Trans Fatty acids lipoprotein effects

Aro, A., Jauhianinen, M., Partanen, R., Salminen, I., and Mutanen, M. (1997). Stearic acid, trans fatty acids, and dairy fat Effects on serum and lipoprotein lipids, apolipoproteins, lipoprotein(a), and lipid transfer proteins in healthy subjects. Am.. Clin. Nutr. 65, 1419-1426. 

Katan, M. B., Zock, P. L., and Mensink, R. P. (1995b). Trans fatty acids and their effects on lipoproteins in humans. Annu. Rev. Nutr. 15, 473-493. 

Judd, J.T., Clevidence, B.A., Muesing, R.A., Wittes, J., Sunkin, M.E. and Podczasy, J. (1994) Dietary trans fatty acids Effects on plasma lipids and lipoproteins of healthy men and women. Am. J. Clin. Nutr., 59, 861-868. 

Mensink, R.P. M.B. Katan. Effects of dietary trans fatty acids on high-density and low-density lipoprotein cholesterol levels in healthy subjects. N. Engl. J. Med. 1990,323, 439—445. 

Fatty acids affect CHD risk, in part, via effects on plasma lipids and lipoproteins. A meta-analysis of 60 controlled trials (Mensink et al., 2003) reported that saturated and trans fatty acids increase low-density lipoprotein cholesterol (LDL-C), whereas unsaturated fatty acids decrease LDL-C. Saturated fatty acids, MUFA, and PUFA all increase high-density lipoprotein cholesterol (HDL-C), whereas trans fatty acids do not. Both MUFA and PUFA decrease the TC to HDL-C ratio, whereas trans fatty acids increase it, and SFA have little effect (Fig. 20.4). 

The adverse effects of trans fatty acids on serum lipids and lipoproteins are thought to be mediated by alterations in lipid catabolism and metabolism. Trans fatty acids increase the catabolism rates of apolipoprotein A-I and decrease apolipoprotein B catabolism rates (Matthan et al., 2004), reduce LDL-C particle size (Mauger et al., 2003), and can increase cholesteryl ester transfer protein (CETP) activity (van Tol et al., 1995). CETP mediates the transfer of cholesterol esters from HDL- to LDL- and very-low-density lipoprotein (VLDL)-C, thereby offering a potential explanation for the LDL-C-raising and HDL-C-lowering effect of trans fatty acids. 

Zock, P.L. M.B. Katan. Hydrogenation alternatives effects of trans fatty acids and stearic acid versus linoleic acid on serum lipids and lipoproteins in humans. J. Lipid Res. 1992, 33, 399-410. 

Unfortunately, not all of the unsaturated fats appear to be equally safe. When we eat partially hydrogenated fats, we increase our consumption of trans-fatty acids. These acids, which are isomers of the naturally occurring ds-fatty acids, have been implicated in a variety of conditions, including heart disease, cancer, and diabetes. The strongest evidence that frans-fatty acids may be harmful comes in studies of the incidence of coronary heart disease. Ingestion of trans-fatty acids appears to increase blood cholesterol levels, in particular the ratio of low-density lipoproteins (LDL, or "bad" cholesterol) to high-density lipoproteins (HDL, or "good" cholesterol). The trans-fatty acids appear to exhibit harmful effects on the heart that are similar to those shown by saturated fatty acids. 

During the 1980s, research indicated that trans fatty acids have an effect on blood cholesterol similar to that of saturated fats, although study results vary. Several studies reported that trans fatty acids raise the levels of LDL-cholesterol, low-density lipoproteins containing cholesterol that can accumulate in the arteries. Some studies also report that trans fatty acids lower HDL-cholesterol, high-density lipoproteins that carry cholesterol to the liver to be excreted. 

Effect of trans Fatty Acids on Plasma Lipoproteins... 

Figure 3 Effects of monounsaturated Ci8 trans fatty acids on lipoprotein cholesterol concentrations relative to oleic acid (c/s-Ci8 i). Data are derived from six dietary comparisons between trans and cis monounsaturated fatty acids differences between diets in fatty acids other than trans and cis monounsaturated fatty acids were adjusted for by using regression coefficients from a meta-analysis of 27 controlled trials. The regression lines were forced through the origin because a zero change in intake will produce a zero change in lipoprotein concentrations. From Zock et al. (1995), reproduced with kind permission of the American Journal of Clinical Nutrition.

The influence of trans fatty acids on plasma lipoproteins in relation to CHD risk would thus appear to be more unfavorable than that of saturated fatty acids, as determined by the effect on the ratio of LDL to FIDL cholesterol. However, the overall magnitude of the effect would be dependent on the relative intakes of trans fatty acids and saturated fatty acids. In the UK trans fatty acids contribute about 2% of dietary energy, in contrast to saturated fatty acids which contribute about 15% dietary energy, and this needs to be considered when formulating dietary advice. The Task Force also estimated, on the same basis, that a reduction of 6% in energy from saturated fatty acids would decrease risk by 37%. 

However, these conclusions of the adverse effect of trans fatty acid on plasma lipoprotein concentrations are not universally accepted. It has been commented that some trials used an inappropriate basis for comparison of the different diets and did not always control for other fatty acids that are known to influence blood cholesterol levels. 

Despite the reported effects of trans fatty acids on blood lipoproteins, experiments with laboratory animals have not provided evidence that dietary trans fatty acids are associated with the development of experimental atherosclerosis, provided that the diet contains adequate levels of linoleic acid. Similarly, there is no evidence that trans fatty acids raise blood pressure or affect the blood coagulation system. However, there has been no thorough evaluation of the effect of trans fatty acids on the coagulation system, and this is an area worthy of investigation. 

It has been commented on that the benefit predicted by the authors, that individuals in the top quintile of intake could halve their risk of myocardial infarction by reducing their intake of trans fatty acids to that of the lowest quintile, seems a large effect in view of the small difference in intakes between these groups (3.3 g). The changes in plasma lipoprotein cholesterol concentrations that would be predicted to occur as a result of lowering trans fatty acid intake would not explain all of the observed increase in risk. Also, the study was carried out in a selected population of women and it is unclear that the findings are applicable to the whole population or to other population groups. 

Elner, VM, 2002. Retinal pigment epithelial acid lipase activity and lipoprotein receptors Effects of dietary omega-3 fatty acids. Trans Am Ophthalmol Soc 100, 301-338. 

Judd, J. D. Baer B. Clevidence et al. Blood lipid and lipoprotein modifying effects of trans mono-unsaturated fatty acids compared to carbohydrate, oleic acid, stearic acid, and C 12 0-16 0 saturated fatty acids in men fed controlled diets. FASEB J. 1998, 12, A229-A229.abstract. 

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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