Role in Management of Hyperlipidemia

Role in Management of Hyperlipidemia. Some forms of dietary fiber lower blood lipids, notably total cholesterol and low-density lipoprotein (LDL) cholesterol. The earliest observations on fiber preparations and blood lipids date from the mid 1930s when there was a fairly extensive investigation of the effects of pectin (polygalacturonic acid). The next period of investigation dates from 1974 when extracted and purified dietary fiber preparations such as guar gum – a glucomannan – were tested in normal subjects, diabetics, and hyperlipidemic subjects and were found to lower blood cholesterol when given in sufficient quantities. 

In very large doses these materials increase fecal excretion of fat and sterol compounds and would be expected to reduce the body bile salt pool. Subsequent work has shown that at lower doses preparations of soluble dietary fiber have a mild cholestyramine-like effect: they bind bile salts rendering them unavailable for reabsorption in the terminal ileum, thus interfering with the normal entero-hepatic cycle of bile salts and depleting the bile salt pool. Total and LDL cholesterol fall as cholesterol is diverted for the resynthesis of lost bile salts. There have been few direct clinical applications of the early experimental work on pectin and guar gum. No pectin compounds have been developed commercially, but there are a few pharmaceutical preparations of guar gum presented primarily as adjuncts to dietary therapy in diabetes rather than for lipid lowering. Dietetic food products containing guar gum have been developed, again for use in controlling diabetes.

Preparations of soluble dietary fiber have been shown to lower blood cholesterol whereas most preparations of predominantly insoluble fiber, such as wheat bran, have little or no effect. The major food sources of soluble fiber are oats, beans, lentils, rye, and barley, and these foods have naturally become the subject of investigations. The addition of oats to the diet in normolipidemic and hyperlipidemic subjects following either their normal diets or where pretreated with low-fat diets has been the subject of extensive research. In sufficient quantity oats, oat products, and oat Beta-glucan (providing at least 3 g oat beta glucan per day) lower blood total cholesterol and LDL cholesterol (usually by 5–10%) while leaving triglycerides and HDL cholesterol largely unchanged. 

A sufficiently large number of good-quality studies have now been done on oats that the Food and Drug Administration (FDA) has allowed the first ever food-specific health claim: ‘‘Soluble fiber from oatmeal, as part of a low saturated fat, low cholesterol diet, may reduce the risk of heart disease.’’ Products that are labeled with this claim must provide at least 0.75 g of soluble fiber (as Beta-glucan) per serving. When considering the above claim the FDA reviewed 37 studies and found that a sufficient number provided convincing evidence of efficacy. An earlier metaanalysis of some of those trials had shown that the efficacy of oats and oat products was influenced by the initial values of blood cholesterol in the subjects: patients with high starting values (over 6.7 mmol per liter total cholesterol) showed the greatest reductions when treated with oats, while healthy young subjects with low–normal starting values showed little response. There was a dose effect: food products providing more than 3 g soluble fiber per day had a greater blood cholesterol lowering effect than diets that provided less than 3 g per day.

Other soluble fiber-containing products have been shown to lower blood cholesterol. Recent extensive studies on psyllium (Plantago ovata) presented both as a pharmaceutical preparation and as a food product (a ready to eat breakfast cereal) have shown blood cholesterol-lowering properties where the dose–effect relationship is such that a useful additional therapeutically meaningful lipid-lowering effect can be achieved by prescribing a daily portion of psyllium-fortified breakfast cereal. Products of this type are now marketed in the US and Australia, and the US FDA has now allowed a food specific health claim for psyllium.

There is also a small literature on the effects of beans on blood lipids and the findings of a blood cholesterol-lowering effect are as expected. Virtually all of the reports of the effects of soluble fiber products on blood lipids report lowering effects on total cholesterol and LDL cholesterol without any effect on HDL cholesterol or triglycerides – this contrasts with the effects of some drugs that may cause slight rises of triglycerides and falls of HDL cholesterol. The relationship between lowering of blood cholesterol and lowering of risk of heart disease is now generally accepted and a proven lipid-lowering effect is taken to mean a beneficial effect on risk of coronary heart disease. This means that in clinical practice it is perfectly reasonable to include advice on use of foods high in soluble dietary fiber in a lipid-lowering diet, and perfectly proper to emphasize the benefits of oats and oat products. 

Generally, a high-soluble-fiber diet is more acceptable when the soluble fiber is drawn from smaller quantities of a larger range of foods; thus the diet includes beans, lentils, rye breads, and barley as well as generous use of oats. A range of foods containing mycoprotein and fungal mycelial cell walls (chitin) may also help to lower blood cholesterol.

Salam

by Umaee

Role in Management of Hiperlipidemia

Source: Nutritional Supplements

Image: Shannonassosiate.com

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