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A CLOSER LOOK AT THE CHOLESTEROL ISSUE
Nita Bishop, Clinical Herbalist
Antioxidants Inhibit Atherosclerotic Damage
Vitamins E and C are antioxidants that may play a role in countering the release of triglycerides, the blood fats that hinder the release of nitric oxide. Nitric oxide helps keep the blood vessels open, thus enabling healthy blood flow to the heart. In one study, plasma blood lipids and vitamin C levels were evaluated in 316 women and 511 men, ranging between 19 to 95 years of age. In a 7-day dietary record of 485 individuals, total fat, saturated fatty acids, and energy from fat and cholesterol intakes were not associated with plasma vitamin C levels. These results suggest a high plasma concentration of vitamin C may lower atherogenic risk. The relationship was even stronger in older men where the mean intakes of vitamin C were well above the recommended daily allowance.
The well-known plant Vaccinium myrtillus (Bilberry or European blueberry) is rich in flavonoids, the polyphenolic compounds that promote antioxidant activity. A study conducted on the antioxidative potential of Vaccinium myrtillus showed potent protective action on LDL particles during in vitro copper-mediated oxidation. The study concluded that this extract may be more potent than either ascorbic acid or butylated hydroxytoluene in the protection of LDL particles from oxidative stress.
A recent study on another well known antioxidant, green tea epicatechins, in the People's Republic of China demonstrated a reduction in serum triglycerides and cholesterol. This was most likely mediated by inhibition of absorption of dietary fat, cholesterol and reabsorption of bile acids, rather than inhibition of cholesterol synthesis.
Soy Protein
Research indicates that serum cholesterol is lowered by soy protein. Although results have been contradictory, it appears that substitution of isolated soy protein for animal protein in a regular diet reduces the risk of cardiovascular disease by lowering circulating LDL cholesterol concentrations. The jury is still out on which particular component of soy lowers the cholesterol, although many investigations have focused on the isoflavone components of soy, including genistein and daidzein, which are also referred to as plant sterols because of their estrogenic activities. A recent study reports that consumption of intact soy protein resulted in a significant decrease in VLDL cholesterol in female rheusus macaques when compared to a diet containing soy protein with isoflavones removed. In another study, the hypocholesterolemic effect of soy protein was found to decrease the plasma concentrations of LDL cholesterol as well as the ratio of plasma LDL cholesterol to HDL cholesterol in a randomized two part crossover study that included 13 normocholesterolemic and 13 hypercholesterolemic men aged 20-50 years old.
Soy and Lactobacillus
Fermented dairy products (yogurt, tofu, miso) can also serve as functional foods to lower elevated cholesterol concentrations in the prevention of cardiovascular disease. Beliefs about the health benefits of fermented milk products can be traced back to the early 1900's. In 1908, Metchnikov wrote that milks fermented by lactic bacteria "prevented intestinal putrefication" and "helped maintain the forces of the body." Human studies in the area of fermented dairy products and cholesterolemia have been conducted since the 1970's. In light of these findings, several fermented dairy products available on the market today have the potential of being classified as useful cholesterol-lowering agents. Bifidus and acidophilus-containing yogurt milk beverages, and kefir, a fermented diary product containing several types of bacteria in symbiosis with yeasts are good examples. Since these products contain live bacteria strains that do not normally colonize the intestine and are quickly eliminated in the feces, daily consumption of probiotic products is necessary for long-term effects of lowering cholesterol metabolism.
The Documented Benefits of Fiber
Fiber comes in many forms, including oats (Avena sativa), guar gum, and pectin. Nearly a dozen studies over the past decade have proven that oat bran lowers cholesterol levels. Recently, the FDA made history by ruling in the first federally sanctioned health claim for manufactured foods that oat-rich cereals and other foods are permitted to advertise their products as "cholesterol lowering." Beta glucan, a viscous gel in the soluable fiber of oats, surrounds cholesterol-rich bile acids and limits their reabsorption by the blood, shuttling them off into fecal excretion. Less bile is consequently returned to the liver which causes the liver to make more bile acids, the production of which uses up more cholesterol floating around in your blood.
However, studies from the University of Toronto have shown that not all beta-glucans are created equal. During the milling of oats into flour, cooking, pressure extrusion and other food processing techniques, the beta-glucan chain may be shortened, thereby limiting its effectiveness.
Guar gum, similar to pectin, is well documented regarding its ability to lower cholesterol levels. However, its principal drawback is its extreme viscosity, making foods containing guar gum very unpalatable. Nonviscous forms have been created via PHCC (partial enzymatic hydrolysis) of the gum's polysaccharide component, but there is some controversy regarding whether these processing techniques actually inhibit the guar gum's lipid lowering effects by reducing its digestibility rather than inhibiting bile reabsorption.
Chitosan is a form of fiber that absorbs dietary fat in the gut and can also inhibit LDL cholesterol while boosting desirable HDL cholesterol levels. The mechanism behind its action may be explained by Chitosan's ability to bind both bile acids and phospholipids, reducing their absorption from the intestines and increasing fecal excretion of cholesterol. Chitosan has been shown to significantly lower plasma cholesterol and reduce the development of atherosclerotic plaques. |