Milk… It does your body good?
Dairy. Ah dairy. For most of us, even if it doesn’t agree with our digestive system, we still seem to consume it… a lot. In milk, yogurt, cheese… And when you think about it, dairy really is everywhere. I love dairy, and as a mom with two young kids who can use all the good fats they can get, I’ve been fine with them drinking milk and consuming large quantities of yogurt. I was excited a year ago when our CSA started delivering bottled milk from a nearby small family farm. Not only was I supporting a local small farm, but also I love bottled milk. It’s got a great fresh taste and there’s almost no waste. And this farm is wonderful: They reuse their water 4 times before discarding it, they use the cow patties to manure their fields, they built (and repair) their buildings with recycled materials, and they’re good to their cattle. All in all a win-win situation, right?
Sadly, no. I recently talked with them and found out that their cattle are fed alfalfa hay/corn silage (aka all dried) mixed with grains/by-product feed. What’s the big deal about this you ask? Even with most organic cows milk, there’s a certain amount of feed used for the cattle. The difference is that organic milking cows are required to have 30% of their Daily Matter Intake from pasture during the pasture growing season (minimum of 120 days). Now, 120 days might not seem like a lot, and it’s true. Most pasture farms in California (read that as Northern California) exceed that by a HUGE number, but in other parts of the country where snow covers the ground for a significant chunk of time, or in my neck of the woods where it’s beyond dry for great stretches of time and green pastures are hard to come by, 120 days is pretty good.
So why is pasture raised cattle important for milk? Well, I found an article (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3857247/) looking at the nutritional quality (and specifically the fatty acid (FA) content) of organic vs. conventional milk to find my answer. It was a study that took samples of organic and conventional milk from small farms throughout the country, every month for 18 months.
Here’s the summary of the important findings:
1. The FA content in conventional and organic milk didn’t change throughout the year and the total amount wasn’t significantly different between the two types. However, there was a significant (and in my opinion very important) difference between the makeup of FA in conventional and organic milk. The ratio of omega 6 to omega 3 fatty acids (ω-6/ω-3) was 2.3 for organic and 5.8 for conventional (other studies have this closer to a ratio of 7 or 8 for conventional, but because of the nature of some of the conventional farms in this study, their average ratio was lower – you’ll see why below).
When looking into the importance of FA content in your diet, the ratio really matters. Too much of one family of FAs can interfere with your ability to metabolize the other. An ideal ratio is 1 to 4x more ω-6, but the typical American diet has 11 to 30x more ω-6 (hypothesized as a significant factor in health related disorders, specifically inflammations disorders), which is why you hear so many touting the ω-3 content of certain foods… overall, we’re lacking.
2. I also liked the 18-month longitudinal aspect of the study. Studies looking at beef samples have noted the rapid drop off of some nutrients when grass-fed cattle are ‘grain finished’ before slaughter. So this was a good way to see if this occurs in milk as well during the months when even grass-fed cattle are indoors. It turns out, for milk, the FA content and ratios (omega 6:omega 3) stayed fairly consistent throughout the 18 months. The only thing to take a significant hit was the CLA (conjugated linoleic acid), which is thought to be a potential potent anti-carcinogen. The study shows that during the winter months, the level of CLA in organic milk drops significantly (within a month of transitioning to grain or dried grass). Conversely, it increases rapidly again in the spring. There isn’t a confirmed recommended amount of CLA, and my understanding is that it’s something you need to get from natural sources. Comparing that to conventional milk, organic has significantly more CLA during the pasture months, and just slightly more during the ‘off season’.
3. Finally, it is important to note that this study is really more about the feed of the cattle as opposed to the “organic” label. In fact, one of the authors admitted as much in response to a comment, and he stated that a more appropriate title would have been "Required Pasture Feeding of Organic Production Enhances Milk Nutritional Quality by Shifting Fatty Acid Composition: A United States–Wide, 18-Month Study." The study was partially funded by Organic Valley, so the organic reference in the title was obviously important. Organic Valley (http://www.organicvalley.coop), is a coop of small farms (over 1000 of them) located all over the U.S. I think they’re a great company, but even so, when I see a direct interest has funded a study I want to check it out more. To do that, I started looking at other papers researching the effect of feed on FA content in cattle.
I found two articles (looking at beef, as opposed to milk), coming at the topic from completely different sides, and coming up with the same conclusion. One was a review of many articles and was a great find (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2846864/#!po=78.0000). This article looks at many different nutritive qualities of beef and compares grass fed/finished and grain fed/finished cattle. I’ve put some of the major findings in a table below. You can check them out there.
The other was an article looking at the ‘optimal’ number of days for cattle to be grain fed after a grass diet in order to reach premium grade status without adding excess fat; i.e. to achieve the “best marbling“ of the meat, which turns out to not be a great thing when it comes to nutrition (http://www.journalofanimalscience.org/content/71/8/2079.full.pdf). The comparison group was the grass fed/grass finished cattle, and they too found a better FA ratio in the grass group than the grain groups (they had samples every 28 days of grain finishing, up to 196 days). Both papers identified a 30-day window of grain finishing that doesn’t hugely affect the nutritive quality of the beef. In other words the highest quality in terms of nutrition would be “grass finished” cattle. However, 30 days or less of grain finished is ok. It’s not until after that time when FA ratios really go south, and you start loosing other major nutrients as well. But, unless you know your farmer, there’s no way to know how long the cattle were grain finished, so talk to your stores, your farmers, and everyone else, so you can figure it out!
But I digress. Coming back to milk, it was with a heavy heart that I discontinued receiving bottled milk from our CSA. I understand the farms reasoning: given the amount of water needed to produce green pastures in this part of the world, it is amazingly difficult to pasture raise cattle, especially given the difficult water situation we’re facing right now. And I believe they’re doing their best. But for my family, my first priority is health, so if we’re not getting health benefits from milk, we’ll stop using it. So, we’re back to getting organic milk from the supermarket (also from a family farm, but not bottled and not quite as local), which really isn’t a bad option, but I do miss the bottles.
MUFA: Monounsaturated Fatty Acid
TVA: Trans Vaccenic Acid (A precursor to CLA & Omega 3FA)
SFA: Saturated Fatty Acid
IMF: Intramuscular Fat
CLA: Conjugated Linoleic Acid (a MUFA)
PUFA: Polyunsaturated Fatty Acid
ω-6: Omega 6 FA
ω-3: Omega 3 FA