The agricultural revolution dramatically changed our diet. When humans started growing their own food rather than foraging for it, and keeping domestic livestock instead of hunting wild game, grains became a staple food. The human diet wasn’t the only one affected; most of the animals raised for food in the United States now eat grain too. These changes in diet and lifestyle have been followed by changes in health, for people as well as livestock. Surely other factors, from pollution to processed foods, have played prominent roles in the rise of chronic diseases that were virtually nonexistent in early human cultures, but researchers are learning that the animal products we consume are an important piece of the puzzle. The differences between pasture-raised animals and their grain-fed counterparts are more significant than we once thought.
Pasture-raised is a more accurate term than grass-fed when it comes to animals that graze. Plants in the pasture compose a salad bar of species: several kinds of grasses, legumes like clover and lupine, and broad-leaf plants such as plantain and dandelion. These greens contain generous amounts of folic acid, beta-carotene, vitamin E and omega-3 fats. Unlike grain-fed animals, cows and chickens that eat wild greens produce meat, milk and eggs with high levels of these nutrients. Their high-fiber, low-starch diet and a lifestyle of continuous movement make these animals leaner and more similar to the wild game our ancestors ate.
Researchers in the Department of Dairy Science at the University of Wisconsin found that meat from pasture-raised cows also contain high levels of conjugated linoleic acid, a fatty acid that is being studied for its role in the prevention of cancer, atherosclerosis, diabetes and obesity.
In the United States, hundreds of millions of animals that would once have grazed in pastures are now raised on factory farms. These confined animal feeding operations (CAFOs) are able to boost productivity and lower costs by raising large numbers of livestock in one location and feeding them grain. Corn is the grain of choice because it is cheap and it causes animals to gain weight quickly, providing more meat in less time than traditional pasture grazing. Due to their different diet, grain-fed animal products lack the omega-3 fats found in those of pasture-fed animals, but they do contain more total fat, saturated fat and omega-6 fats.
The diet of animals raised in CAFOs also includes by-products of other animals, medications to buffer gas and acid in the rumen that result from an unnatural diet of grains and antibiotics to thwart infections that are common in crowded quarters. Not surprisingly, CAFOs also contribute to air and water pollution, toxic waste production, antibiotic resistance, loss of biodiversity and dependence on the fossil fuels necessary to grow and transport so much corn.
Fatty Acid Composition
Although grain-fed animal products lack the folic acid, beta-carotene and vitamin E of those that eat their natural diet of wild greens, changes in fatty acid composition may be the most important difference. Experts estimate that the dietary ratio of omega-6 to omega-3 fatty acids was close to 1:1 for our ancient ancestors, but the ratio found in the average American diet is much higher (closer to 20:1) as a result of too many omega-6 fats and too few omega-3 fats.
Both omega-6 and omega-3 fats are essential elements in our diet because our bodies need them but cannot make them. However, more is not always better. Too many omega-6 fats, like those found in grain-fed animal products, and too few omega-3 fats, like those found in pasture-fed animal products, can have serious consequences for our health.
Effects on Human Health
Studies have shown that excessive intake of omega-6 fats is associated with autoimmune diseases such as rheumatoid arthritis, Crohn’s disease, ulcerative colitis and lupus erythematosis. These conditions have in common high levels of inflammatory leukotrienes derived from omega-6 fats. Supplementation with omega-3 fats, which lowers the fatty acid ratio, has been shown to decrease disease activity and reduce the need for anti-inflammatory medications.
Studies in Italy found that, in vitro, prostaglandins derived from omega-6 fats have carcinogenic properties and omega-3 fats have the opposite effect. Omega-3 fatty acids antagonize the formation of inflammatory prostaglandins, which may explain their anticancer action. Research has also shown that omega-3 fats play an important role in the prevention of breast and prostate cancers.
Other illnesses that have been linked to too many omega-6 and too few omega-3 fats include cardiovascular disease, type two diabetes mellitus, asthma, hay fever, depressive disorders and dry eye syndrome. Furthermore, researchers at the University of California in San Diego found that a high ratio was associated with decreased bone mineral density in both men and women, regardless of age, body mass index, lifestyle factors and hormone replacement therapy.
The Bottom Line
Clearly, the fats in our diet, and the animals we eat, have a significant impact on our health. Raising the animals we eat on pasture supports not only a healthier planet, but healthier people as well.