Stephan, question: I read somewhere (possibly here?) that the carbohydrate in rice is converted to some extent to Palmitic acid by the liver. If this is the case, it could be one factor explaining the incidence of coronary events in Asian vs. Western populations. Carb source, as you have noted before, trumps carb percentage in the diet. Again, if this is the case, then Asian populations may in effect be consuming a high saturated fat diet even if rice forms the foundation of their meals. I'm certainly not sure how the conversion of carb from rice into lipids in the liver compares to conversion from other carb sources. I may be totally off base in this comment. Scott W PS - I've been diligently reading your posts, just too busy with summer activities to comment much.
Stephan, this post is an amazing wealth of gold nuggets, beautifully arranged. It is amazing to see all this information pulled together into a logical and very clear picture. Next time I see my doctor, I'll be sure to take this along, because he'll want to talk 'statin's' again. Then again, maybe I shouldn't waste my time by going to see him.
Scott W, Jack, exciting info! rice consumption increases Palmitic Acid! A reference for this would be great, if available. What acids would be produced by the liver after wheat production? This is getting into some very interesting aspects of diet and its effect on the digestive system.
Starch, whether from rice, wheat, or whatever, is rapidly broken down into glucose and dumped into the circulation. Glucose is glucose, regardless of its source. Excess glucose not needed for energy or to replenish glycogen stores is converted by the liver to palmitic acid.
Jen, yeah, I guess if I'd thought it through I would have figured that out...it's not like grains of rice are delivered to the liver by the bloodstream, having passed through the intestine undigested! So, then, the key to effectively using carbs as a fuel source would be to get a pure a source for glucose production as possible. Meaning that all starches break down to glucose, which can be converted to palmitic acid, but some carbs carry the baggage of unwanted stuff, such as gluten. So rice fits that bill, to the benefit of Asians, but so would tubers such as taro or skinless potato, or high starch/low fructose fruits such as plantains. But we shouldn't make too much of this, of course. Eating high starch is not necessarily the best road to a coronary-event-free life, but according to the Kitavans, and others, it certainly does not preclude such a heart-healthy condition. And the action of excess carb being coverted to palmitic acid could play a role in that. What I find really intersting is this: The body, when faced with an overabundance of glucose, converts that glucose to saturated fat. We certainly evolved to be able to consume carb, and therefore evolved to handle it appropriately, so the fact that we use it to make saturated fat and not some other kind of fat should indicate that the body prefers it. Or at least has evolved to thrive on it. Scott W
Scott, As Jen mentioned, all carbohydrate in excess of what can be immediately burned or stored as glycogen is turned into palmitic acid by the liver, whether it's from rice or any other source. The higher the glycemic index, the larger the proportion that's converted to palmitic acid. That's because there's a brief rush of glucose so more gets turned into fat rather than burned as glucose as it trickles into the bloodstream more slowly. I also think it's telling that the body chooses to convert carbs to palmitic acid, when we have the enzymes necessary to monounsaturate it. Hi Kurt, That sounds reasonable, although I do think there's some value to LDL particle count. I'm skeptical of the "reverse cholesterol transport" hypothesis of HDL, it just seems implausible on the surface. But I haven't really looked into it so maybe there's good evidence. I think it could easily just be acting as a marker of diet. Homertobias, I did notice he's on the fructose paper. He's done some great research over the years! Robert, I'll be posting on animal models of atherosclerosis at some point in the next few weeks because I think it's interesting. In general, the only animals that you can give atherosclerosis by feeding saturated fat are species that react to sat fat by dramatically increasing LDL. I'm talking about 3-10 fold or more in some cases. Typically but not always aided by large amounts of dietary cholesterol. Then there are the species that react more modestly to sat fat (like humans), where it doesn't produce atherosclerosis on its own. Often researchers use what they call an "atherogenic diet" that's a mix of large amounts of cholesterol, saturated fat (often hydrogenated) and sugar, on the background of an otherwise highly refined diet. Feed this to an animal that's mostly or totally vegetarian and you're almost guaranteed to get blood lipid disturbances and massive atherosclerosis.