Organic Milk Contains More PUFA?

[marcuswhybrow]

I'd assumed that if a cow was grass-fed and raised organically that the PUFA in it's milk would be lower than that of a grain-fed, inorganic cow. Kate Deering's book How To Heal Your Metabolism also recommends organic, grass-fed cows milk. However, every study I can find on the differences between conventional and grass-fed milk suggests that PUFA is increased with more grass-feeding. This 2011 study in the northeast of England typifies what I'm seeing.

Organic milk, they say, contained "significantly higher concentrations of LA (15%), CLA9 (32%), α-LN (57%), EPA (62%), n-3 (60%), n-6 (12%), and total PUFA (24%)" when compared with conventional milk. They're talking as a proportion of total fat, but I think the total fat amount is equal.

What do they mean by organic? Well, here they equate greater grazing-based diets with greater PUFA profiles: "feeding conserved forage reduces the concentrations of nutritionally desirable PUFA (including CLA and α-LN) in milk fat and increases SFA concentrations (Elgersma et al., 2003). This results in seasonal variation in the fatty acid profile in milk from UK dairy systems, which tend to use grazing-based diets during the summer and ensiled forage diets during the indoor winter period (Lock and Garnsworthy, 2003). Farm surveys report that milk collected during the grazing period has higher concentrations of PUFA, including CLA9 and α-LN, compared with milk produced during the housed period when cows were fed silage-based diets."

I'm going to try and figure this out, perhaps there's a reason I'm missing. Does anyone know why grass-fed, organic milk is considered low PUFA?

 

[MaxVerstappen]

It's probably mostly ideology. Humans aren't usually very logical, we believe what we want to believe, not what is actually the case.

Pufa bad
Natural food good
Therefore, natural food low pufa.

But it doesn't seem to be the case when it comes to dairy as you point out. I wonder if conventional dairy farming has affected the biohydrogenation of the cows, but idk. I also wonder what type of grass the cows prefer. Types of grass can greatly vary in linoleic acid content. I've seen great selectability of types of plants in smaller ruminants like sheep but they also seem to increase the concentration of linoleic acid of their milk when grazing.

Most ruminant animals have significantly lower PUFA in their fat when eating grass compared to those that eat grains, so I presume some people may have generalized from the fat to the composition of the milk.

I'm still drinking grass fed milk tho, it tastes way better.

 

[marcuswhybrow]

A study by the College of Animal Science, Inner Mongolia Agricultural University, China found that for non-pastured cows fed more (cheaper) corn stalks affected fatty acid profiles in the milk as I would have expected:

Against a control diet of "3.7% Chinese wild rye, 26.7% corn silage, and 23.4% alfalfa hay" a corn stalk diet "using corn stalks formulated to provide a similar chemical nutrient level" or "a similar forage level" produced up to 5.14% less saturated fats, and up to 17.50% more unsaturated fats in the cows milk.

The plot thickens...

 

[tankasnowgod]

It's probably mostly ideology. Humans aren't usually very logical, we believe what we want to believe, not what is actually the case.

Pufa bad
Natural food good
Therefore, natural food low pufa.

But it doesn't seem to be the case when it comes to dairy as you point out.

Ha. Did you actually look at the PUFA levels in milk?

Milk, whole, 3.25% milkfat Nutrition Facts & Calories

nutritiondata.self.com

So, if that contained 24% more PUFA, instead of 0.5g, you would have 0.62g. Insane!

This is basically a trivial amount, when looking at the effects that various types of feed can have on the PUFA levels of pigs and chickens. While the "24% more" sounds huge, it's likely that PUFA levels from both cow's milk are still in that 3-4% total PUFA range. Compare that to the different PUFA levels of lard based on the feed of different pigs-

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There is a difference between 6-28% of PUFA in fat content, which is a lot bigger.

 

[PeskyPeater]

6. CONCLUSION The alteration of the FA composition of cow’s milk fat has been a long-term strategy. Even though forages contain relatively low levels of FAs bound in lipids, they are the cheapest and often the major source of unsaturated FAs in ruminant diets. Losses of PUFAs due to their oxidation occur during prolonged wilting prior to ensiling, field drying to hay and also during the silage feed out period. Extensive lipolysis during ensiling enhances the rate of PUFA biohydrogenation in the rumen. Milk from cows fed fresh forage, especially from species-rich grasslands or forage legumes, has thus a considerably higher ratio of UFAs to SFAs and a higher content of nutritionally beneficial transfatty acids (such as CLA and vaccenic acid) than milk from cows fed silage or hay. Milk fat from cows fed grass or legume silages seems to have the nutritionally more propitious composition than fat from cows fed maize silage. However, the former fats are more prone to oxidation. Nevertheless, the milk fat composition is a result of complex effects of numerous feed, animal and environmental factors, among which the type of forage is the only one element.

-source