Flutterby™! : Saturated fat good for you 2011-09-15 16:10:19.378393+00

Saturated fat good for you

2011-09-15 16:10:19.378393+00 by Dan Lyke 4 comments

Effects of Diet on High-Density Lipoprotein Cholesterol.:

Multiple dietary factors have been shown to increase high-density lipoprotein cholesterol (HDL-C) concentrations, and HDL-C has been inversely associated with coronary heart disease (CHD) risk. Replacement of dietary carbohydrate with polyunsaturated, monounsaturated and saturated fat has been associated with progressively greater increases in HDL-C (7-12%) in addition to other lipid changes. Added sugars, but not high glycemic carbohydrates, have been associated with decreased HDL-C. Alcohol consumption has been associated with increased HDL-C (9.2%) independent of changes in other measured lipids. Modest effects on HDL-C (~4-5%) among other lipid and non-lipid CHD risk factors have also been observed with weight loss by dieting, omega-3 fatty acids, and a Mediterranean diet pattern. The CHD benefit of increasing HDL-C is unclear given the inconsistent evidence from HDL-raising pharmacologic trials. Furthermore, pleiotropic effects of diet preclude attribution of CHD benefit specifically to HDL-C. Investigation into functional or other properties of HDL may lend further insight.

Via Healty Diet and Science which points out that this is exactly the opposite from the advice that organizations like the American Heart Association have been giving us for years: Saturated fats are, in fact, good for your heart. This also meshes with the papers I've read about how fructose gets metabolized; if you're going to look at foods which do bad things to your cholesterol balance, point your finger there.

Bonus: Excercise at work boosts productivity.

It took over thirty years to realize that the trans forms of fat present in partially hydrogenated margarine was worse for cardiac outcomes than butter. I have little hope that the mechanisms of lipid metabolism will be elucidated any time soon.

Carbohydrate metabolism is much simpler, and that isn't clearly understood either. I will give you two counter-intuitive examples.

Patients who exercise extremely tight control of A1c (glycosylated hemoglobin, a measure of the glucose history levels) result in poorer outcomes than patients with moderately controlled A1c levels.

The glycemic index of a food is a measure of its impact on blood glucose levels. Straight glucose has a high glycemic index, fish a low one. Yet baked potato has a higher glycemic index than ice cream. That is probably fairly reasonable in that the baking process would be expected to break a lot of the starch into shorter, very rapidly digestible chains, though it is startling to expectations. More interesting is that a slice of bread will have a lower glycemic index than a slice of bread with cheese. It is clear that glycemic indexes must each be measured with significantly large groups of people, and that simple estimation based biochemical knowledge is an inadequate prognosticator.

Yeah, it also seems like we're a long way from understanding what leads to all the HDL and LDL subtypes. I expect a whole bunch more science to actually reveal stuff while people slave away with misguided dietary restrictions...

To demonstrate additional factors in the complexity of this process, it has been shown that short plant RNA sequences (microRNA), containing up to 22 nucleotides can be found circulating in the blood of plant eating mammals including humans. At least one of the microRNA's from cruciferous vegetables binds to LDLRAP1 mRNA, and reducing the levels of LDLRAP1, impairing LDL removal.

How significant this factor is not known. What it does show is that there are no simple answers involved in the complex mechanism of lipid metabolism.

I saw a paper recently that indicated heart disease was associated with certain subfractions of HDL. Currently HDL can be separated into 10 or more subfractions, some of which seem to be associated with a lower risk of heart disease, while others, particularly the smaller denser ones HDL8-10 are associated with an increased risk. HDL2 and HDL3 presently appear to be the the "good cholesterol."

Lipid, and in particular cholesterol metabolism, is a puzzle wrapped in an enigma and so on. There has been so much work in this area that it makes it obvious that there are not going to be any easy answers on this one.