Cholesterol dietary sources

In more recent studies the use of HPLC allowed isolation and counting of individual sterols after administration of labelled precursors. The sterols isolated from mantles and viscera of the nudibranch Doris verrucosa were identified as cholestanol, cholesterol, 24-dehydrocholesterol and 7-dehydrocholesterol [103]. After injection of dl-[2-14C]-mevalonic acid DBED salt, cholesterol (57) and 7-dehydrocholesterol (58) were isolated as the acetates by reversed phase HPLC. Both sterols were found significantly labelled specific radioactivity associated with 7-dehydrocholesterol was higher by one order of magnitude than that associated with cholesterol. This fact would indicate either that the reduction of the A1 double bond of 7-dehydrocholesterol to afford cholesterol occurs at a low rate, or that the cholesterol found in D. verrucosa comes partly from a dietary source. 

An elevated level of plasma cholesterol, particularly that carried in LDLs, is an independent risk factor for developing cardiovascular disease. Cholesterol comes from dietary sources and is made in the body, largely in the liver. 

The answer is a. (Hardman, pp 875-898.) In type I hyperlipoproteinemia, drugs that reduce levels of lipoproteins are not useful, but reduction of dietary sources of fat may help. Cholesterol levels are usually normal, but triglycerides are elevated. Maintenance of ideal body weight is recommended in all types of hyperlipidemia. Clofibrate effectively reduces the levels of VLDLs that are characteristic of types 111, IV, and V hyperlipoproteinemia administration of cholestyramine resin and lovastatin in conjunction with a low-cholesterol diet is regarded as effective therapy for type 11a, or primary, hyperbetalipoproteinemia, except in the homozygous familial form. 

Tea is another important dietary source for flavonoids, In fact, about half of the flavonoid intake in western populations is derived from black tea. Tea was the major source of flavonoids in the Dutch [6,13] and Welsh studies [17]. Only a small number of studies investigated the association between tea consumption and cardiovascular disease risk. No association between tea consumption and cardiovascular disease risk were reported in Scottish men and women [28] and in U.S. men in the Health Professionals follow-up study [29]. However, in a Norwegian population an inverse association was reported between tea intake, serum cholesterol, and mortality from coronary heart disease [30]. Several studies reported that tea consumption did not affect plasma antioxidant activity [31] and hemostatic factors [32]. However, a recent prospective study (the Rotterdam study) of 3,454 men and women 55 years and older followed for 2 to 3 years, showed a significant, inverse association of tea intake with severe (> 5 cm the length of the calcified area) aortic atherosclerosis. Odds ratios decreased approximately 70 % for drinking more than 500 mL/day (4 cups per day). The associations were stronger in women than in men. However, the risk reductions for moderate and mild atherosclerosis were only weak or absent [33]. 

Vitamin D. Vitamin D is a steroidlike hormone that can be obtained from dietary sources or synthesized in the skin from cholesterol derivatives in the presence of ultraviolet light. Vitamin D produces several metabolites that are important in bone mineral homeostasis.27,31 In general, vitamin D derivatives such as 1,25 dihydroxyvitamin D3 increase serum calcium and phosphate levels by increasing intestinal calcium and phosphate absorption and by decreasing renal calcium and phosphate excretion.27,46... 

Cholesterol is an essential component of cellular membranes. In addition to dietary sources, we can also synthesize cholesterol. Cholesterol is transported in the blood as a lipoprotein, which is an aggregate of water-soluble proteins, cholesterol, and other lipids, including triglycerides. Proteins are denser than lipids,... 

Vitamin D-active substances are required in the diets of growing children and pregnant women, but normal adults receiving sufficient doses of sunshine can manufacture sufficient amounts of these compounds to meet their needs. Active vitamin D compounds can by synthesized in such individuals from 7-dehydro-cholesterol (see Table 6.2), an intermediate in cholesterol biosynthesis. Dietary sources also include cholecalciferol, which is produced from 7-dehydrocholesterol and ergosterol (Table 6.2). 7-Dehydrocholesterol and ergosterol are often referred to as provitamins. 

Cholesterol is an extremely important biological molecule that modulates the fluidity of animal cell membranes and is the precursor of steroid hormones (such as progesterone, testosterone, oestradiol and cortisol) and bile acids. Cholesterol is either derived from the diet or synthesised de novo. Regardless of the source, cholesterol is transported through the circulation in lipoprotein particles, as are cholesterol esters, the cellular storage form of cholesterol. The amount of cholesterol synthesised daily in the liver of a normal person is usually double that obtained from dietary sources. Other sites of cholesterol synthesis include the intestine, and the degree of production is highly responsive to cellular levels of cholesterol. Over 1.2 g of cholesterol is lost in the faeces daily in the form of free sterol or as bile acids. 

The chemical composition of the egg (Table 2.1) is rather stable. As the only source of food for the embryo, it contains all substances essential for life. There is about 6.6 g of very well-balanced proteins in one egg. About two thirds of yolk mass are lipids, mainly unsaturated. Cholesterol makes up about 2.5% of the dry mass of the yolk. The egg is also a source of vitamins A, B, D, E, and K and the best dietary source of choline. The minerals S, K, Na, P, Ca, Mg, and Fe are in free form or bound to proteins and lipids. 

Since Insects lack the capacity to biosynthesize the steroid nucleus, they generally require a dietary source of sterol for normal development and reproduction U). This is an important area of biochemical difference, between insects and many other organisms, that might be exploited to develop new pest control strategies. Cholesterol will satisfy this dietary requirement in all but two known cases in which dietary A -sterols are essential (2,2). In addition, some insects may obtain an adequate supply of sterol from symbionts or intestinal microorganisms. 

Morton, G.M. et al. (1995). Intakes and major dietary sources of cholesterol and phytosterols in the British diet, J. Human Nutr. Dietet., 8, 429. 

EXAMPLE 12.16 What are the main dietary sources of cholesterol ... 

Plant oils, such as com oil and rapeseed oil, are major dietary source of phytosterols, whereas phytostanols occur mainly in cereals, such as wheat, rice, and rye [129-131]. With respect to health aspects, phytosterols, phytostanols, and their esters have been shown to decrease the risk of certain types of cancer [132-135] and cardiovascular disease (CVD) [136,137], inhibit cholesterol absorption [138], and enhance immune functions [139], among others. Furthermore, numerous... 

EFAs are present in all the body s cells, and especially concentrated in the brain and central nervous system. Properties attributed to EFAs include regulation of cholesterol metabolism and inflammatory processes. Table 8.1 lists some of the main dietary sources of EFAs. The quality of these dietary sources depends not only on the levels of the essential fatty acids, but also on their ratios. Many vegetable oils contain moderate levels of saturated fatty acids such as palmitic acid—they too provide therapeutic benefits. 

Not a significant source of calories from fat. saturated fat. trans fat, cholesterol, dietary fiber, sugars, vitamin A, vitamin C and iron. Percent Daily Values are based on a 2,000 calorie diet. 

The most important substrates handled by the peroxisomal fatty acid oxidation system from the perspective of peroxisomal disorders are (1) very-long-chain fatty acids (VLCFA), notably hexacosanoic acid (C26 0), (2) pris-tanic acid (2,6,10,14-tetramethylpentadecanoic acid), as derived from dietary sources either directly or indirectly from phytanic acid and (3) di- and trihydroxycholestanoic acid (DHCA and THCA). The latter two compounds are intermediates in the formation of the primary bile acids cholate and chenodeoxycholate from cholesterol in the liver. 

The cholesterol in the body is derived from both dietary sources and endogenous synthesis. 

The major dietary sources of fat in the American diet are meat, poultry, fish, dairy products, and fats and oils. Animal products tend to be higher in both total and saturated fats than most plant sources. Also, dietary cholesterol is found only in foods of animal origin. 

Chylomicrons are the largest of the lipoproteins and have the lowest density at 0.95 g/ml. As mentioned earher, a major role of chylomicrons is to transport lipids originating from dietary sources from the small intestine to other tissues and ultimately to the liver. After triglycerides are deposited in peripheral tissues by the action of lipoprotein lipase, the chylomicron remnants are transferred to the hver, where they are endocytosed. As the remnant is hydrolytically degraded, the cholesterol released from the chylomicron regnlates the rate of biosynthesis of cholestraol in the liver. 

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