Why (LDL particle) size matters.

Having gone through the math(s) with several people, I thought I'd stick it in a blog post for posterity.

I know that this is a diagram of a chylomicron, but bear with me!

Cholesterol synthesised in the liver is exported in LDL particles. The more cholesterol that's synthesised, the more particles there need to be to carry it.

∴ LDL-P (particle number) ∝ LDL-C (total amount of cholesterol)

The particles are roughly spherical with a very thin wall (consisting of a phospholipid mono-layer, the yellow wiggly lines with a green end bit in the above diagram).

Volume of a sphere = 4/3 * π * r³, where r = half the diameter.

If there's a 10% reduction in LDL particle size, the volume reduces to 0.729, relative to the original size. Therefore, to carry the same amount of cholesterol requires 1/0.729 = 1.37 times more particles, which is a 37% increase in the number of LDL particles, relative to the original size.

∴ LDL-P (particle number) ∝ 1/LDLsize³

As it's LDL particle number that determines the infiltration of LDL cholesterol into the media of artery walls, it's advisable to keep cholesterol synthesis to a minimum by keeping fat intake to a reasonable level * (i.e. not Nutritional Ketosis level) and keeping LDL particle size to a maximum by keeping sugars & fast starches intake to a reasonable level*.

Before someone asks, what I mean by a reasonable level is a level that is burned by the body without having a chronic excess. An acute excess can be stored, provided that mean intake is less than mean burning.

How COULD I write a post about LDL-P and forget to include THIS?

The Conflation Game.

Li-i-ife, is the name of the game, and I wanna play the game with you.....


People have been "grinding my gears" by conflating carbohydrates with sugars. All sugars are carbohydrates, but not all carbohydrates are sugars. See Carbs Carbs Carbs. to find out about the five basic different types of carbohydrates.

Krauss et al has done it again. In Separate effects of reduced carbohydrate intake and weight loss on atherogenic dyslipidemia, at the bottom of Table 1 is "carbohydrate, 50% simple and 50% complex". The carbohydrates consisted of half sugars and half starches.

The effect of such a sugary diet is as follows:-

The percentage of pattern B (small, dense) LDL particles increases significantly in proportion to the percentage of Dietary "carbohydrate". The implication of this study (also A very-low-fat diet is not associated with improved lipoprotein profiles in men with a predominance of large, low-density lipoproteins ) is that high-carb, low-fat diets are atherogenic.

This is not on.

A high sugar diet is atherogenic, but carbs from new potatoes (especially if eaten cold), Basmati rice (especially if eaten cold), sweet potatoes, beans & whole fruits aren't.

Carbs, Carbs, Carbs, Carbs and Carbs.

Carbohydrates seem to get the blame for everything nowadays. "Carbohydrates made me fat". "Carbohydrates burned-out my pancreas". "Carbohydrates raised my blood glucose". "Carbohydrates raised my blood triglycerides". "Carbohydrates stole mer jerb!". O.K, I made the last one up!
If carbohydrates are responsible for all of these bad things, then how come a diet of only potatoes had the opposite effect? See 20 Potatoes a day.

Also, Blue Zone populations eat a diet with a high percentage of total energy (%E) from carbohydrates. See Low serum insulin in traditional Pacific Islanders--the Kitava Study and The Kitava Study. The Kitavans eat ~70%E from carbohydrates, ~20%E from fats and ~10%E from proteins. They don't eat a significant amount of Western crap-in-a-bag/box/bottle.

Maybe it has something to do with the type of carbohydrates and with what they're eaten. In A very-low-fat diet is not associated with improved lipoprotein profiles in men with a predominance of large, low-density lipoproteins , (emphasis, mine) "The very-low-fat, high-carbohydrate experimental diet was designed to supply less than 10% of energy from fat (2.7% saturated, 3.7% monounsaturated, and 2.6% polyunsaturated), with 75% from carbohydrate (with equal amounts of naturally occurring and added simple and complex carbohydrate) and 15% from protein." Simple carbohydrates are sugars.

The experimental diet which did bad things contained 37.5%E from sugars. I declare shenanigans!

1. There are simple carbs, there are simple carbs and there are simple carbs. In the previous post, the graph of plasma triglycerides after an OGTT showed that 100g of glucose had no significant effect on plasma triglycerides over a 6 hour period. If it had been 100g of fructose, there would have been a significant increase in plasma triglycerides. Galactose is taken-up by the liver and has minimal effect on blood glucose, but I don't know its effect on plasma triglycerides.

2. There are complex carbs, there are complex carbs and there are complex carbs. Overcooked starch is high in amylopectin which is highly-branched, which means that it hydrolyses rapidly into glucose which gives it a very high glycaemic index. Raw & refrigerated potato starches have very low glycaemic indices, due to the presence of amylose, or other resistant starches. Rice contains a mixture of starches which varies with rice type, cooking time and subsequent refrigeration.

3. There are oligosachharides e.g. FOS.

4. There are polysaccharides e.g. inulin.

5. There is soluble fibre/fiber e.g. cellulose.

Although overeating sugars containing fructose & starches that rapidly hydrolyse into glucose makes the liver fatty, overeating fats also makes the liver fatty. See Pathogenesis of type 2 diabetes: tracing the reverse route from cure to cause.

It's the chronic over-consumption of crap-in-a-bag/box/bottle (high in sugars and/or starches and/or fats), not just carbohydrates, that causes over-fatness and other health problems.

Boiled potatoes & Area Under the Curve (AUC): some thoughts.

Here are three "curves"... a 4 x 1 rectangle, a 2 x 2 square and a 1 x 4 rectangle.

The AUC for all three "curves" = 4.

Imagine that the three curves are for blood glucose level increase above baseline vs time.

a) "X" grams of a high-Glycaemic Index (GI) carb e.g. glucose, maltodextrin or amylopectin result in a large glucose response that goes away rapidly, as the carbs leave the gut rapidly, pass into the blood rapidly and are cleared from the blood rapidly due to the large insulin response.

b) "X" grams of a 50:50 mixture of high & low-GI carbs result in a lower but longer sustained glucose & insulin response, as some carbs leave the gut rapidly but some carbs leave the gut slowly, pass into the blood slowly and are cleared from the blood slowly due to the small insulin response.

c) "X" grams of a low-GI carb e.g. amylose or resistant starch result in an even lower glucose & insulin response that is sustained for even longer, as the carbs leave the gut very slowly, pass into the blood very slowly and are cleared from the blood very slowly due to the very small insulin response.

Will a), b) & c) produce the same satiety? I think not. I think that a) results in lower satiation than b) and b) results in lower satiation than c). Whether returning hunger is caused by a sudden drop in blood insulin level or by a sudden drop in the amount of food in the gut, I don't know.

The reason for this post is A satiety index of common foods (scanned image of full study here) and the related study An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods.

In the first study, boiled potatoes produced the highest satiety, yet in the second study, boiled potatoes produced one of the highest glucose & insulin AUCs. How can this be? Consider the preparation method for the Russet potatoes:-
"Peeled, boiled for 20 min, and stored at 4 °C overnight; reheated in a microwave oven for 2 min immediately before serving."

Potato starch when refrigerated produces resistant starch RS3, which gives it a low GI (see item 605 in International table of glycemic index and glycemic load values: 2002). Therefore, refrigerated potatoes contain a mixture of high & low-GI starches. This, I believe, is why boiled, refrigerated & reheated potatoes produced the highest satiety. The combination of water, fibre & resistant starch kept hunger pangs away the longest. I suspect that boiled potatoes that are eaten without being refrigerated won't produce quite as much satiation, as they contain no resistant starch.

EDIT: From https://en.wikipedia.org/wiki/Resistant_starch#Definition_and_categorization :-
"RS3 Resistant starch that is formed when starch-containing foods are cooked and cooled, such as pasta. Occurs due to retrogradation, which refers to the collective processes of dissolved starch becoming less soluble after being heated and dissolved in water and then cooled."
RS3 forms a gel in the stomach, which delays stomach emptying. This is most likely the reason for the increased satiation.