While I was looking through some of the references cited by Krauss in his discussion paper about the roll of omega 3 fatty acids in the lowering of triglycerides, I came across this paper from 1999 on the effects of high and low fat diets on LDL subclasses. I read the abstract, re read it and read it again, scratching my head. Then I slogged through the whole paper. I just couldn't make out whether Krauss considered saturated fats to produce atherogenic changes in plasma lipids or not. After reading the paper I still couldn't decide what his conclusions were! Here are some quotes from the discussion:
"Change in dietary saturated fat was associated positively with mass of larger LDL particles and with peak LDL particle diameter and LDL flotation rate. These results suggest, therefore, that feeding saturated fat is associated with increased mass of larger LDL"
I think this means that saturated fats make "good" bad cholesterol. What do you think? What do you think Krauss thinks? Can you tell?
"In the present study, correlation analyses revealed significant positive relations of change in intake of the long-chain saturated fatty acids myristic and palmitic acids with change in plasma concentrations of large LDL particles. These findings are consistent with studies showing that, of the long-chain saturated fatty acids, myristic and palmitic are the most hypercholesterolemic"
Gasp, saturated fats are hypercholesterolaemic. Good or bad? Surely hypercholesterolaemis is bad? Keys said so. But large LDLs... atherogenic or benign????
"In summary, the present study showed that changes in dietary saturated fat are associated with changes in LDL subclasses in healthy men. An increase in saturated fat, and in particular, myristic acid, was associated with increases in larger LDL particles (and decreases in smaller LDL particles [did you spot this inset???? It matters]). LDL particle diameter and peak flotation rate were also positively associated with saturated fat, indicating shifts in LDL-particle distribution toward larger, cholesterol-enriched LDL"
Now, would you eat something which produced "cholesterol enriched" particles?
"Although there is a possibility that a subset of large LDL particles may be atherogenic (46), earlier results (37) point to a differential benefit of low-saturated-fat diets on LDL concentrations in individuals who have an atherogenic lipoprotein profile denoted by a predominance of small LDL particles"
What on earth does "a differential benefit of low-saturated-fat diets" mean? Your guess is as good as mine on that one. Answers on a postcard to Hyperlipid.
From the results, from whence it didn't seem to make it to the discussion, except in that little inset in brackets I highlighted:
"During the high-fat diet, saturated fat was correlated negatively with mass of smaller LDL particles"
What does this mean? Isn't that good? Does this mean the small dense LDLs are less dense?
As far as I can see, saturated fats improve every lipid marker they looked at BUT just look at this comment, again from the discussion:
"An increase in dietary saturated fat has been associated with the progression of CAD independent of LDL-cholesterol concentrations (56), and in cross-cultural studies, higher intakes of dietary saturated fat are associated with higher prevalence rates of CAD (57)"
Translates as: Never mind the lipid paramenetrs, saturated fats are BAD. Full stop. I think it's called nailing your colours to the mast.
BTW Ref 57 is Keys. Scraping the barrel a bit there!
So what did I do? I was beginning to doubt anything I'd read about lipid particle sub types, so I googled something along the lines of "LDL particle size CAD" or the like.
This was the first hit. Really, no kidding.
It's clear cut, cutting edge science from 1994:
"The lowest quintile--those with the smallest and most dense LDL particles--had more than three times the risk of heart attack as the quintile with the largest LDL particles"
Classic quote from: Ronald M Krauss, circa 1994.