Hypocholesterolemic effects

Various mechanisms have been proposed to explain the hypocholesterolemic effect of GA (Annison et al., 1995 Tiss et al., 2001). Some studies have suggested that the viscosity of fermentable dietary fiber contributes substantially to the reduction of lipids in animals and humans (Gallaher et al., 1993 Moundras et al., 1994). However, other studies suggested that this property is not related to plasma lipids (Evans et al., 1992). The mechanism involved is clearly linked to increased bile acid excretion and fecal neutral sterol or a modification of digestion and absorption of lipids (Moundras et al., 1994). 

The current weight of evidence suggests that soy does have a beneficial effect on cardiovascular health however, the active component has yet to be identified. Studies have also demonstrated that dietary inclusion of phytoestrogen-rich foods can lower plasma cholesterol levels (Ridges et al., 2001). However, these data do not conclusively demonstrate that phytoesfrogens are responsible for the hypocholesterolemic effect, and it is possible that some other component in soy may be responsible (Erdman and Fordyce, 1989 Ling and Jones, 1995). 

POTTER s M (1995) Overview of proposed mechanisms for the hypocholesterolemic effect of soy. J Nutr. 125 (3 Suppl) 606S-611S. 

In our study, consumption of rye bread or rye bread with phloem did not have an effect on serum lipids (total, LDL or HDL cholesterol or triglycerides) (Table 14.4). This is contrary to a recent finding suggesting that soluble fiber from rye bread decreased the concentrations of cholesterol (Leinonen et al., 2000). In that study ingestion of rye bread (220 g/d) with naturally high amounts of insoluble (18 g/d) and soluble fiber (4 g/d) decreased the LDL concentrations by 8% in hypercholesterolemic men. The researchers speculated that soluble fiber, maybe P-glucan, was responsible for the hypocholesterolemic effect. The amount of rye bread (70 g/d vs 220 g/d), the amount of total (5.9-11.8 g/d vs 22.1 g/d) and soluble fiber (0.6-1.3 g/d vs 4 g/d) ingested in this study was considerably less, and could explain the lack of effects on blood lipids in our study. 

Cardiovascular disease (CVD) is characterized by the involvement of the heart and allied vascular system. High cholesterol, associated lipid abnormahties and high blood pressure are recognized as the major risk factors of CVD. There have been several animal experiments and clinical studies using rice bran and rice bran oil, which have demonstrated a hypocholesterolemic effect (Raghuram et al., 1989 Rukmini and Raghuram, 1991 Sugano and Tsuji, 1997). The mechanisms involved are briefly summarized. 

KAHLON T s, CHOW F I (1997) Hypocholesterolemic effect of oat, rice and barley dietary fibers and fractions. Review. Cereal World, 42(2) 86-92. 

Fuhrman, B. et al., Hypocholesterolemic effect of lycopene and beta-carotene is related to suppression of cholesterol synthesis and augmentation of LDL receptor activity in macrophages, Biochem. Biophys. Res. Commun., 233, 658, 1997. 

The importance of some pectic substances (pectin or pectins) either due to the great amounts that certain raw materials contain, or the existence of any specific food use, as well as its hypocholesterolemic effect (based in in vitro and in vivo studies) would explain the increasing interest on deepening physico-chemical studies of pectic substances. 

Bile acids and salts have been found to enhance the absorption of both calcium and vitamin D hence, to increase calcium absorption both directly and indirectly (3,37). However, the ability of some dietary fibers such as lignin and pectin to absorb conjugated and deconjugated bile salts onto their surfaces to be excreted in the feces (a mechanism credited to the hypocholesterolemic effect of some dietary fibers) may result in an overall decrease in calcium absorption from the gastrointestinal tract (7,33,38-40). 

Ramage. Hypocholesterolemic effect of barley foods on healthy men. Nutr Rep Int 1989 39(4) 749-760. 

Deng, R. (2009). Food and food supplements with hypocholesterolemic effects. Recent Pat. Food. Nutr. Agric. 1,15-24. 

The hypothesis that dairy foods contain a cholesterol-lowering milk factor evolved from the observation that Maasai tribesmen of East Africa have low serum concentrations of cholesterol and a low incidence of cardiovascular disease in spite of their consumption of 4 to 5 liters/day of fermented whole milk (Mann and Spoerry 1974). Subsequently, sufficient amounts of yogurt, as well as unfermented milk (whole, lowfat, skim), were reported to exhibit a hypocholesterolemic effect both in humans and in laboratory animals in several studies (Mann 1977 Howard and Marks 1977, 1979 Nair and Mann 1977 Kritchevsky et al 1979 Richardson 1978 Hussi etal. 1981). However, not all investigators have observed a hypocholesterolemic effect of milk. This inconsistency may be explained in part by differences in the experimental design and in the specific type of dairy food used by investigators. 

Richardson, T. J. 1978. The hypocholesterolemic effect of milk—a review. J. Food Protection 41, 226-235. 

Hypocholesterolemic effects of soybean saponins have been dimonstrated. Isolated soybean saponins reduced diet-induced hypercholesterolemia in rats through an increase in bile acid excretion... 

Hypercholesterolemia is well established as a risk factor for atherosclerosis. Dietary flavonoids are thought to protect against the disease by exerting hypocholesterolemic effects. However, clinical studies are not conclusive enough to provide the supporting evidence. Recent clinical studies on both normo- and hypercholesterolemic subjects with different flavonoids sources lasting 1-13... 

This research lead to search for a "milk factor" that could be responsible for the observed hypocholesterolemic effects. Several components of milk were named as being the responsible component, for example, orotic acid, whey, calcium, lactose, casein, B12, and B6 (Eichholzer and Stahelin, 1993). This search for a single factor may have been too simplistic bearing in mind that the matrix of nutrients and bioactive components contained within the different dairy foods may have been responsible for the observed effects. 

In studying results from both chickens and man, Fisher et al. (67) concluded that pectin has a hypocholesterolemic effect only when fed with dietary cholesterol. On cholesterol-free diets, plasma cholesterol is not affected by dietary pectin. Subjects fed pectin with a cholesterol-containing diet had plasma cholesterol levels that were lower relative to those of subjects on the cholesterol control diet, but not relative to those of subjects on a cholesterol-free control diet. 

Pfeffer et al. (82) have found that bile salt binding activity of commercial citrus pectins was lost if these products were dissolved, filtered, centrifuged, and reprecipitated before testing. Binding activity was concentrated in the residue pellet from centrifugation, which was found to be fine diatomaceous earth. This contaminant was probably introduced during filtration steps in processing and purification of pectin. The authors concluded that any hypocholesterolemic effect of commercial pectin was due solely to its diatomaceous earth contamination. 

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