From Beta-carotene to Omega-3s: The ABCs of Health and Nutrition in Grassfed Meats
By Wylie Harris
Field Notes (the newsletter of the Kerr Center for Sustainable Agriculture)
Spring 2005
When talk turns to community food security, foods from grassfed livestock come up early and often. Many consumers search out grassfed products to help keep their local ecologies and economies healthy. But most are interested for the sake of their own personal health as well, and they face a bewildering variety of conflicting claims about the health effects of meat, dairy, and eggs from grassfed livestock.
Much of the confusion stems from differences in the desired standard of proof. For some people, it’s enough to know that foods from grassfed livestock contain higher levels of substances associated in some general way with increased health.
Others want to see such beneficial health effects scientifically demonstrated in animals whose biology is similar to that of people – which is why laboratory rats can find jobs. Still others withhold belief until medical research documents those effects in human beings.
The state of scientific knowledge about the health benefits of grassfed food products is more advanced for some claims than others. For instance, there is now widespread agreement that the meat from just about any ruminant will be leaner if the animal was raised on grass. Grassfed beef's lower fat content alone is enough to make devoted customers of many health-conscious eaters (a 4 oz. typical serving: 7-10 grams saturated fat, compared to 14-16 grams for corn-fed). At the same time, though, a growing aversion to fat has pushed others away from meat of any kind.
Ironically, a growing body of scientific evidence suggests that grass-fed meat not only has less fat overall; it also has more of the kinds of fat that have, or may have, beneficial health effects.
Omega-3s
The most solidly documented of those effects are those associated with omega-3s. “Omega-3” is shorthand for “omega- 3 fatty acid,” meaning that the molecule is unsaturated, with a double bond at the third carbon atom from the omega end.
Both omega-3 and omega-6 fatty acids occur naturally in human diets, with the omega-6 form predominating.
The relative amount of omega-3 fatty acids in beef is higher in pasture finished animals than in those fed grain only. A relatively high intake of omega-3 relative to omega-6 fatty acids increases HDL (the so-called “good” cholesterol) and reduces blood cholesterol levels, as well as reducing the incidence of cardiovascular disorders such as heart arrhythmia and atherosclerosis (hardening of the arteries).
Increasing the amount of omega-3 relative to omega-6 fatty acids in rats’ diets has also been shown to inhibit the formation of breast cancers.
Omega-3s are also important building blocks of brain tissue, and a higher dietary intake of them has been linked to decreased risk for a variety of mental illnesses ranging from depression to Alzheimer’s.
Conjugated Linoleic Acid (CLA)
Linoleic acid, another kind of unsaturated fatty acid, occurs naturally in beef and dairy products. It’s one of two essential fatty acids – those necessary for human metabolism, but not produced by the human body itself.
During digestion, bacteria in the rumen rearrange the two double bonds in the linoleic acid molecule, putting them on adjacent carbon atoms to form what’s known as “conjugated linoleic acid,” or CLA.
The bacteria responsible for CLA formation thrive in relatively less acidic conditions. But a diet of grain makes the rumen more acidic, reducing the abundance of these bacteria, and thus the amount of CLAs produced in the animal’s digestive process.
Pasture-finished cattle can have 2 to 6 times more CLAs in their meat, and five times as much in their milk than those fed silage and/or grain. CLAs are resistant to processing and cooking, as well as the human digestive process, so that the more CLA-rich foods you eat, the more CLAs you’ll have in your body.
Once in your body, linoleic acid and CLAs have strikingly different effects for two molecules whose chemical structures are so similar. Linoleic acid has been associated with increased risks of obesity, diabetes, and tumor growth.
CLAs, on the other hand, have been shown to decrease all of these risks in laboratory animals. Moreover, CLAs also lower the likelihood of atherosclerosis (hardening of the arteries), thereby lessening the risk of heart disease. These effects are thought to be due to CLAs’ anti-inflammatory and anti-oxidant actions.
CLAs also inhibited the growth of human cancer cells in laboratory cultures in one study, while another showed that women eating diets of grass-fed meat and dairy foods had a 60% lower risk of breast cancer than those eating the grain-fed equivalents.
Among natural anti-cancer agents, CLAs are unusual for a couple of reasons: they come from animal-derived foods rather than plant-derived, and the amount eaten in a normal dietary intake of those foods constitutes an effective dose.
Vitamins
Healthier fats aren’t the only nutritional cards that grassfed foods can play. They also have elevated levels of other health-promoting substances – sort of like a vitamin capsule in a steak.
Beef from pasture-finished cattle has been found to contain three times more vitamin E than the meat from cattle fed a conventional grain ration.
The characteristic yellow color of fat from grassfed meat comes from the fact that it contains more beta-carotene than meat from grain-fed animals.
Beta-carotene, a precursor of Vitamin A, is also what gives carrots their orange color (and their reputation for preserving eyesight).
The feedlot system grew out of pressure to produce large amounts of meat as quickly as possible. Ironically, that system’s success at generating huge quantities of beef, dairy, and eggs has robbed those products of some essential nutrients.
For example, one researcher estimates that over the past 50 years, the switch to feedlot based livestock production, combined with declining per capita meat consumption, has decreased the amount of CLA in North American diets by two-thirds.
As the evidence increasingly shows, certain essential nutrients– and the health benefits that accompany them – can be restored to livestock-based food products simply by putting the livestock back where they started: on grass.
Additional websites with information on nutritional aspects of grassfed livestock
www.usu.edu/trdhiman/homepage.html