Monday, April 22, 2013

HDL Cholesterol

Recall from the blog entry “Is a Low-Fat Diet Healthiest?” that a low-fat diet is not necessarily the best diet to prevent heart disease because

·        triglycerides increase
·        HDL’s decrease, and
·        insulin-resistance gets worse! 

In previous blogs I discussed insulin-resistance and triglycerides, but what exactly are HDL’s? 

HDL ("high-density lipoprotein") is affectionately known as the "good cholesterol".  Cholesterol is a waxy steroid of fat, and HDL is one of 5 forms of lipoprotein which carry cholesterol in the blood
(the lipoproteins are chylomicrons, VLDL “very low-density lipoprotein”, LDL “low-density lipoprotein”, IDL “intermediate-density lipoprotein” and HDL).  HDL is known as “good” cholesterol because it transports cholesterol away from arteries and veins, and LDL cholesterol is known as “bad” cholesterol because it transports cholesterol to arteries and veins.  [Recent evidence indicates that the “baddest” LDL cholesterol is small, dense lipoprotein(a), also known as Lp(a)].

Shortly after we eat fat, huge globules called “chylomicrons” begin to show up in the blood.  These are transported throughout the body to be available to be burned for energy or fat production by tissues.  However, since chylomicrons are made up largely of triglycerides (fat), and since fat and water don’t mix very well, the excess fat is transported to the liver (portal circulation) where it gets packaged in a protein package called “lipoproteins”, or fat (lipo) in a protein package (VLDL, IDL, LDL and HDL) which more easily transports the cholesterol around the body in the blood.  The two major players are LDL (bad) and HDL (good) cholesterol. 

The American Heart Association classifies low HDL as a major risk factor for heart disease, defining “low HDL” < 40 mg/dL in men, 
and < 50 mg/dL in women. 
An HDL of 60 mg/dL and above is considered protective against heart disease. 

Many people know their LDL, but how many of you know your HDL number?  HDL is being recognized as a strong, perhaps even more important, risk factor in cardiovascular disease risk.

It is also very helpful to know the ratio of total cholesterol (TC):HDL to determine risk for cardiovascular disease.  The ratio TC/HDL < 3.5 is a more accurate indicator of actual risk for cardiovascular disease than just TC or LDL cholesterol.  The higher the “good” HDL cholesterol the lower the ratio.  Most American men have a ratio of 5.0, most American women 4.5 (but we want 3.5 or lower).  Think of LDL’s as garbage and HDL’s as garbage men, and a true story to help understand: 

New York is (or at least it used to be) a really dirty city (its “cholesterol” is 500+) but the city doesn't die of a heart attack--in fact, it thrives.  However, one year the garbage men (HDL’s) went on strike, and by Friday the city nearly died (heart attack).  Garbage was piled up on city sidewalks, businesses shut down, and you couldn’t even go out to eat.  The ratio of garbage to garbage men got out of whack and the city nearly died.

The TC/HDL ratio is very important in a borderline case, such as mine.  Years ago I had a total cholesterol of 217.  When the lab called to share my serum cholesterol breakdown they were impressed to tell me that my ratio of TC/HDL was 2.7, an extremely good number (considerably below 3.5) in spite of my borderline high TC (217, which was over 200) because my HDL’s were unusually high (73).  I had been exercising heavily for quite some time, which undoubtedly resulted in a higher-than-normal HDL.  In this borderline case, I was actually healthier to have a slightly high total cholesterol because it was resulting from a high amount of good HDL “garbage men” which added to the number.  It would have been less healthy (in this borderline case) to have a lower total cholesterol number--my TC was slightly high because I had a lot of garbage men cleaning me up!  Of course, once you pass borderline numbers it is difficult or impossible to have enough HDL’s to take care of how high the LDL’s get as they contribute to the higher total cholesterol numbers.          

HDL’s normally run from a low of 30 to a high of 75+ (even 90, usually in avid exercisers).  According to the recommendation of HDL > 50-60 mg/dL for women, my HDL of 73 was just fine. 

To Increase HDL’s:
  • EXERCISE!!!
  • Trans Fat (these “partially hydrogenated” processed fats deliver a “double-whammy” as they both raise LDL cholesterol like saturated fats do, and they reduce HDL cholesterol)
  • Stop Smoking
  • Maintain normal body weight (being overweight, and also having high triglycerides, can result in lower HDL’s)
  • Once again, the recommendation to eat a monounsaturated-rich plant-based diet with small portions of fish, lean poultry, and meat, with olive oil as the principal fat and nuts for snacks works for HDL’s too.  While monounsaturated fats do not raise HDL’s, they also do not lower HDL’s as trans fats and low-fat diets do (and mono fats also lower cholesterol and triglycerides).  No matter what physical parameter we look at, this dietary recommendation is the same! 
  • Alcohol, in moderation, seems to have a positive effect on HDL’s.  However, I cannot recommend drinking alcohol as a treatment modality for preventing heart disease in a country where alcoholism is such a big problem.  

So know your HDL’s and make any necessary diet and exercise modifications to keep them above 60 mg/dL. 

One more great reason to exercise!

Diane Preves, M.S., R.D.


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