Lipids are fats, one of the three types of macronutrients. Chemically, fats are composed of a long chain of carbon atoms, with hydrogen atoms attached along the length of the chain. Lipids are necessary for cellular processes, for the formation of microstructures - for example, cell walls -- and for brain and nervous system function. Essential fatty acids (EFAs), such as omega-3 and omega-6, are categories of lipids that must be consumed because the body cannot manufacture them.
Fatty Acids
A common saturated fatty acid is stearate, or steric acid, and is found in animal fat and most nuts. Unsaturated and polyunsaturated fatty acids are the so-called "good fats." Linoleate is a dietary example of a polyunsaturated EFA. According to researchers at the University of Maryland, linoleate, and omega-6 fatty acid, is abundant in foods common to the American diet: vegetable oils, poultry, eggs, avocado, most nuts, whole grain breads, as well as in evening primrose, borage, and black current seed oils, dietary supplements available at most grocery stores. However, supplementation of omega-6 fatty acids is likely unnecessary. Researchers at Oregon State University have found most Americans err in abundance of omega-6, well over omega-3, fatty acid consumption. Circulation, the journal of the American Heart Association, recommends that omega-3 fatty acids be consumed in excess of omega-6 fatty acids at a ratio of at least 2 to 1. Omega-3 fatty acids, sometimes called alphalinoleatic acids, are abundant in fish such as salmon and mackerel, walnuts, and in flax oil.
Glycerols
Triglycerides are one of the infamous fats found in the bloodstream, due to the association of high triglycerides with cardiovascular disease. According to the American Heart Association, normal blood triglycerides, when measured after 12 hours of fasting, are 150 or fewer mg/dl. Border-line high is 151-199 mg/dl; high is 200-499 mg/dl; and very high is 500 mg/dl and above. Eating a diet low in saturated fat and higher in mono and polyunsaturated fat is protective against heart disease. Foods high in mono and polyunsaturated fat are those that contain omega-3 and omega-6 EFAs. Foods high in saturated fat are red meats, and those with partially hydrogenated oils, an additive in many processed foods.
Cholesterol
The other infamous blood lipid is cholesterol. High-density lipoprotein (HDL) is often called "good cholesterol," and low-density lipoprotein (LDL) is often called "bad cholesterol." HDL is associated with cholesterol metabolism, for cellular processes, whereas LDL is associated with fat storage as adipose tissue, the subcutaneous fat you may see on your thighs and hips. The American Heart Association recommends fasting blood-levels of HDL above 50 mg/dl for women and above 40 mg/dl for men. LDL below 100 mg/dl is optimal, and LDL above 160 mg/dl is considered high. Consuming polyunsaturated fats, such as those contained in aforementioned varieties of fish and nuts may reduce LDL, and increase HDL cholesterol in your blood, consequently reducing your risk for heart disease.
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