Organic Milk, Grass-fed Cows and Omega-3 Fatty Acids

The skeptical cardiologist has to admit that when he drinks milk or puts it in his coffee or cooks with it he almost exclusively drinks “organic”, non-homogenized milk obtained from dairy cows which are grass-fed and spend most of their lives grazing in a pasture.. In previous blogs I’ve laid out the evidence that supports that dairy products in general do not increase the risk of heart and vascular disease and, in fact, may lower that risk.

Full fat dairy has gotten a bad rap because it contains high levels of saturated fat. However, just as total fats were inappropriately labeled as bad , it is now clear that all saturated fats are not bad for the heart.

Although I recommend full fat dairy products to my patients I haven’t emphasized the organic or grass-fed aspect because I didn’t think there was enough good evidence that this is healthier than other kinds of milk and it is more expensive. There is evidence from small studies that cows consuming a more natural diet of grass and legumes from a pasture have higher levels of omega-3 fatty acids in their milk than those confined indoors and eating corn.

I keep my eyes (and ears) open for papers in this area.. One such paper appeared in the online peer-reviewed publication PLOS recently. I was driving to the hospital, listening to NPR when I first heard about it. Melissa Block was interviewing NPR correspondent Allison Aubrey . Her take, in a more subdued written form here is similar to many news outlets.

Allison summarized the findings as follows

The researchers compared organic and conventional milk head-to-head. They analyzed about 400 samples over an 18-month period, to account for seasonal differences. And the samples were taken from, you know, all different parts of the country. And they found that organic milk had about 62 percent more of the heart healthy omega-3s, compared to conventional milk.

When asked for an explanation she said

It really comes down to watch what the cows were eating. Organic milk is produced from cows that spend a lot more time out on pasture, and they’re munching on grasses and legumes. And these greens are rich in omega-3 fatty acids. So as a result, the milk they produce has more omega-3 fatty acids.

Wait a minute! I said , you’re confusing “organic” and “grass-fed” or “pasture raised ” they are two totally different things although they can overlap. I totally get the concept of a healthier diet for the cows increasing omega-3s in their milk but I haven’t seen anything that would suggest reducing pesticide or antibiotic usage does that. The radio did not respond. Also, I asked, is it possible to use the term omega-3 without prefacing it with “heart healthy”?

Once you start demanding to know more about the conditions of the cows that made the milk you drink things can become complicated. A cow can be grass-fed but not pasture raised, meaning that it stayed indoors and was fed hay. A cow can be outside “grazing ” but be given corn to eat. Prior to looking at the PLOS one article, I did not assume organic implied anything about how the cows were fed or grazed.

It turns out that in 2010 the USDA announced guidelines that mandated, among other things, for a dairy to be called “organic”, its dairy cows had to spend at least 120 days grazing on pasture.Thus, there is some correlation between organic and pasture raised/grass-fed but not a complete one.

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.

Allison Aubrey went on to say

But you know, I should say that there’s a trade-off here because in order to get all these extra omega-3s, you’ve got to drink whole milk. And you know, if you opt for the low-fat dairy – say, 1 percent fat -you’ve skimmed off most of these omega-3s. So the question is, you know, can you afford the extra calories in fat. If you choose the whole milk, you might need to trim a few calories from elsewhere in your diet.

To which I responded “Yes, by all means drink whole milk, there is no evidence that it adds to obesity. You will naturally want less calories down the line and you will get the benefit of good saturated fats.”

I'll continue to pay extra to drink milk from Trader's Point Creamery that I pick up at Whole Foods. I like their milk because I've visited their farm in Indiana and talked to their (plastic surgeon) owner and I like what he says on the website about their milk (ignoring the part about a “better immune system”.

We let our cows graze on 140 acres of pesticide free pasture, which results in milk with more healthy fats like Omega 3 and CLA (conjugated linoleic acid). Grassfed milk also contains more nutrients like beta carotene and vitamins A and E than milk produced using standard feeds. To all of us this means more nourishment and a better immune system for our bodies.

I’m going to end with the summary from the PLOS one article (DMI=dry matter intake, LA=linolenic acid, an omega-6 fatty acid) which emphasizes the importance of grazing and forage-based feeds not the organic aspects of milk.

We conclude that increasing reliance on pasture and forage-based feeds on dairy farms has considerable potential to improve the FA profile of milk and dairy products. Although both conventional and organic dairies can benefit from grazing and forage-based feeds, it is far more common—and indeed mandatory on certified organic farms in the U.S.—for pasture and forage-based feeds to account for a significant share of a cow’s daily DMI. Moreover, improvements in the nutritional quality of milk and dairy products should improve long-term health status and outcomes, especially for pregnant women, infants, children, and those with elevated CVD risk. The expected benefits are greatest for those who simultaneously avoid foods with relatively high levels of LA, increase intakes of fat-containing dairy products, and switch to predominantly organic dairy products.

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