Oils, called "Fats" in scientific and nutritional literature, are both essential to health and dangerous to health, depending on quantity, type, and which body of "experts" you chose to listen to. Outlined here are "currently accepted medical opinion" and some strenuous exceptions taken by medical researchers of differing stripes.
The material herein is gathered from sometimes controversial literature openly available to the public and is not intended as medical advice in any way.
Welcome to the wonderful wacky world of nutritional science, where all sides on any issue justifiably point to the others as "junk science" supported by faulty studies and distorted by commercial interests, and where today's "medical knowledge" is tomorrow's snake oil. All sides in any heated health controversy are likely right in part and wrong in part, but since this is America, and big money and politics are involved, the truth is very difficult to know.
We will start out with the "science" that is pretty much agreed upon by all sides in the oils vs. health battles, then move into the controversy.Fats & the Body
Fats are found in all the cells of the body as energy storage, as a structural component of cell walls, and are the transport for a number of essential vitamins (known as "fat soluble vitamins") through the body. Fats also play a very important part in regulating the level and types of cholesterol in the bloodstream, which in turn affect various hormones and general health.
A diet deficient in fat will result in itchy, flaky skin and other problems, but a diet that deficient takes real determination to achieve since fats are found not only in animal products but in grains, nuts, beans and just about anything else considered edible.
A diet with too much fat, and especially too much of the wrong kind of fat, presents a high risk of heart attack, stroke, obesity, diabetes and certain types of cancer. It may also make you appear ugly and undesirable to many people, possibly resulting in social, employment and emotional problems. On the flip side, "supermodel thin" is pretty ugly and unhealthy too.Fats & Cholesterol
Cholesterol is essential for health and key to production of certain hormones, including estrogen and testosterone, and in production of bile essential for digestion. Cholesterol is a major component of your brain and essential for neurotransmitter function (O22).
The two major varieties of Cholesterol are low density lipoprotein - LDL ("bad" cholesterol), and high density lipoprotein - HDL ("good" cholesterol). LDL tends to build up on the inside of arteries as "plaque", resulting in heart attacks and stroke.
"Dietary cholesterol" is cholesterol consumed in food, and it only comes from animal foods. Most people are not particularly sensitive to the amount of dietary cholesterol they consume because nearly all their "blood cholesterol" is manufactured by the liver, but some people are sensitive to dietary cholesterol so it is included in nutritional labeling. Brain cholesterol is made entirely in the brain.
Cholesterol level is important because excessive blood cholesterol, particularly LDL, can deposit on the inside of arteries as "plaque", possibly resulting in heart attack and/or stroke (blood flow blockage to the brain).
The amount and type of fats consumed are thought by many medical researchers to affect both the level and type of cholesterol in the bloodstream. Since heart, arteries and brain are often considered important parts of the body, it follows that what type and quantity of fats you consume is important. Unfortunately, this is where agreement among experts breaks down completely. Types of Fats
Fats are a mixture of "fatty acids", which fall into several categories, each of which has an impact on cholesterol and general health. The nature of, and healthfulness of a particular fat or oil depends on the proportion among the fatty acids it is composed of. Our Oil Composition Chart provides an overview of the composition of many common oils.
"Accepted Medical Knowledge" has held these things to be true:
This viewpoint is promoted by the American Heart Association and has the full financial backing of the giant grain and seed oil traders (Cargill Inc., ADM Inc. etc.) and the food processing industry. All of them are happy to finance as much "research" and political pressure as needed to back the health claims in their advertising.
One side effect of the industry campaign against saturated fats is a spectacular increase in trans fats consumed in the American diet - fats that all sides now agree are very bad for you. No safe limits have been established but, the US FDA (United States Food and Drug Administration) says to consume "as little as possible".
This doctrine, sometimes called the "Lipid Hypothesis", despite its popularity and support even from the U.S. Congress (as if Congress critters knew anything about nutrition), has some spectacular weaknesses which threaten to expose it all as hocum and snake oil.
Opponents of the accepted viewpoint have suggested a more persuasive case can be made that these diseases start to appear when a population adopts large quantities of refined carbohydrates such as sugar and white flour (also darlings of the grain traders and food processors) and large amounts of vegetable oils and shortenings.
In the United States, Crisco, the first partially hydrogenated vegetable shortening, was invented in 1911 and became popular, promoted as a "healthier alternative" to lard, during the 1920s - about the same time heart disease and cancer started being significant killers. This is not to say Crisco was the cause or that there weren't other factors, but it certainly wasn't saturated fats causing the problem.
One group particularly vocal against the "accepted knowledge" has been the tropical oils partisans who maintain coconut oil is the most healthy cooking oil you can use even though it's about 92% saturated fat. Palm oil is lower in saturated fat and higher in monounsaturated fats with a composition profile very similar to lard and tallow.
The American Heart Association is dead set against tropical oils claiming their saturated fat will clog your arteries, but once again, ethnic populations making heavy and daily use of these oils show no arterial clogging, in fact quite the opposite. Further, the only formal research condemning coconut oil is invalid because it used hydrogenated oils (O12).Trans Fats Bad! - No Longer Controversial
Trans fats are a major component of "partially hydrogenated vegetable oil", an industrial product the aim of which is to convert liquid oils into fats that are solid at room temperature and resistant to rancidity just as saturated fats are. The American Heart Association spent decades promoting trans fats as a "safer" alternative to the natural fats we evolved with.
All sides of the fats controversy now agree that trans fats are bad for you (O4). Just how bad depends on how much of your income depends on them. Apologists claim they are no more artery clogging than saturated fats. Others say they are far worse, pointing out that not only do they clog arteries faster, but also contribute strongly to other diseases, particularly diabetes and brain damage. A recent study found they contribute significantly to dementia and Alzheimer's disease (O23).
Nonetheless, trans fats are not going away quickly because they are a darling of the fast food industry in particular and the food processing industry in general, for good (to them) reasons.
Health advocates brought intense pressure against the fast food industry for its heavy use of beef fat, particularly for deep frying. Since beef fat is high in saturated fats the "accepted knowledge" of the time implicated it in killing tens of thousands of Americans every year.
Responding to this pressure, the fast food industry decided to move to the vegetable oils promoted by the do-gooders, but quickly found them unusable. Beef fat is very durable at high temperatures and resistant to rancidity. A fry tank of beef fat will work fine for nearly a month. Vegetable oils, especially those high in polyunsaturated fats, degrade quickly at high temperatures, becoming rancid, laden with toxins, and don't taste real good. You'd have to change the oil on practically a daily basis - totally unaffordable in the fast food industry.
The fast food solution was to use partially hydrogenated vegetable oils, in other words, evil trans fats. These are so resistant to heat breakdown and rancidity a tank of fry oil can be run for as much as 40 days (with topping up) before it must be discarded.
Food processors favor trans fats for similar reasons. They provide baked goods and other products with an attractive texture, and they resist rancidity resulting in a long shelf life for the products - and you can claim "no saturated fats" on the label.
Unfortunately for both industries, the FDA (Food and Drug Administration) issued new rules requiring trans fats be included in labeling and in nutritional information sheets by 1 Jan 2006. This caused a scramble to find alternatives - some of which may be even worse than trans fats. In many cases they're turning to Interesterafied Oils. These unnatural industrial products seem to have all the problems of trans fats, plus raising blood sugar levels, but products using them can advertise "zero trans fats" (O19, O21).
Crisco, the original trans fat producer, has come up with a vegetable shortening formula using fully hydrogenated oils (hard as a hockey puck) whipped up with enough unhydrogenated oils to achieve an acceptable texture while maintaining a level of trans fats they are allowed to call "zero".
Of course fully hydrogenated oils are actually saturated fats, the very thing vegetable shortening was supposed to get you away from - and they are artificial saturated fats at that. Do not expect a big health campaign against these saturated fats because they are made from the vegetable oils the giant grain traders promote in their "heart healthy" advertising. There will be no industry sponsored "studies" to rile up the do-gooders.Polyunsaturated Oils and Cancer
Now here we have a raging controversy pitting the full wealth of the grain traders and food processors against vocal opponents.
All sides seem to be in agreement that monounsaturated fats are pretty safe, promote arterial health and may reduce risk of cancer, but monounsaturates dominate only in olive oil, canola oil and nut oils. Polyunsaturates dominate in all other vegetable oils. Canola oil is suspected of other evils (O17) and nut oils are expensive and have a low smoke point, so that pretty much leaves olive oil.
Polyunsaturated oils are far more vulnerable to rancidity, and the products of rancidity are often free radical carcinogens (promoting cancer). Opponents of the vegetable oil industry say polyunsaturates are so vulnerable to rancidity that the heat of cooking causes them to go rancid almost immediately. The vegetable oil industry, while admitting vulnerability to rancidity, says it doesn't happen in normal cooking usage, but these oils have been found completely unsuitable for restaurant deep fry use.
While studies tend to show polyunsaturated fats promote (vs. cause) cancer growth (O6. O7), much more study needs to be done. Most of the studies so far have been small and on rats, but enough evidence is accumulating to take this point seriously.
One thing that is showing up fairly strongly though is that one class of polyunsaturated oils, called Omega-3 fatty acids appears to suppress cancer. Omega-3 oils are found mainly in oily fish, crustaceans, flaxseed oil and canola oil (O8) but the vegetable forms are different from the fish and crustacean forms and their effectiveness is in question - again more study is needed. Further, some research suggests Omega-3 may be damaging to the heart if not accompanied by sufficient saturated fats (O20).
Unfortunately there are other problems with Omega-3 fats. They go rancid very quickly when heated. While raw canola oil may be high in Omega-3 fats (whether effective or not), the refining process uses high temperatures, and after de-odorizing (to remove products of rancidity) there may be almost no Omega-3 left in the product as bottled.Links
Note that a number of links originally listed here had to be removed. They no longer worked due to rapid changes in medical opinion.
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