Thursday, July 14, 2011

Dear Doctor, Part I: High LDL Readings

The letter below is the first of a series of letters to my doctor about the impact of my low carb lifestyle on my health. I have no idea how she will react to my health tests, so these are "just in case." But I thought it would be useful to collect the relevant information in one place, so I (and others) can show physicians why statin drugs may not be appropriate in every case. Where possible, I will link to the relevant studies from the medical literature. Future letters will discuss HbA1c results, diabetes drugs, cardiovascular health, "healthy" eating, and any other subjects I find interesting.

Dear Doctor:

I have been following a low carb diet for over six months now and you recently prescribed a lipid profile for me. The results are in and they are generally good. My HDL cholesterol level is up, my triglycerides are down, and my total cholesterol number is acceptable. Yet you want to prescribe a statin drug for me because my LDL cholesterol reading is high.

Consider this: the LDL cholesterol in my blood was never measured; it was calculated, using this formula[1]:

   LDL=Total Cholesterol -[HDL + (triglycerides/5)]

Why is this calculation a problem? It overestimates the presence of LDL cholesterol. If we assume that a low carb diet lowered my triglycerides (a good thing), but total and HDL cholesterol numbers stayed the same, this is what we would have:

                               Total              HDL         TRI         LDL (Calculated)
Before LC Diet          200               60           200            100
After LC Diet            200                60            75             125

So lowering triglycerides (a good thing), causes the LDL number to go up (a bad thing, in your opinion), based on the above equation. But what is my actual LDL, not the calculated LDL? We don't know, because you did not test for it. You could have ordered an NMR lipoprofile test to learn the actual measure, but you did not. So all we are left with is a problematic calculated value.

Also, are all LDL particles equally bad? The calculated number says nothing about the size of the LDL particles. Are they large and fluffy (also referred to as pattern A particles), or small and dense (also referred to as pattern B particles)? The large and fluffy LDL particles are not dangerous, and may even be somewhat beneficial, but recent research also shows that the small, dense, and sticky LDL particles are the real danger signal for heart disease.

But that new test to determine particle size may be expensive. Fortunately, there is a workaround. Take the ratio of my triglycerides to HDL (Triglycerides/HDL), which is an effective surrogate of the NMR lipoprofile test. If the ratio is below 3.5, I probably have pattern A and if it is above 3.5, I probably have pattern B. If I have pattern A LDL particles, I do not need a statin drug to lower my cholesterol.

Since my HDL went up and my triglycerides went down, I probably have pattern A particles, which are beneficial, not dangerous. So I respectfully decline your invitation to put me on statin drugs.


[1] I learned much of the information in this letter from reading The Art and Science of Low Carbohydrate Living by Jeff S. Volek, Ph.D., R.D. and Stephen D. Phinney, M.D., Ph.D., pp. 91-95. The example used is taken from these pages.

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