Retrospective #406: Are Your Triglycerides Calculated or “Direct”?

Michael R. Eades, MD, is a blogger, a prolific author, and a voracious reader. He and his wife, Mary Dan (MD), also an MD, were early backers of the LCHF Way of Eating and authors of “Protein Power” (1996), and “Protein Power Lifeplan” (2000), and many other books. He blogs at www.proteinpower.com/drmike. A recent post that I read was titled, “How to Lower Your Cholesterol, using diet to keep your doctor off your back.”

In that post I had a question about a screen shot of his lab LDL-C so I emailed him, and he replied that his LDL was not “Calculated” by the Friedewald equation but was “Direct.” (The report actually said that; I just missed it.) He then provided me with a link to a post he wrote a few years ago, “Low carbohydrate diets increase LDL: debunking the myth.” This is another post about the effect of Low Carb diets on TGLs and LDL-C. You’ll need to read to the end of Dr. Mike’s long post to get to it, so I’’ get right to the point here. LOL

Eades writes about a study in the American Journal of Clinical Nutrition. “This study…demonstrates that subjects following the low-carb diet experience a decrease in triglyceride levels and an increase in HDL-cholesterol (HDL) levels; and that these changes are accompanied by a minor increase in LDL-cholesterol (LDL)…” This concerns doctors, he says, since “most people who go on low-carb diets do so to deal with obesity issues, and since obesity is a risk factor for heart disease,…this small increase in LDL… could put these dieters at risk” (for heart disease).

So, noting that the benefits to HDL and triglycerides are offset by “this small increase in LDL-cholesterol seen in those following a low-carb diet,” Eades wondered how the LDL in the study was calculated; the “Methods” link in the study provided the answer: the Friedewald equation: LDL = TC – HDL – TGL/5. IT WAS CALCULATED! What’s that? It’s not a DIRECT (assayed) measurement? No, and every standard lab lipid test uses* this method.

Interestingly, when Friedewald, et al. developed that formula in 1972, they made an exception for people who had a triglyceride >400mg/dl; however, since most people’s test results were in the 150 – 250mg/dl range, they made NO exception for TGL values of <100mg/dl. As readers here know, people who follow a Very Low Carb or LC/HF diet usually have TGLs in the range of 40 – 90mg/dl. The average of my last 50 tests (since 2002) was 54mg/dl.

So, Dr Eades searched the archives for scientific papers describing differences between calculated and directly measured LDL-cholesterol in people with low triglycerides. And lo and behold, he found two! One was a case presentation where a 63yo man had a TC of 263, an HDL of 85 and a TGL of 42.  The Friedewald calculated LDL was 170 but it was just 126 when measured directly. Another paper concluded, “Statistical analysis showed that when triglyceride is <100mg/dl, calculated LDL is significantly overestimated (12.17mg/dl average).”

In addition to the over calculation of LDL for low-carbers who have TGLs consistently <100mg/dl, Eades reminds us: LOW-CARBERS TYPICALLY HAVE THE LARGE FLUFFY, GOOD TYPE OF LDL, NOT THE SMALL, DENSE TYPE.

Dr. Mike sums this up better than I could: “The moral of this story is that if you have been following a low-carb diet and your triglycerides are low (or if your triglycerides are just low) and your LDL reading comes out a little high – or even a lot high, don’t let anyone mule you into going on a statin or undergoing any therapy for an elevated LDL.  Demand to have a direct measurement of your LDL done.”

And Dr Eades coup de grace: “Now when you hear people say that low-carb diets may help you lose weight but run your LDL levels up and increase your risk for heart disease, you’ll know this is just so much gibberish.  Sadly, your doctor will probably spout the same thing, and it will be up to you – who after reading this post will know more about this point than 99.9 percent of doctors practicing today – to educate your trained professional.”

*N.B.: This post was originally published in November 2017. Some time in 2018, Quest Labs discontinued using the Friedewald equation and switched to Martin/Hopkins, “a better LDL calculation method,” for lower LDLs. The change is discussed in detail in The Nutrition Debate: Type 2 Nutrition #476, published March 10, 2019.