Sunday, February 17, 2013

Fat Thoughts on Cholesterol . . .

As a medical bariatrician and family practitioner specializing in low-carbohydrate diets, I often see the panic stricken look on people's faces when they look at their cholesterol profiles just after starting a carbohydrate restriction life-style.  
First, it is very important to understand that if you check your cholesterol within the first 4-6 weeks of dietary changes, there will be a transient rise in the cholesterol profile as your adipose tissues (fat cells) release your new fuel source into the blood stream and the mitochondria in the one trillion cells in your body convert from the use of glucose to the use of ketones (derived from triglycerides) as the primary fuel source.  This is not a problem as the body is designed to handle this increase in triglyceride and cholesterol. I explain to patient's that we are essentially making the figurative change from "un-leaded fuel to diesel fuel."
Second, the standard cholesterol profile does not give you a true picture of what is occurring at a cellular level.  The standard cholesterol panel checks Total cholesterol (all the forms of cholesterol), HDL (the good stuff), LDL-C (the bad stuff) and triglycerides.  It is important to recognize that the "-C" stands for a calculation usually completed by the lab. 
Total cholesterol, HDL and triglycerides are usually measured and LDL-C is measured using the Friedewald equation [LDL = total cholesterol – HDL – (triglycerides/5)].
Third, it is also important to realize that HDL and LDL are actually transport molecules (the buses for the triglycerides (the passengers). HDL is taking triglycerides to the fat cells and LDL is taking triglycerides from the fat cells to the muscles and other organs for use as fuel. 
When you being a low carbohydrate diet, your blood glucose availability as the primary fuel source drops and triglycerides become the primary source.  It takes your body 4-6 weeks to increase the number of mitochondria necessary to effectively use triglycerides as the primary fuel.  (This is why many athletes and patients who are active will feel slightly sluggish during their exercise for the first few weeks). 
Once your body accommodation to the new fuel, there will be a notable drop in LDL-C and a rise in the HDL.
But this still doesn't answer the question and relieve the panic seen above. A deep sigh and the look of relief occurs when I explain that LDL-C doesn't give us the real story. 
To make it simple and understandable, LDL is made up of three main sub-types  big fluffy ones, medium sized ones, and small dense ones. It's the small dense ones that contain lipoprotien A [Lp(a)] found in increased vascular risk. Recent studies reveal that heart disease and atherosclerosis is caused by the small dense LDL molecules. 
A low carbohydrate diet causes the small dense cholesterol to drop and there is a rise in the two other sub-types   This shift in sub-types can actually elevate the Total Cholesterol number and occasionally the LDL-C. 
If you are following a low carbohydrate diet, get your cholesterol levels checked.  It is more ideal to get an NMR Lipoprofile or VAP Cholesterol test that will give you an LDL particle number and this can be explained more fully by your doctor. 
Now, off to the fridge . . . where did I put that package of bacon . . . ?

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