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Week: 559.6 Guest: Dr. Nilo Cater, Nutrition scholar, Univ. Of Texas Southwestern Medical Center, Dallas Topic: Popular medium chain oil does cause cholesterol to rise Producer/Host: Steve Girard
NEMA: This story concerns a product called MTC oil, which is used by some as a nutritional supplement, touted to give quick access to energy...and by others as a cooking oil that has been reported not to raise the levels of LDL cholesterol - the 'bad' cholesterol...with us is Dr. Nilo Cater, of the Center for Human Nutrition in Dallas, Texas....
CATER: MTC oil, or medium chain triglycerides, has been around since the 1950's, it was used in patients who wouldn't be able to absorb the more common fats in the diet. Medium chain triglyceride oil is composed mainly of what's called medium chain fatty acids, all fats are composed of fatty acids, and so fats are either saturated...monounsaturated or polyunsaturated...so when we say something is a saturated fat, it's actually composed of all sorts of fatty acids, but the predominant type of fatty acid is what determines how we classify it. So, the medium chain fatty acids which make up medium chain triglyceride oil is metabolized in a way that's different from the way that longer chain fatty acids are metabolized...in that it is quickly absorbed and is quickly transported to the liver, where it is quickly broken down. The use in patients with malabsorbtion...that's pretty clear cut, and it's beneficial for those people. But as far as it's use as a source of quick energy or in promoting weight loss, most of the studies that are used to support those ideas have been done in animals...in rats or chickens, in dogs...and very few studies have actually been done in humans. I should say in terms of the interest in promoting weight loss, the few human studies that have actually addressed that have not found that it really does promote weight loss. So, it's been a controversial area. And, so the interest in medium chain triglycerides or fatty acids has been that if it's true, that it's absorbing this way and broken down, many people have thought it should not raise your cholesterol. Of course that has a lot...if it really is true, then it has a lot of potential uses. For example, since it's a saturated fat, then it has all the physical properties that we like in fat: the mouth feel, the preparation properties...and in fact, there's a company that is now promoting medium chain triglyceride oil as a cooking oil, as an alternative to the cholesterol raising cooking oils. And it also is thought to have potential in other foods, if you could design a fat that's composed of these fatty acids, then again, you'd still have the properties of saturated fat, without the cholesterol raising properties. But then again, the actual experimental evidence supporting those theories or those claims have been very limited. And so, we decided to conduct a study which would help put to rest this controversy of whether these fatty acids really do or don't raise or lower cholesterol.
NEMA: So people were hoping that this would be the basis for a lot of products but your study is saying that medium chain triglyceride oil...or MCT oil...is just as big a cholesterol raising factor as the worst of the saturated fats. I used MCT oil for a while...as part of a very low fat diet, and went with it because I believed it would be a fat that gave me energy because it was broken down easily, and wouldn't be stored...but was metabolized. And I used it only before exercise as a training enhancer.... not as a cooking oil. Tell me please about the physiology behind why it was believed it would not raise cholesterol....
CATER: It again has to do with the differences in metabolism. The more common fats or fatty acids in the diet are what we call long chain fatty acids or fats, and these MCT's contain medium chain...and it boils down to the fact that the medium chain fatty acids or triglycerides are readily absorbed and quickly transported to the liver, where the long chain fats have to be processed in a different way, and it takes them much longer to end up in the liver. And once in the liver, these long chain fats really aren't further broken down, whereas the medium chain fatty acids or medium chain triglycerides...once reaching the liver, are quickly broken down. What I mean by that is that all of these fatty acids contain a certain number of carbons...or carbon atoms...the long chain fats have 12 to 18 carbon atoms, whereas the medium chain fats have 8 to 10. Well, what we know is that once in the liver, these 8 and 10 carbon chain fatty acids are quickly broken down to 2- carbon fragments. I don't think there's much controversy about that. So it's for that reason that people thought, since it is quickly broken down, then it couldn't possibly raise your cholesterol. What actually happens after the body breaks down these 8 and 10 carbon fatty acids into 2-carbons, is that the liver then reuses them as building blocks...resynthesizes them...into even longer chain fatty acids. So that the end of fact is that the blood is enriched in long chain fatty acids, in palmitic acids...because when we measured blood levels of these fatty acids after patients had been on a medium chain triglyceride diet for three weeks, we detected no medium chain fatty acids in the blood. Rather what we detected was palmitic acids and longer chain fatty acids. So that apparently is the explanation, because what we found was in terms of the total cholesterol and the LDL or the bad cholesterol levels...those levels on the MCT diet were similar to the levels found when we fed our patients the palm oil diet. And those two values were significantly higher than the values found when patients ate a monounsaturated fat diet. So the oil, the MCT oil, raises cholesterol...especially the bad cholesterol, the LDL cholesterol, to the same extent as palm oil, which is traditionally known to be a very notoriously cholesterol raising fat.
NEMA: You mentioned that the medium chain fats are broken down quickly in the liver....does that mean there's some positive effect on the energy side?
CATER: That's really a separate issue that we did not address, and which we did not intend to address. You know, what other...and again there's a very limited amount of data in humans..most of the studies that people refer to are in rats, and occasionally chickens and dogs....and that's important to realize. There have been a few studies in humans that have shown that there is increase thermogenesis, or increased breakdown of these 8 and 10 carbon chain and perhaps in that way, we can get a boost of energy. But again, we did not statistically address that and the literature is still unclear. Despite these wide beliefs that it has these other benefits. And the weight loss is the other purported benefit. But again, there's very little data...most of the data that supports that is in animals, and the few studies that have addressed that in humans have not conclusively shown that that really is beneficial in weight loss.
NEMA: While we're talking about the makeup of fatty acids and how they affect our cholesterol levels...tell me why beef can be a healthy part of a person's protein allowance....
CATER: A lot of the saturated fatty acids come from stearic acid...and that goes back to my earlier comment in that all fats are composed of a mixture of fatty acids...you know, you'll have some monos, polys and different types of saturated. And it's whatever the predominant fatty acid is in the fat that determines it's cholesterol raising potential...so fats that have...now stearic acid is in that group of long chain fatty acids. Palmitic acid is the most common saturated fatty acid in the diet, and that clearly is cholesterol raising, there's no question about that. Going back to the discussion about the carbon links - that has 16 carbons. Stearic acid has 18 carbons, and my colleagues here at the Center for Human Nutrition in Dallas have clearly shown that stearic acid does not have the properties of the long chain fatty acids. Stearic acid does not raise cholesterol, rather, it's action is more like that of a monounsaturated fatty acid...like the fatty acids you find in olive oil. So, you know, the conventional thinking was that although we say saturated fatty acids raise your cholesterol, that's true, because the three most common fatty acids in the diet: palmitic, maristic and luric acid, clearly have been shown by my colleagues to raise cholesterol...whereas stearic acid, which is the fourth most common saturated fatty acid in the diet, does not. And we've done the study here at the Center for Human Nutrition...what we found was that there is actually a rank order in that beef and cocoa butter do not raise your cholesterol to the same extent that butter does...and it comes somewhere in between the cholesterol properties of butter and olive oil. And it's probably because some of the fatty acids come from stearic acid, which you would not expect to raise cholesterol.
NEMA: So, something to take away from today's program...Medium Chain Triglyceride Oil, thought not to raise bad cholesterol, does so on the level with the worst of the saturated fats, palm oil. And stearic acid, though a long chain fatty acid, has a neutral effect on cholesterol, making a modest portion of beef a good part of your dinner plan. Thanks to Dr. Nilo Cater, of the Center for Human Nutrition at the University of Texas Southwestern Medical Center. I'm Steve Girard.
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