High-density lipoprotein cholesterol saturated fatty acid effect

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). 

Fig. 10. Polyunsaturated fatty acids (PUFA) modulate the effects of the APOA-IG-A polymorphism on high density lipoprotein (HDL)-cholesterol concentrations in a gender-specific manner [data from Ordovas etal. (115), reproduced with permission]. In women carriers of the A allele, higher PUFA intakes were associated with higher HDL cholesterol concentrations, whereas the opposite effect was observed in G/G women. Adjusted for age, body mass index, alcohol, smoking, intake of energy, saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids. Interaction of G x PUFA, P< 0.005.

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. 

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