Points to Consider: Organic and Conventional Milk are Nutritionally Indistinguishable

Points to Consider: Organic and Conventional Milk are Nutritionally Indistinguishable

Organic advocates often claim foods produced through organic methods are superior in one way or another to other foods. Time and again research has failed to corroborate these claims Yet the convictions of organic advocates remain undented, reinforced by uncritical reporting and/or misleading papers. A classic in this genre is a recent publication wrongly claiming the nutritional superiority of organic milk. We take a closer look.

Original Paper:  Charles M. Benbrook, Gillian Butler,  Maged A. Latif,  Carlo Leifert,  Donald R. Davis.  2013 (December 9). Organic Production Enhances Milk Nutritional Quality by Shifting Fatty Acid Composition: A United States–Wide, 18-Month Study.   PLoS ONE 8(12): e82429. doi:10.1371/journal.pone.0082429

Published Analysis: Tamar Haspel, A Paper Touting the Benefits of Organic Milk for Heart Health May be Overselling the Drink, Washington Post, January 27, 2014

Primary Claims of the Original Paper: Organic milk is nutritionally superior because of higher levels of ω-3 fatty acids.

Salient Facts: The study reaffirms something long known: that cows fed diets rich in pasture and forage have higher levels of ω-3 fatty acids than those fed primarily grain-based diets.

Rebuttal: 

• The central claim advanced in the title of the paper is false, and designed to mislead.

• The beneficial ω-3 fatty acid MILK composition is a direct result of diet. It is seen in grass fed/pastured cattle regardless of whether they were raised with organic methods, and is only indirectly (and seasonally) correlated with organic production methods.  Organic milk derived from cattle fed on grain (most often indoors), which the organic standard permits, produce milk lacking the favorable fatty acid profile.

• Benbrook et al. argue the benefit is due to dietary ω-6/ω-3 ratios. Experts believe what is important is not this ratio, but rather the absolute quantity of ω-3 fatty acids in the cows diet.

• Other dietary sources of ω-3 fatty acids (e.g., salmon, walnuts, flaxseed, eggs from chickens fed high-omega-3 diets) are far superior to organic milk.

Caveat: Benbrook concedes in interviews, and the study mentions, that the reported result is a diet-effect. But both attempt to conflate it with organic production methods per se, based on the argument that “USDA organic standards require that the cows graze outdoors, on pasture, for as long as the grazing season allows.” The study, and much mainstream media coverage, artlessly downplays this fact in an attempt falsely to cast organic methods favorably as the cause, per se.

Analysis of Specific Claims Made by the Author:

Specific Claim: “Averaged over 12 months, organic milk contained 25% less ω-6 fatty acids and 62% more ω-3 fatty acids than conventional milk, yielding a 2.5-fold higher ω-6/ω-3 ratio in conventional compared to organic milk (5.77 vs. 2.28).”

Critique: Averaging over 12 months obscures the seasonal variation which is correlated with the varying ω-3 levels, allowing the result to be wrongly attributed to organic methods rather than the presence of grass in the diet.

Specific Claim: “All individual ω-3 fatty acid concentrations were higher in organic milk—α-linolenic acid (by 60%), eicosapentaenoic acid (32%), and docosapentaenoic acid (19%)—as was the concentration of conjugated linoleic acid (18%).”

Critique: This is an unsurprising consequence of the presence of grass in the diet of “organic” cattle. This dietary cause is obscured by the statistically inappropriate 12 month averages used.

Specific Claim: “We report mostly moderate regional and seasonal variability in milk fatty acid profiles.”

Critique: If these data were presented, in detail, they would demonstrate the dietary basis for the difference otherwise unrelated to organic production methods.

Specific Claim: “Hypothetical diets of adult women were modeled to assess milk fatty-acid-driven differences in overall dietary ω-6/ω-3 ratios.”

Critique: “Dariush Mozaffarian, an associate professor of medicine and epidemiology at the Harvard School of Public Health, says that the evidence for the ratio’s importance just isn’t there: “One cannot find any series of systematic evidence from human studies that shows that the ‘ratio’ is significantly associated with poor health outcomes when omega-3 levels are high — i.e., when the ‘ratio’ is not simply driven by low omega-3s.”  Washington Post 27 January 2014

Specific Claim: “Diets varied according to three choices: high instead of moderate dairy consumption; organic vs. conventional dairy products; and reduced vs. typical consumption of ω-6 fatty acids…The three [different diet] choices together would decrease the ω-6/ω-3 ratio among adult women by ~80% of the total decrease needed to reach a target ratio of 2.3, with relative impact “switch to low ω-6 foods” > “switch to organic dairy products” ≈ “increase consumption of conventional dairy products.” “

Critique: “Dariush Mozaffarian, an associate professor of medicine and epidemiology at the Harvard School of Public Health, says that the evidence for the ratio’s importance just isn’t there: “One cannot find any series of systematic evidence from human studies that shows that the ‘ratio’ is significantly associated with poor health outcomes when omega-3 levels are high — i.e., when the ‘ratio’ is not simply driven by low omega-3s.” Washington Post 27 January 2014

Specific Claim: “Based on recommended servings of dairy products and seafoods, dairy products supply far more α-linolenic acid than seafoods, about one-third as much eicosapentaenoic acid, and slightly more docosapentaenoic acid, but negligible docosahexaenoic acid.”

Critique: Dietary recommendations favor low fat or skim milk, which have much lower levels of the beneficial fatty acids than reported in the paper. “An eight-ounce serving of salmon has 6.82 grams of omega-3s, or the amount in 88 cups of milk. Compare that milk to walnuts, a rich source of ALA, and you find that a one-ounce serving of shelled walnuts has 2¹ / ₂ grams of ALA, which is as much as 2¹ / ₂ gallons of organic milk… (The U.S. Dietary Guidelines recommend that people stick to fat-free or low-fat milk and other dairy products, but such forms of milk have negligible amounts of omega-3 fats.)  A tablespoon of flaxseed has 2.3 grams of omega-3 fats. A dozen oysters have about a gram, depending on the variety. Two omega-3 eggs (from chickens fed high-omega-3 diets) can have over a gram…, if omega-3s are what you’re after, there are better ways to get it than organic milk.” Washington Post 27 January 2014

Specific Claim: “Milk from cows consuming significant amounts of grass and legume-based forages contains higher concentrations of ω-3 FAs and CLA than milk from cows lacking routine access to pasture and fed substantial quantities of grains, especially corn [15]–[23], [32]. In turn, lactating women consuming such milk have an increased CLA concentration in their breast milk [33].”

Critique: This is true, whether the cattle are raised in accordance with organic standards or not.

Specific Claim: “… increased reliance on fresh herbage in dairy cow diets does elevate the ω-3 content of milk produced [15]–[23], [32].”

Critique: This is true, whether the cattle are raised in accordance with organic standards or not.

Specific Claim: “The U.S. National Organic Program (NOP) requires that lactating cows on certified organic farms receive at least 30% of daily Dry Matter Intake (DMI) from pasture during that portion of the year when pasture grasses and legumes are actively growing, with a minimum of 120 days per year[35]. Pasture and conserved, forage-based feeds account for most of the DMI year-round on a growing portion of organic dairy operations in the U.S. [36].”

Critique: This is true, but irrelevant to the fact that milk from conventional cattle fed a similar diet will have the same oil profiles. The benefit derives from feed consumed, not organic standards per se.