Lauric acid cholesterol levels

It is important to bear in mind when discussing the effect of dairy fat in association to heart disease that dairy products contain many different saturated fatty acids that do not exert the same biological response in terms of, for example, cholesterol levels. The saturated fatty acids in milk fat include shorter and medium chain fatty acids (2 0-10 0), lauric acid (12 0), myristic acid (14 0), palmitic acid (16 0), and stearic acid (18 0). Other fatty acids in milk fat are oleic acid (18 1) and linoleic acid (18 2n-6) as indicated in Table 1.2. 

The longer chained fatty acids, lauric, myristic, and palmitic acids are all cholesterol elevating fatty acids and it is possible that myrictic acid is the most cholesterol elevating fatty acid. Stearic acid is, however, different from the other longer chained fatty acids present in dairy fat since it may have neutral effects on cholesterol level (Katan et ah, 1994). The proportion of stearic acid in milk fat is about 11% (Lindmark-Mansson et ah, 2003). 

It is now known that not all saturated fatty acids are equally hypercholesterole-mic. For example, medium-chain saturated fatty acids of carbon length 8-10, as well as stearic acid (18 0), have little or no effect on serum cholesterol concentrations. In contrast, evidence indicates that palmitic acid (16 0), the principle fatty acid in most diets, can increase serum cholesterol concentrations in humans. However, in normocholesterolemic humans, dietary palmitic and oleic acids have been shown to exert similar effects on serum cholesterol, suggesting that only humans or animal species sensitive to dietary cholesterol and selected fats ( hyperresponders ) may exhibit significant changes in semm cholesterol in response to dietary fat intake. Myristic acid (14 0) and, to a lesser extent, lauric acid (12 0), which are relatively high in coconut oil, both can raise serum cholesterol and LDL-cholesterol levels. Overall, it is not clear why humans respond so differently to cholesterol or... 

Saturated fatty acids. The adverse effect of saturated fat on blood cholesterol level and its implication in cardiovascular disease has stimulated concern over the level of saturated fatty acids in the diet. Canola oil contains a very low level (<7%) of saturated fatty acids about half the level present in corn oil, olive oil, or soybean oil and about one-quarter the level present in cottonseed oil. Furthermore, canola oil contains only 4% of the saturated fatty acids (viz., lauric, myristic, and palmitic) that have been found to increase blood cholesterol level. Hence, canola oil fits well with the recommendation to reduce the amount of saturated fat in the diet. 

A number of plants and phytochemicals have attracted attention for their ability to reduce many of the risk factors associated with cardiovascular disease. Research into these diseases has shown the relationship between lesions, fatty streaking and plaque formation in blood vessels and the development of strokes and myocardial infarctions. These effects are linked to levels of plasma lipids which comprise triglycerides, cholesterol and other fat substances. It is known that the biosynthesis of lipids involves the condensation of several molecules of acetylcoenzyme A and malonylcoenzyme A in a gradual process of elongation of the fatty acid chain involving the sequential addition of two carbon units giving rise to fatty acids such as lauric acid (12 carbons) and eventually to palmitic acid (16 carbons). Palmitic acid is the precursor... 

Because high blood cholesterol, especially LDL cholesterol, concentrations are positively associated with risk of cardiovascular disease (Keys et al., 1965) there has been much interest in the influence of dietary fatty acids on these and other blood lipid concentrations. Early studies showed that saturated fatty acids with a chain length of <12 carbons failed to raise serum total cholesterol levels, while those with a chain length of 12-16 carbon atoms (i.e. lauric, myristic and palmitic acids) increased serum total and LDL cholesterol concentrations (Katan et al., 1995). The order of their effects on raising total and LDL cholesterol levels is ... 

Both studies found that changes in dietary stearic acid did not fit the formula. Since those formulae were introduced a number of newer formulae have appeared, which provide a coefficient for every individual fatty acid, but the original formulae are still used most frequently. Under metabolic ward conditions it has been shown that lauric (Ci2 o) myristic (Ci4 o), and palmitic (Cig o) acids raise both LDL and HDL cholesterol levels, and that oleic (Cig i) and linoleic (Cigtz) acids raise HDL and lower LDL levels slightly. Thus, the type of fat is the determining factor in considering dietary fat effects on serum cholesterol. Experiments in which subjects were fed... 

Of the saturated fatty acids, lauric and myristic acids have the strongest potency to raise total and LDL cholesterol concentrations. In addition, both of these saturated fatty acids raise HDL cholesterol levels. Palmitic acid raises total and LDL cholesterol levels compared with carbohydrates but is less potent than lauric and myristic acids. Stearic acid does not raise LDL and HDL cholesterol concentrations compared with carbohydrates. Lauric, myristic, and palmitic acids increase factor VII activity in a similar way, whereas the effects of MCFA and stearic acid seem limited. 

Chain length has a significant effect on the ability of saturated fatty acids to raise plasma total cholestrol and LDL cholestrol, and only lauric (C12 0), myristic (C14 0) and palmitic (C16 0) acids are effective, especially at low levels of linoleic acid. Stearic acid (C18 0) does not increase LDL cholesterol, apparently because it is rapidly converted to oleic acid by desaturation (Figure 13.10). Palmitic and stearic acids make up about 36 0% of the fatty acids of animal fats and 11-16% of the fatty acids of vegetable fats. Although myristic... 

---