milk-cows-thumbsup-thumbsdownAccording to an important new study, organic milk sold in England delivers significantly higher levels of healthy fatty acids than does conventional milk. The study, funded by the European Union and published in the peer-reviewed Journal of Dairy Science, can be accessed for free here.  

The researchers compared fat composition and protein content of 10 organic and 12 conventional brands found on supermarket shelves in northeast England. Researchers found that the organic milk had only slightly higher overall fat content, but much higher levels of what it calls “beneficial fatty acids.”

The differences are significant in public-health terms. In America and Great Britain alike, people on average don’t get enough essential fatty acids. For example, one of the fatty acids in question, conjugated linoleic acid (CLA), has been shown to lower heart disease and cancer risks, the researchers say. The meat and milk of ruminant animals are “almost our exclusive source of dietary CLA,” the researchers support — and organic milk has significantly more of it. By switching to organic milk, the U.K. public could increase its average CLA intake by as much as 40 percent, the authors reckon.

On the other hand, levels of other beneficial fatty acids like α-linolenic acid and eicosapentaenoic acid (EPA) were found to be on average 60 percent higher in organic milk than conventional — enough to “make a useful contribution in a balanced diet,” but not enough to offset the deficiency our diets have on average in these substances. These fatty acids are found most plentifully in oily fish like sardines, which few people eat much of these days.

Grist thanks its sponsors. Become one.

Before we ramp up the old debate over whether organic foods are more nutritious, it’s worth noting that what this study really seems to be detecting is differences in bovine feeding regimes. The results suggest that the more grass and other fresh forage cows get, the healthier the fat profile in the resulting milk. In addition to organic trumping conventional in the essential fatty acid department, the study found that milk harvested in the grass-rich summer months beat winter-season milk, when cows feed on hay. (The differences between organic and conventional milk were still there in the winter months, but at smaller levels.)

One way to sum up the study is this: by switching away from grass as the chief feed for lactating cows, we’ve stripped vital nutrients out of our diets.

Grist thanks its sponsors. Become one.

Their glass is half full, ours is half empty

What can we U.S. consumers draw from this study? First, we have to look at differences in U.S. and U.K. dairying styles, both conventional and organic. Here’s how the study characterizes dairy farming in northeast England, the source of its milk samples:

Previous farm surveys in northeast England showed that, in this region, most dairy production systems (under both conventional and organic management) allow cows to graze during the summer, with fresh forage making a significant contribution to their diets, although lower levels of supplementation and hence higher estimated intakes of fresh forage were recorded on farms under organic management.

In the region covered by the study, all dairy cows got fresh grass in summer; the nutritional differences in the resulting milk stem, evidently, from the fact that organic cows get more grass. Here in the United States, large-scale industrial dairies have moved almost exclusively to year-round confinement systems based on corn. So, according to the logic of the study, conventionally raised U.S. milk would have even lower levels of desirable fats than conventional U.K. milk.

And what of organic? Until last February, U.S. organic standards were vague on the grass question: they stipulated that organic cows have “access to pasture.” But as the organic-milk market has boomed, large-scale dairies have arisen that mimic conventional operations but rely on organic corn as feed. How did they get around the “access to pasture” stipulation? They tended to locate in dry places where not much exists, according to the organic watchdog Cornucopia Institute. The U.K. study’s findings suggest that “organic” milk from such operations wouldn’t be nutritionally much different than conventional milk.

The future of pasture

Last February, though, the USDA significantly tightened organic-dairy standards. Organic dairy cows must now “graze pasture during the grazing season, which must be at least 120 days per year” and “obtain a minimum of 30 percent dry matter intake from grazing pasture during the grazing season.” So now, during the growing season at least, any “organic” milk should at least be getting some grass — and thus deliver a healthier fat profile. (I’ve asked Cornucopia’s Mark Kastel for his take on how the big dairies are handling the new rules. Stay tuned for an update.)

It would be extremely interesting to see the U.K. researchers’ methodology applied to our own organic and conventional milk brands. Until that happens, the study’s message seems clear: Learn as much about the growing practices of the dairies that produce your milk — and buy grass-fed when you can.