Low Carb Diet - LDL & HDL Cholesterol
Heart disease risk is determined by measuring how much cholesterol is being transported to body cells for use in cell walls and hormone production, as opposed to how much cholesterol is being removed from body cells for disposal.
In simplified terms, total cholesterol as measured in the laboratory on a blood sample consists of LDL or "bad" cholesterol plus HDL or "good" cholesterol. (There are other sub fractions, which enter into the equation, but this is the basic terminology).
Criticisms
Low carb diet cause increased cholesterol? If it means total cholesterol, the answer is negative. The reason: there is no way to know the measures of HDL and LDL for fractions of cholesterol.
High fat intakes with low carb diets increases heart disease? This is typically based on the studies showing exactly that effect in high carbohydrate diets (50% or more of total calories obtained from carbohydrate). It is a scientific error to ignore the difference in carbohydrate content of the diet.
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.
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.