Saturday, March 12, 2011

A Tale of Two LDL's

When looking at blood lipid profiles, doctors tend to stress LDL cholesterol to their patients, but high LDL levels alone don't necessarily indicate high risk of heart disease.  It turns out, further research has uncovered that there are in fact two types of LDL.  You have pattern A LDL, which is large and fluffy, and you also have pattern B, which is small and dense.  The large, fluffy type is not associated with an increased risk of heart attacks, while the small, dense type very much is.  People with these larger LDL particles tend to have normal levels of other risk factors:  they typically have high HDL and low triglycerides.  People with small LDL experience the opposite:  they typically have low HDL and elevated triglycerides.  These two types of LDL clearly exhibit the exact opposite effect in terms of cardiovascular health, so why are we still so concerned with LDL?  Well, probably because doctors don't normally test for LDL particle size.  Maybe they should hop on that.

The discovery that there are two very different types of LDL has far-reaching implications, most notably in the saturated fat debate.  For years, the USDA Dietary Guidelines have stressed to us that we should reduce saturated fat and cholesterol intake because they raise LDL levels.  So what if they raise LDL levels?  Do they raise pattern A or pattern B LDL?  Research shows, saturated fat in the diet tends to raise the benign, large, fluffy pattern A LDL.  This study from Sweden shows that people who consume more milk fat (whole milk, cheese, butter, etc.) have predominantly large, fluffy LDL.  This study from UConn and this one out of Mexico both show that consumption of eggs, which are high in both saturated fat and cholesterol, result in the non-atherogenic large, fluffy LDL.  This of course makes evolutionary sense as well.  It is estimated that hunter-gatherers consumed at least 10-15% of their calories from saturated fat.  The Dietary Guidelines say we should keep it under 10%.  Maybe the USDA should actually read research instead of making recommendations that will sell more processed foods made from corn and soy.

My advice:  pay no attention to your overall LDL level and don't fear saturated fat or cholesterol.  Your total LDL number is meaningless unless you know which type of LDL you predominantly have.  Even if your doctor doesn't check for LDL particle size, though, there is still a good way to predict which type of LDL you've got.  If your HDL is high and your triglycerides low, you're probably safe regardless of your LDL count because it's going to be the large and fluffy pattern A.  If your HDL is low and your triglycerides high, then you're in trouble, even if your LDL level isn't high.  In the end, it looks like total LDL just isn't all that important of a predictor of heart disease.  If you've read this and my previous blog post, you have to wonder...  why is everyone so concerned about cholesterol??

1 comment:

  1. Great Post!

    I'm printing this one out for pops ;-)

    Backup studies are phenomenal