Here’s a bit of lipid tedium that might nonetheless help you one day decipher the meaning of shifts in your cholesterol panel.
Recall from prior discussions that conventional LDL cholesterol is a calculated value. Contrary to popular opinion, LDL is usually not measured, but calculated from the Friedewald equation:
LDL cholesterol = Total cholesterol – HDL cholesterol – triglycerides/5
For the sake of simplicity, let’s call total cholesterol TC; HDL cholesterol HDL, and triglycerides TG.
We’ve also talked in past how a low HDL makes calculated LDL inaccurate, sometimes wildly so. (See Low HDL makes Dr. Friedewald a liar.)
Here’s yet another source of inaccuracy of the Friedewald-calculated LDL: any increase in triglycerides.
Let’s say, for instance, that starting lipid panel shows:
TC 170 mg/dl
LDL 100 mg/dl
HDL 50 mg/dl
TG 100 mg/dl
You’re advised to follow a standard low-fat, whole grain-rich diet advocated by “official” agencies (the diet I bash as knuckleheaded). Another panel a few months later shows:
TC 230 mg/dl
LDL 140 mg/dl
HDL 50 mg/dl
TG 200 mg/dl
(Obviously, I’ve oversimplified the response for the sake of argument. HDL would likely go down, LDL would change more depending on body weight, small LDL tendencies, and other factors. You’d also likely get fat.)
Now your doctor declares that your LDL has gone up and you “need” a statin agent.
Nonsense, absolute nonsense.
What has really happened is that the increased dietary intake of wheat and other “healthy whole-grain foods” has caused triglycerides to skyrocket. LDL increases, in turn, by a factor of TG/5, or 40 mg/dl. Thus, LDL has been inflated by the triglyceride-raising effect of whole grains.
This is yet another reason why the standard lipid panel, full of hazards and landmines, needs to be abandoned. But calculated LDL in particular is an exercise in frustration.
Though the example used is hypothetical, I’ve witnessed this effect thousands of times. I’ve also seen many people placed on statin drugs unnecessarily, due to the appearance of a high LDL cholesterol that really represented increased TG/5, usually induced by an excessive carbohydrate intake, including those commonly misrepresented as healthy such as whole grains.
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