Good Fat, Bad Fat
THE USDA Food Guide Pyramid places all fats at the top of the "eat sparingly" category together with sweets.
The Healthy Eating Pyramid of Dr. Walter Willett of the Harvard School of Public Health places plant oils (which contain monounsaturated and polyunsaturated fat) at the bottom with the advice "eat at most meals." Nuts and fish (which also contain mono and poly fat) are in the third and fourth levels, and the tip of the pyramid is reserved for red meat and butter, which contain saturated fat.
Trans-fat does not appear anywhere on the pyramid because Willett believes it has absolutely no place in a healthy diet.
Although the Healthy Eating Pyramid is a step in the right direction because it is more specific than the old pyramid, putting dietary fat into good and bad categories is not as straightforward a process as it is with carbohydrates.
One of the Harvard studies used by Willett in designing his pyramid involved 100,000 men and women.
The study found that the risk of getting heart disease is "strongly influenced by the type of fat eaten." The results indicated that trans-fat increased heart-disease risk the most, saturated fat increased it slightly, and monounsaturated and polyunsaturated fat decreased the risk.
There doesn't seem to be much of an argument about trans-fat. Majority of scientists believe that it is bad for you. But when it comes to other fats, it is simplistic to say that all saturated fats are bad for you or that all unsaturated fats are good for you.
The fat we eat is composed of building blocks called fatty acids, which are divided into three main categories: saturated, monounsaturated and polyunsaturated. Three fatty acid chains are attached to a glycerol molecule, and that's why fats are technically called "triglycerides."
The word "saturation" refers to how many hydrogen atoms are attached to the fat molecule. A saturated fat is completely saturated with hydrogen while unsaturated fats are not.
The prefixes "mono" and "poly" refer to double bonds that the hydrogen atoms are attached to. A monounsaturated fat contains one double bond while a polyunsaturated fat contains several double bonds.
Trans-fat is created when a polyunsaturated fat is hydrogenated to make it have the characteristics of a saturated fat (firmer consistency and less prone to becoming rancid).
All fats are mixtures of the three kinds of fatty acids, although one type usually predominates. So even though olive oil is called a monounsaturated fat, it also contains saturated and polyunsaturated fatty acids.
The three main types of fatty acids can further be subdivided into individual fatty acids that each have a specific effect on the body.
Saturated fat from animal sources (beef, pork, lamb and whole-milk dairy products) has been implicated in increasing heart-disease risk because of its effect on cholesterol levels.
The liver uses saturated fat to make cholesterol so when it is eaten in excess, it raises LDL or bad cholesterol significantly (though it also raises HDL or good cholesterol slightly).
The four most common types of saturated fat in the human diet are myristic, palmitic, stearic and lauric acids.
Myristic and palmitic acids are the ones that cause the greatest increases in bad cholesterol. A 14-year Harvard study led by Dr. Frank Hu and published last year in the American Journal of Clinical Nutrition discovered that myristic raised cholesterol more than the other saturated fatty acids did.
Myristic is found in coffee creamer, palm oil, hard cheeses and full-fat dairy products. Earlier studies in the 1960s also found that myristic had the greatest effect on cholesterol, followed closely by palmitic acid.
It has been known since the 1940s that stearic acid has a neutral effect on cholesterol. Some recent studies have shown that it may even have a lowering effect. Stearic acid is found in substantial quantities in cocoa and beef.
It is the unique effect of stearic acid on cholesterol that anti-carb advocate Dr. Robert Atkins uses as one of the arguments to defend his theory that it is carbohydrates, and not the saturated fat from steaks and pork chops, that are to blame for heart disease.
There is solid evidence that a high intake of refined carbohydrates raises insulin levels, which in turn raises triglyceride levels, lowers good cholesterol and increases blood clotting. The liver also turns excess carbohydrates into saturated fat, particularly palmitic acid.
Red meat contains a mixture of both good (stearic) and bad (palmitic) saturated fat. Atkins says this means that the fat in red meat has no effect on cholesterol because the lowering effect of stearic acid cancels out the raising effect of palmitic. His other argument is that red meat (beef in particular) is only 38 percent saturated fat. It also contains 42.1 percent monounsaturated fat and 3.4 percent polyunsaturated fat. Pork and lamb have a similar composition.
Other scientists like Hu counter that it is very difficult to separate the different kinds of saturated fat because they come bundled together (when you eat red meat, you can't separate stearic from palmitic acid).
Hu also found that stearic acid was associated with an increased risk of coronary heart disease for other still unknown reasons besides raising cholesterol levels. This is an important finding because cholesterol is not the only factor involved in heart disease. Another question that still needs to be answered by research is the exact role of red meat in the development of colon cancer.
Dr. Gerard Reaven, insulin-resistance expert, does not recommend eating large quantities of saturated fat because he says that although saturated fat keeps insulin levels down (fat has no effect on insulin), it raises bad cholesterol. In his opinion, you would be solving one problem (high insulin levels) but creating another (high LDL cholesterol levels).
Personally, I would like future research to explain the Masai tribe phenomenon. The Masai are African cattle herdsmen who subsist mainly on a diet of milk, blood and beef. In spite of this strange diet, they have no heart disease, obesity, diabetes, osteoporosis or cancer. They are also known for being exceptionally tall and having great aerobic and muscular endurance.
My bet is that it is the absence of processed food in their diet and the many hours they spend daily walking with their cattle that protect them from any ill-effects of all the saturated fat that they eat.
I'm sure that meat lovers everywhere would love to be told that beef, pork and lamb are health foods. But this isn't going to happen any time soon because many more studies are needed to prove this theory. Till further notice, it is better to be safe than sorry. Just follow doctors' advice to eat red meat, butter and whole-milk dairy products sparingly.
Coconut oil was previously grouped with animal fat as unhealthy for the heart. However, scientists now know that the saturated fat in coconut oil is primarily lauric acid, the same kind of fat in mother's milk. Lauric acid slightly increases cholesterol but it decreases triglyceride levels and it contains anti-viral, anti-bacterial and anti-protozoal properties.
Coconut oil contains 45 percent lauric acid and only 17 percent myristic and 8 percent palmitic acid, which are the bad kinds of saturated fat. Palm kernel oil has a similar composition as coconut oil, and thus is qualified to join the "good fat" club. But palm oil contains 44 percent palmitic and is still considered a bad fat.
Before you buy coconut oil, make sure it is not hydrogenated. Additionally, most commercial coconut oils are refined, bleached and deodorized, so look for "virgin cold pressed" coconut oil.
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