Low HDL makes Dr. Friedewald a liar

17. March 2007 William Davis (5)
There's a $22 billion industry based on treating LDL cholesterol, a fictitious number.

LDL cholesterol is calculated from the following equation:

LDL cholesterol = Total cholesterol - HDL cholesterol - triglycerides/5

So when your doctor tells you that your LDL cholesterol is X, 99% of the time it has been calculated. This is based on the empiric calculation developed by Dr. Friedwald in the 1960s. Back then, it was a reasonable solution, just like bacon and eggs was a reasonable breakfast and a '62 Rambler was a reasonable automobile.

One of the problems with Dr. Friedewald's calculation is that the lower HDL cholesterol, the less accurate LDL cholesterol becomes. If it were just a few points, so what? But what if it were commonly 50 to 100 mg/dl inaccurate? In other words, your doctor tells you that your LDL is 120 mg/dl, but the real number is somewhere between 170 and 220 mg/dl. Does this happen?

You bet it does. In my experience, it is an everyday event. In fact, I'm actually surprised when the Friedewald calculated LDL closely approximates true LDL--it's the exception.

Dr. Friedewald would likely have explained that, when applied to a large population of, say, 10,000 people, calculated LDL is a good representation of true LDL. However, just like saying that the average weight for an American woman is 176 lbs (that's true, by the way), does that mean if you weigh 125 lbs that you are "off" by 41 lbs? No, but it shows how you cannot apply the statistical observations made in large populations to a single individual.

The lower HDL goes, the more inaccurate LDL becomes. This would be acceptable if most HDLs still permitted reasonable estimation of LDL--but it does not. LDL begins to become significantly inaccurate with HDL below 60 mg/dl.

How to get around this antiquated formula? In order of most accurate to least accurate:

--LDL particle number (NMR)--the most accurate by far.

--Apoprotein B--available in most laboratories.

--"Direct" LDL

--Non-HDL--i.e., the calculation of total cholesterol minus HDL. But it's still a calculated with built-in flaws.

--LDL by Friedewald calculation.

My personal view: you need to get an NMR if you want to know what your LDL truly is. A month of Lipitor costs around $80-120. A basic NMR costs less than $90. It's a relative bargain.
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Comments (5) -

  • Mike

    3/18/2007 1:52:00 AM |

    What is shocking is that enormous prescriptions for statins are written based on the calculated LDL.

  • Dr. Davis

    3/18/2007 1:16:00 PM |

    Yes, $22 billion last year, in fact. All prescribed for a number that is a crude estimate, sometimes a complete fiction. Imagine your state trooper ticketed you because his radar device said you were doing 60 mph when you were really doing 35 mph.

  • Anonymous

    2/6/2008 1:37:00 AM |

    Why NMR over the other tests Berkeley Heart Lab or VAP?

  • Anonymous

    7/2/2008 7:02:00 PM |

    I don't understand.  If in this example, the doctor (wrongly) thinks the LDL number is 120mg/dl, how does that cause the prescription of Lipitor? Unless I'm reading it backwards, and the doctor is actually telling the patient their LDL is 170mg-220mg, but unwittingly, it's actually 120mg/dl.

    And, if a low HDL causes the LDL number to be inaccurate, does that also cause the total cholesterol number to be inaccurate too?

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(Lack of ) Quality of nutritional supplements

(Lack of ) Quality of nutritional supplements

16. May 2007 William Davis (0)
In my last post, I blogged about how we must not confuse marketing with truth. They are often two different things.

A patient I saw today was absolutely convinced that his fish oil was the best available in the world: purer, uncontaminated by mercury or pesticides--"not like that other crap on the shelves." I asked him how he knew this. "They say so," he proudly declared.

Do you recognize this? He fell for the marketing. While there may be some truth in the manufacturer's claims, you can't believe it from the mouth of the manufacturer. True judgements about quality and purity have to come from an independent source like Consumer Reports, Consumer Lab, or the FDA.

But the FDA doesn't regulate the quality and purity of nutritional supplements. On the positive side, this has allowed supplement manufacturers to keep costs down, not having to navigate arcane and complex regulatory restrictions.

On the negative side, a fair number of supplement manufacturers get away with 1) producing supplements that fail to contain the stated amounts of ingredients, occasionally containing none of the essential ingredient(s), 2) contain contaminants like lead, and 3) make extravagant and often unfounded claims like "superior", "more effective", and "purer". (DHEA, for instance, is a particular landmine of poor quality. I recently suggested that a patient take DHEA; despite consistently taking 50 mg of a specific brand for several months, the blood level of DHEA-S didn't budge one bit--there was likely little or none in the capsule.)

The Fanatic Cook at http://fanaticcook.blogspot.com has posted some very insightful discussions on this issue and the proposed FDA regulations of supplements. They're worth perusing.

I really wish regulation weren't necessary and that the industry could have policed itself. But it clearly has failed and perhaps federal oversight is not such a bad thing, as long as the FDA regulations restrict themselves to oversight over quality and purity and not to efficacy. It's the efficacy regulation that could hogtie innovation in supplement development.
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