Myristic 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. 

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. 

Palmihc add (16 0) iS the primary saturated fatty acid in most diets. This compound constitutes about 25% of the fatty acids of beef or pork fat, but only 6-10% of Ihc fatly acids of sunflower, safflower, peanut, or soy oils (see Table 6.8). Dietary palmitic add increases LDL-cholesterol (Grundy and Denke, 1990), Myrislic acid (14 0) is present at high levels in butter fat and in the "tropical oils" palm oil and coconut oil. Although myristic add elevates LDL-cholesterol, it is generally a rather minor component of the diet. Stearic acid (18 0) is also a major component... 

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... 

As mentioned earlier, saturated fatty acids (SFA) of foods are regarded as the cause of a high-risk pattern of blood lipoproteins octadecanoic (stearic, Cig) acid and tetradecanoic (myristic, C14) acid and also all trans acids are considered to be the most damaging. With increasing consumption of SFA, blood levels of cholesterol and LDL are raised. Conversely, the polyunsaturated fatty acids (PUFA) are judged to be beneficial, although the various families of PUFA differ in their effects the n-6 PUFA (which occur mainly in plant lipids) reduce the blood concentration of LDL, and the n-3 PUFA (from fish lipids) reduce VLDL. It is considered desirable to have a balance in the diet of n-6 to n-3 PUFA the recommended maximum ratio is 4 1. In between the SFA and PUFA are the monounsaturated fatty acids (MUFA), such as octadecenoic (oleic, 18 1) acid, which are regarded as neutral or possibly beneficial to blood lipoproteins. 

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