Are milk and butter from grass-fed cows better for you?

Question

Is there any evidence that grass fed milk and butter are better for you as claimed broadly in this Lacross Tribune article:

New study shows evidence milk from grass-fed cows is healthier

Cows that feed on pasture grasses and dry forage produce milk with more beneficial fatty acids than cows that eat supplemental grains like corn and soybeans, ...

Answer 1

TL;DR: There is not a great deal of difference about organic milk when compared to conventionally produced milk in terms of nutrients once the different factors that influence milk production were compared or adjusted from a 2015 review of close to 200 publications.

Therefore in terms of nutrients in milk, there is nothing distinct about organic milk that makes it unique from conventionally produced milk once the different factors that influence milk production are compared or adjusted for. If animal genetics, health, breed, diet, management, or environment differs, then so will the composition of the milk produced. Source: Organic and Conventional Milk – Comparing Apples to Apples?

Milk and butter quality estimation in terms of its composition is complex since this is affected by various other factors like genetics, raising and lactation stage/season and not only by the feed (pasture/grass fed) of the cows.

The fatty acid levels in milk (even if the ratios are meaningful) do not necessarily have anything to do with organic methods. Milk composition is determined by breeding (genetics), the feed cows consume, how the cow is raised, lactation stage and season. Source: Got (Healthier) Milk? How Activist Scientists And Journalists Bungled Report On Organic Foods

Evidence:

1. Organically produced butter is not found to have a more favourable effect than conventionally produced better on blood cholesterol.

The blood cholesterol (especially low density lipoprotein cholesterol) raising effects of butter fat are well established and mainly attributed to its high saturated fatty acid content, but its trans fatty acid content also contributes. Recent research1 has shown that trans vaccenic acid, the trans isomer naturally found in butterfat, raises blood cholesterol as much as industrially produced trans fatty acids. There is no evidence to show that organically produced butter has a more favourable effect on blood cholesterol. Source: Claims of nutritional superiority of organic milk, meat challenged by scientists

Butter is mostly fat and dairy items highest in fat are noted to be the most concentrated food sources of persistent, bioaccumulative and toxic pollutants. It is also advised that moderating consumption of dairy, particularly high-fat varieties will reduce the intake of these PBTs.

The US EPA estimates that approximately 35% of an adult’s daily intake of dioxins is derived from dairy products. The percentage for children is even higher. Persistent, bioaccumulative and toxic pollutants (PBTs), including dioxins, bioaccumulate through the food chain and ultimately result in low-level contamination in most animal fats. It is important to understand the PBT levels in milk, as milk fat may be one of the highest dietary sources of PBT exposure. Analysis of milk also allows the opportunity to investigate geographic variability, as milk is produced and distributed on a regional scale. Source: GRASSFED VS. ORGANIC BUTTER, AND WHICH ONE WILL KILL YOU FASTER.

Grain-fed cows might be less contaminated by dioxins than grass fed cows.

For terrestrial animals, the intake of vegetation or roughages is considered the most important dioxin exposure factor (Fries 1995a). Feeds derived from seeds contain lower concentrations of dioxins, since the seed is not directly exposed to the air. Ruminants therefore are more vulnerable to dioxin exposure than poultry and swine, as their feed source is predominantly roughage based…Finishing cattle in feedlots is thought to significantly reduce concentrations of dioxins in beef. This is hypothesized to be due to the feeding of a predominantly grain based diet for several months before slaughter (Lorber, et al. 1994). Source: GRASSFED VS. ORGANIC BUTTER, AND WHICH ONE WILL KILL YOU FASTER.

2. Research shows that increasing pasture and forage-based feeds for cows has considerable potential to improve the fatty acid profile of milk and dairy products.

The PLOS one study looked at geographical variation in the difference between organic and conventional milk fatty acid content. Northern California was the only region in which there was no significant difference. The authors speculated that this was because conventional farmers in Norther California usually have cows that roam on the pasture and eat grass and legumes. Thus, it appears the differences between organic and conventional milk are primarily due to what the cows were eating rather than the presence or absence of pesticides, antibiotics, GMOs, or hormones. Source: ORGANIC MILK, GRASS-FED COWS AND OMEGA-3 FATTY ACIDS

3. A meta-analytic review of 196 papers of comparison between organic and conventional milk found that organic milk has a better fatty acid composition than conventional milk.

It is concluded that organic bovine milk has a more desirable fatty acid composition than conventional milk. Meta-analyses also showed that organic milk has significantly higher α-tocopherol and Fe, but lower I and Se concentrations. Redundancy analysis of data from a large cross-European milk quality survey indicates that the higher grazing/conserved forage intakes in organic systems were the main reason for milk composition differences. Source: Higher PUFA and n-3 PUFA, conjugated linoleic acid, α-tocopherol and iron, but lower iodine and selenium concentrations in organic milk: a systematic literature review and meta- and redundancy analyses.

However, experts feel most differences between organic and conventionally farmed products such as milk are very small when they are evaluated as part of the whole human diet.

Prof. Ian Givens, Professor of food chain nutrition at the University of Reading: “Overall, this is very detailed and valuable work, but the differences between organic and conventionally farmed produce should be evaluated as part of the whole human diet. When they are, most differences are very small indeed.” Prof. Margaret Rayman, Professor of Nutritional Medicine at the University of Surrey, said: Using the figures in the paper, we have calculated that while a glass of full-fat organic milk (200 ml) will give 2% more of the daily requirement for long-chain omega-3 PUFAs (6.4% vs. 4.4%), it will provide 14% less of the adult daily iodine requirement (21.2% vs. 35.2%). This may have implications for public health as milk and dairy products are the main source of iodine in the UK diet and we have shown that iodine deficiency in pregnant women is linked to lower IQ in their children. Prof. Tom Sanders, Professor emeritus of Nutrition and Dietetics at King’s College London, said: The review found milk yield was 23% lower for organic milk and there were some minor differences in fatty acid composition which are more related to the production systems rather than whether they were organic or not. Source: expert reaction to differences between organic and conventional milk and meat

Neither milk nor red meat are significant sources of omega-3 fatty acids, and therefore even a 50% relative increase in this small amount likely has few health implications. For example, if you drank a half liter of whole milk every day, consuming grain-fed milk would provide 11% of the recommended daily intake of omega-3, while drinking grass-fed would provide 16%. If you drink 2% or 1% milk the effect is even smaller. Simply put, you are not going to reach your targets of omega-3 by consuming milk. Source: Organic vs Conventional Meat and Milk

Answer 2

The basis of most of the grass-fed claims I've heard are based on the fact that the natural grass-based diet in cows and other ruminants leads to a much higher level of Conjugated Linoleic Acids (CLAs) in the foods derived from them. So, two questions have to be addressed to this specific claim - 1) Is the CLA content (and other anti-oxidants if you want to address broader claims) higher in grass-fed beef? 2) Are there any health benefits to higher CLA intake?

A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef

Grass-based diets have been shown to enhance total conjugated linoleic acid isomers, trans vaccenic acid (a precusor to CLA), and omega-3 Fatty Acids on a g/g fat basis.

This increase in CLAs is also shown in the milk and milk-derived products, as well -

Hannina Campos of the Harvard School of Public Health in Boston and her colleagues found, in a study of 4000 people, that the people with the highest concentrations of CLAs -- the top fifth among all participants -- had a 36 percent lower risk of heart attack compared to those with the lowest concentrations.

"Because pasture grazing leads to higher CLA in milk....." she told Reuters

Reuters - Is milk from grass-fed cows more heart-healthy

NIH: Conjugated linoleic acid in adipose tissue and risk of myocardial infarction - Liesbeth A Smit, Ana Baylin, and Hannia Compos

The claim is that these particular fatty acids help the body to metabolize and reduce fat mass. However, evidence of a pronounced effect was not a given back when I first heard the claims.

There was a 2007 meta study on this, and the conclusion was:

Given at a dose of 3.2 g/d, CLA produces a modest loss in body fat in humans.

So the answer would be "yes, but not magically or dramatically." - within the narrow parameters of body fat and, possibly, other anti-oxidants.

Efficacy of conjugated inoleic acid for reducing fat mass: a meta-analysis in humans