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Nutrition and Atherosclerosis Slide 10-12. The synergistic effects of dietary fiber and inhibitors of cholesterol biosynthesis are shown here. Examples of dietary substances inhibiting absorption and promoting excretion include fiber and phytosterols. Naturally occurring inhibitors of cholesterol biosynthesis exist in small amounts in over 30 species of mushrooms and fungi as Monacolins. Chinese red rice yeast has been shown to reduce cholesterol levels, presumably by inhibition of cholesterol biosynthesis. Slide 10-13. The common dietary fats have very different fatty acid compositions shown here. Among the saturated fats, coconut oil is the most atherogenic. Vegetable oils such as corn oil, safflower oil, and soybean oil contain large amounts of linoleic acid. While polyunsaturated fats lower cholesterol by comparison to saturated fats when calories are held constant, it has been shown that metabolites of linoleic acid may promote atherogenesis through effects on the scavenger monocytes. Slide 10-14. Linoleic acid metabolites induce the CD-36 scavenger cell cholesterol receptor, which promotes atherogenesis. Oxidized cholesterol is taken up by these cells, and as the number of CD-36 surface receptors is increased, the process becomes more efficient. The cellular basis of atherosclerosis involves the action of monocytes expressing a CD-36 receptor which binds oxidized cholesterol. Linoleic acid increases oxidation of cholesterol and provides a stimulus to increased synthesis of the CD-36 receptors. Slide 10-15. Linoleic acid oxidation can lead to a chain reaction as the oxidized fatty acid itself serves as a pro-oxidant. This reaction can be demonstrated both in the test tube and in the body. Endogenous antioxidants such as vitamin E are often removed during processing of vegetable fats and oils so that the polyunsaturated fats in the diet can contribute to oxidation processes including oxidation of cholesterol. Slide 10-16. Obesity results in increased cholesterol and triglyceride levels through effects on very low density lipoprotein synthesis in the liver. These data collected from the NHANES survey for adult males are typical of the association of mixed hyperlipidemia with obesity. This problem affects over 40 million Americans and is the most common cause of elevated cholesterol. Slide 10-17. The American Heart Association Step 2 diet (30% fat calories, < 200 mg cholesterol /day, < 7% saturated fat) was compared to drug therapy with Lovastatin. It was found that diet only resulted in a 5% reduction in cholesterol, while drug therapy accounted for a 27% reduction in cholesterol. Slide 10-18. Effects of a high fat, refined sugar diet on increasing serum triglycerides and cholesterol are shown. These effects are the result of both increasing insulin levels which increase production of hepatic triglycerides, and reducing clearance by muscle lipoprotein lipase. At the same time, there is an increased deposition of triglycerides in fat depots demonstrating the tissue-specific regulation of lipoprotein lipase following changes in dietary intake. Slide 10-19. The absorption of dietary lipids begins with the formation of a micelle which permits the enzymes in the unstirred water layer on the intestinal mucosal cell to digest the lipids contained in the mixed micelle releasing fatty acids, free cholesterol, lysolecithin and monoglycerides into the intestinal cell where they are reassembled into cholesterol esters and triglycerides. These are incorporated into chylomicrons and exported from the intestinal mucosal cell into the bloodstream. Slide 10-20. Rich sources of soluble fiber include cereals, beans and peas, and certain fruits and vegetables. A mixture of these foods yielding a total intake of 25 to 35 grams of dietary fiber should assure an adequate intake of soluble fiber.
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Nutrition
101 - Natural
Remedies - Weight
Management - Physician
Education |
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