Dietary n-3 polyunsaturated fatty acids and amelioration of cardiovascular disease: possible mechanisms

Article Abstract:

The consumption of dietary fat generally contributes to the elevation of lipids in the blood, which is a major risk factor for atherosclerosis and heart disease. But some populations, most notably Eskimos, consume an enormous amount of fat in their diet without suffering a high rate of heart disease; the difference is attributed to the specific composition of the fats they consume. Fats from fish contain fatty acids which are unsaturated at the n-3 position along their carbon chain. These fatty acids, variously called n-3 or omega-3 fatty acids, are thought to confer some protection against atherosclerosis and heart disease, but the mechanisms behind this protection are not fully understood. In an extensive review (which includes 418 references) of the ways in which the body's metabolic use of fats may be altered by n-3 polyunsaturated fatty acids (n-3 PUFAs), the authors point out where the protective effects of these compounds are most likely to be exerted. The n-3 PUFAs decrease the levels of blood lipids by depressing triglyceride synthesis in the liver. These PUFAs also directly influence the synthetic pathways of the prostaglandins and related compounds. The multitude of effects includes the reduction of thromboxane synthesis, which decreases the tendency of the platelets to aggregate, or clump. Platelet aggregation plays a role in both normal blood clotting and that which contributes to a heart attack. While even normal clotting is measurably inhibited by fish oil, the effect is less than that of aspirin. It is believed that the n-3 PUFAs depress the metabolism of eicosanoid compounds in platelets, which may inhibit the formation of atherosclerotic plaques. It is difficult to isolate a specific cause of the reduction in heart disease because of the wide variety of different cells which may be affected by the n-3 PUFAs. These fatty acids not only reduce blood pressure and reduce blood viscosity, but also change the membrane fluidity of virtually every cell, with whatever influence that may have on receptors and enzyme functions. The authors point out that one potentially serious side effect of the dietary use of n-3 polyunsaturated fatty acids may be the impairment of absorption of vitamin E. They suggest that any diet involving an increased consumption of fish oils might also require supplementation with vitamin E. (Consumer Summary produced by Reliance Medical Information, Inc.)

Cardiovascular diseases, Physiological aspects

---

Dietary canola oil: effect on the accumulation of eicosapentaenoic acid in the alkenylacyl fraction of human platelet ethanolamine phosphoglyceride

Article Abstract:

Much research in recent years has focused on the possible beneficial health effects of eating fish or taking fish oil supplements. The omega-3 fatty acids found in fish oil, one of which is eicosapentaenoic acid (EPA), appear to reduce the tendency of blood platelets to clump together and adhere to the inside walls of blood vessels. Consequently, EPA may prevent the formation of blood clots and the narrowing of the coronary arteries, which may lead to heart attack. While EPA is found primarily in fish oil, it is also known that linolenic acid, a component of some vegetable oils, can be converted to EPA. It is not known to what extent this conversion occurs in the human body; this was studied in a group of eight young men. They followed two different diets for 18 days each; one was high in canola oil, which supplies linolenic acid, and the other diet was rich in sunflower oil. Blood samples were taken to analyze the lipid (fat) composition of the platelets. The specific substances in platelets that were studied were the phospholipids, including the alkenylacyl fraction of ethanolamine phosphoglyceride. EPA was found in significantly greater concentrations in platelets after the canola oil diet, compared with levels obtained after the sunflower oil diet and during the pre-experimental period, when subjects followed a mixed-fat diet. It appears that the linolenic acid in the canola oil was converted in the human body into EPA, which was thereby increased in the platelets. In addition to the moderate increases in platelet EPA, there were changes in the amounts of other fatty acids in the platelets. Consumption of canola oil may have a protective effect against formation of blood clots, but a reduction in platelet clumping can also lead to prolonged bleeding times following injury. (Consumer Summary produced by Reliance Medical Information, Inc.)

Blood platelets, Cell aggregation, Canola oil

---

Dietary alpha-linolenic acid is as effective as oleic acid and linoleic acid in lowering blood cholesterol in normolipidemic men

Article Abstract:

The relationship between coronary heart disease (CHD) and high blood levels of cholesterol and fats (lipids) is well established. Previous studies have shown that the diet plays an important role in determining blood cholesterol levels. There is evidence that saturated fatty acids (SFAs) promote cholesterol formation, while unsaturated fatty acids, such as linoleic acid (LA) and oleic acid (OA), lower blood cholesterol levels. More recently, it has been suggested that alpha-linolenic acid (LNA) may be beneficial in reducing the risk of CHD because it can reduce blood clot formation. However, it is not clear whether LNA is as effective as LA or OA in lowering blood cholesterol levels. To clarify this issue, eight men with normal blood cholesterol levels (normolipidemic) followed each of four different diets, containing different amounts of OA, LA and LNA, each for an 18-day period. The four experimental diets included sunflower and olive oil; canola oil; soybean oil; or sunflower, olive, and flax oils. A mixed-fat (typical) diet containing twice as much saturated fat as the other diets was fed for six days before and after each experimental diet. All diets, except for the mixed-fat diet, reduced total cholesterol, low-density-lipoprotein cholesterol, very-low-density-lipoprotein cholesterol, apolipoprotein B and A-I, by 18 percent, 22 percent, 41 percent, 19 percent and 9 percent, respectively. All the experimental diets were equally effective in lowering cholesterol and apolipoprotein levels. These findings indicate that dietary OA, LA and LNA are equally effective in lowering blood cholesterol levels. (Consumer Summary produced by Reliance Medical Information, Inc.)

Linolenic acids, Linolenic acid, Blood cholesterol, Lipoproteins, Blood lipoproteins, Unsaturated fatty acids, Linoleic acids, Linoleic acid, Oleic acid

Similar abstracts:

• Abstracts: Comparing outcomes of care before and after implementation of the DRG-based prospective payment system. The effects of the DRG-based prospective payment system on quality of care for hospitalized Medicare patients: an introduction to the series
• Abstracts: Measuring quality of care with explicit process criteria before and after implementation of the DRG-based prospective payment system. part 2
• Abstracts: Obesity in the Pima Indians: its magnitude and relationship with diabetes. Type 2 diabetes mellitus and periodontal disease
• Abstracts: In vitro fertilization in unstimulated cycles: a clinical trial using hCG for timing of follicle aspiration. A preliminary report on oocyte donation extending reproductive potential to women over 40
• Abstracts: Magnetic-resonance imaging used for determining fat distribution in obesity and diabetes. Effect of obesity on bioelectrical impedance

This website is not affiliated with document authors or copyright owners. This page is provided for informational purposes only. Unintentional errors are possible.