Cholesterol Confusion

LDL is the one thing doctors always pay attention to when they do cholesterol blood test.

Too high and they shout you need statins.

The problem is when you are on a low carb diet like Atkins or Protein Power, after a while your triglycerides will be low while your high-density lipoprotein cholesterol (HDL) is high. The problem is LDL is expensive to measure in a laboratory, hence they generally calculate out this value using the Friedewald estimation.

ie, LDL-C (calc.) = CH − HDL − (TG/5)^2.

However this formula only works for triglycerides under 400mg/dl (4.52 mmol/l) and more importantly above 100mg/dl ( 1.13 mmol/l). When triglycerides are  above 400mg/dl, the labs generally warn in the report that it cannot be calculated. But then don’t warn if its below 100mg/dl.

The problem is that if you are on low carb diet for a while, your triglycerides will naturally fall below 100mg/dl. Then then abnormal LDL will be inflated by as much as 58%.

Hence the Cholesterol Confusion

For better estimates you would use the Iranian formula from this medical paper.

Or better ask for a direct LDL measurement

Do note that you can only use this formula if TG < 100mg/dl (1.13 mmol/l) AND TC > 250mg/dl (6.46mmol/L)

For mmol/L you would use

LDL (mmol/L) = TC/1.19 + TG/0.81 – HDL/1.1 – 0.98

For mg/dL

LDL (mg/dl) = TC/1.19 + TG/1.9 – HDL/1.1 – 38

If a doctor tries to press you to use Statins, please ask him to refer to the following articles

For the doctor:

Low Triglyceride Levels Affect Calculation of Low-Density Lipoprotein Cholesterol Values

The impact of low serum triglyceride on LDL-cholesterol estimation

The accuracy in using modified Friedewald equation to calculate LDL from non-fast triglyceride: a pilot study

For us layman:

Low-carbohydrate diets increase LDL: debunking the myth

Making Dr Friedewald an honest man