Scientific Evidences
Dating back as far as 1977, scientific studies considered that: carbohydrate and fat content of the diet causes increased HDL cholesterol. The mechanism for this is the production of a protein called Apo A-I, which is a major component in the cell wall of the HDL molecule. In addition, saturated fat was shown to increase the production of Apo A-I more than polyunsaturated or monounsaturated fat.
Adding to this the evidence, the human body uses dietary carbohydrates for energy before using fat. This explains why a diet higher in carbohydrates causes an increase in LDL cholesterol. If adequate calories are present in the carbohydrate content of a meal, then the fat in the same meal is transported for storage. The molecules that ultimately transport the bulk of this fat are the LDL molecules. The fat itself is in the form of triglycerides, but a fairly constant amount of cholesterol is included in each LDL.
It is therefore no surprise that a shift to a low carbohydrate diet that contains more saturated fat than recommended can lower LDL cholesterol and raise HDL cholesterol at the same time. Sometimes the increase in HDL is dramatic - in these instances, the total cholesterol may very well increase above normal levels - but it is very desirable high cholesterol to have.
It should be noted that there are persons who have various genetic conditions in which too much LDL cholesterol is manufactured, or is not cleared appropriately from the bloodstream. These people may not obtain same benefits in cholesterol measurements from a low carb diet. They may require medications to lower cholesterol despite optimal dietary practices. This does not mean that the low carb diet does not work for them - it is still the healthiest way for them to eat, as long as the LDL cholesterol level is controlled.
