Lipids are naturally occurring fatty or oily substances found in plants and animals, and cholesterol is a lipid. In small amounts lipids and cholesterol assist the body’s function. Cholesterol is key to hormone production, specifically the production of estrogen, testosterone and cortisol. It also assists in cell repair, helps the body produce vitamin D, and supports digestion by helping to form bile. Another type of lipid, triglyceride, is vital to the formation of cell membranes and is also an energy source.
The body can store lipids in adipose or fat tissue as an energy, but these lipids are not the body’s first choice for energy. Carbohydrates are much easier for the body to convert into energy. In large amounts cholesterol and other lipids can be destructive to the coronary system, because they can build up on the walls of blood vessels by forming plaque. Plaque is made out of cholesterol, calcium and tissue, and it can cause blockages in the arteries and make them less flexible and prone to rupture. The medical term for this build-up of plaque is atherosclerosis.
Lipids and cholesterol need to be coated with protein in order to travel in the bloodstream. The combination of lipids and proteins that float like rafts in the blood are known as lipoproteins. The lipid levels in the blood are measured based on two lipoproteins and the level of triglycerides; hyperlipidemia is the medical term for an elevation of harmful lipids in the blood. Low density lipoprotein (LD) is known as bad cholesterol, while high-density lipoprotein (HDL) is called good cholesterol.
High levels of HDL seem to protect against heart disease, while low levels of HDL point to an increased risk of heart disease. The incidence of heart disease in the United States has increased markedly since the 1950s. This increase has been attributed to lower activity levels and diet.
Health experts often recommend a low-fat diet as a preventative measure to lower the level of blood lipids and cholesterol. Ironically, some people with longer life spans, the Swiss and the Japanese for instance, often consume large amounts of fat. The French experience half the rate of heart attacks as those living in the US. They also consume great quantities of eggs, cheese, butter and cream.
Genetics and exercise play a great role in the level of lipids and cholesterol in the blood. A defect in chromosome 19 can result in a genetic predisposition to high cholesterol, but this condition is relatively rare. Studies have shown aerobic exercise can increase levels of good cholesterol and decrease levels of bad cholesterol.