Triglycerides
95% of the fats that we consume and that are stored in our bodies are triglycerides, which consist of three fatty acids combined with a glycerol. Excess dietary fats are stored in the body within adipocytes (fat cells) and represent about 60% of our bodies resting energy requirements. Fat also serves as a transporter; carrying (and breaking down) micronutrients such as vitamins A, D, E and K.
Phospholipids
Phospholipids are essentially identical to triglycerides except for one main difference: phosphate. Phospholipids have one phosphate compound substituted in place of one its three fatty acids. The properties of said phosphate allows fats to work in a liquid environment without sticking together. This brings us to why phospholipids are so important; they serve as emulsifiers in the body. Emulsifiers allow us to digest fat and help carry carried in the bloodstream.
There are two main emulsifiers in our body:
- Bile which is a watery substance produced by the liver (and stored in the gallbladder)
Phospholipids are also found naturally in foods. Lecithin in that regard, refers to a combination of phospholipids that come from plants. So just to be clear---in the body, lecithin refers to a specific type of phospholipid known as phosphatidylcholine. When lecithin is referred to in foods or supplements, it is actually talking about a general group of phospholipids that come from plants.
In food service applications, lecithin allows ingredients to mix that normally would be unable to (ex: oil and water). It is added to salad dressings and coffee creamers as well as chewing gum to increase shelf life. Egg yolk, soybeans, and peanuts are sources of naturally occurring lecithin.
Sterols
A sterol is a type of steroid; not the kind produced in a lab but instead one produced by the body. The most noteworthy of course is cholesterol. Lets take a look at the many benefits of cholesterol along with risks associated with elevated levels. Cholesterol is used as a precursor for many different substances including:
- Vitamin D
- Sex Hormones (estrogens and androgens)
- Bile
- Other sterol hormones such as: progesterone, glucocorticoids and mineralcorticoids
Fortunately for us, our body produces enough cholesterol that we really have no need to ensure that our diets contain it.
How cholesterol is transported in the body
Lipids in general are typically not water soluble, meaning they do not dissolve or mix well in watery substances. In order to travel throughout the bloodstream and digestive tract, structures known as lipoproteins are utilized. Lipoproteins differ amongst themselves in regards to size, density, and composition and thus contribute to different health effects.
| Lipoprotein | Composition | Function |
| Chlyomicron | Mostly triglyceride | Carries dietary fat from the small intestine to cells |
| Very Low Density Lipoproteins (VLDL) | Apprx. 2/3 triglycerides | Transports lipids made by the liver to cells |
| Low Density Lipoproteins (LDL) | More than 1/2 cholesterol | Transports cholesterol made by the liver to cells |
| Intermediate Density Lipoproteins (IDL) | Apprx. 40% triglycerides | Acquires cholesterol from high density lipoproteins, becomes converted to LDL in the liver. |
| High Density Lipoproteins (HDL) | Mostly protein | Helps remove cholesterol from cells and in turn, the body. |
As you can see from the table, low density lipoproteins (LDL) play an important role in providing cells with the cholesterol they need to in turn, produce hormones and other important compounds. The risk associated with having high levels of LDL in the body is the development of atherosclerosis. Atherosclerosis refers to a hardening of the arteries, where cholesterol (among other substances) builds up in artery walls and in turn, impedes blood flow.
Research on Lipid Profile
Several studies have examined the relationship between blood lipid (and triglyceride) levels and cardiovascular disease (CVD). Among these include the Helsinki Heart Study and the Framingham Heart Study. There are scoring systems in place to allow physicians to identify those at higher risk of CVD and determine whether (and to what extent) they can benefit from lipid lowering drugs. The Framingham scoring system is the most widely used, though is has its drawbacks; namely due to the majority of risk scores being developed from data from a predominately middle aged white population.
| Predicted risk of CHD events at 7.5 years according to original Framingham functions, recalibrated Framingham functions and Health ABC functions. Click for larger image The table above shows predictive and actual data from the original Framingham risk scoring system, a readjusted Framingham scoring system, and from the Health, Aging, and Body Composition Study. |
Ratings of Blood Lipoprotein Levels
| Lipoprotein | Rating |
| Total Cholesterol | |
| < 200 | Desirable |
| 200-239 | Borderline High |
| 240 or Greater | High |
| LDL-Cholesterol | |
| <100 | Optimal |
| 100-129 | Near Optimal |
| 130-159 | Borderline high |
| 160-189 | High |
| 190 or Greater | Very High |
| HDL-Cholesterol | |
| <40 | Low |
| 60 or Greater | High |
| Triglycerides | |
| <100 | Optimal |
| 100-149 | Near Optimal |
| 150-199 | Borderline High |
| 200-499 | High |
| 500 or Greater | Very High |
According to National Cholesterol Education Program (NCEP) guidelines, everyone 20 years or older should get a blood lipoprotein profile done every 5 years. The NCEP also created tables (including the one above) to help determine one's risk of developing heart disease. Heart disease is the leading cause of death in the U.S. and while genetics play a role, the type and amount of fat we consume does as well.
References
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