RESUMEN
Consumer demand for milk and meat from grass-fed cattle is growing, driven mostly by perceived health benefits and concerns about animal welfare. In a U. S.-wide study of 1,163 milk samples collected over 3 years, we quantified the fatty acid profile in milk from cows fed a nearly 100% forage-based diet (grassmilk) and compared it to profiles from a similar nationwide study of milk from cows under conventional and organic management. We also explored how much the observed differences might help reverse the large changes in fatty acid intakes that have occurred in the United States over the last century. Key features of the fatty acid profile of milk fat include its omega-6/omega-3 ratio (lower is desirable), and amounts of total omega-3, conjugated linoleic acid, and long-chain omega-3 polyunsaturated fatty acids. For each, we find that grassmilk is markedly different than both organic and conventional milk. The omega-6/omega-3 ratios were, respectively, 0.95, 2.28, and 5.77 in grassmilk, organic, and conventional milk; total omega-3 levels were 0.049, 0.032, and 0.020 g/100 g milk; total conjugated linoleic acid levels were 0.043, 0.023, and 0.019 g/100 g milk; and eicosapentaenoic acid levels were 0.0036, 0.0033, and 0.0025 g/100 g milk. Because of often high per-capita dairy consumption relative to most other sources of omega-3 fatty acids and conjugated linoleic acid, these differences in grassmilk can help restore a historical balance of fatty acids and potentially reduce the risk of cardiovascular and other metabolic diseases. Although oily fish have superior concentrations of long-chain omega-3 fatty acids, most fish have low levels of α-linolenic acid (the major omega-3), and an omega-6/omega-3 ratio near 7. Moreover, fish is not consumed regularly, or at all, by ~70% of the U. S.
RESUMEN
Over the last century, intakes of omega-6 (ω-6) fatty acids in Western diets have dramatically increased, while omega-3 (ω-3) intakes have fallen. Resulting ω-6/ω-3 intake ratios have risen to nutritionally undesirable levels, generally 10 to 15, compared to a possible optimal ratio near 2.3. We report results of the first large-scale, nationwide study of fatty acids in U.S. organic and conventional milk. 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). 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%). We report mostly moderate regional and seasonal variability in milk fatty acid profiles. Hypothetical diets of adult women were modeled to assess milk fatty-acid-driven differences in overall dietary ω-6/ω-3 ratios. 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 choices together would decrease the ω-6/ω-3 ratio among adult women by â¼80% 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." 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. We conclude that consumers have viable options to reduce average ω-6/ω-3 intake ratios, thereby reducing or eliminating probable risk factors for a wide range of developmental and chronic health problems.