Preventing and Treating Heart Disease

Heart disease is the leading cause of death in the United States. More than one in four Americans has some form of cardiovascular disease. Many of the risk factors for heart disease are influenced by lifestyle. For example, smoking lack of exercise, and consumption of a high fat diet all contribute to risk. A heart-healthy diet is important for both prevention and treatment of cardiovascular disease. Soybeans have a favorable nutrient.

Nutrients in Soybeans

The Dietary Guidelines for Americans and the National Cholesterol Education Program both recommend that no more than 30% of calories in the diet should come from fat, and no more than 10% from saturated fat. Consumption of dietary cholesterol should not exceed 300mg. per day. In the typical American diet, most of the saturated fat comes from meats and dairy products. Cholesterol is found only in animal foods. Soyfoods are an excellent choice for a heart-healthy diet, and can take the place of the more atherogenic foods, soybeans provide high quality protein, but are low in saturated fat, and contain no cholesterol.
About 85% of the fat in soybeans is unsaturated. Soybean oil is rick in the essential fatty acids, linoleic and linoleic acids. Before processing, soybean oil is very high in the fat-soluble vitamin E. processing removes more than 30% of the vitamin E. which becomes a valuable byproduct. The finished oil is still considered a good source of vitamin E. because one serving (1 teaspoon) contains more than 10% of the daily requirement. Another important byproduct from soybean oil is lecithin, which is used extensively in the food industry as an emulsifier.

Soybeans are high in soluble fiber, which is extremely fermentable in humans. Whole soybeans, miso, natto, tempeh and soy nuts are all good sources of soy fiber. Unfortunately, many other soyfoods do not contain the fiber which is present in the whole beans. The fiber is often extracted and used as a supplement in other foods, such as enteral nutrition products.

▲Top

Soy and Heart Disease Risk

High blood cholesterol is a major risk factor for heart disease. There is a great deal of evidence that soy protein helps lower blood cholesterol levels. Replacing animal protein with soy protein in the diet lowers total and LDL cholesterol levels in people with high cholesterol. A meta-analysis of 38 research studies concluded that soy protein lowers total and LDL cholesterol and triglycerides, without lowering HDL cholesterol in hypercholesterolemic humans. In these studies, the average consumption of soy protein was 47 grams per day.

The greatest decreases in cholesterol were seen in those with the highest starting levels. Even adding soy protein to an omnivorous diet has been shown to produce this effect. As little as 25 grams of soy protein per day may be enough to lower cholesterol levels. One research study with rhesus monkeys found that isoflavones associated with soy proteins enhance the cholesterol-lowering effects. Another study suggests that soy protein inhibits LDL oxidation. If this is true in vivo, it will help reduce the risk of atherosclerosis. Soybean oil consumed within the dietary guidelines supports heart health. A meta-analysis of 27 studies concluded that replacing dietary saturated fat with unsaturated fat lowers total cholesterol levels, and also improves the ratio of HDL to LDL cholesterol. This was found to be true even with no change in total fat consumption, as long as obesity was not present. About 7% of the fat in soybean oil is a-linolenic acid, making soybean oil a fairly good source. This essential polyunsaturated fat may help lower risk for stroke or heart attack by inhibiting formation of blood clots. Serum levels of a -linolenic acid, which reflect dietary intake of this fat, are associated with a lower risk of stroke in men with multiple risk factors. Dietary supplementation with a-linolenic fat in healthy male and female subjects had the same inhibitory effect on blood clotting as did fish oil.

Certain soy products, which are sometimes used as food additives, have also been studied for their possible benefits to heart health. Supplementation with 25 grams per day of soy-soluble fiber resulted in a significantly greater decrease in plasma total and LDL cholesterol than that achieved by a low fat diet in patients with high cholesterol. Soy lecithin was shown to have a cholesterol-lowering effected in normal rats. A diet enriched with soy phytosterols was found to lower total and LDL cholesterol, and improve the ratio of HDL to LDL cholesterol, in healthy human subjects.

It is interesting that so many different aspects of soybeans are being studied for possible cardiovascular benefits. Perhaps when taken together in the form of whole soyfoods there may be a synergy among the various compounds, we still do not have a complete understanding of the physiological effects which have been reported by the researchers in this field. Possible mechanisms which have been proposed for the cholesterol-lowering effects of soy include: enhanced bile acid excretion, change in endocrine hormone levels, or direct effects on the metabolism of cholesterol in the liver.

Conclusion: Soyfoods and soy products are highly nutritious, and contain several biologically active components which may help reduce risk for heart disease.

▲Top