Abstract
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. population.
Highlights
Half of Americans suffer from one or more diet-driven chronic conditions including cardiovascular disease (CVD), overweight and obesity, and diabetes (DHHS, 2015; Massiera et al, 2010; FDA, 2015; ARS, 2010)
We modeled hypothetical diet scenarios based on those in Benbrook et al (2013) to test the potential effects of switching whole-fat dairy products made from conventional milk, to organic milk, and, in this study, to grassmilk
We find that nearly 100% grass- and legume-based feeding of lactating dairy cows typically yields milk fat with ratios of linoleic acid (LA)/ALA and ω-6/ω-3 close to 1, compared to 5.8 for milk from cows on conventionally managed farms, and 2.3 for typical organic dairy farms
Summary
Half of Americans suffer from one or more diet-driven chronic conditions including cardiovascular disease (CVD), overweight and obesity, and diabetes (DHHS, 2015; Massiera et al, 2010; FDA, 2015; ARS, 2010). Seven of the 10 leading causes of death in the United States were diet-related in 2013 (IHME, 2016a), and none are curable via medical intervention alone, despite health care spending in the United States that is the highest per capita in the world (IHME, 2016b) These sober facts are among the reasons why there is growing interest in the United States among scientists and consumers in altering diets to prevent or slow the progression of metabolic, cardiovascular, and other chronic diseases. Potential diet alterations include reducing intakes of omega-6 (ω- 6) fatty acids (FAs) and increasing intakes of omega-3 (ω-3) FAs, decreasing dietary ω-6/ω-3 ratios These ratios have become historically high in Western diets during the last century, reaching about 15, compared to estimated evolutionary ratios near 1 (Hibbeln, Nieminen, Blasbalg, Riggs, & Lands, 2006; Simopoulos, 2006). Modern grain feeding of farm animals has contributed to these ω-6 increases and ω-3 decreases in Western diets
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