When good cholesterol isn't

First we were told to lower our cholesterol.  This was back in the 1960's, when the first results of the then major new epidemiological project, the Framingham Heart Study, were released.  If the Framingham Heart Study taught us anything, it was that high cholesterol was a major risk factor for heart disease.  So we all started eating oat bran and granola and eschewing beef.

And then,  in the 80's we were told that it's not all cholesterol we need to be concerned about, that there's a good and a bad cholesterol, and we should be raising one and lowering the other.  How?  Eat healthy -- no eggs, no butter, no red meat.

Egg in a spiral eggcup; Wikimedia

And then it turned out that the people living on the Mediterranean had known all along what eating healthy is -- everything in moderation, except for olive oil and red wine, two foods that we should all be consuming more of.  From the Mayo Clinic:

Key components of the Mediterranean diet

The Mediterranean diet emphasizes:

• Eating primarily plant-based foods, such as fruits and vegetables, whole grains, legumes and nuts
• Replacing butter with healthy fats, such as olive oil
• Using herbs and spices instead of salt to flavor foods
• Limiting red meat to no more than a few times a month
• Eating fish and poultry at least twice a week
• Drinking red wine in moderation (optional) [not clear which is optional here, the red wine or the moderation]

So, follow these new rules and live as long as the Italians do.  Somewhere along the line, though, eggs were taken off the list of forbidden foods, and the usual American replacement for butter, margarine, turned out to have transfats which are bad for you, and anyway, saturated fats -- the stuff that's hard at room temperature, like margarine -- aren't good for you in any form.

And it turns out it's hard to lower your bad cholesterol with diet.  So, maybe try doing it with drugs.  Statins are good.  Indeed, the more people taking statins the merrier.  But whether statins are lowering all the risky components of LDL is still open to question (e.g., this paper).  Statins are designed to control circulating lipids (fats), which confer heart-disease risk. They inhibit an enzyme called 'HMG-CoA reductase' which is expressed in liver cells as they produce cholesterol from raw ingredients and secrete it into the blood stream. Lower enzyme activity, lower circulating lipids. Whether this is what they are doing is still not entirely clear, however.  There is evidence that statins may be reducing inflammation in irritated arteries and veins, which may be what reduces risk of heart disease rather than any effect on cholesterol.  Perhaps heart disease is an inflammatory process more than one affected by cholesterol levels, after all.

Oh, but then a rather confusing study was published last year, showing that Australian men who switched polyunsaturated fat for the saturated fats in their diet did in fact lower their LDL, but they also were more likely to die of a heart attack than those who hadn't changed their diets.  Indeed, most people who have heart attacks don't have high LDL.

But ok, assuming the cholesterol model of heart disease, along with lowering LDL, it would make sense to also raise your HDL, the good cholesterol.  But now it turns out that it's possible to have too much of a good thing.  A new paper in Nature Medicine (paywall) reports that while HDL normally should keep arteries clear and protect against heart disease, in arterial walls, HDL acts quite differently from circulating HDL, and can lead to arterial blockage and heart attack.

The BBC reports that the authors say people should still "eat healthily".  But, what this means, when the definition of a healthy diet keeps changing, and today's healthy diet can be the cause of ill health, is not at all clear.

Everything in moderation seems good to go with.