and replacing it with unsaturated fats, especially polyunsaturated fats, will lower the incidence of CVD [coronary vascular disease]” Although you noted that “It is where the scientific evidence lies,” many health researchers now contest the assumption that that the saturated fats in dairy foods increase health risks and some have provided evidence that dairy foods such as whole-fat cheese and unsweetened yogurt reduce health risks. Three points in relation to the health risks or benefits whole-fat dairy foods.
    1. The American Heart Association statement presented a biased review that left out recent systematic reviews and meta-analyses based on prospective, cohort studies. In their Table they showed the saturated fat content for butter (63%). But later they refer to dairy foods which contain much less saturated fat. The substitution analyses they reported on page e14 (substituting polyunsaturated fats for saturated fats) are hypothetical and not verified by any actual substitution studies. Two recent large meta-analyses that compared high levels of dairy food consumption with little or no dairy food consumption reported no differences in mortality rates (1). These meta-analyses were based on studies that combined whole-fat and low-fat dairy foods and did not distinguish between regular and sugar-added dairy foods so the meta-analyses do not provide information about the relative health benefits or risks for specific types of dairy foods.
    2. Some prominent cardiovascular researchers such as Dariush Mozaffarian contest the assumption that whole-fat dairy foods are a health risk. He commented that;
    ‘It is astounding, and unforgiveable, that nearly all our dietary recommendations about dairy foods (including the conventional emphasis on low-fat dairy) are derived from theories about isolated nutrient contents (e.g. calcium, vitamin D, and saturated fat) rather than direct empiric evidence on health effects. …. the current evidence provides little support to promote low-fat dairy, and suggests that whole-fat products, in particular yogurt and cheese, may be beneficial.’ (2)
    3. Emerging evidence supports the view that whole-fat dairy foods, particularly fermented dairy foods such as cheese and yogurt are health-protective. Nearly all these studies are prospective cohort studies which are mostly ignored by groups such as the American Heart Association because they are not RCTs (randomised control trials). I have summarised some of these studies in a blog earlier this year at

    The reality is that there are (and will be) very few RCTs on food groups such as whole-fat dairy foods because they are too difficult and expensive to conduct over 10-15 years. Long-term prospective studies are essential to determine the health impacts of specific food groups and currently comprise the best available evidence on the health impacts of dairy food consumption.

    (1). Guo, J., Astrup, A., et al (2017). Milk and dairy consumption and risk of cardiovascular diseases and all-cause mortality: dose–response meta-analysis of prospective cohort studies. European Journal of Epidemiology, 32(4), 269-287. doi:10.1007/s10654-017-0243-1
    Schwingshackl, L., Schwedhelm, C., et al (2017). Food groups and risk of all-cause mortality: a systematic review and meta-analysis of prospective studies. American Journal of Clinical Nutrition, Online 26 April. doi:10.3945/ajcn.117.153148
    (2) Mozaffarian, D. (2016). Natural trans fat, dairy fat, partially hydrogenated oils, and cardiometabolic health: the Ludwigshafen Risk and Cardiovascular Health Study.
    European Heart Journal, 37(13), 1079-1081. doi:10.1093/eurheartj/ehv595

    • Keith Woodford says:

      Thanks David
      This is appreciated.
      This is a debate that needs to be had.
      I am a bit time-pressed now, but will aim to respond later.
      Keith W

    • Keith Woodford says:

      I would be interested in your thoughts on this paper
      As you will see, it is not about fat per se, but it is about milk.
      I agree that there is a body of evidence that says we need to consider the health effects of yoghurt and perhaps cheese as being different to other dairy products.
      Keith W

  6. Thanks for another good piece of writing. You may already know, but at the recent meetings Fonterra had with farmers they talked a bit about the FEI and PKE. The main points were:
    – PKE use has correlated with butter “fracturing” like dry cheese which doesn’t meet customer specs. They are aware that communication is poor.
    – Much research is being done as there are still more questions than answers about how much can be fed.
    – The FEI baseline is grass.
    – 3kg of fodder beet has the same effect on the FEI as `1kg of PKE.
    – Grains tested so far appear not to cause FEI grades.

    • And there is currently wide variation between different farms FEI scores even if they are feeding the same rations, and some that are feeding no PKE are grading…

      Still more questions than answers!

    • Keith Woodford says:

      Thanks James
      This is new information for me.
      I need to learn more about the biochemistry of ‘fracturing’
      Keith W

  7. Sam Lind says:

    Isn’t NZ out of the ‘Grass Fed’ game anyway since we feed maize silage (or it would at least seem that way based on standards used internationally)?

    • Keith Woodford says:

      Sam, Yes, this is another issue needing clarification. Maize does not meet my understanding of a grass. And of course neither is fodder beet. Do you have anything available on international standards re use of maize?

      • Sam Lind says:

        I believe the old USDA guidelines (which the USDA has since recalled and doesnt manage any more) have Maize as an exclusion. This private scheme in the UK has it in their standard as a no-no also

      • All members of the family Poaceae can rightfully be called grasses, but maize silage and green- feed maize are very different in composition. The same applies to the other cereal grasses.

      • Paul says:

        I thought maize & cereal silage fitted ‘grassfed’ in USDA as it is not wholegrains.
        Find this all interesting as you support A2 & Synlait valued add (including Munchkin), but you are now doing trips overseas with shed building company…any bias?

    • These days most farmers buy in their maize silage as part of their dairy support, preferring to keep the milking platform in pasture as far as possible.
      Tougher regulations in regard to nitrogen losses could see an end to this practice.

  8. Tim says:

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

    I live in Seattle area in the US. Here are some milks you can get here and what I have think I have seen for a gallon of them at supermarkets I often visit. I would say premiums for grass-fed milk are alive and well!

    General milks:
    Lucerne/darigold milk $2
    A2 milk $3.95
    Smith brothers milk I can’t remember, I think it was $2-$4

    Special milks:
    Organic milk $4-$5
    ‘Pure Eire’ Grass-fed milk can’t remember, I think it was $3.50-$5 depending on where
    Organic Valley Grassmilk $4.95+
    Other local grass-fed milk around $5, plus you need a $2 deposit for the glass bottles

  9. Tim says:

    PS Sugars are bad for you right? Maybe the *real* health benefit of grass-fed milk is not the PFA, just that it has less lactose!! And that unfortunately by adding lactose to whole milk powder, we could be throwing the baby out with the bathwater. Anyone looked into that?

  10. Pingback: Rural round-up | Homepaddock

  11. That was a really helpful entry. Thanks!

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