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A lot has happened to the human diet since then.
About 10,000 years ago, humans developed agriculture and discovered it was possible — even desirable — to settle in, tend the land, develop the mind, create art and populate the Earth. In living this new, good life, our diet shifted from that of the widely diverse hunter-gatherer's to one consisting of more fats, dairy products, grain-derived carbohydrates and sugars from cultivated fruits.
Now, fast-forward to the 1950s, when the U.S. food industry was beginning to take off, already capitalizing on cheap fossil fuels and cheap raw materials from the farm that were about to become a lot cheaper thanks to astronomical government subsidies. Rather than producing meat, eggs and dairy products from animals raised on pasture and supplemented with grain, the United States shifted to livestock production systems that removed animals from pasture and fed them much higher quantities of grain. That swap caused some big changes in the composition of the fats from those animals.
In 1956, nutrition scientist Ancel Keys drew the spotlight to the lipid hypothesis, which held that a high-fat diet — particularly one high in saturated fat — contributed to high cholesterol, which in turn led to heart disease in the form of plaque buildup in the arteries. Following suit, the food industry, medical community and media all jumped on the low-fat bandwagon, vilifying saturated fats (mostly animal fats) and promoting vegetable fats and low-fat diets. Interestingly, at the time, plenty of money stood to be made in processing cheap vegetable oils into their solid, hydrogenated forms to then be used in making cheap, processed foods — far more money than could be made in marketing traditional animal fats.
Cut to the present, and the idea that corn, soy and other vegetable oils are preferred for optimal health continues to be dominant, yet the United States still has high rates of cardiovascular disease. We are overweight and unhealthy despite five decades of low-fat and no-fat health advice and faddism. How could the medical community, our Food and Drug Administration and so many others be so wrong about dietary fats? To untangle this mess — which involves shunning the widely held nutritional belief condemning saturated fats — let's go back to basics.
The Fundamentals of Fat
Fat is essential for the human body to function. Fat supplies calories and essential fatty acids, and it helps the body absorb vitamins A, D, E and K. The oversimplified notion that reducing or eliminating one's fat intake will solve any health or weight problems is plain wrong. Our brains actually thrive on a high-fat diet, and for adults, 20 to 35 percent of daily calories should come from fat. Not consuming enough fat — less than that 20 percent — creates its own set of problems, such as heart damage and immune system impairment.
Fats come from a host of plant and animal sources. At room temperature, they can be solid (such as butter, lard and shortening) or liquid (such as canola, olive and peanut oils). Most dietary fats include three fatty acid chains. Fatty acids are either saturated or unsaturated, and all of the fats we eat are combinations of saturated and unsaturated fatty acids. Nutritionally speaking, there are good fats, not-so-good fats and bad fats.
Saturated Fat: It Does a Body Good
Fats are "saturated" if all of the potential bonding sites on the fatty acid molecules are occupied (saturated) by hydrogen atoms. Saturated fats are likely solid or semisolid at room temperature. They're found in animal products — all types of meat, eggs, butter, cheese, whole milk and cream — and in some tropical oils, such as coconut, palm and palm kernel.
Saturated fats continue to be in the news because of the good evidence that eating too much saturated fat can make your arteries less elastic, especially in the two or three hours following a meal. Stiff arteries contribute to a heart attack or stroke, and large amounts of some types of saturated fats can contribute to heart disease. (Those double cheeseburgers with bacon aren't a good idea!) Moderate amounts of saturated fats, however — especially the "stearic" saturated fats found in lean meat and chocolate — can make a positive contribution to your health, increasing your HDL (good) cholesterol without increasing your LDL (bad) cholesterol.
As Mother Earth News reported in 2002, the fats in grass-fed beef and dairy products, pastured pork and free-range poultry are actually good for you (see Pasture Perfect). Several studies have confirmed that pastured products contain more beneficial omega-3 fatty acids than products from grain-fed animals do (keep reading for more on omega-3s), and dairy products and meat from grazing animals are richer in a cancer-fighting fat known as conjugated linoleic acid (CLA), which the animals make from healthy fats in the grasses they consume (see "CLA: Powerhouse on the 'Good Fat' Scene" near the end of this article for more about CLA). As an added bonus, grass-fed meat and dairy products are also richer in vitamin E, beta carotene and other key antioxidants. The eggs from pastured hens are much more nutritious, too, with 25 percent less saturated fat, one-third less cholesterol and two times the omega-3 fatty acids of industrial eggs.
Such research has shown that much of the conventional wisdom about fat is wrong, yet Americans continue to be told they should eat less fat, and whole industries of food manufacturing are still perpetuating a national fat phobia.
Unsaturated Fat: The Good and the Bad
Unsaturated fats come mostly from vegetable sources and are more likely than saturated fats to be liquid at room temperature. Although canola, olive and other unsaturated fats have long received good press, these fats do have some drawbacks.
In natural conditions, the chemical structure of most unsaturated fats is in what scientists call the cis configuration. But when food manufacturers hydrogenate cheap vegetable oils — to convert them into solid fats (such as shortening) for use in processed foods — natural cis fats morph into unnatural trans fats. After 50 years of being advised to use (hydrogenated, trans fat-laden) margarine instead of butter, we've now learned the trans fats in margarine are actually bad for us.
Recent research has indicated that man-made hydrogenated saturated fats are far more harmful to us than the natural saturated fats such as butter and lard. Substituting manufactured margarine for butter and lard was a horrible idea nutritionally (but a smart idea for corporate profitability), and the overall shift to hydrogenated vegetable oils from traditional, unadulterated animal fats hasn't reduced heart and artery disease in the United States.
Almighty Omegas
Possibly the most famous class of beneficial cis fats is the omega-3 series. Omega-3s include the essential fatty acids alpha-linolenic acid (ALA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The "essential" means our bodies need them, yet aren't able to make them.
Top food sources of omega-3 fatty acids include walnuts, flaxseed, canola and fatty fish. The fat in meat and dairy products from grass-fed animals is also a good source of omega-3s, as are eggs from pasture-raised hens.
As a group, omega-3s have heart-health qualities (EPA and DHA especially), they reduce heart attack risk, and they've been linked to reduced blood pressure and reduced fibrin concentrations (fibrin contributes to blood clotting and arterial scarring from plaque). Some studies have suggested that omega-3 fatty acids can decrease symptoms of depression and lower the risk of certain types of cancer, and they've also been linked to healthy brain, eye and nervous system development.
Like omega-3s, omega-6 fatty acids are found in meat, eggs, olive oil and vegetable oils. But while omega-6s are essential to normal cell receptor activity, these fatty acids should be eaten in moderation, otherwise they can neutralize the health benefits of omega-3s. So, even though omega-3 and omega-6 fatty acids both include essential components, most people need to consume them in a ratio of 4:1 (four omega-6s for every omega-3) or lower for best health. Prehistoric diets probably had a ratio of about 1:1. The typical modern American diet likely contains a ratio of 10:1 or higher, with the imbalance coming from consumption of too much grain and seed oil and meat from grain-fed animals. So even if you eat mostly unsaturated fats from only vegetable sources, the unnatural ratio of omega fats is actually increasing your risk of heart and artery disease, and possibly cancer.
Consider the Source
Now that you know some types of fat are good for your health and others should be eliminated or consumed in moderation, you can make healthier choices.
Eating meat, eggs and dairy products from grass-fed animals will give you healthy fats in better proportions. Choosing monounsaturated oils is best, as is opting for oils that are labeled "cold-pressed." (Less expensive processes use hexane extraction and/or generate heat, which degrades the oil's quality and nutritional value.)
Aim to eat four times as many omega-6s as omega-3s. Serve grass-fed beef (omega-6 to omega-3 ratio of about 3:1) and sprinkle walnuts on your salad at dinner (4:1) for a well-balanced (and flavorful!) meal. Other good sources of omega-3s are pastured pork, lamb and poultry, milk and butter from pastured dairy animals, flaxseed, salmon, shrimp and tuna. Dark greens such as broccoli, collards and kale provide omega-3s as well.
Don't eat too much saturated fat, and avoid all man-made trans fats (hydrogenated oil) — stick with fats that are in their most natural form.
What Should I Eat?
- Your body needs saturated and unsaturated fats.
- Saturated fats from grass-fed animals are good for you; those from industrially raised animals, less so. Don't eat too much saturated fat.
- Avoid trans fats (hydrogenated oil) in processed foods.
- Top food choices for a healthy fats diet include walnuts, flaxseed, salmon, shrimp, tuna, grass-fed meat, eggs and dairy products, olive and peanut oils, and dark green vegetables.
An important family of unsaturated fats is the group of compounds known collectively as conjugated linoleic acids, or CLA. Dietary sources of CLA are mostly limited to ruminant (cattle, sheep, goat) meat, butter and other dairy products. Grass-finished meat and dairy products have significantly higher levels of CLA than products from industrial systems do.
Emerging evidence suggests CLA is a powerful anti-carcinogenic agent, and certain kinds significantly reduce risk of heart and artery disease and arterial inflammation. This class of fats has also been linked to healthy body weight (although the findings are somewhat conflicting). Studies have found that nursing mothers who consumed organic meat and dairy products passed twice as much CLA to their infants in breast milk as nursing mothers who didn't eat organic meat and dairy products.
About the author
Hank Will is the Editor-in-Chief of Grit magazine.His fascination with the color of fats earned him a Ph.D. in biochemistry from the University of Chicago, along with a taste for carotene-rich butter and cheese.
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